NONSELECTIVE CATION CHANNELS OF THE PLASMA MEMBRANE

Abstract

Nonselective cation channels (NSCCs) are defined as the channel exhibiting better selectivity for cations over anions. This nomenclature is however confusing, because the channels which fall into this category show a high degree of heterogeneity in their biophysics, physiology and pharmacology. Since little molecular information is yet available for most types of NSCC (except for the fast extracellular ligand-gated NSCC), one useful criterion to sub-classify them is the mode of activation. Based on this, more than 10 subclasses of NSCC, including the G-protein-coupled NSCC as a newly emerging member, can be distinguished (Table 1). Furthermore, the biophysical and pharmacological profile of these subclasses of NSCC suggest that varying extents of structural similarities may exist. Such a duality, i.e. heterogeneity and similarity of NSCC is on one hand, the obstacle to exploiting selective drugs for NSCCs, but on the other hand, may account for a broad repertoire of functions that NSCCs subserve under various patho-physiological conditions. This short paper briefly overviews, from such an aspect, the physiology and pharmacology of NSCCs of the plasma membrane, which have rather poorly been elucidated so far.