Kv3

Four mammalian Kv3 genes have been identified, each of which generates by alternative splicing multiple protein products. Kv3.1 and Kv3.2 genes express very similar delayed rectifier K+ currents in heterologous expression systems. Kv3.1 is highly enriched in neurons that fire at high frequencies, such as fast spiking interneurons of the cortex and hippocampus and neurons in the globus pallidus. Their unusually rapid activation and deactivation rates allow channels containing Kv3.1 alpha subunits to repolarize action potentials quickly without compromising the threshold for action potential generation by promoting a rapid afterhyperpolarization period, thus minimizing the rate of recovery of sodium channel inactivation. Pharmacological or genetic disruption of Kv3 currents leads to impaired fast spiking in inhibitory neurons and increased seizure susceptibility. [15]

Both rodents and humans possess four Kv3 genes: Kv3.1, Kv3.2, Kv3.3 and Kv3.4. All four Kv3 genes generate multiple protein isoforms by alternative splicing, which produces versions with different intracellular C-terminal sequences. There are now 13 different Kv3 proteins known in mammals (Kv3.1a–Kv3.1b, Kv3.2a–Kv3.2d, Kv3.3a–Kv3.3d and Kv3.4a–Kv3.4c), yet the currents expressed in heterologous expression systems by the spliced isoforms of each Kv3 gene are virtually indistinguishable. [302]

Resemblance of Kv3 family

There are now 13 different Kv3 proteins known in mammals (Kv3.1a–Kv3.1b, Kv3.2a–Kv3.2d, Kv3.3a–Kv3.3d and Kv3.4a–Kv3.4c), yet the currents expressed in heterologous expression systems by the spliced isoforms of each Kv3 gene are virtually indistinguishable [302]

The Kv3 subfamily, consisting of four genes (encoding Kv3.1, Kv3.2, Kv3.3 and Kv3.4), have some distinct functional properties. They activate at high thresholds (−10 mV) and activate and deactivate more rapidly than other Kv channels; these properties enable neurons to fire at high frequencies [2]. The predicted membrane topology of a Kv3 subunit shows six transmembrane domains (S1–S6), a voltage sensor in S4, and a pore loop between S5 and S6