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TGF‐β receptor expression on human keratinocytes: A 150 kDa GPI‐anchored TGF‐β1 binding protein forms a heteromeric complex with type I and type II receptors
Author(s) -
Tam Betty Y.Y.,
Germain Lucie,
Philip Anie
Publication year - 1998
Publication title -
journal of cellular biochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.028
H-Index - 165
eISSN - 1097-4644
pISSN - 0730-2312
DOI - 10.1002/(sici)1097-4644(19980915)70:4<573::aid-jcb13>3.0.co;2-i
Subject(s) - receptor , heterotrimeric g protein , immunoprecipitation , biology , microbiology and biotechnology , keratinocyte , r smad , tgf beta receptor 2 , tgf alpha , biochemistry , g protein , in vitro , growth factor , gene
Keratinocytes play a critical role in re‐epithelialization during wound healing, and alterations in keratinocyte proliferation and function are associated with the development of various skin diseases. Although it is well documented that TGF‐β has profound effects on keratinocyte growth and function, there is a paucity of information on the types, isoform specificity and complex formation of TGF‐β receptors on keratinocytes. Here, we report that in addition to the types I, II, and III TGF‐β receptors, early passage adult and neonatal human keratinocytes display a cell surface glycosylphosphatidylinositol (GPI)‐anchored 150 kDa TGF‐β1 binding protein. The identities of the four proteins were confirmed on the basis of their affinity for TGF‐β isoforms, immunoprecipitation with specific anti‐receptor antibodies, sensitivity to phosphatidylinositol specific phospholipase C and dithiothreitol, and 2‐dimensional electrophoresis. Interestingly, the antitype I TGF‐β receptor antibody immunoprecipitated not only the type I receptor, but also the type II receptor and the 150 kDa component, suggesting that the 150 kDa component form heteromeric complexes with the signalling receptors. In addition, two‐dimensional (nonreducing/reducing) electrophoresis confirmed the occurrence of a heterotrimeric complex consisting of the 150 kDa TGF‐β1 binding protein, the type II receptor, and the type I receptor. This technique also demonstrated the occurrence of types I and II heterodimers and type I homodimers of TGF‐β receptors on keratinocytes, supporting the heterotetrameric model of TGF‐β signalling proposed using mutant cells and cells transfected to overexpress these receptors. The keratinocytes responded to TGF‐β by markedly downregulating all four TGF‐β binding proteins and by potently inhibiting DNA synthesis. The demonstration that the 150 kDa GPI‐anchored TGF‐β1 binding protein forms a heteromeric complex with the TGF‐β signalling receptors suggests that this GPI‐anchored protein may modify TGF‐β signalling in human keratinocytes. J. Cell. Biochem. 70:573–586, 1998. © 1998 Wiley‐Liss, Inc.