Functional characterization of P2Y1 versus P2X receptors in RBA-2 astrocytes: Elucidate the roles of ATP release and protein kinase C
✍ Scribed by Ju-Yun Weng; Tsan-Ting Hsu; Synthia H. Sun
- Publisher
- John Wiley and Sons
- Year
- 2008
- Tongue
- English
- Weight
- 483 KB
- Volume
- 104
- Category
- Article
- ISSN
- 0730-2312
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✦ Synopsis
Abstract
A physiological concentration of extracellular ATP stimulated biphasic Ca^2+^ signal, and the Ca^2+^ transient was decreased and the Ca^2+^ sustain was eliminated immediately after removal of ATP and Ca^2+^ in RBA‐2 astrocytes. Reintroduction of Ca^2+^ induced Ca^2+^ sustain. Stimulation of P2Y~1~ receptors with 2‐methylthioadenosine 5′‐diphosphate (2MeSADP) also induced a biphasic Ca^2+^ signaling and the Ca^2+^ sustains were eliminated using Ca^2+^‐free buffer. The 2MeSADP‐mediated biphasic Ca^2+^ signals were inhibited by phospholipase C (PLC) inhibitor U73122, and completely blocked by P2Y~1~ selective antagonist MRS2179 and protein kinase C (PKC) activator phorbol 12‐myristate 13‐acetate (PMA) whereas enhanced by PKC inhibitors GF109203X and Go6979. Inhibition of capacitative Ca^2+^ entry (CCE) decreased the Ca^2+^‐induced Ca^2+^ entry; nevertheless, ATP further enhanced the Ca^2+^‐induced Ca^2+^ entry in the intracellular Ca^2+^ store‐emptied and CCE‐inhibited cells indicating that ATP stimulated Ca^2+^ entry via CCE and ionotropic P2X receptors. Furthermore, the 2MeSADP‐induced Ca^2+^ sustain was eliminated by apyrase but potentiated by P2X~4~ allosteric effector ivermectin (IVM). The agonist ADPβS stimulated a lesser P2Y~1~‐mediated Ca^2+^ signal and caused a two‐fold increase in ATP release but that were not affected by IVM whereas inhibited by PMA, PLC inhibitor ET‐18‐OCH~3~ and phospholipase D (PLD) inhibitor D609, and enhanced by removal of intra‐ or extracellular Ca^2+^. Taken together, the P2Y~1~‐mediated Ca^2+^ sustain was at least in part via P2X receptors activated by the P2Y~1~‐induced ATP release, and PKC played a pivotal role in desensitization of P2Y~1~ receptors in RBA‐2 astrocytes. J. Cell. Biochem. 104: 554–567, 2008. © 2007 Wiley‐Liss, Inc.