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

LUCILA G PESCIO; NICOLÁS O FAVALE; NORMA B STERIN-SPEZIALE

New Orleans- Lousiana-USA

Congreso; 2009 Experimental Biology; 2009

ASBMB

We have reported that hypertonicity induces MDCK cell differentiation by a GlucosylCeramide Synthase (GCS) dependent mechanism. Ceramide substrate can stem from the de novo synthesis or 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 or kept under isotonicity. GSL metabolism was determined by using 14C-Galactose (14C-Gal) and 14C-Palmitic Acid (14C-PA) as radioactive precursors in the presence of Fumonisin B1 (FB1), a ceramide synthase inhibitor, or Cycloserine (CS), a serine palmitoiltransferase inhibitor. Under isotonic conditions, 14C-Gal/GlcCer formation was FB1/CS sensitive, while hipertonicity induced a 14C-Gal/GlcCer increase partially sensitive to FB1 but not to CS. In control cultures, 14C-Gal/GlcCer accounted for 23% of total GSLs formed, while 14C-PA/GlcCer represented 44% of total GSLs. Over 24h of hypertonicity, 14C-Gal/GlcCer synthesis increased to 43%, while 14C-PA/GlcCer levels decreased significantly. The results suggest that the pool of Cer involved in the hypertonicity induced MDCK cell differentiation comes from the recycling but not from de novo synthesis pathway.