Diacylglycerol kinase epsilon in bovine and rat photoreceptor cells. Light-dependent distribution in photoreceptor cells

作者：Natalini Paola M; Zulian Sandra E; Ilincheta de Boschero Monica G; Giusto Norma M^*

来源：Experimental Eye Research, 2013, 112: 139-150.

DOI：10.1016/j.exer.2013.04.012

• diacylglycerol kinase epsilon
• vertebrate photoreceptor cells
• rod outer segment
• light-dependent distribution
• retina
• phosphatidic acid
• diacylglycerol
• lipid second messenger

The present study shows the selective light-dependent distribution of 1,2-diacylglycerol kinase epsilon (DAGK epsilon) in photoreceptor cells from bovine and albino rat retina. Immunofluorescence microscopy in isolated rod outer segments from bleached bovine retinas (BBROS) revealed a higher DAGK epsilon signal than that found in rod outer segments from dark-adapted bovine retinas (BDROS). The light-dependent outer segment localization of DAGK epsilon was also observed by immunohistochemistry in retinas from albino rats. DAGK activity, measured in terms of phosphatidic acid formation from a) [H-3]DAG and ATP in the presence of EGTA and R59022, a type I DAGK inhibitor, or b) [gamma-P-32]ATP and 1-stearoyl, 2-arachidonoylglycerol (SAG), was found to be significantly higher in BBROS than in BDROS. Higher light-dependent DAGK activity (condition b) was also found when ROS were isolated from dark-adapted rat retinas exposed to light. Western blot analysis of isolated ROS proteins from bovine and rat retinas confirmed that illumination increases DAGK epsilon content in the outer segments of these two species. Light-dependent DAGK epsilon localization in the outer segment was not observed when U73122, a phospholipase C inhibitor, was present prior to the exposure of rat eyecups (in situ model) to light. Furthermore, no increased PA synthesis from [H-3]DAG and ATP was observed in the presence of neomycin prior to the exposure of bovine eyecups to light. Interestingly, when BBROS were pre-phosphorylated with ATP in the presence of 1,2-dioctanoyl sn-glycerol (di-C8) or phorbol dibutyrate (PDBu) as PKC activation conditions, higher DAGK activity was observed than in dephosphorylated controls. Taken together, our findings suggest that the selective distribution of DAGK epsilon in photoreceptor cells is a light-dependent mechanism that promotes increased SAG removal and synthesis of 1-stearoyl, 2-arachidonoyl phosphatidic acid in the sensorial portion of this cell, thus demonstrating a novel mechanism of light-regulated DAGK activity in the photoreceptors of two vertebrate species.

• 出版日期2013-7