Diversity in the Structure and Function of Ion Channels

Voltage clamp and patch clamp techniques are used to reveal heterogeneity of ion currents carried through voltage-dependent sodium, calcium, and potassium channels. Advances in channel molecular biology have made it clear that the diversity of ion channels is even greater than was suspected from these electrophysiological measurements. This diversity is achieved by several different mechanisms, including the existence of multiple genes for the pore-forming α‎ subunits of ion channels, alternative splicing of the messenger RNA transcribed from each individual gene, formation of heterotetramers containing different α‎ subunits of potassium channels, and modulation of channel properties by auxiliary subunits that may themselves comprise a large and diverse family of proteins. Moreover, potassium channels can be further categorized into voltage-dependent, calcium-dependent, sodium-dependent, two-pore, and inward rectifier channels. Emerging evidence suggests that many human diseases are associated with dysfunction of individual classes of ion channels in neurons.