G-protein αolf subunit promotes cellular invasion, survival, and neuroendocrine differentiation in digestive and urogenital epithelial cells

The heterotrimeric G-protein subunits Galpha and Gbetagamma are involved in cellular transformation and tumor development. Here, we report the expression of Galphaolf in human digestive and urogenital epithelial cells using RT-PCR and Western blot. When the constitutively activated form of GalphaolfQ214L (AGalphaolf) was stably transfected in canine kidney MDCKts.src and human colonic HCT-8/S11 epithelial cells, it induced cellular invasion in collagen gels. AGalphaolf-mediated invasion was abrogated by agonists of platelet activating factor receptors (PAF-R) and protease-activated receptors -1 (PAR-1), pharmacological inhibitors of P13'-Kinase (wortmannin), protein kinase C (Go6976 and GF109203X), Rho GTPase (C3T exoenzyme), but was independent of protein kinase A. Accordingly, the invasive phenotype induced by AGalphaolf in HCT-8/S11 cells was reversed by the RhoA antagonist RhoD (G26V). Although AGaolf protected MDCKts.src cells against serum starvation-mediated apoptosis via a Rho-independent pathway, both AGalphaolf and Rho inhibition by C3T induced neuroendocrine-like differentiation linked to extensive neurite outgrowth and parathyroid hormone-related protein expression in human prostatic LNCaP-AGalphaolf cells. Since prostate tumors with a larger neuroendocrine cell population display increased invasiveness, persistent activation of the G-protein alphaolf may exert convergent adverse effects on cellular invasion and survival in solid tumors during the neoplastic progression towards metastasis.