Departments of 1 Medicine, 2 Physiology, and Biophysics and 3 Program in Biomedical Engineering, State University of New York at Stony Brook, Stony Brook, New York 11794-8152
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ABSTRACT |
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Caveolae, flask-shaped invaginations of the plasma membrane occupying up to 30% of cell surface in capillaries, represent a predominant location of endothelial nitric oxide synthase (eNOS) in endothelial cells. The caveolar coat protein caveolin forms high-molecular-weight, Triton-insoluble complexes through oligomerization mediated by interactions between NH2-terminal residues 61-101. eNOS is targeted to caveolae by cotranslational N-myristoylation and posttranslational palmitoylation. Caveolin-1 coimmunoprecipitates with eNOS; interaction with eNOS occurs via the caveolin-1 scaffolding domain and appears to result in the inhibition of NOS activity. The inhibitory conformation of eNOS is reversed by the addition of excess Ca2+/calmodulin and by Akt-induced phosphorylation of eNOS. Here, we shall dissect the system using the classic paradigm of a reflex loop: 1) the action of afferent elements, such as fluid shear stress and its putative caveolar sensor, on caveolae; 2) the ways in which afferent signals may affect the central element, the activation of the eNOS-nitric oxide system; and 3) several resultant well-established and novel physiologically important effector mechanisms, i.e., vasorelaxation, angiogenesis, membrane fluidity, endothelial permeability, deterrance of inflammatory cells, and prevention of platelet aggregation.
endothelial nitric oxide synthase
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INTRODUCTION |
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THE CONTEMPORARY MODEL OF the plasma membrane views it as a combination of lipid-disordered and lipid-ordered microdomains, or lipid rafts (83), enriched in glycosphingolipids and cholesterol (9). The lipid composition of these latter domains, characterized by tight acyl chain packing, explains their liquid-ordered phase, intermediate between the fluid and gel phases (10, 45). Multiple functions have been proposed for these domains, such as anchorage of various receptors, docking of elements of intracellular signaling cascades and different enzymes, trafficking of cholesterol, and regulation of permeability, among others. A distinct subpopulation of these lipid rafts containing caveolin (64, 79), and referred to as caveolae, has been identified.
Caveolae, flask-shaped invaginations of the plasma membrane occupying
up to 30% of cell surface in capillaries, represent an ostensibly
predominant location of endothelial nitric oxide synthase (eNOS) in
endothelial cells (36). They harbor the bradykinin B2 receptor; epidermal growth factor (EGF) and
platelet-derived growth factor (PDGF) receptors; mitogen-activated
protein (MAP) kinase; src family nonreceptor tyrosine kinases; G
proteins; protein kinase C (PKC); cationic arginine transporter-1;
class B, type I scavenger receptor for high-density lipoprotein; H-Ras;
Ca2+ ATPases; and inositol 1,4,5 triphosphate-dependent
Ca2+ channels, among others (60, 71,
73). Caveolin, the caveolar coat protein (36,
79), forms high-molecular-weight, Triton-insoluble complexes
through oligomerization mediated by interactions between NH2-terminal residues 61 and 101. (80) eNOS is
targeted to caveolae by cotranslational N-myristoylation and
posttranslational palmitoylation (36). Caveolin-1
coimmunoprecipitates with eNOS; interaction with eNOS occurs via the
caveolin-1 scaffolding domain (NH2-terminal residues
81-101) and appears to result in the inhibition of NOS activity
(52, 62). The inhibitory conformation of eNOS is reversed
by the addition of excess Ca2+/calmodulin (26,
27) and by Akt-induced phosphorylation of eNOS
(34). These aspects of caveolar-eNOS
interaction have been comprehensively discussed in several recent
reviews (23, 51). Here, we shall dissect the system using
the classic paradigm of a reflex loop: 1) the action of
afferent elements, such as fluid shear stress and its putative caveolar
sensor, on caveolae; 2) the ways in which afferent signals
may affect the central element, the activation of the eNOS-nitric oxide
(NO) system; and 3) the several resultant well-established
and novel physiologically important effector mechanisms, i.e.,
vasorelaxation, angiogenesis, endothelial permeability,
deterrance of inflammatory cells, and prevention of platelet
aggregation, to name a few (Fig. 1).
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FUNCTIONAL MORPHOLOGY AND SUBCELLULAR LOCALIZATION OF ENOS |
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Although lipid-rich domains, present on the exoplasmic leaflet of the plasma membrane, are highly dynamic structures undergoing constant entropy-driven dispersal, they are nonetheless constrained and marginalized, in part, by the cortical actin cytoskeleton (48). Although caveolin-1 oligomeric lattices tend to stabilize caveolae, stabilization of the rafts is believed to be achieved through the annexin-dependent formation of membrane-cytoskeleton complexes (4). It is not known whether eNOS is sequestered in both of these lipid-rich domains or in caveolae only. Most recently, direct evidence for eNOS localization to rafts has been presented in a series of studies in cells lacking caveolin-1 or caveolae (87). Therefore, in the following discussion, although eNOS-caveolar relationships are described, it is quite possible that a broader sense is applicable, inclusive of eNOS-lipid-rich domains. A recent demonstration of an interchange between caveolae and rafts lends additional support to this proviso: experiments showed that by abolishing glycosylphosphatidylinositol-anchored proteins, a constituent of rafts, the number of rafts does not change, whereas the number of caveolae increases (1). The situation has become even more complicated since a recent description of a caveolin-1-enriched, noncaveolar lipid-rich domain, novel type of raft (93). In addition to caveolae, eNOS has been localized to fenestrae: immunoelectron microscopy of liver sinusoidal cells disclosed both eNOS and caveolin-1 colocalized in endothelial fenestrae (95). This finding may indicate that the biogenesis of fenestrae represents a step in the evolution of fused endocytosed caveolae (see CAVEOLAE, NO, AND VASCULAR PERMEABILITY).
The present consensus is that caveolae are dynamic structures constantly recycled between the plasma membrane, endosomes, and the trans-Golgi network. If this is the case, caveolae-harbored receptors, elements of signaling pathways, and eNOS may undergo parallel internalization and recycling, tracking the caveolin-1 pathway. Indeed, eNOS has been previously localized to the cytoplasmic vesicles and trans-Golgi network, suggesting that the above recycling path does exist. Using surrogate cells transfected with eNOS fused to green fluorescent protein (GFP), Sowa et al. (86) demonstrated that ~50% of the total eNOS is localized to the plasma membrane and 35% to the Golgi apparatus. Interestingly, a palmitoylation-deficient eNOS mutant showed no distribution to the plasma membrane and was concentrated in the Golgi apparatus and the cytoplasm. These findings are in concert with a broader view that protein palmitoylation targets it to lipid-rich domains, rafts, and caveolae. In this regard, palmitoyltransferase activity has been found to be highly enriched in low-density membranes. Depletion of cellular cholesterol results in the inhibition of this activity and translocation of palmitoyltransferase to high-density, noncaveolar membranes (21).
Site-directed mutagenesis of the putative caveolin-binding motif of eNOS (from FSAAPFSGW to ASAAPASGA; single-letter amino acid coding) blocked the ability of caveolin-1 to inhibit eNOS activity (35). However, the pharmacological consequences of caveolin-1 scaffolding domain peptides appear controversial. According to two groups, they, as well as caveolin-1 itself, are capable of inhibiting eNOS activity in vitro (37, 52). A similar peptide (residues 82-101) injected systemically into rats appeared to enhance the activity of eNOS (11). Bucci et al. (11) have demonstrated that injection of the scaffolding domain, residues 82-101, results in selective inhibition of acetylcholine-induced vasorelaxation and NO production. It is possible that these disparate effects may be explained on the basis of different activities of neutral sphingomyelinase, an enzyme catalyzing formation of ceramide and activation of eNOS, because it is inhibited by a caveolin scaffolding domain (92). The issue awaits resolution.
The fact that an excess of Ca-calmodulin could override these
inhibitory interactions has established the foundation for a hypothesis
that the caveolin-calmodulin cycle regulates eNOS activity (61), as schematically illustrated in Fig.
2. This hypothesis has been strengthened
most recently with the independent demonstration by two groups that
caveolin-1 knockout mice exhibit enhanced eNOS activity (17,
75).
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MOLECULAR CASCADE RECRUITED IN SIGNAL TRANSDUCTION FROM THE CAVEOLAR SHEAR STRESS SENSOR TO ENOS STIMULATION |
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The constant adjustment of vascular tone to the
changing blood flow and shear stress it exerts on the vascular
endothelium is a requisite of physiological regulation of hemodynamics.
This adaptation is governed by the shear stress-induced stimulation of
eNOS (76). It has been demonstrated that activation of
protein kinase B-Akt serves as an intermediary between a caveolar
sensor and activation of caveolin-anchored eNOS (16, 33).
However, the identity of the sensor remains unknown, as well as the
detailed molecular mechanism activating Akt. Rizzo et al.
(76) proposed that flow-induced mechanical strain on
caveolae causes conformational changes in eNOS. Other potential
coupling mechanisms include eNOS phosphorylation by Akt or allosteric
modulation by calmodulin. It has recently been demonstrated that
mechanosensitive 1-integrins are compartmentalized in
endothelial caveolae. We have confirmed this finding in human umbilical
vein endothelial cells (HUVEC) transfected with GFP-caveolin and
stained with antibodies to
1-integrins. Several potential kinases
may be activated by shear stress and stimulate eNOS; these include
integrin-linked kinase (ILK), which is a known activator of protein
kinase B/Akt, integrin cytoplasmic domain-associated protein-1
(ICAP-1), as well as integrin-linked Ca2+ located in
caveolae. Indeed, a recently described stretch-activated cation channel
present in endothelial cells is activated by fluid shear stress in a
tyrosine kinase- and protein kinase C-dependent manner
(7). A cation channel with similar properties is also activated by sphingosine-1-phosphate in human endothelial cells (66). All of these may serve as plausible
mechanisms interfacing the sensor with eNOS. Several integrins have
been shown to be associated with Ca2+ channels
(81). Both
1- and
3-integrins have been implicated in sensing shear stress
in endothelial cells (50, 65). ILK is a 59-kDa
serine-threonine kinase associated with
1-integrins (44). ICAP-1 is associated with
1-integrins, and their ligation enhances ICAP-1
phosphorylation, whereas removal of the ligand results in its
dephosphorylation (12). Moreover, we would argue that the
previously proposed mediators of caveolar shear stress- and
flow-induced signaling to eNOS could be triggered by the ligation of
integrins (Akt activation, activation of Ca2+ channels, and
calmodulin), thus suggesting the role of these heterodimeric proteins
in sensing shear stress. This possibility is further strengthened by
the fact that Arg-Gly-Asp peptides, ligands for several integrins, have
been found to induce vasorelaxation (63).
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TOPOLOGICAL FEEDBACK REGULATION OF SIGNALING BY NO |
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The idea of the topological proximity of elements of signaling cascades playing an important role in the regulation of eNOS activation-inactivation, as well as in regulating the flow of information along signaling elements, is further supported by our recent finding that NO, produced endogenously or added to cultured endothelial cells, can dissociate oligomeric caveolin-1 (57). Using caveolin-1 fused to a temperature-tolerant GFP mutant, the fluorescence of which is modulated by the distance between adjacent GFP molecules, we demonstrated that NO leads to a reversible dissociation of caveolin-1 platforms, the appearance of caveolin-1 monomers in higher abundance, and the temporary silencing of signal transduction initiated via receptors harbored in caveolae. These data implicate NO generated in the process of endothelial cell activation in the termination of some signaling cascades, perhaps as a result of the distancing of the sequentially coupled elements (Fig. 2). This endothelial paradigm of topological forward and feedback regulation of signaling cascades has its neuronal equivalent in the activation of the N-methyl-D-aspartate (NMDA) receptor, leading to the generation of NO and suppression of the NMDA receptor (53).
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ROLE OF LIPID COMPONENTS OF CAVEOLAE IN ENOS SIGNALING |
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Compartmentalization of eNOS to lipid-rich domains like caveolae
engenders remarkable substrate parsimony and biochemical plasticity.
This is illustrated by the finding that components of these domains,
sphingolipids, participate in the Ca2+-independent
activation of eNOS through the generation of ceramides. Igarashi et al.
(47) have demonstrated that the ceramide analog N-acetylsphingosine increases eNOS activity and NO
production in bovine aortic endothelial cells, the effect of which is
sustainable even in the presence of an intracellular Ca2+
chelator. Furthermore, the authors showed that bradykinin, acting via
its B2 receptor, induces ceramide generation by endothelial cells. These findings establish the participation of a lipid mediator, derived from the topologically proximal lipid-rich membrane, in the
regulation of eNOS. In turn, NO produced may inhibit the rate of
ceramide generation; it has been demonstrated that tumor necrosis factor--induced generation of ceramide in a monocytic cell line is
suppressed by NO, thus preventing cell apoptosis
(15). Another example of a lipid-rich membrane component,
cholesterol, participating in signal transduction has been provided by
Liu et al. (58). By introducing oxidized cholesterol into
caveolae, these investigators were able to disrupt PDGF
receptor-mediated tyrosine kinase phosphorylation of downstream
substrates but not activation of the receptor itself.
In fact, a remarkable cooperativity exists between cholesterol synthesis and expression of caveolin on the one hand and activity of eNOS on the other. Cellular cholesterol homeostasis is dependant on the balance among cholesterol biosynthesis, efflux, and salvage through the low-density lipoprotein receptor pathway (49). Newly formed free cholesterol (FC) is destined mainly to caveolae and, subsequently, to pre-high-density lipoprotein (HDL). It has been demonstrated that caveolin-1 trafficks from the endoplasmic reticulum to caveolae as a cytosolic complex containing chaperone proteins and cholesterol. Thus caveolin-1 effectively delivers newly synthesized cholesterol from endoplasmic reticulum to caveolae, which may also serve as sites of cholesterol efflux (29, 30, 85, 90).
The physiological significance of caveolae in cholesterol homeostasis is further supported by the observation that an HDL receptor, type I, class B scavenger receptor, as well as a multifunctional receptor, CD36 (74), are harbored in caveolae (54). Furthermore, the bidirectional flow of cholesterol between HDL particles and the cell occurs in caveolae (3, 41). The high concentration of cholesterol in caveolae and the tight association of cholesterol with caveolins (67, 88) underscore their mutual coregulation. Cells transfected with caveolin-1 cDNA have increased caveolin mRNA and protein levels, caveolar FC, and FC efflux. Cells transfected with caveolin-1 antisense DNA have 50% of the caveolin levels of control cells, and the FC efflux from these cells is proportionately reduced (28, 96).
On the other hand, caveolae are considered to be sensors of the FC content of the cell (30, 89). Depletion of caveolar cholesterol leads to the downregulation of caveolin-1 at the protein and mRNA levels, resulting in a decreased expression of caveolae on the cell surface (28, 43). Depletion of cellular cholesterol with either nystatin or cholesterol oxidase causes retrieval of caveolin-1 from the plasma membrane lipid-rich domains (14, 84). Restoring cellular cholesterol causes caveolin-1 to return to plasma membrane caveolae.
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NO AND MEMBRANE FLUIDITY |
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It has been established that NO is at least six times more soluble in lipid bilayers than in the aqueous phase (31, 59). This partitioning of NO in lipid-rich biomembranes appears to have regulatory functions. We have recently found that an elevation of ambient NO increases membrane fluidity, consistent with temporal dispersal of lipid microdomains. The high solubility of NO in lipids and proximity of the NO source to lipid-rich domains provide an ideal microenvironment for the observed changes in the biophysical properties of lipid rafts. The implications of this finding may be far-reaching.
Deformability of the plasma membrane of the formed elements and the endothelium has been recognized as a key contributor to blood rheology and microvascular perfusion (6, 19, 82). Fluid shear stress per se has been found to increase membrane fluidity in endothelial cells (42). These data are consistent with the observed NO-induced reversible increase in membrane fluidity of endothelial cells.
Constitutive NO production is an important regulator of vascular tone:
inhibition of eNOS by nitroarginine inhibitors or eNOS gene deletion
invariably results in the development of hypertension (46,
72). This has been attributed to the reduction of the endothelium-derived relaxing factor-induced vasorelaxation. Our recent
observations (Li H and Goligorsky MS, unpublished observations) may
provide a mechanistic explanation for these findings (Fig. 3). States of deficient NO production by
the endothelial cells may result in increased membrane rigidity, thus
leading to deceleration and trapping of formed elements in the
capillary circulation (82), increased peripheral
resistance to blood flow, and the development of hypertension. Hence,
we propose that apart from the well-established NO regulation of
vascular smooth muscle tone at the level of conduit and resistance
vessels, it may exert its effects at the luminal boundary between the
endothelium and circulating erythrocytes at the level of capillaries.
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CAVEOLAE AND LOCOMOTION: A ROLE PLAYED BY NO IN ANGIOGENESIS |
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Growing in vitro and in vivo evidence suggest that functional eNOS in endothelial cells plays a permissive role in the acquisition of migratory phenotype in response to stimuli like vascular endothelial growth factor (VEGF) or endothelin (ET) (69). Studies from our laboratory and by others provided convincing evidence that NO production is a prerequisite for endothelial cell migration, wound healing, and angiogenesis (39, 71). On the basis of these observations, we propose that endothelial cell migration and angiogenesis require simultaneous action of at least two signals, functional eNOS generating NO and guidance cues, e.g., ET-1 or VEGF, to secure the necessary direction of movement.
Studies of the mode(s) of NO action on endothelial cell migration have
revealed that NO stimulates micromotion in cultured endothelial cells,
the process that we termed "podokinesis," indicative of accelerated
turnover of focal adhesions (71). Second, when endothelial
cells were cultured on a flexible silicon rubber substratum and a
wrinkling phenomenon was recorded using time-lapse videomicroscopy, it
was possible to document that addition of NO donors resulted in the
resolution of tractional forces on the substratum whereas NOS
inhibition enhanced them (39). When one considers the fact that both eNOS and 1-integrins are localized to caveolae
in endothelial cells, one can envisage a possible link between caveolae
and eNOS and cell adhesion, locomotion, and angiogenesis. Several lines of evidence provide circumstantial support for this link. First, double-labeling studies of endothelial cells revealed colocalization of
caveolin-1 and
1-integrins (94). Second,
migrating endothelial cells dislocate caveolin-1 and
5
1-integrins to the leading and trailing edges (Li H and Goligorsky M, unpublished
observations). Third, both cholesterol and sphingolipids
directly interact with
5
1-integrins, and
cholesterol depletion renders
V
3
integrins dysfunctional (2, 40).
Hence, in this model, NO production provides the cell with a fork-tuning mechanism to adjust the tightness of cell-matrix adhesions to the physiologically required rate of cell migration. For instance, in the resting state, the endothelial cell phenotype is that of a spread, tightly attached cell that, on activation and NO generation, develops an intermediate strength of adhesion and is prepared for vectorial locomotion. When such a cell is presented with guidance cues (ET or VEGF), their chemical gradient results in a gradient of tyrosine phosphorylation/dephosphorylation of focal adhesion kinase and paxillin, thus determining the leading and trailing edges. Indeed, when cells are migrating toward a VEGF source, application of a tyrosine kinase inhibitor, genistein, significantly inhibits vectorial movement. These data further emphasize the relationship between scalar and vectorial motion in endothelial cells. When the level of NO production becomes supraphysiological, cells tend to detach from the matrix, whereas subphysiological levels of NO generation lead to the excessively tight cell-matrix adhesion; in both instances, endothelial cells are unable to respond appropriately to angiogenic stimuli. In fact, recent findings of defective angiogenesis in eNOS knockout mice are consistent with the above contention (68). It is important to emphasize that the requirement for podokinetic motion should be fulfilled for vectorial cell movement along the gradient of angiogenic substances to occur. This working hypothesis may explain some pathological situations accompanied by the inappropriate generation of NO.
Recently, in parallel with the acceptance of an idea that angiogenesis is an integral function of vascular endothelium, effects of various pharmacological maneuvers on endothelial cell motility have been examined. Along the lines discussed above, hypercholesterolemia has been implicated in the reduced angiogenesis, whereas treatment with statins was found to accelerate it (8). Similarly, constitutively active Akt stimulates angiogenesis, and the opposite effect can be achieved with the dominant-negative form of Akt (55). All of these maneuvers are ultimately mediated via modulation of eNOS activity and NO generation by migrating endothelial cells.
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CAVEOLAE, NO, AND VASCULAR PERMEABILITY |
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The morphological route(s) for increased endothelial permeability has been an issue of lasting debate (22, 24, 77, 78). At least three different mechanisms regulating microvascular permeability have been described. First, nonselective permeability occurs due to gap formation between endothelial cells (5), which may be responsible for the leakage of intravascular macromolecular and cellular components into the interstitium under inflammatory conditions. Second, fenestrae form in endothelial cells subjected to the paracrine effect of elevated local VEGF production (78). This phenomenon may be operative in tumor neovasculature but could occur in other conditions, resulting in the stimulation of neovascularization (therapeutic neovascularization is one of the areas requiring further study). Because of the size of fenestrae, increased permeability of the vasculature to macromolecules ensues. Third, VEGF results in the formation of vesiculovacuolar organelles, which represent invaginated caveolae fused in a vectorial fashion to create transcellular channels (25).
Roberts and Palade (77, 78) consider caveolae as
structures, which are plausibly involved in the increase of endothelial permeability. Indeed, several investigators have demonstrated in fixed
cells that caveolae, if studied by serial sectioning, extend far beyond
the plasmalemmal vesicles to form extensive invaginations. In an
attempt to resolve some of the existing problems in reconstructing the
three-dimensional organization of caveolae, we have generated a
GFP-caveolin-1 vector to enable intravital microscopy of endothelial
cells subjected to VEGF (13). Using the caveolin-1-GFP
vector, we were able to intravitally monitor the dynamics of caveolin
in endothelial cells stimulated with VEGF. Confocal microscopy
disclosed that the probe decorates transcellular channel-like
structures, which become conspicuous after exposure to VEGF. These data
demonstrate in vivo that caveolin is organized into elongated
cell-spanning structures in cells exposed to VEGF. Electron microscopic
studies confirmed and further extended these observations by
demonstrating the enrichment in caveolae, their fission, and their
fusion after an application of VEGF. An alternative route for increased
permeability via fenestrae could not be detected in HUVEC or renal
microvascular endothelial cells at early time points after the
application of VEGF. However, 36 h after the addition of VEGF,
HUVEC and renal microvascular endothelial cells exhibited diaphragmed
fenestrae. Vasile et al. (91) have recently provided
additional evidence of VEGF-induced clustering of caveolae, resulting
in formation of vesiculovacuolar organelles in bovine microvascular
endothelial cells cultured on floating Matrigel-collagen gels. It is
conceivable that VEGF elicits a rapid increase in vascular permeability
via mobilization of caveolae, whereas the long-term effect requires
formation of fenestrae. Recently, eNOS and caveolin have been found in
sinusoidal fenestrae (95), further supporting the
idea that fusion of caveolae eventually leads to the biogenesis of
fenestrae (Fig. 4).
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NO appears to regulate these processes. In vivo, NG-nitro-L-arginine methyl ester application resulted in a rapid increase in albumin extravasation, adherence and immigration of leukocytes, and increased generation of reduced oxygen intermediates in postcapillary venules (56). In addition, NG-nitro-L-arginine methyl ester potentiated a thrombin-induced increase in macromolecular permeability of endothelial cell monolayers, an effect that was counteracted by exogenous 8-bromo-cGMP or stimulation of endogenous cGMP production (sodium nitroprusside or atrial natriuretic peptide), further suggesting that activation of eNOS and generation of NO may reduce endothelial permeability stimulated by agents like thrombin (18). However, it is important to emphasize that the concurrent increase in the production of reduced oxygen intermediates in proinflammatory states, for instance, could reverse the above effect of NO, resulting in peroxynitrite-induced elevation of endothelial permeability. Our scanning electron microscopic data on the integrity of endothelial monolayers subjected to sodium nitroprusside or peroxynitrite demonstrate a remarkable effect of the latter on gap formation (38). In conclusion, basal NO generation by endothelial cells is necessary for the maintenance of the barrier functions of these cells. Inhibition of eNOS results in increased vascular permeability. Overproduction of NO, especially when inducible NO synthase (iNOS) is expressed, similarly leads to increased vascular permeability. It is not known, however, whether the cellular routes for the increase in endothelial permeability to macromolecules under conditions of deficient or excessive NO generation are uniform or dissimilar. Recent studies of vascular permeability in eNOS- and iNOS-deficient mice provide some insight into this question. Fukumura et al. (32) have demonstrated that the VEGF-induced increase in vascular permeability was blunted in eNOS-deficient mice but not in iNOS knockout mice. These mice, together with caveolin knockout animals, should provide the field of vascular permeability with invaluable models.
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CONCLUDING REMARKS |
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This brief overview of eNOS interactions with lipid-rich domains, including caveolae, highlights the plethora of functional implications. Incoming signals, signals emanating from these organelles, as well as their modulation and termination, utilize these platforms for integrating information and sorting the elements of signaling cascades. The richness of such interactions is underscored by the versatility of functional outputs: from the regulation of NO synthesis to the modulation of cell adhesion, migration, and permeability. Among the unresolved questions are problems related to the possible alternative sorting of eNOS to caveolae or rafts and the functional competence of eNOS in the Golgi apparatus, in caveolae that underwent fission and fusion, in fenestrae, and in mitochondria. When one takes into consideration the possibility that at each of these sites eNOS can function as a coupled or an uncoupled enzyme, thus resulting in the generation of NO or superoxide, respectively, the number of such questions doubles. From the therapeutic standpoint, it remains to be established whether different peptides or peptidomimetics, i.e., peptides derived from the caveolin-1 scaffolding domain, have beneficial effect(s) on hemodynamics. Thus again a protean molecule, NO, and the enzyme producing it are occupying the center stage of endothelial cell biology and pose challenges.
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ACKNOWLEDGEMENTS |
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The authors realize that many important contributions have been left unreferenced and sincerely apologize for these omissions. They are not due to neglect, but rather to space limitations.
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FOOTNOTES |
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These studies were supported in part by National Institute of Diabetes and Digestive and Kidney Diseases Grants DK-45462 and DK-52783 (M. S. Goligorsky) and postdoctoral Fellowship awards from the National Kidney Foundation of New York/New Jersey (H. Li) and the American Heart Association (S. Brodsky).
Address for reprint requests and other correspondence: M. S. Goligorsky, Dept. of Medicine, New York Medical College, Valhalla, NY 10595 (E-mail: Michael_Goligorsky{at}nymc.edu).
10.1152/ajprenal.00377.2001
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REFERENCES |
---|
1.
Abrami, L,
Fivaz M,
Kobayashi T,
Kinoshita T,
and
Parton RG.
Cross-talk between caveolae and glycosylphosphatidylinositol-rich domains.
J Biol Chem
276:
30729-30736,
2001
2.
Anilkumar, N,
Bhattacharya AK,
Manogaran PS,
and
Pande G.
Modulation of alpha 5 beta 1 and alpha V beta 3 integrins on the cell surface during mitosis.
J Cell Biochem
61:
338-349,
1996[ISI][Medline].
3.
Babitt, J,
Trigatti B,
Rigotti A,
Smart EJ,
Anderson RG,
Su S,
and
Krieger M.
Murine SR-BI, a high density lipoprotein receptor that mediates selective lipid uptake, is N-glycosylated and fatty acylated and colocalizes with plasma membrane caveolae.
J Biol Chem
272:
13242-13249,
1997
4.
Babyichuk, E,
and
Draeger A.
Annexins in cell membrane dynamics. Ca-regulated association of lipid microdomains.
J Cell Biol
150:
1113-1123,
2000
5.
Baluk, P,
Hirata A,
Thurston G,
Fujiwara T,
Neal C,
Michel C,
and
McDonald DM.
Endothelial gaps: time course of formation and closure in inflamed venules of rats.
Am J Physiol Lung Cell Mol Physiol
272:
L155-L170,
1997
6.
Bateman, R,
Jagger J,
Sharpe M,
Ellsworth M,
Mehta S,
and
Ellis CG.
Erythrocyte deformability is a nitric oxide-mediated factor in decreased capillary density during sepsis.
Am J Physiol Heart Circ Physiol
280:
H2848-H2856,
2001
7.
Brakemeier, S,
Eichler I,
Hopp H,
Kohler R,
and
Hoyer J.
Up-regulation of endothelial stretch-activated cation channels by fluid shear stress.
Circ Res
53:
209-218,
2002.
8.
Brouet, A,
Sonveaux P,
Dessy C,
Moniotte S,
Balligand JL,
and
Feron O.
Hsp90 and caveolin are key targets for the proangiogenic nitric oxide-mediated effects of statins.
Circ Res
89:
866-873,
2001
9.
Brown, D,
and
Rose J.
Sorting of GPI-anchored proteins to glycolipid-enriched membrane subdomains during transport to the apical cell surface.
Cell
68:
533-544,
1992[ISI][Medline].
10.
Brown, D,
and
London E.
Structure of detergent-resistant membrane domains: does phase separation occur in biological membranes?
Biochem Biophys Res Commun
240:
1-7,
1997[ISI][Medline].
11.
Bucci, M,
Gratton JP,
Rudic RD,
Acevedo L,
Roviezzo F,
Cirino G,
and
Sessa WC.
In vivo delivery of the caveolin-1 scaffolding domain inhibits nitric oxide synthesis and reduces inflammation.
Nat Med
6:
1362-1367,
2000[ISI][Medline].
12.
Chang, DD,
Wong C,
Smith H,
and
Liu J.
ICAP-1, a novel 1 integrin cytoplasmic domain-associated protein, binds to a conserved and functionally important NPXY sequence motif of
1 integrin.
J Cell Biol
138:
1149-1157,
1997
13.
Chen, J,
Braet F,
Brodsky S,
Weinstein T,
Romanov V,
Noiri E,
and
Goligorsky MS.
VEGF-induced mobilization of caveolae and increase in permeability of endothelial cell.
Am J Physiol Cell Physiol
282:
C1053-C1063,
2002
14.
Conrad, PA,
Smart EJ,
Ying YS,
Anderson RG,
and
Bloom GS.
Caveolin cycles between plasma membrane caveolae and the Golgi complex by microtubule-dependent and microtubule-independent steps.
J Cell Biol
131:
1421-1433,
1995[Abstract].
15.
DeNadai, C,
Sestili P,
Cantoni O,
Lievremont JP,
Sciorati C,
Barsacchi R,
Moncada S,
Meldolesi J,
and
Clementi E.
Nitric oxide inhibits tumor necrosis factor--induced apoptosis by reducing the generation of ceramide.
Proc Natl Acad Sci USA
97:
5480-5485,
2000
16.
Dimmeler, S,
Fleming I,
Fisslthaler B,
Hermann C,
Busse R,
and
Zeiher M.
Activation of nitric oxide synthase in endothelial cells by Akt-dependent phosphorylation.
Nature
399:
601-605,
1999[ISI][Medline].
17.
Drab, M,
Verkade P,
Elger M,
Kasper M,
Lohn M,
Lauterbach B,
Lindschau C,
Mende F,
Luft F,
Schedl A,
Haller H,
and
Kurrzalia T.
Loss of caveolae, vascular dysfunction and pulmonary defects in caveolin-1 gene-disrupted mice.
Science
293:
2449-2452,
2001
18.
Draijer, R,
Atsma D,
van der Laarse A,
and
van Hinsbergh V.
CGMP and nitric oxide modulate thrombin-induced endothelial permeability.
Circ Res
76:
199-208,
1995
19.
Driessen, G,
Scheidt-Bleichert H,
Sobota A,
Inhoffen W,
Heidtmann H,
Haest C,
Kamp D,
and
Schmid-Schonbein H.
Capillary resistance to flow of hardened (diamide-treated) red blood cells.
Pflügers Arch
392:
261-267,
1982[ISI][Medline].
21.
Dunphy, JT,
Greentree W,
and
Linder ME.
Enrichment of G-protein palmitoyltransferase activity in low-density membranes.
J Biol Chem
276:
43300-43304,
2001
22.
Dvorak, H,
Brown L,
Detmar M,
and
Dvorak A.
Vascular permeability factor/vascular endothelial growth factor, microvascular hyperpermeability, and angiogenesis.
Am J Pathol
146:
1029-1039,
1995[Abstract].
23.
Everson, WV,
and
Smart EJ.
Influence of caveolin, cholesterol, and lipoproteins on nitric oxide synthase. Implications for vascular disease.
Trends Cardiovasc Med
11:
246-250,
2001[ISI][Medline].
24.
Feng, D,
Nagy J,
Hipp J,
Dvorak H,
and
Dvorak A.
Vesiculo-vacuolar organelles and the regulation of venule permeability to macromolecules by vascular permeability factor, histamine, and serotonin.
J Exp Med
183:
1981-1986,
1996[Abstract].
25.
Feng, D,
Nagy J,
Hipp J,
Pyne K,
Dvorak HF,
and
Dvorak AM.
Reinterpretation of endothelial cell gaps induced by vasoactive mediators in guinea-pig, mouse and rat: many are transcellular pores.
J Physiol
504:
747-761,
1997[Abstract].
26.
Feron, O,
Michel JB,
Sase K,
and
Michel T.
Dynamic regulation of endothelial nitric oxide synthase: complementary roles of dual acylation and caveolin interactions.
Biochemistry
37:
193-200,
1998[ISI][Medline].
27.
Feron, O,
Saldana F,
Michel J,
and
Michel T.
The endothelial nitric-oxide synthase-caveolin regulatory cycle.
J Biol Chem
273:
3125-3128,
1998
28.
Fielding, CJ,
Bist A,
and
Fielding PE.
Caveolin mRNA levels are upregulated by free cholesterol and downregulated by oxysterols in fibroblast monolayers.
Proc Natl Acad Sci USA
94:
3753-3758,
1997
29.
Fielding, PE,
and
Fielding CJ.
Plasma membrane caveolae mediate the efflux of cellular free cholesterol.
Biochemistry
34:
14288-14292,
1995[ISI][Medline].
30.
Fielding, PE,
and
Fielding CJ.
Intracellular transport of low density lipoprotein derived free cholesterol begins at clathrin-coated pits and terminates at cell surface caveolae.
Biochemistry
35:
14932-14938,
1996[ISI][Medline].
31.
Ford, PC,
Wink DA,
and
Stanbury DM.
Autoxidation kinetics of aquous nitric oxide.
FEBS Lett
326:
1-3,
1993[ISI][Medline].
32.
Fukumura, D,
Gohongi T,
Kadambi A,
Izumi Y,
Ang J,
Yun CO,
Buerk DG,
Huang PL,
and
Jain PK.
Predominant role of endothelial nitric oxide synthase in vascular endothelial growth factor-induced angiogenesis and vascular permeability.
Proc Natl Acad Sci USA
98:
2604-2609,
2001
33.
Fulton, D,
Gratton J,
McCabe T,
Fontana J,
Fujio Y,
Walsh K,
Franke T,
Papapetropoulos A,
and
Sessa WC.
Regulation of endothelium-derived nitric oxide production by the protein kinase Akt.
Nature
399:
597-601,
1999[ISI][Medline].
34.
Garcia-Cardena, G,
Fan R,
Stern DF,
Liu J,
and
Sessa WC.
Endothelial nitric oxide synthase is regulated by tyrosine phosphorylation and interacts with caveolin-1.
J Biol Chem
271:
27237-27240,
1996
35.
Garcia-Cardena, G,
Martasek P,
Masters BS,
Skidd P,
Couet J,
Li S,
Lisanti MP,
and
Sessa WC.
Dissecting the interaction between nitric oxide synthase and caveolin: functional significance of the NOS caveolin binding domain in vivo.
J Biol Chem
272:
25437-25440,
1997
36.
Garcia-Cardena, G,
Oh P,
Liu J,
Schnitzer JE,
and
Sessa W.
Targeting of nitric oxide synthase to endothelial cell caveolae via palmitoylation: implications for nitric oxide signaling.
Proc Natl Acad Sci USA
93:
6448-6453,
1996
37.
Ghosh, S,
Gachhui R,
Crooks C,
Wu C,
Lisanti MP,
and
Stuehr DJ.
Interaction between caveolin-1 and the reductase domain of eNOS. Consequences for catalysis.
J Biol Chem
273:
22267-22271,
1998
38.
Goligorsky, MS.
Endothelial cell dysfunction and nitric oxide synthase.
Kidney Int
58:
1360-1376,
2000[ISI][Medline].
39.
Goligorsky, MS,
Abedi H,
Noiri E,
Tachtajan A,
Lense S,
Romanov VI,
and
Zachary I.
Nitric oxide modulation of focal adhesions in endothelial cells.
Am J Physiol Cell Physiol
276:
C1271-C1281,
1999
40.
Gopalakrishna, P,
Chaubey SK,
Manogaran PS,
and
Pande G.
Modulation of alpha5beta1 integrin functions by the phospholipid and cholesterol contents of cell membranes.
J Cell Biochem
77:
517-528,
2000[ISI][Medline].
41.
Graf, GA,
Connell PM,
van der Westhuyzen DR,
and
Smart EJ.
The class B, type I scavenger receptor promotes the selective uptake of high density lipoprotein cholesterol ethers into caveolae.
J Biol Chem
274:
12043-12048,
1999
42.
Haidekker, M,
L'Heureux N,
and
Frangos JA.
Fluid shear stress increases membrane fluidity in endothelial cells: a study with DCVJ fluorescence.
Am J Physiol Heart Circ Physiol
278:
H1401-H1406,
2000
43.
Hailstones Sleer, LS,
Parton RG,
and
Stanley KK.
Regulation of caveolin and caveolae by cholesterol in MDCK cells.
J Lipid Res
39:
369-379,
1998
44.
Hannigan, GE,
Leung-Hagesteijn C,
Fitz-Gibbon L,
and
Coppolino M.
Regulation of cell adhesion and anchorage-dependent growth by a new 1 integrin-linked protein kinase.
Nature
379:
91-96,
1996[ISI][Medline].
45.
Hooper, NM.
Detergent-insoluble glycoshingolipid/cholesterol-rich membrane domains, lipid rafts and caveolae.
Mol Membr Biol
16:
145-156,
1999[ISI][Medline].
46.
Huang PL, Huang Z, Mashimo H, Bloch KD, Moskowitz MA, Bevan JA, and
Fishman MC. Hypertension in mice lacking the gene for endothelial
nitric oxide synthase. Nature 377: 239-242.
47.
Igarashi, J,
Thatte H,
Prabhakar P,
Golan D,
and
Michel T.
Calcium-independent activation of endothelial nitric oxide synthase by ceramide.
Proc Natl Acad Sci USA
96:
12583-12588,
1999
48.
Ikonen, E.
Roles of lipid rafts in membrane transport.
Curr Opin Cell Biol
13:
470-477,
2001[ISI][Medline].
49.
Ioannou, YA.
Multidrug permeases and subcellular cholesterol transport.
Nat Rev Mol Cell Biol
2:
657-668,
2001[ISI][Medline].
50.
Ishida, T,
Peterson T,
Kovach N,
and
Berk BC.
MAP kinase activation by flow in endothelial cells. Role of 1 integrins and tyrosine kinases.
Circ Res
79:
310-316,
1996
51.
Joles, JA,
Stroes ES,
and
Rabelink TJ.
Endothelial function in proteinuric renal disease.
Kidney Int Suppl
71:
S57-S61,
1999[Medline].
52.
Ju, H,
Zou R,
Venema VJ,
and
Venema RC.
Direct interaction of endothelial nitric oxide synthase and caveolin-1 inhibits synthase activity.
J Biol Chem
272:
18522-18525,
1997
53.
Kim, WK,
Choi YB,
Rayudu PV,
Das P,
Asaad W,
Arnelle DR,
Stamler JS,
and
Lipton SA.
Attenuation of NMDA receptor activity and neurotoxicity by nitroxyl anion, NO.
Neuron
24:
461-469,
1999[ISI][Medline].
54.
Krieger, M,
and
Kozarsky K.
Influence of the HDL receptor SR-BI on atherosclerosis.
Curr Opin Lipidol
10:
491-497,
1999[ISI][Medline].
55.
Kureishi, Y,
Luo Z,
Shiojima I,
Bialik A,
Fulton D,
Lefer DJ,
Sessa WC,
and
Walsh K.
The HMG-CoA reductase inhibitor simvastatin activates the protein kinase Akt and promotes angiogenesis in normocholesterolemic animals.
Nat Med
6:
1004-1010,
2000[ISI][Medline].
56.
Kurose, I,
Wolf R,
Grisham M,
Aw T,
Specian R,
and
Granger DN.
Microvascular response to inhibition of nitric oxide production.
Circ Res
76:
30-39,
1995
57.
Li, H,
Brodsky S,
Basco M,
Romanov V,
De Angelis DA,
and
Goligorsky MS.
Nitric oxide attenuates signal transduction: possible role in dissociating caveolin-1 scaffold.
Circ Res
88:
229-236,
2001
58.
Liu, P,
Wang P,
Michaely P,
Zhu M,
and
Anderson RGW
Presence of oxidized cholesterol in caveolae uncouples active platelet-derived growth factor receptors from tyrosine kinase substrates.
J Biol Chem
275:
31648-31654,
2000
59.
Liu, X,
Miller M,
Joshi M,
Thomas D,
and
Lancaster JR.
Accelerated reaction of nitric oxide with O2 within the hydrophobic interior of biological membranes.
Proc Natl Acad Sci USA
95:
2175-2179,
1998
60.
McDonald, KK,
Zharikov S,
Block ER,
and
Kilberg MS.
A caveolar complex between the cationic amino acid transporter 1 and endothelial nitric oxide synthase may explain the "arginine paradox."
J Biol Chem
272:
31213-31216,
1997
61.
Michel, JB,
Feron O,
Sase K,
Prabhakar P,
and
Michel T.
Caveolin versus calmodulin. Counterbalancing allosteric modulators of endothelial nitric oxide synthase.
J Biol Chem
272:
25907-25912,
1997
62.
Michel, T,
and
Feron O.
Nitric oxide synthases: which, where, how and why.
J Clin Invest
100:
2146-2152,
1997
63.
Mogford, J,
Davis G,
Platts S,
and
Meininger G.
Vascular smooth muscle alphaVbeta3 integrin mediates arteriolar vasodilation in response to RGD peptides.
Circ Res
79:
821-826,
1996
64.
Monier, S,
Parton RG,
Vogel F,
Behlke J,
Henske A,
and
Kurzchalia TV.
VIP 21-caveolin, a membrane protein constituent of the caveolar coat oligomerizes in vivo and in vitro.
Mol Biol Cell
6:
911-927,
1995[Abstract].
65.
Muller, J,
Chilian W,
and
Davis MJ.
Integrin signaling transduces shear stress-dependent vasodilation of coronary arterioles.
Circ Res
80:
320-326,
1997
66.
Muraki, K,
and
Imaizumi Y.
A novel function of sphingosine-1-phosphate to activate a non-selective cation channel in human endothelial cells.
J Physiol
537:
431-441,
2001
67.
Murata, M,
Peranen J,
Schreiner R,
Wieland F,
Kurzchalia TV,
and
Simons K.
VIP21/caveolin is a cholesterol-binding protein.
Proc Natl Acad Sci USA
92:
10339-10343,
1995[Abstract].
68.
Murohara, T,
Asahara T,
Silver M,
Bauters C,
Masuda H,
Kalka C,
Kearney M,
Chen D,
Chen D,
Symes JF,
Fishman MC,
Huang PL,
and
Isner JM.
Nitric oxide synthase modulates angiogenesis in response to tissue ischemia.
J Clin Invest
101:
2567-2578,
1998
69.
Noiri, E,
Hu Y,
Bahou WF,
Keese C,
Giaever I,
and
Goligorsky MS.
Permissive role of nitric oxide in endothelin-induced migration of endothelial cells.
J Biol Chem,
272:
1747-1752,
1997
70.
Noiri, E,
Lee E,
Testa J,
Quigley J,
Colflesh D,
Keese C,
Giaever I,
and
Goligorsky MS.
Podokinesis in endothelial cell migration: role of NO.
Am J Physiol Cell Physiol
274:
C236-C244,
1998
71.
O'Brien, AJ,
Young H,
Povey J,
and
Furness J.
Nitric oxide synthase is localized predominantly in the Golgi apparatus and cytoplasmic vesicles of vascular endothelial cells.
Histochemistry
103:
221-225,
1995[ISI][Medline].
72.
Palmer, RM,
Ashton DS,
and
Moncada S.
Vascular endothelial cells synthesize nitric oxide from L-arginine.
Nature
333:
664-666,
1988[ISI][Medline].
73.
Parton, RG.
Caveolae and caveolins.
Curr Opin Cell Biol
8:
542-548,
1996[ISI][Medline].
74.
Pussinen, PJ,
Karten B,
Wintersperger A,
Reicher H,
McLean M,
Malle E,
and
Sattler W.
The human breast carcinoma cell line HBL-100 acquires exogenous cholesterol from high-density lipoprotein via CLA-1 (CD-36 and LIMPII analogous 1)-mediated selective cholesteryl ester uptake.
Biochem J
349:
559-566,
2000[ISI][Medline].
75.
Razani, B,
Engelman J,
Wang X,
Schubert W,
Zhang X,
Macaluso M,
Russell R,
Li M,
Pestell R,
DiVisio D,
Hou H,
Knietz B,
Lagaud G,
Christ G,
Edelman W,
and
Lisanti MP.
Caveolin-1 null mice are viable, but show evidence of proliferative and vascular abnormalities.
J Biol Chem
276:
38121-38138,
2001
76.
Rizzo, V,
McIntosh D,
Oh P,
and
Schnitzer J.
In situ flow activates eNOS in luminal caveolae of endothelium with rapid caveolin dissociation and calmodulin association.
J Biol Chem
273:
34724-34729,
1998
77.
Roberts, WG,
and
Palade GE.
Neovasculature induced by vascular endothelial growth factor is fenestrated.
Cancer Res
57:
765-772,
1997[Abstract].
78.
Roberts, WG,
and
Palade GE.
Increased microvascular permeability and endothelial fenestration induced by vascular endothelial growth factor.
J Cell Sci
108:
2369-2379,
1995
79.
Rothberg, KG,
Heuser JE,
Donzell WC,
Ying YS,
Glenney JR,
and
Anderson RGW
Caveolin, a protein component of caveolae membrane coats.
Cell
68:
673-682,
1992[ISI][Medline].
80.
Sargiacomo, M,
Scherer PE,
Tang Z,
Kobler E,
Song KS,
Sanders MC,
and
Lisanti MP.
Oligomeric structure of caveolin: implications for caveolae membrane organization.
Proc Natl Acad Sci USA
92:
9407-9411,
1995[Abstract].
81.
Schwartz, MA.
Integrins as signal transducing receptors.
In: Integrins: Molecular and Biological Responses to the Extracellular Matrix, edited by Cheresh DA,
and Mecham RP.. San Diego, CA: Academic, 1994, p. 33-48.
82.
Simchon, S,
Jan K,
and
Chien S.
Influence of reduced red cell deformability on regional blood flow.
Am J Physiol Heart Circ Physiol
253:
H898-H903,
1987
83.
Simons, K,
and
Ikonen E.
Functional rafts in cell membranes.
Nature
387:
569-572,
1997[ISI][Medline].
84.
Smart, EJ,
Ying YS,
Conrad PA,
and
Anderson RG.
Caveolin moves from caveolae to the Golgi apparatus in response to cholesterol oxidation.
J Cell Biol
127:
1185-1197,
1994[Abstract].
85.
Smart, EJ,
Ying YS,
Donzell WC,
and
Anderson RGW
A role for caveolin in the transport of cholesterol from endoplasmic reticulum to plasma membrane.
J Biol Chem
271:
29427-29435,
1996
86.
Sowa, G,
Liu J,
Papapetropoulos A,
Rex-Haffner M,
Hughes T,
and
Sessa WC.
Trafficking of endothelial nitric-oxide synthase in living cells.
J Biol Chem
274:
22524-22531,
1999
87.
Sowa, G,
Pypaert M,
and
Sessa WC.
Distinction between signaling mechanisms in lipid rafts vs caveolae.
Proc Natl Acad Sci USA
98:
14072-14077,
2001
88.
Thiele, C,
Hannah MJ,
Fahrenholz F,
and
Huttner WB.
Cholesterol binds to synaptophysin and is required for biogenesis of synaptic vesicles.
Nat Cell Biol
2:
42-49,
2000[ISI][Medline].
89.
Thyberg Calara, F,
Dimayuga P,
Nilsson J,
and
Regnstrom J.
Role of caveolae in cholesterol transport in arterial smooth muscle cells exposed to lipoproteins in vivo and in vitro.
Lab Invest
78:
825-837,
1998[ISI][Medline].
90.
Uittenbogaard, A,
and
Smart EJ.
Palmitoylation of caveolin-1 is required for cholesterol binding, chaperone complex formation, and rapid transport of cholesterol to caveolae.
J Biol Chem
275:
25595-25599,
2000
91.
Vasile, E,
Dvorak HF,
and
Dvorak AM.
Caveolae and vesiculo-vacuolar organelles in bovine capillary endothelial cells cultured with VPF/VEGF on floating matrigel-collagen gels.
J Histochem Cytochem
47:
159-167,
1999
92.
Veldman, R,
Maestre N,
Aduib O,
Medin J,
and
Salvayre R.
A neutral sphingomyelinase resides in sphingolipid-enriched microdomains and is inhibited by the caveolin-scaffolding domain: potential implications in tumor necrosis factor signaling.
Biochem J
355:
859-868,
2001[ISI][Medline].
93.
Waugh, MG,
Minogue S,
Anderson J,
Santos MD,
and
Hsuan J.
Signalling and non-caveolar rafts.
Biochem Soc Trans
29:
509-511,
2001[ISI][Medline].
94.
Wei, Y,
Yang X,
Liu Q,
Wilkins JA,
and
Chapman HA.
A role for caveolin and the urokinase receptor in integrin-mediated adhesion and signaling.
J Cell Biol
144:
1285-1295,
1999
95.
Yokomori, H,
Oda M,
Ogi M,
Kamegaya Y,
Tsukada N,
and
Ishii H.
Endothelial nitric oxide synthase and caveolin-1 co-localized in sinusoidal endothelial cells.
Liver
21:
198-206,
2001[ISI][Medline].
96.
Zha, XH,
Links P,
and
Marcel Y.
Caveolin-1 expression and its role in cholesterol efflux in rat hepatoma cells (Abstract).
Mol Cell Biol
9:
562S,
1998.