TRANSFORMING GROWTH-FACTOR-BETA RECEPTORS ON HUMAN ENDOMETRIAL CELLS - IDENTIFICATION OF THE TYPE-I, TYPE-II, AND TYPE-III RECEPTORS AND GLYCOSYLPHOSPHATIDYLINOSITOL-ANCHORED TGF-BETA BINDING-PROTEINS

In the present study, we have characterized the cell surface receptors for transforming growth factor-beta (TGF-beta) on monolayer cultures of stromal cells prepared from human endometrial biopsies, and on a hu man endometrial epithelial cell line (RL95-2) using affinity cross-lin k labeling techniques. On the stromal cells, five TGF-beta binding pro teins were identified. Analysis of the sensitivity of these proteins t o dithiothreitol and phosphatidylinositol-specific phospholipase C, to gether with results from immunoprecipitations with antibodies against the type II and III TGF-beta receptors, confirmed that three of these binding proteins correspond to the cloned type I, II, and III TGF-beta receptors. The other two binding proteins observed exhibit the charac teristics of isoform-specific GPI-anchored TGF-beta binding proteins. On RL95-2 cells, three TGF-beta binding proteins, corresponding to the type I, II, and III TGF-beta receptors, were identified. The receptor s which we have characterized on endometrial cells are responsive to p hysiological concentrations of TGF-beta as demonstrated by the effect of TGF-beta on endometrial cell proliferation. Accordingly, these rece ptors have the potential to respond to the TGF-beta isoforms which hav e recently been detected in the endometrium in an autocrine and/or par acrine manner.