Transforming growth factor-beta receptor expression on human skin fibroblasts: dimeric complex formation of type I and type II receptors and identification of glycosyl phosphatidylinositol-anchored transforming growth factor-beta binding proteins.
Fibroblasts play a critical role in wound repair and in the development of fibrotic diseases, and transforming growth factor-beta (TGF-beta) has been shown to profoundly modulate fibroblast function. However, there is limited information on the TGF-beta receptor types, isoform specificity, and complex formation in skin fibroblasts. Here, we report that normal adult human skin fibroblasts display two isoform-specific, cell surface glycosyl phosphatidylinositol (GPI)-anchored, TGF-beta binding proteins in addition to the type I, II, and III TGF-beta receptors. The identities of these proteins are confirmed on the basis of their affinity for TGF-beta isoforms, immunoprecipitation with specific antireceptor antibodies, and other biochemical analyses. Immunoprecipitation results also indicated oligomeric complex formation between type I and II and between type II and III TGF-beta receptors. Furthermore, by using affinity labeling and two-dimensional electrophoresis, we demonstrate the occurrence of type I and II heterodimers and type I homodimers of TGF-beta receptors on these cells. Because the type I receptor does not bind TGF-beta in the absence of type II receptor, these results indicate that one molecule of TGF-beta induces the formation of a heterooligomeric complex containing more than one molecule each of type I and II TGF-beta receptors on these cells. These cells respond to TGF-beta by markedly down-regulating all five binding proteins and by potently augmenting DNA synthesis. These results allow the expansion of the proposed heteromeric TGF-beta receptor signaling paradigm using mutant cells that are unresponsive to TGF-beta and cell lines that have been transfected to overexpress these receptors, to include normal TGF-beta-responsive cells. In addition, the definition of TGF-beta receptor profiles in human skin fibroblasts provides important information for studying their alterations in these cells in various skin diseases.
Tam
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Division of Plastic Surgery, Montreal General Hospital, Quebec, Canada.
Philip
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D030201:Activin Receptors, Type I; D000906:Antibodies; D000975:Antioxidants / Q000494:pharmacology; D002478:Cells, Cultured; D019281:Dimerization; D004229:Dithiothreitol / Q000031:analogs & derivatives / Q000494:pharmacology; D015180:Electrophoresis, Gel, Two-Dimensional; D005347:Fibroblasts / Q000737:chemistry / Q000166:cytology; D017261:Glycosylphosphatidylinositols / Q000032:analysis*; D006706:Homeostasis / Q000502:physiology; D006801:Humans; D007536:Isomerism; D043265:Phosphatidylinositol Diacylglycerol-Lyase; D011233:Precipitin Tests; D011485:Protein Binding / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases / Q000096:biosynthesis* / Q000737:chemistry / Q000276:immunology; D000077293:Receptor, Transforming Growth Factor-beta Type I; D000077294:Receptor, Transforming Growth Factor-beta Type II; D018125:Receptors, Transforming Growth Factor beta / Q000096:biosynthesis* / Q000737:chemistry / Q000276:immunology; D015398:Signal Transduction / Q000502:physiology; D012867:Skin / Q000737:chemistry / Q000166:cytology*; D014162:Transfection; D016212:Transforming Growth Factor beta / Q000737:chemistry / Q000378:metabolism; D010738:Type C Phospholipases / Q000494:pharmacology
D000906:Antibodies; D000975:Antioxidants; D017261:Glycosylphosphatidylinositols; D018125:Receptors, Transforming Growth Factor beta; D016212:Transforming Growth Factor beta; C085285:dithiothreitol tetraacetate; D017346:Protein Serine-Threonine Kinases; D030201:Activin Receptors, Type I; D000077293:Receptor, Transforming Growth Factor-beta Type I; D000077294:Receptor, Transforming Growth Factor-beta Type II; D010738:Type C Phospholipases; D043265:Phosphatidylinositol Diacylglycerol-Lyase; D004229:Dithiothreitol