Phosphoinositide synthesis in bovine rod outer segments.
Phosphoinositide turnover has been implicated in signal transduction in a variety of cells, including photoreceptors. We demonstrate here the presence of a complete pathway for rapid synthesis of phosphoinositides in isolated bovine retinal rod outer segments (ROS) free of microsomal contaminants. Synthesis was measured by the incorporation of label from radioactive precursors, [gamma-32P]ATP and [3H]inositol. [gamma-32P]ATP also produced large amounts of labeled phosphatidic acid. Incorporation of [3H]inositol required CTP and Mn2+. Mn2+ increased 32P incorporation into phosphatidylinositol 4-phosphate, while spermine increased phosphoinositide labeling generally. ROS that had been washed to remove soluble and peripheral proteins incorporated less label than unwashed ROS into phosphatidic acid and phosphatidylinositol. No effects of light were detected. Inhibitory effects of high concentrations of nonhydrolyzable GTP analogues were probably due to competition with ATP.
Gehm
B D
BD
Department of Biochemistry, Michigan State University, East Lansing 48824.
Mc Connell
D G
DG
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D002417:Cattle; D003570:Cytidine Triphosphate / Q000494:pharmacology; D066298:In Vitro Techniques; D007294:Inositol / Q000378:metabolism; D008670:Metals / Q000494:pharmacology; D008861:Microsomes / Q000378:metabolism; D010716:Phosphatidylinositols / Q000096:biosynthesis*; D010786:Photoreceptor Cells / Q000378:metabolism*; D012374:Rod Cell Outer Segment / Q000187:drug effects / Q000378:metabolism*; D013096:Spermine / Q000494:pharmacology
D008670:Metals; D010716:Phosphatidylinositols; D013096:Spermine; D007294:Inositol; D003570:Cytidine Triphosphate; D000255:Adenosine Triphosphate