Regional expression of the splice variants of Kv4.3 in rat brain and effects of C-terminus deletion on expressed K+ currents

In situ hybridization and RT-PCR analyses have revealed that, among three K v4.3 splice variants (a, b, and c) with distinct C-terminal cytoplasmic dom ains, the mRNA for Kv4.3a is abundant in cerebral cortex, cerebellum, olfac tory bulb, and medulla oblongata, whereas the mRNA for Kv4.3c is localized mainly to hippocampus. Three new distinct splice variants of Kv4.3 (Kv4.3d, e and f), which consist of 601, 635, and 628 amino acids, respectively, an d have distinct C-terminal cytoplasmic domains, were isolated from rat brai n by RT-PCR. Kv4.3b, d, e and f were expressed at much lower levels in brai n. Mutagenesis which removed 149 amino acids in C-terminal domain of Kv4.3a significantly slowed its rate of recovery from inactivation as measured in heterologous expression in HEK293 cells. Surprisingly, however, neither th e rate of inactivation nor voltage dependence of the activation and inactiv ation were changed. (C) 2001 Elsevier Science Inc. All rights reserved.