INIBIOLP   05426
INSTITUTO DE INVESTIGACIONES BIOQUIMICAS DE LA PLATA "PROF. DR. RODOLFO R. BRENNER"
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
The mitochondrial NEM sensitive isoform of glycerol-3-phosphate acyltransferase (GPAT2) is active in wild type mouse and rat testis.
Autor/es:
CATTANEO, E.R.; PELLON-MAISON, M.; COLEMAN, R.A.; GONZALEZ-BARO, M.R.
Lugar:
Vermont Academy, Saxtons River, VT, USA
Reunión:
Congreso; FASEB Summer Research Conferences - Lipid Droplets: Metabolic Consequences of the Storage of Neutral Lipids.; 2007
Institución organizadora:
FASEB
Resumen:
Four different isoforms of glycerol-3-phosphate acyltransferase have been described in mammalian cells. Two of them are located in the ER (GPATs 3 and 4), and two in the mitochondria (GPATs 1 and 2).  The two mitochondrial isoform s can be differentiated by their sensitivity to sulfhydryl reagents (like N-ethylmaleimide, NEM) and fatty-acyl-substrate  preference. GPAT1 is NEM-resistant, and have preference for palmitoyl-CoA  whereas  GPAT2 is NEM-sensitive and has no acyl-CoA substrate preference and was first recognized in liver from GPAT1 null mice. GPAT2 cDNA has been cloned from mouse testis. The open reading frame encodes a protein of 797 amino acids with a calculated mass of 89 kDa and 27% amino acid identity to GPAT1. Over-expression studies have demonstrated that GPAT2 increased the incorporation of [14C]oleate into TAG and cholesterol esters.  Because GPAT2 mRNA expression was 50-fold higher in testis than in liver or brown adipose tissue, the aim of this study was to characterize the GPAT2 activity in highly purified mitochondria from wild type mouse and rat testis.  We obtained highly-purified mitochondrial fraction from wild-type (GPAT1+/+) mice as well as rats, using liver and testis as the starting material.  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 correspond to the GPAT2 isoform because GPAT2 mRNA expression was more than 10 times higher in testis than in any other tissue.  Although GPAT1 mRNA was 5-fold higher in liver than in testis, NEM-resistant GPAT 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 in liver.