Fluoroaluminates mimic guanosine 5′-γ-thiotriphosphate in activating the polyphosphoinositide phosphodiesterase of hepatocyte membranes. Role for the guanine nucleotide regulatory protein Gp in signal transduction

Fluoride and guanosine 5'-gamma-thiotriphosphate (GTP gamma S) both activate the hepatocyte membrane polyphosphoinositide phosphodiesterase (PPI-pde) in a concentration-dependent manner. AlCl3 enhances the fluoride effect, supporting the concept that A1F4- is the active species. Analysis of the products of inositol lipid hydrolysis demonstrate that phosphatidylinositol bisphosphate is the major lipid to be hydrolysed. Guanosine 5'-beta-thiodiphosphate (GDP beta S) is an inhibitor of activation of PPI-pde by both fluoride and GTP gamma S. These observations suggest that the guanine nucleotide regulatory protein (termed Gp) bears a structural resemblance to the well-characterized G-proteins of the adenylate cyclase system and the cyclic GMP phosphodiesterase system in phototransduction.