Molecular mechanism of the phospholipid synthesis activation by c-Fos

ANDRES M CARDOZO GIZZI; ADOLFO R. ALFONSO PECCHIO; RENNER ML; BEATRIZ LEONOR CAPUTTO

Rosario

Congreso; 50 Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2014

SAIB

The oncoprotein c-Fos activates phospholipid synthesis through a mechanism independent of its genomic AP-1 activity. To accomplish an overall activation of this synthesis, only key metabolic steps are positively affected. c-Fos is capable of increasing the activity of Phosphatidate Phosphohydrolase, CDP-diacylglycerol synthase and Phosphatidylinositol 4-Kinase II. The kinetic constant Vmax is increased in all the enzymes activated by c-Fos that were analyzed while no effect was seen on the Km (a measure of the substrate enzyme affinity). Furthermore, we have proved the activation in a purified in vitro system that contains only c-Fos, PAP1 enzyme and the substrate. In order to understand the mechanism of enzyme activation, we performed analysis of protein-protein interactions by Forster Resonance Energy Transfer (FRET). We have established a direct association specifically between c-Fos and the enzymes it activates; no association is observed between c-Fos and the enzymes it does not activate. Results point to a shared mechanism of phospholipid synthesis enzyme activation: c-Fos directly interacts with those whose metabolic steps it activates to satisfy cell phospholipid requirements such as membrane biogenesis. It also reinforces the concept of a protein capable of increasing pivotal enzymatic activities per se.