Activation of bovine rod outer segment phospholipase C by arrestin

• Published in: The Journal of biological chemistry Vol. 267; no. 25; pp. 17977 - 17982
• Main Authors: GHALAYINI, A. J, ANDERSON, R. E
• Format: Journal Article
• Language: English
• Published: Bethesda, MD American Society for Biochemistry and Molecular Biology 05-09-1992
• Subjects: activation; Analytical, structural and metabolic biochemistry; Animals; Antigens - isolation & purification; Antigens - physiology; Arrestin; Biological and medical sciences; Cattle; Darkness; Electrophoresis, Polyacrylamide Gel; Enzyme Activation; Enzymes and enzyme inhibitors; Eye Proteins - isolation & purification; Eye Proteins - physiology; Fundamental and applied biological sciences. Psychology; Hydrolases; Kinetics; Light; Membrane Proteins - physiology; Models, Biological; Phosphatidylinositol 4,5-Diphosphate; Phosphatidylinositols - metabolism; phospholipase C; photoreceptors; Rod Cell Outer Segment - enzymology; rod outer segment membranes; Type C Phospholipases - metabolism; Binding protein; Vertebrata; Mammalia; Enzymatic activity; Bovine; Enzyme; Molecular interaction; Artiodactyla; Ungulata; Phospholipase C
• ISSN: 0021-9258; 1083-351X
• DOI: 10.1016/S0021-9258(19)37139-X

Phospholipase C (PLC) enzyme activity in rod outer segment (ROS) membranes bleached in the presence of ATP and GTP was assayed
using exogenously added [3H]phosphatidylinositol 4,5-bisphosphate vesicles as substrate. The addition of the soluble ROS protein
arrestin (also known as S-antigen or 48K protein) to ROS membranes activated PLC 2-3.4-fold. This activation was dose-dependent,
and maximal activation was observed at an arrestin concentration of congruent to 110-220 nM. PLC activation by arrestin was
dependent on ROS protein concentration and free Ca2+. Soluble PLC (s-PLC) enzyme activity present in hypotonic extracts of
bleached ROS was also activated 2-4-fold by arrestin. Maximum activation of s-PLC by arrestin was observed at free Ca2+ of
80 nM. Arrestin activation of s-PLC was not affected by urea-treated and extensively washed ROS membranes, suggesting that
rhodopsin was not required for the observed effect of arrestin on s-PLC. The results are indicative of a direct interaction
of arrestin with s-PLC, resulting in the activation of the latter. Based on these results and the documented binding of arrestin
to bleached and phosphorylated rhodopsin, a model for the light activation of PLC in ROS is proposed.