Lipid synthesis in testis: GPAT2 activity and expression

CATTANEO, E.R.; PELLON-MAISON, M.; BRENNER, R.R.; COLEMAN, R.A.; GONZALEZ-BARO, M.R.

Mar del Plata, Argentina

Congreso; XLIII Reunión Anual de la Sociedad Argentina de Investigación Bioquímica (SAIB); 2007

Sociedad Argentina de Investigacion Bioquimica y Biologia Molecular

Four different isoforms of glycerol-3-phosphate acyltransferase have been described in mammalian cells. GPATs 1 and 2 are located in the mitochondria. GPAT2 is sensitive to sulfhydryl reagents (NEM), has no acyl-CoA substrate preference and was first recognized in liver from GPAT1 null mice. GPAT2 cDNA cloned from mouse testis encodes a protein of 797 aa (89 kDa) and 27% aa identity to GPAT1. Because GPAT2 mRNA expression was very high in testis, the aim of this study was to characterize the GPAT2 activity in highly purified mitochondria from wild type mouse and rat testis. The purity of the subcellular fractions was confirmed by marker enzymes and proteins. For the first time, NEM-sensitive GPAT activity was detected in purified mitochondria from wild type mouse and rat testes.We assume that this activity corresponds to the GPAT2 isoform because GPAT2 mRNA expression was more than 10 times higher in testis than in any other tissue. Although GPAT1 mRNAwas 5-fold higher in liver than in testis, NEM-resistantGPAT activity in testis was 3-fold higher than in purified mitochondria from liver. In contrast, GPAT2 mRNA was 50-fold higher in testis than in liver, and, consistently, the NEM-sensitive activity in purified mitochondria was high in testis and was not detectable inliver.