Roles of protein kinase C in regulation of P2X₇ receptor-mediated calcium signalling of cultured type-2 astrocyte cell line, RBA-2

The role of protein kinase C (PKC) on regulation of P2X₇ receptor-mediated Ca²⁺ signalling was examined on RBA-2 astrocytes. Activation of PKC decreased the receptor-mediated Ca²⁺ signalling and the decrease was restored by PKC inhibitors. Down regulation of PKC also caused a decrease in the Ca²⁺ signalling. Thus PKC might play a dual role on the P2X₇ receptor signalling. Successive stimulation of the P2X₇ receptor induced a gradual decline of Ca²⁺ signalling but PKC inhibitors failed to restore the decline. Nevertheless, PMA stimulated translocation of PKC-α, -βI, -βII, and -γ, but only anti-PKC-γ co-immunoprecipitated the receptors. To examine the role of PKC-γ, Ca²⁺ signalling was measured by Ca²⁺ imaging. Our results revealed that the agonist-stimulated Ca²⁺ signalling were reduced in the cells that the transfection of either P2X₇ receptor or PKC-γ morpholino antisense oligo was identified. Thus, we concluded that PKC-γ interacted with P2X₇ receptor complex and positively regulated the receptor-mediated Ca²⁺ signalling.