Differential effects on intracellular calcium levels, PKC translocation and cell differentiation by sphingosylphosphorylcholine in neuroblastoma
Abstract number: P4.1-09
Diaz-Puig E., Miguel B.G., Mata F., Catalan R.E., Martinez A.M.
Bioquimica y Biología Molecular I, Fac. Biología, Universidad Complutense de Madrid, Madrid Biologia Molecular, Centro de Biologia Molecular Severo Ochoa, Universidad Autonoma de Madrid, Madrid, Spain. E-mail: neuro@bbm1.ucm.es
Sphyngolipid derivatives represent a new class of second messengers able to mediate numerous cellular processes. Sphingosylphosphorylcholine (SPC), the N-deacylated derivative of sphingomyelin, has been shown to possess a wide spectrum of biological activity. SPC elicits release of calcium from intracellular stores. Although sphingolipid derivatives are abundant in the nervous system, the mechanisms of these compounds for mobilizing calcium has not been characterized. In the present study, we have investigated the mechanism of action of SPC, and its structurally related sphingosine (SPH) and sphingosine-1-phosphate (S1P) on calcium release in neuroblastoma Neuro 2a cells. Cells were loaded with Fura 2AM and changes in calcium concentration by sphingolipid derivative treatment were monitored by fluorimetry. Cell stimulation with SPC, in the presence or the absence of external calcium, led to a dose-dependent increase in cytosolic calcium concentration. However, S1P had little effect and SPH had no effect on intracellular calcium levels. SPC-induced calcium release was partially inhibited in the presence of nimodipine. This finding may suggest an involvement of L-type calcium channels in SPC releasing calcium from the intracellular stores. In agreement with previous data reported by us in synaptosomes, SPC could to act through a specific intracellular sphingolipid-gated nimodipine sensitive calcium channel. We have also investigated the action of SPC on PKC isozymes redistribution. Isozymes were analyzed by immunoblotting using specific PKC antibodies. We must point out that SPC failed to increase translocation of calcium-dependent PKC isozymes. However SPC evoked the translocation of calcium-independent PKC d and PKC zetaisozymes. Translocation of PKC zeta was inhibited by wortmannin treatment, indicating that the activation of phosphatidylinositol 3-kinase is required. This finding appear to be related with the inhibition of cell differentiation evoked by SPC in neuroblastoma Neuro 2a cells. In conclusion, SPC-induced translocation of PKC isozymes appears to be independent of calcium mobilization, and may contribute to a decrease of cell differentiation.
| Date: |
01/08/2007
|
| Time: |
00:00-00:00
|
| Session name: |
XXIst ISTH Congress |
| Subject: |
4.1. Cell physiology and lipid signaling |
| Location: |
Oxford, UK |
| Presentation type: |
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