PHOSPHOLIPASE C-GAMMA(1) IN BOVINE ROD OUTER SEGMENTS - IMMUNOLOCALIZATION AND LIGHT-DEPENDENT BINDING TO MEMBRANES

We have investigated the isozymes of a phosphoinositide-specific phosp holipase C (PLC) in bovine retina using several monoclonal antisera to PLC beta(1), gamma(1), and delta(1). Immunoblot analysis showed that all three isozymes were present in the retina. Immunocytochemical loca lization in frozen bovine retina sections showed that PLC gamma(1) was present in the photoreceptor cell layer, outer plexiform cell layer, inner plexiform cell layer, and ganglion cell layer, Immunoreaction wi thin the photoreceptor cell layer was dependent on dark/light adaptati on slate of retinas, Immunoblot analysis of rod outer segments (ROS) w ith monoclonal or polyclonal antibodies to PLC gamma(1) showed the pre sence of an immunoreactive band of 140 kDa. ROS prepared from retinas light-adapted in vitro had more PLC gamma(1) on immunoblots than ROS f rom dark-adapted retinas. PLC enzyme activity in ROS from light-adapte d retinas was 69 and 46% higher than ROS from dark-adapted retinas, wh en assayed in the presence and absence of ATP, respectively. This incr ease in enzyme activity was observed at [Ca2+](free) between 0.32 and 100 mu M. These results demonstrate the presence of PLC gamma(1) in bo vine ROS and show that ROS prepared from light-adapted retinas are enr iched in this isozyme, suggesting that light may promote the binding o f this isozyme to bleached ROS membranes.