Polarized targeting of ion channels in neurons

Since the time of Cajal it has been understood that axons and dendrites perform distinct electrophysiological functions that require unique sets of proteins [Cajal SR Histology of the nervous system, Oxford University Press, New York, (1995)]. To establish and maintain functional polarity, neurons localize many proteins specifically to either the axonal or the somatodendritic compartment. In particular, ion channels, which are the major regulators of electrical activity in neurons, are often distributed in a polarized fashion. Recently, the ability to introduce tagged proteins into neurons in culture has allowed the molecular mechanisms underlying axon- and dendrite-specific targeting of ion channels to be explored. These investigations have identified peptide signals from voltage-gated Na(+) and K(+) channels that direct trafficking to either axonal or dendritic compartments. In this article we will discuss the molecular mechanisms underlying polarized targeting of voltage-gated ion channels from the Kv4, Kv1, and Na(v)1 families.