PIP₂ Hydrolysis is Responsible for Voltage Independent Inhibition of CaV2.2 Channels in Sympathetic Neurons

GPCRs regulate Ca(V)2.2 channels through both voltage dependent and independent inhibition pathways. The aim of the present work was to assess the phosphatidylinositol-4,5-bisphosphate (PIP2) as the molecule underlying the voltage independent inhibition of Ca(V)2.2 channels in SCG neurons. We used a double pulse protocol to study the voltage independent inhibition and changed the PIP(2) concentration by means of blocking the enzyme PLC, filling the cell with a PIP(2) analogue and preventing the PIP(2) resynthesis with wortmannin. We found that voltage independent inhibition requires the activation of PLC and can be hampered by internal dialysis of exogenous PIP(2). In addition, the recovery from voltage independent inhibition is blocked by inhibition of the enzymes involved in the resynthesis of PIP(2). These results support that the hydrolysis of PIP(2) is responsible for the voltage independent inhibition of Ca(V)2.2 channels.