The recycling ceramide is a precursor of hypertonicity induced increase of glucosylceramide síntesis

LUCILA G PESCIO; NORMA STERIN-SPEZIALE

Carlos Paz, Córdoba

Congreso; Reunión anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2008

SAIB

We have previously reported that hypertonicity induces MDCK cell differentiation by a GlucosylCeramide Synthase (GCS) dependent mechanism. GCS catalizes the conversion of Ceramide (Cer) to Glucosylceramide (GlcCer), and it can use as a substrate de novo synthetized Cer or Cer produced by the recycling pathway. In this study we evaluate the involvement of both pathways in the hypertonicity induced increase of Glycosphingolipid (GSL) synthesis. Confluent MDCK cells were submitted to high NaCl concentration for 24 h or kept in isotonicity as control cultures. GSL metabolism was determined by using 14C-Galactose (14C-Gal) and 14C-Palmitic Acid (14C-PA) as radioactive precursors to radiolabel total GlcCer or GlcCer formed from de novo synthesis pathway, respectively. Under isotonic conditions, 14C-Gal/GlcCer accounted for 23% of total GSLs formed, and the rest was equitatively distributed among LactosylCer, TrihexosylCer and GM3; while 14C-GlcCer accounted for 44% of total GSLs formed from 14C-PA. Over 24h of hypertonicity, GlcCer synthesis increased to 43% in the cultures incubated with 14C-Gal, while 14C-PA/GlcCer remained constant. The results suggest that the pool of Cer involved in hypertonicity induced MDCK cell differentiation comes from the recycling but not from de novo synthesis pathway.