Enhancement of ATP-induced Currents by Phospholipase D1 Overexpressed in PC12 Cells

Using phospholipase D1 (PLD1) -overexpressing PC12 (PLD1-PC12) cells, the regulatory roles of PLD1 on ATP-induced currents were investigated. In control and PLD1-PC12 cells, ATP increased PLD activity in an external Ca2+ dependent manner. PLD activity stimulated by ATP was substantially larger in PLD1-PC12 cells than in control cells. In whole-cell voltage-clamp mode, ATP induced transient inward and outward currents. The outward currents inhibited by TEA or charybdotoxin were significantly larger in PLD1-PC12 cells than in control cells. The inward currents known as Ca2+ permeable nonselective cation currents were also larger in PLD1-PC12 cells than in control cells. However, the difference between the two groups of cells disappeared in Ca2+ -free external solution, where ATP did not activate PLD. Finally, ATP-induced 45Ca uptakes were also larger in PLD1-PC12 cells than in control cells. These results suggest that PLD enhances ATP-induced Ca2+ influx via Ca2+ permeable nonselective cation channels and increases subsequent Ca2+ -activated K+ currents in PC12 cells.

Regulatory effect of Zn~(2+) on P2X receptor-mediated,ATP-induced currents in different autonomic ganglion neurons in rats / 第二军医大学学报

Objective:To compare the effects of Zn~(2+)onthe P2X receptor-mediated,ATP-induced currents in neurons separated from rat superior cervical ganglion(SCG),nodose ganglion(NG),and otic ganglion(OTG).Methods: Whole-cell patch clamp recording technique was used to study the regulatory effects of Zn~(2+) on ATP/??-me ATP-induced currents in the above 3 ganlglion neurons.Results: All SCG neurons responded to ATP with a sustained current,while no neurons responded to ??-me ATP;Zn~(2+) potentiated ATP-induced sustained currents to(1 442?34)% of the original value.All NG neurons responded to ATP and ??-me ATP with a similar sustained current;coapplication of Zn~(2+)(10 ?mol/L) potentiated their responses to(180?12)% and(262?28)%,respectively.All OTG neurons responded to both ATP and ??-me ATP with a sustained current.Coapplication of Zn~(2+)(10 ? mol/L) did not significantly potentiate the sustained currents induced by 10 ?mol/L ATP,but when ATP was at 30 ?mol/L,Zn~(2+)(10-100 ?mol/L) inhibited ATP-induced sustained currents in a dose dependent manner.If TNP-ATP(100 nmol/L) was first used to inhibit ATP-induced current to(26?2)% of the original value,Zn~(2+) at 10 ?mol/L potentiated the inhibited current to(127?9)% of its original value.Coapplication of Zn~(2+)(10 ?mol/L) potentiated ??-me ATP-induced currents to(146?5)% of the control.Zn~(2+)(300 ?mol/L) had no effect on ?_(on) and ?_(off) of ATP-and ??-me ATP-induced(30 ?mol/L) currents in OTG neurons.Conclusion:(1) Zn~(2+) is an allosteric modulator of P2X_(2) and P2X_(2/3) receptors in SCG and NG neurons and can potentiate the currents they induced.(2)The predominant receptor subtypes in OTG appear to be homomeric P2X_(2/3) and a little P2X_(2).Zn~(2+) has an inhibitory effect on the ATP-induced currents in OTG neurons,suggesting some novel members of the P2X purinoceptor exist in these neurons.