Abstract
The type V transforming growth factor beta (TGF-beta) is a 400-kDa nonproteoglycan membrane protein that co-expresses with the type I, type II, and type III TGF-beta receptors in most cell types. The type V TGF-beta receptor exhibits a Ser/Thr-specific protein kinase activity with distinct substrate specificity (Liu, Q., Huang, S. S., and Huang, J. (1994) J. Biol. Chem. 269, 9221-9226). In mink lung epithelial cells, the type V TGF-beta receptor was found to form heterocomplexes with the type I TGF-beta receptor by immunoprecipitation with antiserum to the type V TGF-beta receptor after 125I-TGF-beta affinity labeling or Trans35S-label metabolic labeling of the cells. The kinase activity of the type V TGF-beta receptor was stimulated after treatment of mink lung epithelial cells with TGF-beta. TGF-beta stimulation resulted in the growth inhibition of wild-type mink lung epithelial cells and to a lesser extent of the type I and type II TGF-beta receptor-defective mutants, although higher concentrations of TGF-beta were required for the growth inhibition of these mutants. TGF-beta was unable to induce growth inhibition in human colorectal carcinoma cells lacking the type V TGF-beta receptor but expressing the type I and type II TGF-beta receptors. These results suggest that the type V TGF-beta receptor can mediate the TGF-beta-induced growth inhibitory response in the absence of the type I or type II TGF-beta receptor. These results also support the hypothesis that loss of the type V TGF-beta receptor may contribute to the malignancy of certain carcinoma cells.
Highlights
Transforming growth factor  (TGF-)1 is the most potent polypeptide growth inhibitor for epithelial cells and plays an important role in the pathophysiology of epithelial cells in human and other species [1,2,3]
Western blot analysis of the type V TGF- receptor purified from bovine liver plasma membranes (A) and TGF-1stimulated phosphorylation (B) and TGF-1-stimulated kinase activity (C) of the type V TGF- receptor in mink lung epithelial cells
insulin-like growth factor binding protein 3 (IGFBP-3) is a nonphysiological substrate for the type V TGF- receptor but contains several SXE motifs that serve as the phosphorylation sites for the type V TGF- receptor kinase activity [7]
Summary
Transforming growth factor  (TGF-)1 is the most potent polypeptide growth inhibitor for epithelial cells and plays an important role in the pathophysiology of epithelial cells in human and other species [1,2,3]. Immunocomplex Kinase Assay of the Type V TGF- Receptor—The immunoprecipitation of the type V TGF- receptor in mink lung epithelial cells treated with and without 0.1 nM TGF-1 at 0 °C for 30 min was carried out in 0.1% Triton X-100 as described above, except the cells were not metabolically labeled.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
