AN ACYL-CoA SYNTHETASE AS OBLIGATORY PROTEIN THE REGULATION OF ARACHIDONIC ACID RELEASE AND STEROIDOGENESIS.

CASTILLO F., MALOBERTI P., CASTILLA R., DUARTE A., CORNEJO MACIEL MF., PAZ C., PODESTÁ EJ.

Iguazú, Misiones, Argentina.

Congreso; XL Reunión Anual de la Sociedad Argentina de Investigación Bioquímica y Biología Molecular.; 2004

Sociedad Argentina de Investigación Bioquímica y Biología Molecular.

We have previously described in adrenal cells an inhibition of steroid synthesis using a specific inhibitor of an Arachidonic acid (AA)- preferring acyl-CoA synthetase (ACS4) that participates in concert action with an acyl-CoA thioesterase (MTE-I). Here in order to give a definitive answer to the role of ACS4 in steroidogenesis we knock down its expression using small interfering RNA (siRNA) methodology. Transfection of Leydig and adrenal cell lines with specific siRNA for ACS4 inhibits the enzyme expression analysed by western blot. This inhibition produced a decrease in hormone induced steroid synthesis (52.1 ± 4.8%; 51.6 ± 12.4% in adrenal and Leydig cells respectively) that was over come by exogenous AA addition. In order to address that ACS4 is working in concert action with MTE-I, we transfected cells with specific siRNA for ACS4 and MTE-I together in a dose that per se is not able to inhibit steroid synthesis. In this case, an inhibition of hormone steroidogenesis was observed. There was not effect of ACS4 siRNA on steroid synthesis when the cells were stimulated with a permeable analogue of cholesterol which by-pass the AA action on the rate-limiting step of steroidogenesis. These results strongly support the obligatory role of ACS4 in a new pathway of AA release involved in steroidogenesis.