The sphingosine 1-phosphate receptor 5 and sphingosine kinases 1 and 2 are localised in centrosomes: Possible role in regulating cell division

We show here that the endogenous sphingosine 1-phosphate 5 receptor (S1P 5, a G protein coupled receptor (GPCR) whose natural ligand is sphingosine 1-phosphate (S1P)) and sphingosine kinases 1 and 2 (SK1 and SK2), which catalyse formation of S1P, are co-localised in the centrosome of mammalian cells, where they may participate in regulating mitosis. The centrosome is a site for active GTP–GDP cycling involving the G-protein, G i and tubulin, which are required for spindle pole organization and force generation during cell division. Therefore, the presence of S1P 5 (which normally functions as a plasma membrane guanine nucleotide exchange factor, GEF) and sphingosine kinases in the centrosome might suggest that S1P 5 may function as a ligand activated GEF in regulating G-protein-dependent spindle formation and mitosis. The addition of S1P to cells inhibits trafficking of S1P 5 to the centrosome, suggesting a dynamic shuttling endocytic mechanism controlled by ligand occupancy of cell surface receptor. We therefore propose that the centrosomal S1P 5 receptor might function as an intracellular target of S1P linked to regulation of mitosis.