DIVERSE GLYCEROLIPID SYNTHESIZING ENZYMES CONTRIBUTE TO THE DAILY RHYTHMS IN PHOSPHOLIPID SYNTHESIS

ACOSTA RODRIGUEZ, VICTORIA A.; MARQUEZ, S.; SALVADOR, G.A.; PASQUARÉ, S.J.; GORNE, LUCAS D.; GARBARINO-PICO, E.; GIUSTO, N.M.; GUIDO, MARIO E.

Mendoza

Congreso; 48 Annual Meeting Argentine Society for Biochemistry and Molecular Biology; 2012

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular - SAIB -

Circadian clocks regulate biochemical processes including lipid metabolism and their disruption may lead to metabolic disorders such as obesity, diabetes, etc. We have previously shown that the 32P-phospholipid synthesis oscillates daily in synchronized fibroblasts; however, little is known about the temporal regulation of glycerophospholipid (GPL) synthesis. We found a circadian change in the incorporation of 3H-glycerol into total GPLs in arrested NIH3T3 cells synchronized with a 2 h-serum shock with lowest levels at 28 and 56 h. A daily variation was also seen in the activity of GPL-synthesizing and -remodeling enzymes phosphatidate phosphohydrolase 1 (PAP1) and lysophospholipid acyltransferases (LPLAT), respectively with distinct and opposite profiles. We further investigated the temporal regulation of phosphatidylcholine (PC) synthesis through the Kennedy pathway with Choline Kinase (ChoK) and CTP:phosphocholine cytidylyltranferase (CCT) as key enzymes. PC labeling exhibited a daily variation, and maximum levels were accompanied by a brief increase in CCT activity peaking at 6 and 35 h together with the oscillation of ChoK mRNA (a isoform) and activity. Our results demonstrate that synchronized fibroblasts undergo a temporal regulation in the synthesis and remodeling of GPLs and particularly of PC involving concerted changes in specific enzyme activities and/or mRNA expression.