Department of Internal Medicine, Division of Gastroenterology, University of Arkansas for Medical Sciences and Central Arkansas Veterans Healthcare System, Little Rock, Arkansas 72205
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ABSTRACT |
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Cross talk between signal transduction pathways augments pepsinogen secretion from gastric chief cells. A-kinase anchoring proteins (AKAPs) associate with regulatory subunits of protein kinase A (PKA), protein kinase C (PKC), and protein phosphatase 2B (PP2B) and localize this protein complex to specific cell compartments. We determined whether an AKAP-signaling protein complex exists in chief cells and whether this modulates secretion. In Western blots, we identified AKAP150, a rodent homologue of human AKAP79 that coimmunoprecipitates with PKA, PKC, and actin. The association of PKA and PP2B was demonstrated by affinity chromatography. Confocal microscopy revealed colocalized staining at the cell periphery for AKAP150 and PKC. Ht31, a peptide that competitively displaces PKA from the AKAP complex, but not Ht31P, a control peptide, inhibited 8-Br-cAMP-induced pepsinogen secretion. Ht31 did not inhibit secretion that was stimulated by agents whose actions are mediated by PKC and/or calcium. However, Ht31, but not Ht31P, inhibited carbachol- and A23187-stimulated augmentation of secretion from cells preincubated with cholera toxin. These data suggest the existence in chief cells of a protein complex that includes AKAP150, PKA, PKC, and PP2B. Disruption of the AKAP-PKA linkage impairs cAMP-mediated pepsinogen secretion and cross talk between signaling pathways.
signal transduction; cAMP; A-kinase anchorin protein 150
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INTRODUCTION |
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PEPSINOGEN SECRETION from gastric chief cells is mediated by at least two major signal transduction pathways (20). In one pathway, secretagogues like secretin, vasoactive intestinal peptide, prostaglandins, and cholera toxin activate adenylyl cyclase, thereby causing an increase in cellular cAMP and activation of cAMP-dependent protein kinase (PKA). In the other pathway, secretagogues like carbamylcholine (carbachol) and cholecystokinin cause activation of phospholipase C and subsequent increases in cellular levels of diacylglycerol (DAG) and calcium. These second messengers activate protein kinase C (PKC) and protein phosphatase 2B (PP2B), also referred to as calcineurin (17, 25, 31). Moreover, secretagogues whose actions are mediated by one mechanism potentiate the actions of secretagogues whose actions are mediated by the other (20, 23). For example, in chief cells preincubated with cholera toxin, but not in control cells, carbachol and the divalent cation ionophore A23187 increase cellular levels of cAMP and cause potentiation of pepsinogen secretion (22). This augmented response is mediated by PP2B (23). Nonetheless, the cellular mechanisms underlying so-called cross talk between secretagogues remain to be fully elucidated.
Over the past few years, it was shown that type II regulatory (RII) subunits of different PKA isoforms are physically associated with members of a family of more than 30 proteins designated A-kinase anchoring proteins (AKAPs) (4, 5). AKAPs sequester the PKA holoenzyme to particular cellular compartments in proximity to their substrates. This compartmentalization of PKA by AKAPs allows close interaction of PKA with cytoskeletal or membrane structures and confers added enzyme specificity on PKA-substrate interactions. In addition to association with PKA, AKAPs also bind other signaling molecules such as PKC and PP2B (3, 13). These AKAP-based protein complexes are thought to play a role in integrating different signaling processes, although the exact mechanisms are unknown.
The aim of the experiments reported here was to determine whether, in
dispersed chief cells from guinea pig stomach, AKAP-involved compartmentalization of PKA plays a role in mediating cAMP-stimulated pepsinogen secretion and the cross talk described above. Our findings support the existence in chief cells of an AKAP-anchored protein complex that includes AKAP150, PKA, PKC, and PP2B and is associated with actin. Moreover, addition of a peptide that competitively displaces PKA from the AKAP complex decreases cAMP-stimulated pepsinogen secretion and potentiated responses in cholera toxin-treated chief cells that result from cross talk between signaling pathways.
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MATERIALS AND METHODS |
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Materials.
Male guinea pigs (150-175 g) were obtained from Harlan Sprague
Dawley (Indianapolis, IN); collagenase (type I), BSA (fraction V),
carbachol, (octylphenoxy)polyethoxyethanol (IGEPAL CA-630), 8-bromo-cAMP, cAMP-agarose beads, Ht31 and Ht31P peptides from Sigma
and Promega; PKA RII subunit from Promega; cholera toxin, A23187, and
PKA catalytic subunit from Calbiochem; MEM amino acids (50-times
concentrated), and essential vitamin solution (100-times concentrated)
from Mediatech (Herndon, VA); Percoll from Pharmacia;
125I-albumin from ICN; 125I-cAMP and
-32P ATP from NEN; ProLong antifade kit, Alexa Fluor 488 donkey anti-goat IgG, Alexa Fluor 488 goat anti-rabbit IgG, and Alexa
Fluor 594 goat anti-mouse IgG from Molecular Probes (Eugene, OR).
Antibodies used include cAMP from Calbiochem; AKAP150, PKA
cat, PKA
II
, PKC
1, PKC
2, PKC
, and actin from Santa Cruz Biotech; PKA
II
from Transduction Laboratories; PKC
,
,
from Upstate
Biotech; PP2B from Chemicon International; and an AKAP150 antibody
kindly provided by Dr. John D. Scott (Vollum Institute, Oregon Health Sciences University).
Chief cell preparation. Dispersed chief cells from guinea pig stomach were prepared by mucosal digestion with collagenase and cell fractionation on a Percoll density gradient as described previously (24) and suspended in standard incubation solution. In this preparation, chief cells constitute more than 95% of the total cell population and trypan blue exclusion is >95% (24). Standard incubation solution contained 24.5 mM HEPES (adjusted to pH 7.4), 98 mM NaCl, 6 mM KCl, 2.5 mM KH2PO4, 1 mM MgCl2, 11.5 mM glucose, 5 mM Na pyruvate, 5 mM Na fumarate, 5 mM Na glutamate, 1.5 mM CaCl2, 2 mM glutamine, 0.1% (wt/vol) BSA, 1% (wt/vol) amino acid mixture, and 1% (wt/vol) essential vitamin mixture. The standard incubation solution was equilibrated with 100% O2, and all incubations were performed with 100% O2 as the gas phase.
Pepsinogen secretion. Pepsinogen secretion was determined as described previously (21) using 125I-albumin as substrate and expressed as the percentage of total cellular pepsinogen that was released into the medium during the incubation.
Preparation of cell lysates, immunoprecipitation, and Western analysis. SDS-soluble or IGEPAL-soluble chief cell lysates were prepared as previously described (32). Immunoprecipitation and Western blotting were performed as described in Research Applications by Santa Cruz Biotech. Briefly, for immunoprecipitations, dispersed chief cells (5 × 106 cells/ml) were lysed in lysing buffer that contained 1 × PBS, 1% IGEPAL CA-630, 0.1% SDS, 0.5% sodium deoxycholate, 100 µg/ml phenylmethylsulfonyl fluoride, 30 µl/ml aprotinin (Sigma), and 1 mM sodium orthovanadate. The lysates were precleared with protein A/G-agarose before incubation with specific antibodies. For SDS lysates, we used 50 µg protein. For immunoprecipitations, we used 150 µg protein to compensate for the loss occurred during the procedure.
RII overlay assay. The presence of AKAPs in chief cells was detected by a solid phase RII overlay assay as previously described (1).
Copurification of PKA and PP2B. cAMP-agarose chromatography was performed as described previously (2). Briefly, chief cell lysates were incubated overnight at 4°C with cAMP-agarose (6% beads). After extensive washing with hypotonic buffer, proteins bound to cAMP were eluted at room temperature over 2 h with 100 mM cAMP.
Immunofluorescence microscopy. Immunofluorescent staining was performed by using the protocol provided by Santa Cruz Biotech. Briefly, newly isolated chief cells were allowed to attach to chamber slides coated with type I collagen (Becton Dickinson) for 2 h in a 37°C incubator. Attached cells were stained with primary antibodies and subsequently with secondary antibodies conjugated to Alexa Fluor 488 or Alexa Fluor 594 (Molecular Probes). Stained cells were mounted with ProLong antifade (Molecular Probes) and viewed under a Zeiss laser scanning confocal microscope. Chief cells comprise >95% of the attached cell population and can be distinguished easily from other gastric mucosal cells by virtue of their smaller size, polarized location of their nuclei observed by staining with 4,6-diamidino-2-phenylindole, and immunofluorescent staining with antibodies against pepsinogen (24).
Peptide delivery. Ht31 and Ht31P peptides were introduced into dispersed chief cells by use of lipofectamine. Freshly isolated chief cells were incubated with 50 µM HT31 or Ht31P peptides in standard incubation solution for 90 min at 37°C with 10 µg lipofectamine (GIBCO BRL) per 105 chief cells. After centrifugation at 800 g for 20 s, cells were resuspended in standard incubation solution, and secretagogues were added for varying times as described for individual experiments.
Measurement of cAMP. Cellular cAMP level was determined by radioimmunoassay as described previously (27). The concentration of chief cells in the incubate was adjusted to maintain cAMP on the linear portion of the standard curve.
Statistical analysis. Significance between two means was determined by Student's t-test; P < 0.05 was considered significant.
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RESULTS |
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Identification of AKAP150 in guinea pig chief cells.
To determine whether AKAPs are present in guinea pig chief cells, we
performed an RII overlay assay (Fig.
1A). We detected one
predominant AKAP of ~150 kDa. To determine whether the 150-kDa protein is AKAP150, we performed immunoprecipitations and/or
Western blots with two anti-AKAP150 antibodies, Ab1 and Ab2, that were raised against different NH2 terminal peptides of mouse
AKAP150. Both antibodies detected a 150-kDa protein from SDS-soluble
chief cell lysates (Fig. 1B). This protein comigrates with
AKAP150 from mouse brain cell lysates and is also present in AKAP150
immunoprecipitates. A third antibody directed at the carboxy terminal
portion of AKAP150 also recognized immunoprecipitated
AKAP150 by Ab1, a polyclonal anti-AKAP150 antibody from Santa
Cruz Biotech (data not shown). Because they were not detected with Ab1,
the two prominent low molecular weight bands seen by Ab2 are probably
nonspecific.
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Chief cell AKAP150 binds PKA II and II
.
To identify the specific RII PKA isoforms that bind AKAP150, we
performed immunoprecipitations with antibodies against PKA II
and
II
from IGEPAL-soluble chief cell extracts. From Western blots, we
determined that AKAP150 was associated with both PKA II
(Fig.
1C) and II
(data not shown).
AKAP150 binds PKC and PP2B.
Human neuronal AKAP79 binds not only PKA, but also PKC and PP2B. Guinea
pig chief cells have been reported to express PKC and -
(19). To determine whether AKAP150 in chief cells is also
associated with PKC and/or PP2B, we performed immunoprecipitation with an anti-AKAP150 antibody (Santa Cruz Biotech) and affinity chromatography with cAMP-agarose. Using a polyclonal antibody that
recognizes the conventional PKC isoforms (
,
,
) (Upstate Biotechnology), we detected PKC in AKAP150 immunoprecipitates (Fig. 2). Because previous experiments
(19) and current data (not shown) indicate that the
isoform is the only conventional PKC isoform expressed in guinea pig
chief cells, the present data indicate that PCK
is associated with
AKAP150.
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Cellular association and colocalization of AKAP150 and PKC.
Subcellular location of AKAP150 and further evidence for the
association of PKC and AKAP150 were provided by
double-immunofluorescence staining of chief cells. In chief cells,
AKAP150 and PKC exhibited a predominantly colocalized staining pattern
at the cell periphery (Fig. 4,
B-D). AKAP150 has no predicted transmembrane
domain, and >80% of AKAP was detected from the IGEPAL-soluble
cytoplasmic fraction compared with that of the cell membrane pellet
(data not shown). This evidence suggests that, like its mammalian
counterpart AKAP75 (16), chief cell AKAP150 is located in
the cytoskeleton near the cytoplasmic surface of the plasma membrane.
Collectively, the immunoprecipitation and immunocytochemistry indicate
that chief cell AKAP150 binds PKC and that this complex occurs in vivo.
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AKAP150 is associated with actin cytoskeleton.
In nonneuronal cells, mammalian AKAP75 accumulates in the
actin-rich, cortical cytoskeleton, in close proximity to the plasma membrane (16). Moreover, in rat pancreatic acinar cells,
it has been reported that the subapical actin cytoskeleton plays a
regulatory role in carbachol-stimulated exocytosis and
membrane retrieval (29). Hence, to determine whether
guinea pig chief cell AKAP150 is associated with actin, we
performed immunoprecipitations and Western blots using Ab1
against AKAP150 and an anti-actin antibody. This experiment
demonstrated coimmunoprecipitation of AKAP150 and actin (Fig.
5). Nevertheless, at present, the
structural basis of this interaction is not clear, nor do we know which
actin isoform is involved.
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The association of PKA and AKAP150 is necessary for maximal
cAMP-induced pepsinogen secretion.
To determine whether the cellular compartmentalization of PKA provided
by AKAP150 anchoring is important in mediating pepsinogen secretion, we
examined the effects of the anchoring inhibitor peptide Ht31 on
secretagogue-induced pepsinogen secretion. Ht31 is a 24-amino acid
peptide containing the minimal region of the PKA RII subunit required
for AKAP binding (1). Ht31 can block the interaction
between AKAPs and RII subunits, thus dissociating PKA from its
anchoring sites and uncoupling cAMP-responsive events (1).
Ht31P is a peptide derived from Ht31 with two prolines replacing
isoleucine residues (1). Because Ht31P is unable to
disrupt the interaction between PKA RII and AKAPs, it was
used as a negative control. Lipofectamine, used as a delivery agent to
introduce Ht31 and Ht31P into dispersed chief cells, did not alter
basal pepsinogen secretion (data not shown). Likewise, the Ht31 and
Ht31P peptides did not alter basal secretion (Fig.
6). However, Ht31 caused a 32% reduction
in 8-Br-cAMP-stimulated pepsinogen secretion (P < 0.01), whereas Ht31P did not alter secretion (Fig. 6). Secretion
stimulated by carbachol and the ionophore A23187, agents whose actions
are not mediated by cAMP, was not altered by addition of either Ht31 or
Ht31P (Fig. 6).
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DISCUSSION |
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Association with anchoring proteins and cellular compartmentalization of protein kinases and phosphatases results in greater efficiency of action (closer proximity of enzyme and substrate) and specificity (decreased potential for interaction with other protein substrates). Subcellular targeting of PKA action by association with AKAPs has emerged as an important mechanism for mediating PKA-dependent signal transduction. Functional studies by Scott and others (6, 10, 11, 14, 15, 30) that examined the consequences of disrupting AKAP-PKA association have proved that anchored PKA is required for maximal expression of various cellular processes including gene transcription, ion-channel regulation, and hormone-mediated insulin secretion. Some AKAPs, like AKAP75/79/150, representing the bovine, human, and rodent AKAP orthologs, respectively, bind PKA and other protein kinases and phosphatases, including PKC and PP2B. Moreover, association of PKC and PP2B with AKAP75/79/150 may inhibit their enzymatic activity, thereby serving an additional regulatory function (8, 9, 12).
As illustrated by the cartoon in Fig. 8,
in chief cells from guinea pig stomach, we propose the existence of an
AKAP150-anchored protein complex that includes AKAP150, PKA, PKC,
and PP2B. We acknowledge the limitation that none of our experiments
proves that these components are associated with AKAP150 concurrently. Nevertheless, the individual experiments support the presence in chief
cells of such an AKAP-anchored complex of signaling molecules. To our
knowledge, the present communication represents the first report of a
functional AKAP complex in a gastrointestinal secretory cell. Although
several novel AKAPs have been detected in gastric parietal cells, these
have not been shown necessary for the acid secretory function of these
cells (7). In chief cells, dissociation of PKA from the
AKAP150-based complex reduces pepsinogen secretion in response to
stimulation by agents whose actions are mediated by cAMP, but not
secretion that is stimulated by agents that increase cellular calcium
concentration or activate PKC. In the cartoon (Fig. 8), the calcium
ionophore A23187 and the muscarinic (M3) receptor are shown as examples
of signaling mechanisms that increase cellular calcium and DAG levels
(17). Both of these mediators are known to activate
conventional forms of PKC (17). Moreover, calcium is an
activator of PP2B (25, 31). The failure of the Ht31
peptide, as well as the Ht31P control peptide, to alter A23187- and
carbachol-stimulated secretion serves as further evidence that the
actions of the peptide are specific to cAMP-mediated events.
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Our experiments show that, in terms of pepsinogen secretion, maximal expression of PKA action requires association with AKAP. Disruption of this association by incubation with the Ht31 peptide reduces cAMP-stimulated pepsinogen secretion by ~30%. Because, in these experiments, we were unable to determine the percentage of PKA dissociated from AKAP150, we do not know whether PKA association with AKAP150 is absolutely necessary for mediation of cAMP-induced secretion. That is, we do not know whether complete dissociation of all molecules of PKA from AKAP150 would completely abolish the ability of increases in cAMP to stimulate pepsinogen secretion.
Previous observations from our laboratory have shown that in guinea pig chief cells potentiating interactions exist between agents that increase cellular cAMP levels and those that increase cellular calcium levels or directly activate PKC (22). Moreover, PP2B activity is required for these potentiating interactions to occur (23). As shown in the cartoon (Fig. 8), the presence of an AKAP150-based complex including PKA, PKC, and PP2B facilitates conceptualization of how these effectors are compartmentalized. Further, it suggests how these kinases and PP2B can interact in sequence to alter the phosphorylation status of substrates that are important for stimulating exocytosis of pepsinogen-containing zymogen granules. When cells were treated with cholera toxin, an activator of adenylyl cyclase, and then with A23187 or carbachol, the addition of the Ht31 peptide reduced potentiation of pepsinogen secretion by ~30%. We measured cAMP levels to confirm that the inhibitory actions of the Ht31 peptide are mediated by disruption of the PKA-AKAP150 association, not by inhibitory effects on the levels of cAMP produced by activation of adenylyl cyclase. These observations confirm that the AKAP150 complex plays an important role in facilitating potentiating interactions between PKA, PKC, and PP2B.
It is of interest to compare our findings to those observed in RINm5F insulin-secreting cells (15). In RINm5F cells, addition of the Ht31 peptide reduced hormone- and cAMP-stimulated insulin secretion. Moreover, in RINm5F cells transfected with plasmids encoding a soluble Ht31 fragment, there is an inverse relationship between the amount of peptide expressed and cAMP-stimulated insulin secretion (15). Hence, as in the above discussion of the reduction in pepsinogen secretion observed with addition of Ht31 to chief cells, without measuring intracellular levels of Ht31 or the degree of PKA-AKAP dissociation, it is not possible to determine more than a limited quantitative relation between dissociation of the PKA-AKAP complex and reduced secretion. Nevertheless, in both chief and RINm5F cells, addition of Ht31 has no effect on cAMP production but reduces the regulated release of the secretory products (insulin and pepsinogen), indicating that PKA-AKAP association is necessary for maximal cAMP-mediated secretion.
Consistent with the report that, in nonneuronal cells, mammalian AKAP75 targets PKA to the cortical actin cytoskeleton (16), we have demonstrated that chief cell AKAP150 is associated with actin. In polarized pancreatic acinar cells, which have cellular machinery similar to that of gastric chief cells (20), the subapical actin cytoskeleton is involved in regulated exocytosis, both as a negative regulator of membrane fusion and as a facilitator of the movement of secretory granules to the sites of fusion (29). In pancreatic acinar cells, zymogen granules engaged in exocytosis are coated with actin before fusion with the plasma membrane. This coating process is tightly coupled to the release of the zymogen granule marker, rab3D, a low-molecular-weight GTP-binding protein (28). The following observations suggest that the actin cytoskeleton plays a role in regulated pepsinogen secretion from chief cells. First, rab3D is also present in guinea pig gastric chief cells (18). Second, disruption of rab3D expression results in defective secretagogue-stimulated pepsinogen secretion (26). Finally, in the present study, we demonstrate that AKAP150 is associated with actin. It remains to be determined whether actin is a substrate for any AKAP150-associated kinases or phosphatases, or whether actin simply acts to place the AKAP-anchored protein complex in close proximity to protein substrates such as adenylyl cyclase and other actin-associated cytoskeletal proteins that regulate exocytosis.
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ACKNOWLEDGEMENTS |
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We thank Dr. John D. Scott (Vollum Institute, Oregon Health Science University) for providing a rabbit polyclonal anti-AKAP150 antibody and Meshelle Helms for assistance in preparing the manuscript.
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FOOTNOTES |
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Address for reprint requests and other correspondence: J.-P. Raufman, Univ. of Arkansas for Medical Sciences, Mail Slot 567, 4301 West Markham St., Little Rock, AR 72205-7199 (E-mail: raufmanjeanpierre{at}uams.edu).
The costs of publication of this article were defrayed in part by the payment of page charges. The article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.
Received 18 February 2001; accepted in final form 11 June 2001.
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REFERENCES |
---|
![]() ![]() ![]() ![]() ![]() ![]() ![]() |
---|
1.
Carr, DW,
Stofko-Hahn RE,
Fraser ID,
Bishop SM,
Acott TS,
Brennan RG,
and
Scott JD.
Interaction of the regulatory subunit (RII) of cAMP-dependent protein kinase with RII-anchoring proteins occurs through an amphipathic helix binding motif.
J Biol Chem
266:
14188-14192,
1991
2.
Coghlan, VM,
Langeberg LK,
Fernandez A,
Lamb NJ,
and
Scott JD.
Cloning and characterization of AKAP 95, a nuclear protein that associates with the regulatory subunit of type II cAMP-dependent protein kinase.
J Biol Chem
269:
7658-7665,
1994
3.
Coghlan, VM,
Perrino BA,
Howard M,
Langeberg LK,
Hicks JB,
Gallatin WM,
and
Scott JD.
Association of protein kinase A and protein phosphatase 2B with a common anchoring protein.
Science
267:
108-111,
1995[ISI][Medline].
4.
Colledge, M,
and
Scott JD.
AKAPs: from structure to function.
Trends Cell Biol
9:
216-221,
1999[ISI][Medline].
5.
Dodge, K,
and
Scott JD.
AKAP79 and the evolution of the AKAP model.
FEBS Lett
476:
58-61,
2000[ISI][Medline].
6.
Dodge, KL,
Carr DW,
Yue C,
and
Sanborn BM.
A role for AKAP (A kinase anchoring protein) scaffolding in the loss of a cyclic adenosine 3',5'-monophosphate inhibitory response in late pregnant rat myometrium.
Mol Endocrinol
13:
1977-1987,
1999
7.
Dransfield, DT,
Bradford AJ,
and
Goldenring JR.
Distribution of A-kinase anchoring proteins in parietal cells.
Biochim Biophys Acta
1269:
215-220,
1995[ISI][Medline].
8.
Faux, MC,
Rollins EN,
Edwards AS,
Langeberg LK,
Newton AC,
and
Scott JD.
Mechanism of A-kinase-anchoring protein 79 (AKAP79) and protein kinase C interaction.
Biochem J
343:
443-452,
1999[ISI][Medline].
9.
Faux, MC,
and
Scott JD.
Regulation of the AKAP79-protein kinase C interaction by Ca2+/calmodulin.
J Biol Chem
272:
17038-17044,
1997
10.
Gao, T,
Yatani A,
Dell'Acqua ML,
Sako H,
Green SA,
Dascal N,
Scott JD,
and
Hosey MM.
cAMP-dependent regulation of cardiac L-type Ca2+ channels requires membrane targeting of PKA and phosphorylation of channel subunits.
Neuron
19:
185-196,
1997[ISI][Medline].
11.
Johnson, BD,
Brousal JP,
Peterson BZ,
Gallombardo PA,
Hockerman GH,
Lai Y,
Scheuer T,
and
Catterall WA.
Modulation of the cloned skeletal muscle L-type Ca2+ channel by anchored cAMP-dependent protein kinase.
J Neurosci
17:
1243-1255,
1997
12.
Kashishian, A,
Howard M,
Loh C,
Gallatin WM,
Hoekstra MF,
and
Lai Y.
AKAP79 inhibits calcineurin through a site distinct from the immunophilin-binding region.
J Biol Chem
273:
27412-27419,
1998
13.
Klauck, TM,
Faux MC,
Labudda K,
Langeberg LK,
Jaken S,
and
Scott JD.
Coordination of three signaling enzymes by AKAP79, a mammalian scaffold protein.
Science
271:
1589-1592,
1996[Abstract].
14.
Klussmann, E,
Maric K,
Wiesner B,
Beyermann M,
and
Rosenthal W.
Protein kinase A anchoring proteins are required for vasopressin-mediated translocation of aquaporin-2 into cell membranes of renal principal cells.
J Biol Chem
274:
4934-4938,
1999
15.
Lester, LB,
Langeberg LK,
and
Scott JD.
Anchoring of protein kinase A facilitates hormone-mediated insulin secretion.
Proc Natl Acad Sci USA
94:
14942-14947,
1997
16.
Li, Y,
Ndubuka C,
and
Rubin CS.
A kinase anchor protein 75 targets regulatory (RII) subunits of cAMP-dependent protein kinase II to the cortical actin cytoskeleton in non-neuronal cells.
J Biol Chem
271:
16862-16869,
1996
17.
Nishizuka, Y.
Protein kinase C and lipid signaling for sustained cellular responses.
FASEB J
9:
484-496,
1995
18.
Raffaniello, RD,
Lin J,
Wang F,
and
Raufman JP.
Expression of Rab3D in dispersed chief cells from guinea pig stomach.
Biochim Biophys Acta
1311:
111-116,
1996[ISI][Medline].
19.
Raffaniello, RD,
and
Raufman JP.
Protein kinase C expression and translocation in dispersed chief cells from guinea-pig stomach.
Biochim Biophys Acta
1224:
551-558,
1994[ISI][Medline].
20.
Raufman, JP.
Gastric chief cells: receptors and signal-transduction mechanisms.
Gastroenterology
102:
699-710,
1992[ISI][Medline].
21.
Raufman, JP,
Berger S,
Cosowsky L,
and
Straus E.
Increases in cellular calcium concentration stimulate pepsinogen secretion from dispersed chief cells.
Biochem Biophys Res Commun
137:
281-285,
1986[ISI][Medline].
22.
Raufman, JP,
and
Cosowsky L.
Interaction between the calcium and adenylate cyclase messenger systems in dispersed chief cells from guinea pig stomach. Possible cellular mechanism for potentiation of pepsinogen secretion.
J Biol Chem
262:
5957-5962,
1987
23.
Raufman, JP,
Lin J,
and
Raffaniello RD.
Calcineurin mediates calcium-induced potentiation of adenylyl cyclase activity in dispersed chief cells from guinea pig stomach. Further evidence for cross-talk between signal transduction pathways that regulate pepsinogen secretion.
J Biol Chem
271:
19877-19882,
1996
24.
Raufman, JP,
Sutliff VE,
Kasbekar DK,
Jensen RT,
and
Gardner JD.
Pepsinogen secretion from dispersed chief cells from guinea pig stomach.
Am J Physiol Gastrointest Liver Physiol
247:
G95-G104,
1984
25.
Shenolikar, S.
Protein serine/threonine phosphatasesnew avenues for cell regulation.
Annu Rev Cell Biol
10:
55-86,
1994[ISI].
26.
Singh, G,
Raffaniello RD,
Eng J,
and
Raufman JP.
Actions of Rab3 effector domain peptides in chief cells from guinea pig stomach.
Am J Physiol Gastrointest Liver Physiol
269:
G400-G407,
1995
27.
Sutliff, VE,
Raufman JP,
Jensen RT,
and
Gardner JD.
Actions of vasoactive intestinal peptide and secretin on chief cells prepared from guinea pig stomach.
Am J Physiol Gastrointest Liver Physiol
251:
G96-G102,
1986[ISI][Medline].
28.
Valentijn, JA,
Valentijn K,
Pastore LM,
and
Jamieson JD.
Actin coating of secretory granules during regulated exocytosis correlates with the release of rab3D.
Proc Natl Acad Sci USA
97:
1091-1095,
2000
29.
Valentijn, KM,
Gumkowski FD,
and
Jamieson JD.
The subapical actin cytoskeleton regulates secretion and membrane retrieval in pancreatic acinar cells.
J Cell Sci
112:
81-96,
1999
30.
Vijayaraghavan, S,
Goueli SA,
Davey MP,
and
Carr DW.
Protein kinase A-anchoring inhibitor peptides arrest mammalian sperm motility.
J Biol Chem
272:
4747-4752,
1997
31.
Wera, S,
and
Hemmings BA.
Serine/threonine protein phosphatases.
Biochem J
311:
17-29,
1995[ISI][Medline].
32.
Xie, G,
Habbersett RC,
Jia Y,
Peterson SR,
Lehnert BE,
Bradbury EM,
and
D'Anna JA.
Requirements for p53 and the ATM gene product in the regulation of G1/S and S phase checkpoints.
Oncogene
16:
721-736,
1998[ISI][Medline].