title: TGF-beta control of cell proliferation.
abstract: This article focuses on recent findings that the type V TGF-beta receptor (TbetaR-V), which co-expresses with other TGF-beta receptors (TbetaR-I, TbetaR-II, and TbetaR-III) in all normal cell types studied, is involved in growth inhibition by IGFBP-3 and TGF-beta and that TGF-beta activity is regulated by two distinct endocytic pathways (clathrin- and caveolar/lipid-raft-mediated). TGF-beta is a potent growth inhibitor for most cell types, including epithelial and endothelial cells. The signaling by which TGF-beta controls cell proliferation is not well understood. Many lines of evidence indicate that other signaling pathways, in addition to the prominent TbetaR-I/TbetaR-II/Smad2/3/4 signaling cascade, are required for mediating TGF-beta-induced growth inhibition. Recent studies revealed that TbetaR-V, which is identical to LRP-1, mediates IGF-independent growth inhibition by IGFBP-3 and mediates TGF-beta-induced growth inhibition in concert with TbetaR-I and TbetaR-II. In addition, IRS proteins and a Ser/Thr-specific protein phosphatase(s) are involved in the TbetaR-V-mediated growth inhibitory signaling cascade. The TbetaR-V signaling cascade appears to cross-talk with the TbetaR-I/TbetaR-II, insulin receptor (IR), IGF-I receptor (IGF-IR), integrin and c-Met signaling cascades. Attenuation or loss of the TbetaR-V signaling cascade may enable carcinoma cells to escape from TGF-beta growth control and may contribute to the aggressiveness and invasiveness of these cells via promoting epithelial-to-mesenchymal transdifferentiation (EMT). Finally, the ratio of TGF-beta binding to TbetaR-II and TbetaR-I is a signal controlling TGF-beta partitioning between two distinct endocytosis pathways and resultant TGF-beta responsiveness. These recent studies have provided new insights into the molecular mechanisms underlying TGF-beta-induced cellular growth inhibition, cross-talk between the TbetaR-V and other signaling cascades, the signal that controls TGF-beta responsiveness and the role of TbetaR-V in tumorigenesis.
authors.affiliation: Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, St. Louis, Missouri 63104, USA. huangss@slu.edu
authors.forename: Shuan S
authors.initials: SS
authors.lastname: Huang
authors.forename: Jung S
authors.initials: JS
authors.lastname: Huang
mesh_terms: D000818:Animals; D049109:Cell Proliferation / Q000187:drug effects*; D004705:Endocytosis / Q000502:physiology; D055504:Insulin Receptor Substrate Proteins; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000378:metabolism; D010750:Phosphoproteins / Q000378:metabolism; D020033:Protein Isoforms / Q000378:metabolism; D018125:Receptors, Transforming Growth Factor beta / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*; D016212:Transforming Growth Factor beta / Q000494:pharmacology*
chemical_list: D055504:Insulin Receptor Substrate Proteins; D018972:Insulin-Like Growth Factor Binding Protein 3; D010750:Phosphoproteins; D020033:Protein Isoforms; D018125:Receptors, Transforming Growth Factor beta; D016212:Transforming Growth Factor beta