Inhibition of Ca^sub V^2.3 channels by NK1 receptors is sensitive to membrane cholesterol but insensitive to caveolin-1

Voltage-gated, Ca^sub V^2.3 calcium channels and neurokinin-1 (NK1) receptors are both present in nuclei of the central nervous system. When transiently coexpressed in human embryonic kidney (HEK) 293 cells, Ca^sub V^2.3 is primarily inhibited during strong, agonist-dependent activation of NK1 receptors. NK1 receptors localize to plasma membrane rafts, and their modulation by G^sub q/11^ protein-coupled signaling is sensitive to plasma membrane cholesterol. Here, we show that inhibition of Ca^sub V^2.3 by NK1 receptors is attenuated following methyl-[beta]-cyclodextrin (MBCD)-mediated depletion of membrane cholesterol. By contrast, inhibition of Ca^sub V^2.3 was unaffected by intracellular diffusion of caveolin-1 scaffolding peptide or by overexpression of caveolin-1. Interestingly, M[Beta]CD treatment had no effect on the macroscopic biophysical properties of Ca^sub V^2.3, though it significantly decreased whole-cell membrane capacitance. Our data indicate that (1) cholesterol supports at least one component of the NK1 receptor-linked signaling pathway that inhibits Ca^sub V^2.3 and (2) caveolin-1 is dispensable within this pathway. Our findings suggest that NK1 receptors reside within non-caveolar membrane rafts and that Ca^sub V^2.3 resides nearby but outside the rafts. Raft-dependent modulation of Ca^sub V^2.3 could be important in the physiological and pathophysiological processes in which these channels participate, including neuronal excitability, synaptic plasticity, epilepsy, and chronic pain.