Light-mediated breakdown of phosphatidylinositol-4,5-bisphosphate in isolated rod outer segments of frog photoreceptor.
When isolated frog (Rana catesbeiana) rod outer segment (ROS) fragments were incubated with [gamma-32P]ATP in the dark, only two of phospholipids, i.e., phosphatidylinositol-4-phosphate (DPI) and phosphatidic acid (PA) incorporated 32P. Upon addition of DPI (100 microM), considerable amount of 32P was incorporated into phosphatidylinositol-4,5-bisphosphate (TPI) as well as DPI and PA. Exposure of the ROS membranes to 5 sec flash of light resulted in approx. 20% decrease in the labeled TPI, while no significant effect was observed on DPI and PA. It was also observed that Ca2+ markedly accelerated the production of PA in the dark, while it reduced the 32P-incorporation into TPI. These results suggest that there is light- and/or Ca2+-dependent TPI-specific phospholipase C in ROS of vertebrate photoreceptors.
Hayashi
F
F
Amakawa
T
T
D000818:Animals; D002118:Calcium / Q000378:metabolism; D002855:Chromatography, Thin Layer; D008027:Light; D019269:Phosphatidylinositol 4,5-Diphosphate; D010716:Phosphatidylinositols / Q000378:metabolism; D010786:Photoreceptor Cells / Q000378:metabolism*; D011892:Rana catesbeiana; D012374:Rod Cell Outer Segment / Q000378:metabolism*
D019269:Phosphatidylinositol 4,5-Diphosphate; D010716:Phosphatidylinositols; D002118:Calcium