CONICET | Buscador de Institutos y Recursos Humanos

Sphingosine Kinase (SK) is a key regulator enzyme that regulates sphingosine-1-Phosphate (S1P) synthesis. S1P is a lipid second messenger that regulates several cellular processes. It has been characterized as a dual function signaling molecule, with the ability to activate in a selective manner different effectors on the basis of subcellular localization. S-1-P exerts its actions extracellularly by binding to S-1-P receptors (S1PRs), which are differentially expressed based on tissue type. The S1PRs regulate diverse biological functions ranging from differentiation, migration, and mitogenesis to effector functions, such as proinflammatory mediator synthesis. Alternatively, S-1-P can act through unidentified intracellular targets, resulting in regulation of cell growth and survival, cytoskeletal changes, cellular motility. For these reason we evaluate the importance of SK activity in renal epithelial cell cycle modulation. For this, MDCK cells were cultured at low density, to allow cell cycle progression and were treated with D,L-threo-dihydrosphingosine (tDHS), a SK1 inhibitor. SK inhibition induced a decrease in cell number after 24 h of incubation with no alteration in cell viability. Besides the treatment for 24 h with an tDHS caused a clear cell cycle arrest in G0/G1 phase with cyclinD1 accumulation. Cell cycle arrest was acompanied with hipophosphorilation of Rb protein. Interestingly this effect was independent of ceramide accumulation and was not reverted by exogenous S1P. These results suggest that intracellular S1P was involved in cell cycle arrest. Morover SK inhibition induced an increase of the cell proportion in G0 phases after of tDHS for 48 and 72 h, suggesting that S1P was selected not only in cell cycle arrest also in G0 cell quiescent induction. This work related S1P whit a possible cell cycle arrest and differentiation.