Article |
Address correspondence to Denise C. Hocking, Department of Pharmacology and Physiology, University of Rochester Medical Center, 601 Elmwood Ave., Box 711, Rochester, NY 14642. Tel.: (716) 273-1770. Fax: (716) 273-2652. E-mail: denise_hocking{at}urmc.rochester.edu
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Abstract |
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Key Words: fibronectin; caveolin; integrin; proteoglycans; growth
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Introduction |
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Current models of FN matrix assembly propose that binding of soluble FN to the cell surface triggers a series of conformational changes that result in the exposure of homophilic binding sites and the subsequent elongation of FN fibrils (Magnusson and Mosher, 1998). The first type III module of FN (III1) contains a binding site for the NH2 terminus of FN that is not exposed within soluble FN (Hocking et al., 1994), but may become exposed on cell surfaces during FN polymerization (Zhong et al., 1998; Tellier et al., 2000). Moreover, proteolytic cleavage of III1 at Ile597 exposes a cryptic heparin-binding activity in III1 (Litvinovich et al., 1992). These data suggest the possibility that during FN polymerization, a "matricryptic" (Davis et al., 2000), heparin-binding activity is exposed in III1, which serves to trigger cellular responses that are unique to ECM FN.
Previous work has shown that FN stimulates cell growth (Sottile et al., 1998) and contractility (Hocking et al., 2000) by a mechanism that requires the polymerization of FN into the ECM. To construct a recombinant FN with properties of matrix FN, we engineered a glutathione-S-transferase (GST) tagged fusion protein in which the cryptic, heparin-binding III1 fragment (III1H) was linked directly to the integrin-binding III810 modules (GSTIII1H,810). FN-null (FN-/-) cells, which do not produce FN and are grown under serum-free conditions (Sottile et al., 1998), were used in conjunction with recombinant FN fragments to eliminate any effects of endogenous FN or FN fragments. Our data indicate that treatment of FN-/- cells with GSTIII1H,810 stimulates a specific increase in cell growth and contractility. A construct in which the III24 modules were substituted for the integrin-binding III810 modules (GSTIII1H,24) retained the ability to stimulate cell contraction, but did not stimulate cell growth. Both GSTIII1H,24 and polymerized FN colocalized with caveolin and fractionated with low-density membrane complexes by a mechanism that required heparan sulfate proteoglycans (HSPGs). Treatment of cells with sterol-binding compounds to disrupt caveolae blocked the localization of GSTIII1H,24 and FN to lipid rafts and inhibited the increase in cell contraction and growth induced by either FN or the III1H-containing constructs. These data suggest that a portion of ECM FN partitions into lipid rafts and differentially regulates cytoskeletal organization and cell growth, in part, through the exposure of a neoepitope within the conformationally labile III1 module.
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Results |
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Effect of III1H on cell contractility
FN polymerization has also been shown to trigger cytoskeletal tension generation (Hocking et al., 2000). To determine the role of III1H in cell contractility, FN-/- cells were imbedded in floating collagen gels in the absence and presence of increasing concentrations of either intact FN or the various fusion proteins. GSTIII1H,810 stimulated an increase in cell contractility to a similar extent as that observed with intact FN (Fig. 4 A). Furthermore, in contrast to the negative results obtained in the growth studies, treatment of cells with GSTIII1H,24 also promoted a significant increase in collagen gel contraction (Fig. 4 A). As with the growth assays, substitution of the heparin-binding III13 module for III1H (GSTIII810,13) failed to stimulate collagen gel contraction (Fig. 4 A). Addition of the III1H fragment resulted in a dose-dependent inhibition of GSTIII1H,810-induced contraction; intact III1 had no effect (Fig. 4 B). Moreover, treatment of cells with GSTIII14, in which III1H was replaced with the intact III1 module, did not stimulate contraction (Fig. 4 C), suggesting that exposure of cryptic residues within III1 is required to induce cytoskeletal tension generation. Constructs in which one or more of the COOH-terminal type III modules were deleted (GSTIII1H,23, GSTIII1H,2, and GSTIII1H) did not stimulate cell contractility (Fig. 4 C), suggesting that secondary sequences contribute to the ability of III1H to stimulate contraction. These data suggest that a cryptic, heparin-binding region within the III1 module of FN plays a unique role in modulating both cell contractility and growth.
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Partitioning of FN to lipid rafts requires FN polymerization and HSPGs
To determine whether intact FN also colocalizes with caveolin, confluent FN-/- cells were incubated with FN for 4 h. Cells were costained for FN and caveolin. As demonstrated in Fig. 8 a, areas of FN (Fig. 8 a, A, arrow) and caveolin (Fig. 8 a, B, arrow) were found to colocalize (Fig. 8 a, C, arrow), particularly along cell edges. In addition, discrete areas of FN fibril staining appeared to terminate at areas enriched with caveolin (arrowhead). To determine whether the localization of FN to caveolin-enriched lipid rafts is similarly dependent on HSPGs, FN-/- cells were pretreated with heparinase before incubation with FN. After 5 h, cells were extracted with 1% Triton X-100 and fractionated. As shown in Fig. 8 b, a portion of the FN from untreated cells migrated to the caveolin-enriched fractions (fractions 5 and 6). Pretreatment of cells with heparinase significantly reduced the amount of FN associated with these fractions (Fig. 8 b, fractions 5 and 6).
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ß-Cyclodextrin removes cholesterol from cell membranes and alters the association of proteins with caveolae (Keller and Simons, 1998). To determine whether disruption of caveolae would disrupt the association of FN with low-density lipid rafts, cells were allowed to polymerize an FN matrix and then were treated with cyclodextrin for 2 h. As shown in Fig. 8 d, cyclodextrin preferentially removed the FN associated with the low-density lipid fractions (fractions 5 and 6); cyclodextrin had no effect on the interaction of nonlipid-associated FN with cells (Fig. 8 d, fraction 12). Taken together, these data indicate that a portion of matrix FN partitions to lipid rafts by a mechanism that requires HSPGs.
III1H-mediated growth and contractility are inhibited by sterol-binding agents
To determine whether the fraction of GSTIII1H,24 and FN that associates with caveolae is biologically active, Fn-/- cells were pretreated with the cholesterol-binding compounds nystatin and filipin III. Cells were then embedded in collagen gels in the presence of either FN or GSTIII1H,24 and collagen gel contraction was assessed. As demonstrated in Fig. 9 A, pretreatment of cells with nystatin inhibited the contraction induced by GSTIII1H,24 and partially inhibited the contraction induced by FN. In contrast, basal contraction was not altered by nystatin treatment (Fig. 9 A). A similar inhibition profile was obtained when cells were pretreated with filipin III (Fig. 9 B).
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Discussion |
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The loss of lipid-associated FN upon treatment of cells with the inhibitor of FN polymerization, 9D2 mAb (Chernousov et al., 1991), suggests that the association of FN with lipid rafts occurs as FN is either assembled or remodeled within the ECM. Furthermore, the cholesterol-binding compound nystatin does not inhibit FN matrix deposition (unpublished data). These data suggest that the formation of an FN matrix does not depend on FN localization to lipid rafts. Rather, these data indicate that as a consequence of FN matrix deposition, a portion of the matrix FN translocates to lipid rafts where it modulates cell function. In support of this, previous work has shown that cell cycle progression is altered in cells that have assembled a matrix consisting of an FN construct in which modules III17 were deleted (Sechler and Schwarzbauer, 1998).
Previous studies have demonstrated that treatment of cells with an isolated fragment of III1, termed III1C (NH2 terminus = Asn600), inhibits lysophosphatidic acidmediated actin organization and tyrosine phosphorylation (Bourdoulous et al., 1998), decreases cell migration (Morla et al., 1994), and inhibits tumor cell angiogenesis (Yi and Ruoslahti, 2001). The ability of III1C to affect cytoskeletal function has been attributed to its ability to either disrupt preexisting FN matrices (Bourdoulous et al., 1998) or to stimulate increased FN matrix deposition (Yi and Ruoslahti, 2001), depending upon its concentration. In the present study, the III1H-mediated increases in cell growth and contraction occurred in the absence of any endogenous FN. These results indicate that, in addition to its ability to affect cellular events by altering matrix composition, the III1 module of FN can also directly affect cell function.
Sottile et al. (2000) recently demonstrated that HSPGs play a role in the stimulation of cell growth induced by FN polymerization. Similarly, in the present study, the stimulation of cell growth by GSTIII1H,810 was inhibited by either heparin or pretreatment of cells with heparinase. In addition, heparinase inhibited the localization of both GSTIII1H,24 and intact FN to caveolae. These data suggest that HSPGs function as the cell surface receptor for the heparin-binding region of III1 and further, that a similar HSPG-dependent mechanism is involved in the partitioning of III1H and matrix FN into caveolae. Previous studies have localized the stress fiberpromoting activity of the COOH-terminal heparin-binding domain of FN to III13 (Bloom et al., 1999). In the present study, GSTIII810,13 was unable to increase cell growth or contraction and did not localize to caveolae. However, addition of excess GSTIII1213 to cells inhibited GSTIII1H,810-stimulated growth, suggesting that III13 can compete with III1H for binding to the glycosaminoglycan chains of the HSPGs. Additional interactions, possibly involving the core protein of the HSPG (Woods, 2001), likely contribute to the subsequent generation of distinct intracellular signals that modulate cell growth and contraction.
The molecular processing of information received by cells from their extracellular environment occurs in specific membrane domains, including caveolae, focal adhesions, and areas of cellcell contact. Caveolae exist as cholesterol- and sphingolipid-enriched microdomains within the cell membrane and play a key role in signal transduction events (Brown and London, 1998). Several growth factor receptor tyrosine kinases as well as nonreceptor signaling proteins, including Src family kinases, MAPK, and PKC, have been shown to localize to caveolae (Brown and London, 1998). The ability of heparin-binding III1 FN fragments, as well as matrix FN, to partition to caveolin-enriched microdomains represents a novel mechanism by which signals derived from the ECM may be transmitted to the interior of the cell to modulate growth and contractility.
During wound healing, migrating epithelial cells and fibroblasts deposit and remodel the ECM in order to support further cell ingrowth and neovascularization (Clark, 1995). Under normal circumstances, the synthesis of ECM proteins gradually decreases during tissue repair (Clark, 1995). However, in the absence of appropriate inhibitory signals, the synthetic phenotype of wound fibroblasts persists and can lead to the development of fibrotic changes within tissues, including excess deposition of FN, stimulation of fibroblast proliferation, and altered organization of collagen fibrils (Clark, 1995). As such, the continuous or inappropriate exposure of the matricryptic, heparin-binding activity of FN's III1 module may contribute to the fibrotic phenotype by enhancing and/or prolonging cell contraction and growth. Developing methods to control the extent and/or duration of the exposure of cells to matrix-specific epitopes may provide useful approaches to promote normal wound healing and prevent fibrosis.
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Materials and methods |
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Cell culture
Mouse embryo cells, derived from FN-/- embryos and adapted to grow under serum-free conditions (Sottile et al., 1998), were provided by Jane Sottile (University of Rochester, Rochester, NY). FN-/- cells were cultured on collagen-coated dishes in a 1:1 mixture of Cellgro® (Mediatech) and Aim V (Life Technologies).
Recombinant FNs
Fig. 10 illustrates the FN constructs used in this study. PCR was used to amplify human FN cDNA (a gift of Jean Thiery, Institut Curie, Paris, France) encoding the following amino acids (Petersen et al., 1989): a COOH-terminal fragment of the first type III module (III1H; bases 18022032; Ile 597Thr 673), III1H plus the III2 module (III1H,2; bases 18022347; Ile 597Thr 778), III1H plus the III2 and III3 modules (III1H,23; bases 18022635; Ile 597Asp 874), III1H plus the III2, III3, and III4 modules (III1H,24; bases 18022905; Ile 597Thr 964), the full-length first through fourth type III modules (III14; bases 17452905; Ser 578Thr 964), a COOH-terminal fragment of the III2 module corresponding to the III1H fragment (III2H; bases 21322347; Val 707Thr 778), the 810th type III modules (III810; bases 37164540; Ala 1326Thr 1600), and the III13 module (III13; bases 53575623; Asn 1873Thr 1961). The sense primer for III1H, III1H,2, III1H,23, and III1H,24 (5'-CCCGGATCCATCCAGTGGAATGCACCACAG-3'), the sense primer for III14 (5'-CCCGGATCCAGTGGTCCTGTCGAAGTATTTAT-3'), and the sense primer for III2H (5'-CCCGGATCCGTCTCCTGGGTCTCAGCTTC-3') contain a BamH1 site (shown in bold) at the 5' end. The sense primer for III810 and III810,13 (5'-CCCAGATCTGCTGTTCCTCCTCCCACTGAC-3') includes a BglII site. The sense primer for III13 (5'-CCCATCGATAATGTCAGCCCACCAAGAAGG-3') includes a Cla site. The antisense primers for III1H (5'-CCCGAATTCCTATGTGCTGGTGCTGGTGGTG-3'), III1H,2 and III2H (5'-CCCGAATTCCTATGTTGTTTGTGAAGTAGACAGG-3'), III1H,23 (5'-CCCGAATTCCTAATCTGAGCGTGGGGTGCCAG-3'), and III1H,24 and III14 (5'-CCCGAATTCCTAGGTTGTCTGTTGAGCAGTCAG-3') contain an EcoRI site. The antisense primers for III810 (5'-CCCCCCGGGCTATGTTCGGTAATTAATGGAAATTG-3') and III810,13 (5'-CCCCCCGGGCTAAGTGGAGGCGTCGATGACCAC-3') include a SmaI site. III1H,810 and III2H,810 were made by PCR amplification of either III1H or III2H with BamHI sites at both the 5' and 3' ends. The sense primers used were the same as those for III1H and III2H. The antisense primers for III1H (5'-CCCGGATCCTGTGCTGGTGCTGGTGGTG-3') and III2H (5'-CCCGGATCCTGTTGTTTGTGAAGTAGACAGG-3') contain BamHI sites. The III810 modules were PCR amplified with BglII and SmaI sites at the 5' and 3' ends, respectively. These restriction enzyme sites generate two additional amino acids (Gly and Ser) between either III1H or III2H and III810. To construct III810,13, an antisense primer for III10 (5'-CCCATCGATAATGTCAGCCCACCAAGAAGC-3') was synthesized with a Cla site, which generates two additional amino acids (Ile and Asp) between III10 and III13. The III910 synergy site mutant (GST/III910R1374,1379A) was produced using the following mutant primers: 5'-GCGGTGCCCCACTCTGCGAATTCCATCACCCTC-3' (sense) and 5'-CGCAGAGTGGGGCACCGCATCTTCTCG-3' (antisense). The outer primers were the same as those used to amplify nonmutant III910 (Hocking et al., 1999). The amplification of III1, III910, III1213, and the heparin-binding domain of vitronectin have been previously described (Hocking et al., 1999). The PCR products were cloned into pGEX-2T (Amersham Biosciences) and transfected into DH5 bacteria (Sambrook et al., 1989). Proteins were isolated on glutathione-agarose (Amersham Biosciences) (Hocking et al., 1994). GSTIII1 and GSTIII1H were digested with TPCK-trypsin (Hocking et al., 1994). III1 was separated from GST by passing the digested material over SP-Sephadex C-25 (Amersham Biosciences). III1H was separated from GST by retention on heparin-Sepharose (Amersham Biosciences). GSTIII810,13 bound to heparin-Sepharose and eluted at a concentration of 0.628 ± 0.009 M NaCl. By comparison, the 30-kD COOH-terminal heparin-binding FN fragment elutes at 0.63 M NaCl (Ingham et al., 1990).
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Growth assays
Growth assays were conducted as previously described (Sottile et al., 1998). For some experiments, recombinant FN constructs, nystatin, cyclodextrin, or heparinase I (5 mU/ml; Seikagaku Corp.) were added to collagen-adherent FN-/- cells 30 min before the addition of test proteins. Heparinase treatment was repeated every 24 h. After a 3- or 4-d incubation, cells were fixed, stained with crystal violet, and the absorbance at 590 nM was determined (Sottile et al., 1998).
Collagen gel contraction assays
Floating type I collagen gels were prepared as previously described (Hocking et al., 2000). Collagen gels imbedded with cells were incubated for 20 h and then removed from the wells and weighed. Collagen gel contraction was measured as a decrease in gel weight (Hocking et al., 2000). Data are reported as percent contraction: (1 - weight of the test gels/weight of gels not containing cells) x 100.
Solid-phase heparin binding assay
Glutathione-coated 96-well plates (Pierce Chemical Co.) were incubated with saturating concentrations of proteins (400 nM; 25 µg/ml GSTIII810,13) in TBS with 0.5% Tween. Plates were then washed and incubated with heparinalbuminbiotin followed by HRP-NeutrAvidin (Pierce Chemical Co.). Parallel plates were incubated with a polyclonal anti-GST antibody followed by an HRP-conjugated goat antirabbit IgG (Bio-Rad Laboratories). The assay was developed using 2,2'-azino-bis (3-ethylbenzthiazoline sulfonic acid) and the absorbance at 405 nm was measured.
Statistical analysis
Data are expressed as mean ± SEM and represent one of at least three separate experiments performed in triplicate or quadruplicate. Significance was determined using one-way analysis of variance (ANOVA) or the t test for unpaired samples. Differences <0.05 were considered significant.
Immunofluorescence microscopy
Collagen-adherent FN-/- cells were incubated for 5 h with 250 nM of the GST fusion proteins. For inhibition studies, cells were pretreated for 0.5 h with 2.5 µg/ml filipin III or an equal volume of ethanol, 5 mU/ml heparinase I (Seikagaku Corp.), 100 mU/ml chondroitinase ABC (Seikagaku Corp.), 25 U/ml neuraminidase (Calbiochem-Novabiochem">Calbiochem-Novabiochem), or an equal volume of DME. In other experiments, FN-/- cells were seeded on coverslips coated with 10 µg/ml vitronectin, grown to confluence, and then incubated with 40 nM FN for 5 h. Cells were fixed with 2% paraformaldehyde and permeabilized with 0.5% Triton X-100. Fusion proteins were visualized using either anti-GST monoclonal or polyclonal antibodies. After staining, cells were examined with an Olympus BX60 microscope equipped with epifluorescence and photographed using a Spot digital camera.
Low-density membrane fractions
Low-density membrane fractions were prepared by extraction with either 1% Triton X-100 or 0.5 M sodium carbonate, pH 11.0 (Schwab et al., 2000). Confluent FN-/- cells were treated with 5 mU/ml heparinase I for 1 h before the addition of either 250 nM GSTIII1H,24 or 40 nM FN for an additional 5 h. Two 150-mm dishes were used for each condition. Cells were washed with PBS and scraped into 2 ml of 1% Triton X-100 in MES-buffered saline (MBS; 25 mM MES, 150 mM NaCl, pH 6.5). In some studies, FN-/- cells were treated with 40 nM FN in the presence of either 25 µg/ml of 9D2 IgG or mouse IgG. After an 18-h incubation, cells were washed and scraped into 2 ml of 0.5 M sodium carbonate, pH 11. 2 ml of cell lysate was mixed with 2 ml of 80% sucrose in MBS. Samples were placed in a centrifuge tube and overlaid with 4 ml each of 30 (Triton extraction) or 35% (carbonate extraction) sucrose followed by 5% sucrose in MBS. Samples were centrifuged at 200,000 g at 4°C for 15 h. Sequential 1-ml fractions were collected and aliquots were analyzed by PAGE and immunoblotting.
Immunoblotting
PAGE and immunoblotting were performed as previously described (Hocking et al., 2000). Gel samples were reduced with 2% ß-mercaptoethanol. Immunoblots were incubated with primary antibody in TBS-T (20 mM Tris, pH 7.6, 137 mM NaCl, 0.1% Tween 20) containing 1% BSA followed by a goat antirabbit, mouse, or rat HRP-linked secondary antibody. Blots were developed using ECL (Amersham Biosciences). After detection, blots were stripped by incubation with 0.2 M glycine, 0.1% SDS, 1% Tween, pH 4.0 (Miller et al., 1997). Blots were then washed, reblocked, and reprobed.
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Footnotes |
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Acknowledgments |
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This work was supported by grants HL60181 and HL64074 from the National Institutes of Health.
Submitted: 10 December 2001
Revised: 20 May 2002
Accepted: 24 May 2002
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References |
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Aota, S., M. Nomizu, and K.M. Yamada. 1994. The short amino acid sequence Pro-His-Ser-Arg-Asn in human fibronectin enhances cell-adhesive function. J. Biol. Chem. 269:2475624761.
Bloom, L., K.C. Ingham, and R.O. Hynes. 1999. Fibronectin regulates assembly of actin filaments and focal contacts in cultured cells via the heparin-binding site in repeat III13. Mol. Biol. Cell. 10:15211536.
Bourdoulous, S., G. Orend, D.A. MacKenna, R. Pasqualini, and E. Ruoslahti. 1998. Fibronectin matrix regulates activation of RHO and CDC42 GTPases and cell cycle progression. J. Cell Biol. 143:267276.
Chernousov, M.A., F.J. Fogerty, V.E. Koteliansky, and D.F. Mosher. 1991. Role of the I-9 and III-1 modules of fibronectin in formation of an extracellular matrix. J. Biol. Chem. 266:1085110858.
Clark, R.A.F. 1995. Wound repair. The Molecular and Cellular Biology of Wound Repair. R.A.F. Clark, editor. Plenum Press, New York. 350.
Davis, G.E., K.J. Bayless, M.J. Davis, and G.A. Meininger. 2000. Regulation of tissue injury responses by the exposure of matricryptic sites within extracellular matrix molecules. Am. J. Pathol. 156:14891498.
Hocking, D.C., J. Sottile, and P.J. McKeown-Longo. 1994. Fibronectin's III-1 module contains a conformation-dependent binding site for the amino-terminal region of fibronectin. J. Biol. Chem. 269:1918319191.
Hocking, D.C., J.S. Sottile, T. Reho, R. Fassler, and P.J. McKeown-Longo. 1999. Inhibition of fibronectin matrix assembly by the heparin-binding domain of vitronectin. J. Biol. Chem. 274:2725727264.
Hocking, D.C., J. Sottile, and K.J. Langenbach. 2000. Stimulation of integrin-mediated cell contractility by fibronectin polymerization. J. Biol. Chem. 275:1067310682.
Hynes, R.O. 1990. Fibronectins. Springer-Verlag New York Inc., New York. 546 pp.
Jockusch, B.M., P. Bubeck, K. Giehl, M. Kroemker, J. Moscher, M. Rothkegel, M. Rudiger, K. Schluter, G. Stanke, and J. Winkler. 1995. The molecular architecture of focal adhesions. Annu. Rev. Cell Dev. Biol. 11:379416.[CrossRef][Medline]
Keller, P., and K. Simons. 1998. Cholesterol is required for surface transport of influenza virus hemagglutinin. J. Cell Biol. 140:13571367.
Magnusson, M., and D.F. Mosher. 1998. Fibronectin: structure, assembly, and cardiovascular implications. Arterioscler. Thromb. Vasc. Biol. 18:13631370.
Miller, T.M., M.G. Tansey, E.M. Johnson, Jr., and D.J. Creedon. 1997. Inhibition of phosphatidylinositol 3-kinase activity blocks depolarization- and insulin-like growth factor I-mediated survival of cerebellar granule cells. J. Biol. Chem. 272:98479853.
Pasqualini, R., S. Bourdoulous, E. Koivunen, V.L. Woods, and E. Ruoslahti. 1996. A polymeric form of fibronectin has antimetastatic effects against multiple tumor types. Nat. Med. 2:11971203.[Medline]
Petersen, T.E., K. Skorstengaard, and K. Vibe-Pedersen. 1989. Primary structure of fibronectin. Fibronectin. D.F. Mosher, editor. Academic Press, New York. 124.
Sambrook, J., E.F. Fritsch, and T. Maniatis. 1989. Plasmid vectors. Molecular Cloning: A Laboratory Manual. Cold Spring Harbor Laboratory Press, Cold Spring Harbor, NY. 1.741.84.
Schwab, R.B., T. Okamoto, P.E. Scherer, and M.P. Lisanti. 2000. Analysis of the association of proteins with membranes. In Current Protocols in Cell Biology. J.S. Bonifacino, M. Dasso, J.B. Harford, J. Lippincott-Schwartz, and K.M. Yamada, editors. John Wiley and Sons, Inc., New York. 5.4.85.4.11.
Sechler, J.L., and J.E. Schwarzbauer. 1998. Control of cell cycle progression by fibronectin matrix architecture. J. Biol. Chem. 273:2553325536.
Sottile, J., D.C. Hocking, and P.J. Swiatek. 1998. Fibronectin matrix assembly enhances adhesion-dependent cell growth. J. Cell Sci. 111:29332943.
Sottile, J., D.C. Hocking, and K.J. Langenbach. 2000. Fibronectin matrix assembly stimulates cell growth by RGD-dependent and -independent mechanisms. J. Cell Sci. 113:42874299.
Tellier, M.C., G. Greco, M. Klotman, A. Mosoian, A. Cara, W. Arap, E. Ruoslahti, R. Pasqualini, and L.M. Schnapp. 2000. Superfibronectin, a multimeric form of fibronectin, increases HIV infection of primary CD4+ T lymphocytes. J. Immunol. 164:32363245.
Woods, A. 2001. Syndecans: transmembrane modulators of adhesion and matrix assembly. J. Clin. Invest. 107:935941.
Yi, M., and E. Ruoslahti. 2001. A fibronectin fragment inhibits tumor growth, angiogenesis, and metastasis. Proc. Natl. Acad. Sci. USA. 98:620624.
Zhong, C., M. Chrzanowska-Wodnicka, J. Brown, A. Shaub, A.M. Belkin, and K. Burridge. 1998. Rho-mediated contractility exposes a cryptic site in fibronectin and induces fibronectin matrix assembly. J. Cell Biol. 141:539551.