Requirement of integrin alpha5beta1 and tyrosine phosphorylation of Shc for proHB-EGF release by GPR30, a seven transmembrane receptor for estrogen
Estrogen acts via a seven transmembrane receptor (7TMR), GPR30, to stimulate an HB-EGF autocrine loop. Here, evidence is provided that integrin α5β1 is a necessary transmembrane signaling intermediary required for matrix metalloproteinase (MMP)-mediated release of proHB-EGF by GPR30. Estrogen stimulation of human SKBR3 breast cancer cells, which lack ERα and ERβ, resulted in recruitment of integrin α5β1 to focal adhesions, formation of actin stress fibers, and assembly of fibronectin (FN) fibrils. Expression of a GPR30 mutant in SKBR3 cells selectively abrogated FN matrix assembly and EGFR tyrosine phosphorylation by estrogen. Disruption of cytoskeletal integrity or inhibition of integrin α5β1 with function-blocking monoclonal antibodies or soluble RGD peptides similarly inhibited both processes. Via GPR30, estrogen induced Src-dependent, integrin α5β1-Shc complexes, whose formation required integrin clustering as shown using monomeric RGD peptides. Expression of Shc317Y/F, which lacks its predominant tyrosyl phosphorylation site, blocked GPR30-dependent EGFR transactivation but did not affect integrin α5β1-Shc association, recruitment of integrin α5β1 to focal adhesions or FN matrix assembly. Thus, estrogen promotes fibronectin matrix assembly and MMP-mediated release of membrane-tethered proHB-EGF via a convergent signaling mechanism. In addition, our results indicate a novel role for She as a signaling effector that triggers MMP-dependent growth factor release. ^
Biology, Molecular|Biology, Cell|Health Sciences, Oncology
Jeffrey Alan Quinn,
"Requirement of integrin alpha5beta1 and tyrosine phosphorylation of Shc for proHB-EGF release by GPR30, a seven transmembrane receptor for estrogen"
Dissertations and Master's Theses (Campus Access).