The ceramide metabolism during MDCK cell differentiation is regulated by hypertonicity

LUCILA G. PESCIO; MONICA GISELA GERARDI; NORMA B. STERIN-SPEZIALE

Potrero de los Funes - San Luis

Congreso; XLVII Annual Meeting of the Argentine Society for Biochemistry and Molecular Biology Research (SAIB); 2011

SAIB

Recently, has been reported that stearic acid besides to enter the sphingolipid metabolic pathway as ceramide synthase (CerS) substrate can also be a substrate for serinepalmitoyl transferase (SPT). Hypertonicity is a condition of MDCK cell differentiation mediated by an increase of complex sphingolipids synthesis. Now we evaluate the ceramide (Cer) metabolism under iso or hypertonicity by submitting confluent MDCK cells to extracellular iso or hypertonic medium. Cer metabolism was determined using 14C-palmitic (PA) or 14C-stearic (SA) acids for 24h in the presence or absence of cicloserine (CS) or fumonisin B1 (FB1). Two bands of radioactive Cer were found in the TLC plate, a slower Cer1 (lower MW) and an upper Cer2 (higher MW). Hypertonicity induced an increase of both radioactive fatty acids in Cer1 and Cer2. Under isotonicity, both 14C-SA Cer1 and Cer2 were inhibited by FB1 but not by CS, while under hypertonicity both agents evoked inhibition. FB1 and CS decreased 14C-PA incorporation to Cer1 and Cer2 under isotonicity while CS had no effect under hypertonicity. The results demonstrated that 14C-PA enters the sphingolipid metabolic pathway as substrate of SPT and CerS under isotonicity but it is not substrate of SPT under hypertonicity. By contrast, 14C-SA enters the pathway only as substrate of CerS at basal conditions, but under hypertonicity can also be a substrate for SPT.