Ca2+ oscillation induced by P2Y2 receptor activation and its regulation by a neuron-specific subtype of PKC (γPKC)

We found that stimulation of P2Y2 receptor (P2Y2R), which is endogenously expressed in CHO-K1 cells, induced intracellular calcium ([Ca2+]i) oscillation with a low frequency of 11.4 ± 2.7 mHz. When CHO-K1 cells expressing GFP-tagged kinase-negative γPKC (γPKC-KN-GFP), which is a neuron-specific subtype of PKC, were stimulated with UDP, γPKC-KN-GFP, but not wild-type γPKC (γPKC-GFP) showed an oscillatory translocation. The oscillatory translocation of γPKC-KN-GFP corresponded with [Ca2+]i oscillation, which was not observed in the cells expressing γPKC-GFP. We examined the mechanism of P2Y2R-induced [Ca2+]i oscillation pharmacologically. γPKC-KN-GFP oscillation was stopped by an extracellular Ca2+ chelator, EGTA, an antagonist of P2Y2R, Suramin, and store-operated calcium channel (SOC) inhibitors, SKF96365 and 2-ABP. Taken together, P2Y2R-induced [Ca2+]i oscillation in CHO-K1 cells is related with Ca2+ influx through SOC, whose function may be negatively regulated by γPKC. This [Ca2+]i oscillation was distinct from that induced by metabotropic glutamate receptor 5 (mGluR5) stimulation in the frequency (72.3 ± 5.3 mHz) and in the regulatory mechanism.