Regulation of brain phosphatidylinositol-4-phosphate kinase by GTP analogues. A potential role for guanine nucleotide regulatory proteins |
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Authors: | C D Smith K J Chang |
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Institution: | Division of Cell Biology, Burroughs Wellcome Co., Research Triangle Park, North Carolina 27709. |
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Abstract: | 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. |
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