An inhibitor of diacylglycerol-activated protein kinase Cs blocks the effects of a diacylglycerol lipase inhibitor, U-57908, on the light-dependent renewal of crab rhabdoms in vitro

Abstract

1. We have previously shown that the regrowth of R1-6 rhabdoms of a crab, Leptograpsus, in darkness after brief illumination is enhanced by an inhibitor of diacylglycerol lipases, U-57908 2. We now show that the effects of U-57908 are blocked by a specific inhibitor of diacylglycerol activation of protein kinase Cs, AMG-C16. However, AMG-C16 alone has no effect when results are compared to Controls in the absence of either drug. 3. After 4 h in darkness, the sizes of R1-6 rhabdoms start to increase, however retinas are treated with drugs. We presume the existence of several regulatory pathways, one of which may relate to the endogenous circadian rhythms that our previous studies have implied. 4. We have previously demonstrated that perturbation of rhabdom renewal by drugs that affect the phosphorylation/dephosphorylation of proteins might implicate factors that regulate the transcription of rhabdomeral membrane precursors. The relevant drugs provoke the differentiation of photoreceptor nuclear envelopes to endoplasmic reticulum which appears to enter the pathway for rhabdomeral renewal demonstrated by Stowe (1980). AMG-C16 blocks such nuclear envelope events. 5. Any system that demands precise regulation of physiological events if it is to function effectively can be expected to rest upon several interlocked regulatory pathways, as our cumulative results from crab retinas imply.