title: Alpha v beta 5 integrin receptor-mediated endocytosis of vitronectin is protein kinase C-dependent.
abstract: Previous studies have demonstrated that the alpha v beta 5 integrin receptor functions in the endocytosis and degradation of matrix-bound vitronectin by human skin fibroblasts (Panetti, T. S., and McKeown-Longo, P. J. (1993) J. Biol. Chem. 268, 11988-11993; Panetti, T. S., and McKeown-Longo, P. J. (1993) J. Biol. Chem. 268, 11492-11495). These earlier studies demonstrated that vitronectin degradation was inhibited by either antibodies to the beta 5 integrin or exogenous heparin, suggesting that both integrin receptors and cell surface heparan sulfate proteoglycans are involved in the endocytosis and degradation of vitronectin. The present study was done to define intracellular signaling pathways involved in endocytosis of vitronectin and to evaluate the relative contribution of cell surface heparan sulfate proteoglycans and the alpha v beta 5 integrin in the activation of these signaling pathways. The addition of the phorbol ester phorbol 12-myristate 13-acetate (PMA), a protein kinase C activator, to monolayers of human skin fibroblasts, increased vitronectin degradation. Staurosporine and calphostin C, inhibitors of protein kinase C, blocked internalization and subsequent degradation of vitronectin, while KT5720, an inhibitor of protein kinase A, had no effect on the degradation of vitronectin. PMA was also able to reverse the inhibition of vitronectin degradation seen when cells were pretreated with heparinase or incubated with exogenous heparin. In contrast, the inhibitory effect of either RGD peptides or anti-alpha v beta 5 antibodies on vitronectin degradation were not overcome by the addition of PMA. These data suggest that the internalization of vitronectin from the matrix is mediated by the alpha v beta 5 integrin following activation of protein kinase C.
authors.affiliation: Department of Physiology and Cell Biology, Albany Medical College, New York 12208, USA.
authors.forename: T S
authors.initials: TS
authors.lastname: Panetti
authors.forename: S A
authors.initials: SA
authors.lastname: Wilcox
authors.forename: C
authors.initials: C
authors.lastname: Horzempa
authors.forename: P J
authors.initials: PJ
authors.lastname: McKeown-Longo
mesh_terms: D001692:Biological Transport; D002478:Cells, Cultured; D004705:Endocytosis / Q000502:physiology*; D005347:Fibroblasts / Q000166:cytology; D006023:Glycoproteins / Q000378:metabolism*; D019812:Heparan Sulfate Proteoglycans; D006497:Heparan Sulfate / Q000378:metabolism; D006801:Humans; D016023:Integrins / Q000378:metabolism*; D009281:Naphthalenes / Q000494:pharmacology; D009842:Oligopeptides / Q000494:pharmacology; D011493:Protein Kinase C / Q000378:metabolism*; D011509:Proteoglycans / Q000378:metabolism; D019030:Receptors, Vitronectin; D015398:Signal Transduction; D012879:Skin Physiological Phenomena; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D019096:Vitronectin
chemical_list: D006023:Glycoproteins; D019812:Heparan Sulfate Proteoglycans; D006497:Heparan Sulfate; D016023:Integrins; D009281:Naphthalenes; D009842:Oligopeptides; D011493:Protein Kinase C; D011509:Proteoglycans; D019030:Receptors, Vitronectin; D013755:Tetradecanoylphorbol Acetate; D019096:Vitronectin; C064660:integrin alphaVbeta5; C046617:arginyl-glycyl-aspartyl-serine; C058819:calphostin C