Regulation of cell proliferation by G proteins

G Proteins provide signal transduction mechanisms to seven transmembrane receptors. Recent studies have indicated that the alpha-subunits as well as the beta gamma-subunits of these proteins regulate several critical signaling pathways involved in cell proliferation, differentiation and apoptosis. Of the 17 alpha-subunits that have been cloned, at least ten of them have been shown to couple mitogenic signaling in fibroblast cells. Activating mutations in G alpha(s), G alpha(12), and G alpha(12) have been correlated with different types of tumors. In addition, the ability of the beta gamma-subunits to activate mitogenic pathways in different cell-types has been defined. The present review briefly summarizes the diverse and novel signaling pathways regulated by the alpha- as well as the beta gamma-subunits of G proteins in regulating cell proliferation.