Depolarisation induces rapid and transient formation of intracellular sphingosine‐1‐phosphate

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Abstract
Formation of sphingosine‐1‐phosphate (SPP) by sphingosine kinase serves as a signalling pathway for various membrane receptors. Here, we show that membrane depolarisation is another mechanism by which this pathway can be activated. Formation of [3H]SPP as well as levels of endogenous SPP were rapidly and transiently increased in PC12 pheochromocytoma cells depolarised with high KCl. Time course and maximum were similar to those induced by bradykinin. Depolarisation‐induced SPP production was also observed in RINm5F insulinoma cells, dependent on extracellular Ca2+ and fully suppressed by verapamil, thus apparently caused by Ca2+ influx via voltage‐gated Ca2+ channels. Studies with sphingosine kinase inhibitors and overexpression of sphingosine kinase revealed a partial contribution of this pathway to depolarisation‐induced noradrenaline release and Ca2+ increase.