guanosine-monophosphate and phosphatidylinositol-4-phosphate

Incorporation of 32P from [gamma-32P]ATP into phosphatidylinositol 4,5-bisphosphate (PIP2) in membranes isolated from rat brain was enhanced in a concentration-dependent manner by the GTP analogue guanosine 5'-O-(thio)triphosphate (GTP gamma S). In contrast, neither the labeling of phosphatidylinositol 4-phosphate in the same membranes nor PIP kinase activity in the soluble fraction were stimulated by GTP gamma S. Synthesis of [32P]PIP2 was not stimulated by GTP, GDP, GMP, or ATP; however, the stimulatory effects of GTP gamma S were antagonized by GTP, GDP, and guanosine 5'-O-thiodiphosphate (GDP beta S). The nucleotide-stimulated labeling of PIP2 was not due to protection of [gamma-32P] ATP from hydrolysis, activation of PIP2 hydrolysis by phospholipase C, or inhibition of PIP2 hydrolysis by its phosphomonoesterase. Therefore, phosphatidylinositol 4-phosphate kinase activity in brain membranes may be regulated by a guanine nucleotide regulatory protein. This system may enhance the resynthesis of PIP2 following receptor-mediated activation of phospholipase C.

Topics: Adenosine Triphosphate; Animals; Brain; Cell Membrane; GTP-Binding Proteins; Guanosine 5'-O-(3-Thiotriphosphate); Guanosine Diphosphate; Guanosine Monophosphate; Guanosine Triphosphate; Magnesium; Male; Phosphatidylinositol 4,5-Diphosphate; Phosphatidylinositol Phosphates; Phosphatidylinositols; Phosphorylation; Phosphotransferases; Phosphotransferases (Alcohol Group Acceptor); Rats; Thionucleotides