Regulation of the sphingolipid metabolism during MDCK cell differentiation

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

Bilbao, Spain

Conferencia; 51st International Conference on the Bioscience of Lipids; 2010

ICBL

We have previously reported that hypertonicity induces MDCK cell differentiation by a glycosphingolipid (GSL) dependent mechanism. While GSLs predominate in the apical membrane, sphingomyelin (SM) is the major sphingolipid (SL) of the basolateral membrane. Ceramide (Cer) is the substrate for GSLs and SM, and it can stem from the de novo synthesis (Cycloserine (CS) sensitive) or the salvage pathway. Both pathways are Fumonisin B1 (FB1) sensitive. In this study we evaluate how the source of Cer is channelled to GSLs or SM under differentiation-induced condition. Confluent MDCK cells cultured under high NaCl concentration media (hypertonicity) or kept in isotonicity (control) were incubated in the presence or absence of CS, FB1 or PDMP (a GSL synthesis inhibitor), and SL metabolism was determined by using [14C]Palmitic Acid and [14C]Galactose as radioactive precursors. [14C]SM and [14C]GSLs showed basal levels, sensitive to CS and FB1, under control conditions. GSL synthesis was also inhibited by PDMP. At early stage of differentiation there was an increase in GSL synthesis CS- and FB1-resistant. However, [14C]SM showed an increase in an advanced stage of differentiation, which was CS- and FB1-sensitive and regulable by PDMP. The results demonstrate that under control conditions GSLs and SM shared the same pool of Cer, whereas under an early stage of differentiation Cer was channelled to GSL synthesis by the salvage pathway and, in later times of differentiation Cer was used to synthesize SM. From these results we conclude that hypertonicity displays a specific SL program required for the differentiation of MDCK cells.