Evidence for phosphatidylinositol-linked forms of human and avian fibronectin receptors.
Phosphatidylinositol (PI)-linked forms of surface molecules have been hypothesized to mediate the initial stages of cell adhesion or signal transduction. We report evidence for the occurrence of a functional PI-linked subset of cell surface fibronectin receptors (FNR). Treatment of human MG63 osteosarcoma cells or primary chicken embryo fibroblasts (CEF) with PI-specific phospholipase C (PI-PLC) reduced cell surface FNR expression by 30% as detected by immunofluorescence. PI-PLC treatment of cell membranes purified from [35S]methionine-labeled CEF or MG63 cells led to a similar loss of membrane-associated immunoprecipitable FNR from the pelleted membranes, while such treatment led to the appearance of FNR in the supernatant of treated MG63 membranes. Biosynthetic labeling of CEF FNR with [3H]palmitate and [3H]ethanolamine demonstrated the acylation and putative PI linkage of avian FNR subunits. PI-PLC treatment of CEF and MG63 cells also reduced fibronectin-specific adhesion in a short-term in vitro assay, suggesting that the avian and human FNR occur in PI-linked isoforms which appear to contribute to cell adhesion to fibronectin.
Symington
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BE
Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, Washington 98104.
Symington
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FW
D000818:Animals; D002448:Cell Adhesion; D002460:Cell Line; D002462:Cell Membrane / Q000276:immunology; D002642:Chick Embryo; D019856:Ethanolamine; D004983:Ethanolamines / Q000378:metabolism; D005347:Fibroblasts / Q000276:immunology; D005353:Fibronectins / Q000378:metabolism; D005434:Flow Cytometry; D006801:Humans; D012516:Osteosarcoma; D019308:Palmitic Acid; D010169:Palmitic Acids / Q000378:metabolism; D043265:Phosphatidylinositol Diacylglycerol-Lyase; D010716:Phosphatidylinositols / Q000032:analysis*; D054801:Phosphoinositide Phospholipase C; D010727:Phosphoric Diester Hydrolases / Q000378:metabolism; D017469:Receptors, Fibronectin; D011971:Receptors, Immunologic / Q000096:biosynthesis / Q000302:isolation & purification*; D014407:Tumor Cells, Cultured / Q000276:immunology
D004983:Ethanolamines; D005353:Fibronectins; D010169:Palmitic Acids; D010716:Phosphatidylinositols; D017469:Receptors, Fibronectin; D011971:Receptors, Immunologic; D019308:Palmitic Acid; D019856:Ethanolamine; D010727:Phosphoric Diester Hydrolases; D054801:Phosphoinositide Phospholipase C; D043265:Phosphatidylinositol Diacylglycerol-Lyase