title: Src phosphorylates Tyr284 in TGF-beta type II receptor and regulates TGF-beta stimulation of p38 MAPK during breast cancer cell proliferation and invasion.
abstract: Genetic and epigenetic events often negate the cytostatic function of transforming growth factor-beta (TGF-beta) in mammary epithelial cells (MEC), which ultimately enables malignant MECs to proliferate, invade, and metastasize when stimulated by TGF-beta. The molecular mechanisms underlying this phenotypic conversion of TGF-beta function during mammary tumorigenesis remain poorly defined. We previously established alpha(v)beta(3) integrin and Src as essential mediators of mitogen-activated protein kinase (MAPK) activation, invasion, and epithelial-to-mesenchymal transition stimulated by TGF-beta in normal and malignant MECs. Mechanistically, beta(3) integrin interacted physically with the TGF-beta type II receptor (TbetaR-II), leading to its tyrosine phosphorylation by Src and the initiation of oncogenic signaling by TGF-beta. We now show herein that Src phosphorylated TbetaR-II on Y284 both in vitro and in vivo. Interestingly, although the expression of Y284F-TbetaR-II mutants in breast cancer cells had no effect on TGF-beta stimulation of Smad2/3, this TbetaR-II mutant completely abrogated p38 MAPK activation by TGF-beta. Accordingly, Src-mediated phosphorylation of Y284 coordinated the docking of the SH2 domains of growth factor receptor binding protein 2 (Grb2) and Src homology domain 2 containing (Shc) TbetaR-II, thereby associating these adapter proteins to MAPK activation by TGF-beta. Importantly, Y284F-TbetaR-II mutants also abrogated breast cancer cell invasion induced by alpha(v)beta(3) integrin and TGF-beta as well as partially restored their cytostatic response to TGF-beta. Our findings have identified a novel alpha(v)beta(3) integrin/Src/Y284/TbetaR-II signaling axis that promotes oncogenic signaling by TGF-beta in malignant MECs and suggest that antagonizing this signaling axis may one day prove beneficial in treating patients with metastatic breast cancers.
authors: Department of Pharmacology, University of Colorado Health Sciences Center, 12801 East 17th Avenue, Aurora, CO 80045, USA.
authors: Amy J
authors: AJ
authors: Galliher
authors: William P
authors: WP
authors: Schiemann
mesh_terms: D048868:Adaptor Proteins, Signal Transducing / Q000378:metabolism; D000818:Animals; D048708:Cell Growth Processes / Q000502:physiology; D004789:Enzyme Activation; D051380:GRB2 Adaptor Protein / Q000378:metabolism; D006801:Humans; D039302:Integrin alphaVbeta3 / Q000378:metabolism; D020935:MAP Kinase Signaling System; D008325:Mammary Neoplasms, Experimental / Q000201:enzymology / Q000378:metabolism* / Q000473:pathology; D051379:Mice; D009361:Neoplasm Invasiveness; D010766:Phosphorylation; D017346:Protein Serine-Threonine Kinases; D000077294:Receptor, Transforming Growth Factor-beta Type II; D018125:Receptors, Transforming Growth Factor beta / Q000378:metabolism*; D055765:Shc Signaling Adaptor Proteins; D051899:Smad2 Protein / Q000378:metabolism; D051900:Smad3 Protein / Q000378:metabolism; D000071425:Src Homology 2 Domain-Containing, Transforming Protein 1; D016212:Transforming Growth Factor beta / Q000378:metabolism*; D048051:p38 Mitogen-Activated Protein Kinases / Q000378:metabolism*; D018909:src Homology Domains; D019061:src-Family Kinases / Q000378:metabolism*
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D051380:GRB2 Adaptor Protein; D039302:Integrin alphaVbeta3; D018125:Receptors, Transforming Growth Factor beta; C528024:SHC1 protein, human; D055765:Shc Signaling Adaptor Proteins; C528034:Shc1 protein, mouse; D051899:Smad2 Protein; D051900:Smad3 Protein; D000071425:Src Homology 2 Domain-Containing, Transforming Protein 1; D016212:Transforming Growth Factor beta; D019061:src-Family Kinases; D017346:Protein Serine-Threonine Kinases; D048051:p38 Mitogen-Activated Protein Kinases; D000077294:Receptor, Transforming Growth Factor-beta Type II