Regulation of Kv2.1 channel inactivation by phosphatidylinositol 4,5-bisphosphate

Abstract

Phosphatidylinositol 4,5-bisphosphate (PIP 2 ) is a membrane phospholipid that regulates the function of multiple ion channels, including some members of the voltage-gated potassium (Kv) channel superfamily. The PIP 2 sensitivity of Kv channels is well established for all five members of the Kv7 family and for Kv1.2 channels; however, regulation of other Kv channels by PIP 2 remains unclear. Here, we investigate the effects of PIP 2 on Kv2.1 channels by applying exogenous PIP 2 to the cytoplasmic face of excised membrane patches, activating muscarinic receptors (M1R), or depleting endogenous PIP 2 using a rapamycin-translocated 5-phosphatase (FKBP-Inp54p). Exogenous PIP 2 rescued Kv2.1 channels from rundown and partially prevented the shift in the voltage-dependence of inactivation observed in inside-out patch recordings. Native PIP 2 depletion by the recruitment of FKBP-Insp54P or M1R activation in whole-cell experiments, induced a shift in the voltage-dependence of inactivation, an acceleration of the closed-state inactivation, and a delayed recovery of channels from inactivation. No significant effects were observed on the activation mechanism by any of these treatments. Our data can be modeled by a 13-state allosteric model that takes into account that PIP 2 depletion facilitates inactivation of Kv2.1. We propose that PIP 2 regulates Kv2.1 channels by interfering with the inactivation mechanism.

The AMIGO1 adhesion protein activates Kv2.1 voltage sensors

“…This degree of cell-to-cell variability does not appear to be unique to our laboratory. Midpoints reported for rat Kv2.1 activation in HEK293 cells span a 36 mV range, from -20.2 mV to 16.4 mV (Aréchiga-Figueroa et al, 2015David et al, 2015;Delgado-Ramírez et al, 2018;Kirmiz et al, 2018a;Li et al, 2015;Liu et al, 2016;Liu et al, 2017;Maverick et al, 2021;Milescu et al, 2009;O'Connell et al, 2010;Park et al, 2006;Peltola et al, 2011). When we calculated VMid standard deviation values from the standard errors and nvalues in these studies, standard deviations ranged from 1 to 17 mV, a range consistent with our standard deviations.…”

“…This degree of cell-to-cell variability does not appear to be unique to our laboratory. Midpoints reported for rat Kv2.1 activation in HEK293 cells span a 36 mV range, from -20.2 mV to 16.4 mV (22,23,67,72,(87)(88)(89)(90)(91)(92)(93)(94)(95). When we calculated VMid standard deviation values from the standard errors and n-values in these studies, standard deviations ranged from 1 to 17 mV, on par with our own.…”

cPLA2α-/- sympathetic neurons exhibit increased membrane excitability and loss of N-Type Ca2+ current inhibition by M1 muscarinic receptor signaling

“…In SCG neurons, a number of K + currents control the length of the AHP including small Ca 2+ -activated K + (SK3) currents [54, 55] and currents arising from the Kv2 channel family [56, 57]. Many of these types of K + channels in SCG neurons bind PIP 2 [58, 59] however, not all PIP 2 sensitive K + channels are affected by cPLA 2 α since we have shown that it has little effect on M-current. Some K + channels, e.g., SK and BK channels are enhanced by both PIP 2 and cPLA 2 α’s metabolite AA [60–63]; whereas other channel activity is enhanced by PIP 2 but inhibited by AA [64].…”

PKC regulation of ion channels: The involvement of PIP2

“…Exogenous application of PIP 2 appears to protect the Kv2.1 channel from current rundown while PIP 2 depletion facilitates it. Additionally, PIP 2 depletion enhances the rate of channel inactivation ( 87 ).…”