A new implication of c-Fos in phospholipid synthesis: Activation of PAP1 activity

CARDOZO GIZZI AM, RENNER ML, CAPUTTO BL.

Mendoza

Congreso; XLVIII Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2012

We have previously shown that c-Fos activates phospholipid synthesis through a mechanism independent of its genomic AP-1 activity. To accomplish an overall activation of the synthesis, only particular enzymatic activities are positively affected. In this work, we showed that recombinant c-Fos increases in vitro Phosphatidate Phosphohidrolase (PAP1) activity from cellular homogenates. PAP1 catalyzes Phosphatidic Acid conversion to Diacylglicerol, both of which have essential functions in signaling cascades and lipid biosynthetic pathways. The regulation of PAP1 activity may govern the pathways by which phospholipids are synthesized and control the cellular contents of important signaling lipids. To precisely characterize the phenomenon, we used purified Lipin1 (responsible of most PAP1 activity in mammals) obtained recombinant from E. Coli. Lipin1 activity was measured with or without c-Fos in PA/Triton X-100 mixed micelles and the kinetic parameters determined. Finally, we established through FRET-FLIM microscopy there was a direct physical association between c-Fos and Lipin1 in cells. Results support our general hypothesis: c-Fos directly interacts with the phospholipid synthesis enzymes whose metabolic steps it activates, and highlight the role of c-Fos in events requiring large amounts of phospholipid synthesis.