Modulation of phosphatidylinositol-4,5-bisphosphate hydrolysis in rat aorta by guanine nucleotides, calcium and magnesium |
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| Authors: | B L Roth |
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| Affiliation: | 1. UR UPJV 7517, MP3CV, CURS, Université de Picardie Jules Verne, Amiens, France;2. Department of Nephrology Dialysis and Transplantation, Amiens University Hospital, Amiens, France;3. Department of Immunology, Amiens University Hospital, Amiens, France;4. Department of Molecular Oncobiology, Amiens University Hospital, 80054, France;5. EA4666 – HEMATIM, CURS, Picardie Jules Verne University, Amiens 80054, France;6. Department of Cardiac Surgery, Amiens University Hospital, Amiens, France;7. Department of Biochemistry, Amiens University Hospital, Amiens, France;8. Department of Cardiology, Amiens University Hospital, Amiens, France |
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| Abstract: | Rat aortic smooth muscle homogenates and membrane preparations contain a phospholipase C which hydrolyzes phosphatidylinositol 4,5-biphosphate (PIP2). We discovered that guanyl-5'yl-imidodiphosphate (Gpp(NH)p) activated the hydrolysis of exogenous PIP2 but not of phosphatidylinositol (PI) in rat aortic membranes. Further, maximal Gpp(NH)p-dependent hydrolysis was dependent on physiological levels of calcium. Also, magnesium inhibited PIP2 hydrolysis and catalyzed the dephosphorylation of PIP2 to phosphatidylinositol-4-phosphate (PIP). The results imply that PIP2 is the primary substrate of the nucleotide-regulated phospholipase C in rat aorta and that calcium and magnesium are physiological regulators of this activity. |
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