The G protein-coupled estrogen receptor-1, GPER-1, coordinates fibronectin (FN) matrix assembly and release of heparan-bound epidermal growth factor (HB-EGF). This mechanism of action results in the recruitment of FN-engaged integrin α5β1 to fibrillar adhesions and the formation of integrin α5β1-Shc adaptor protein complexes. Here, we show that GPER-1 stimulation of murine 4 T1 or human SKBR3 breast cancer cells with 17β-estradiol (E2β) promotes the formation of focal adhesions and actin stress fibers and results in increased cellular adhesion and haptotaxis on FN, but not collagen. These actions are also induced by the xenoestrogen, bisphenol A, and the estrogen receptor (ER) antagonist, ICI 182, 780, but not the inactive stereoisomer, 17α-estradiol (E2α). In addition, we show that GPER-1 stimulation of breast cancer cells allows for FN-dependent, anchorage-independent growth and FN fibril formation in “hanging drop” assays, indicating that these GPER-1-mediated actions occur independently of adhesion to solid substrata. Stable expression of Shc mutant Y317F lacking its primary tyrosyl phosphorylation site disrupts E2β-induced focal adhesion and actin stress fiber formation and abolishes E2β-enhanced haptotaxis on FN and anchorage-dependent growth. Collectively, these data demonstrate that E2β action via GPER-1 enhances cellular adhesivity and FN matrix assembly and allows for anchorage-independent growth, cellular events that may allow for cellular survival, and tumor progression.
G‐protein estrogen receptor (GPER) positively associates with breast tumor progression, including tumor size and extramammary metastases. Via activation of integrin α5β1, GPER coordinates two cellular activities that facilitate breast tumor cell survival, fibronectin matrix assembly and the release of membrane‐tethered proHB‐EGF. RNAi knockdown of either MMP‐3 or PTPN12 inhibits both of these cellular processes regulated by effectors on opposing sides of the plasma membrane. Moreover, PTPN12 knockdown also negatively influences the ability of GPER to promote the centripetal movement of integrin α5β1 from focal to fibrillar adhesions, the site of fibronectin fibril formation, and results in the accumulation of the Shc adaptor protein on the cytoplasmic tail of integrin α5β1. In support of the concept that PTPN12 is necessary for activated integrin α5β1, SKBR3 cells stably expressing PTPN12 shRNA showed reduced formation of anchorage independent colonies. Efforts to further understand the influence of PTPN12 knockdown on “inside‐out” integrin signaling events required for EGFR transactivation are underway with particular interest in understanding its impact on MMP‐3 activation and HB‐EGF release. A better understand of the molecular mechanism of GPER induced EGFR transactivation may lead to the development of future therapeutic strategies that target this receptor and prevent metastatic disease.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.