Maintenance of Ca2.2 channel-current by PIP unveiled by neomycin in sympathetic neurons of the rat.

Membrane lipids are key determinants in the regulation of voltage-gated ion channels. Phosphatidylinositol 4,5-bisphosphate (PIP), a native membrane phospholipid, has been involved in the maintenance of the current amplitude and in the voltage-independent regulation of voltage-gated calcium channels (VGCC). However, the nature of the PIP regulation on VGCC has not been fully elucidated. This work aimed to investigate whether the interacting PIP electrostatic charges may account for maintaining the current amplitude of Ca2.2 channels. Furthermore, we tested whether charge shielding of PIP mimics the voltage-independent inhibition induced by M muscarinic acetylcholine receptor (MR) activation. Therefore, neomycin, a polycation that has been shown to block electrostatic interactions of PIP was intracellularly dialyzed in superior cervical ganglion (SCG) neurons of the rat. Consistently, neomycin time-dependently diminished the calcium current amplitude letting the channel exhibit the hallmarks of the voltage-independent regulation. These results support that interacting PIP charges not only underly the maintenance of the channel-current but also that charge screening of PIP by itself unveils the voltage-independent features of Ca2.2 channels in SCG neurons.