Guo Weinong, Li Huilin, Aimond Franck, Johns David C, Rhodes Kenneth J, Trimmer James S, Nerbonne Jeanne M
Department of Molecular Biology and Pharmacology, Washington University School of Medicine, St. Louis, Mo 63110, USA.
Circ Res. 2002 Mar 22;90(5):586-93. doi: 10.1161/01.res.0000012664.05949.e0.
Previous studies have demonstrated a role for Kv4 alpha subunits in the generation of the fast transient outward K+ current, I(to,f), in the mammalian myocardium. The experiments here were undertaken to explore the role of homomeric/heteromeric assembly of Kv4.2 and Kv4.3 and of the Kv channel accessory subunit, KChIP2, in the generation of mouse ventricular I(to,f). Western blots reveal that the expression of Kv4.2 parallels the regional heterogeneity in I(to,f) density, whereas Kv4.3 and KChIP2 are uniformly expressed in adult mouse ventricles. Antisense oligodeoxynucleotides (AsODNs) targeted against Kv4.2 or Kv4.3 selectively attenuate I(to,f) in mouse ventricular cells. Adenoviral-mediated coexpression of Kv4.2 and Kv4.3 in HEK-293 cells and in mouse ventricular myocytes produces transient outward K+ currents with properties distinct from those produced on expression of Kv4.2 or Kv4.3 alone, and the gating properties of the heteromeric Kv4.2/Kv4.3 channels in ventricular cells are more similar to native I(to,f) than are the homomeric Kv4.2 or Kv4.3 channels. Biochemical studies reveal that Kv4.2, Kv4.3, and KChIP2 coimmunoprecipitate from adult mouse ventricles. In addition, most of the Kv4.2 and KChIP2 are associated with Kv4.3 in situ. Taken together, these results demonstrate that functional mouse ventricular I(to,f) channels are heteromeric, comprising Kv4.2/Kv4.3 alpha subunits and KChIP2. The results here also suggest that Kv4.2 is the primary determinant of the regional heterogeneity in I(to,f) expression in adult mouse ventricle.
先前的研究已证明Kv4α亚基在哺乳动物心肌中快速瞬时外向K⁺电流I(to,f)的产生中发挥作用。本文进行的实验旨在探究Kv4.2和Kv4.3的同聚体/异聚体组装以及Kv通道辅助亚基KChIP2在小鼠心室I(to,f)产生中的作用。蛋白质免疫印迹显示，Kv4.2的表达与I(to,f)密度的区域异质性平行，而Kv4.3和KChIP2在成年小鼠心室中均匀表达。针对Kv4.2或Kv4.3的反义寡脱氧核苷酸（AsODNs）可选择性减弱小鼠心室细胞中的I(to,f)。腺病毒介导的Kv4.2和Kv4.3在HEK-293细胞和小鼠心室肌细胞中的共表达产生了具有与单独表达Kv4.2或Kv4.3时不同特性的瞬时外向K⁺电流，并且心室细胞中异聚体Kv4.2/Kv4.3通道的门控特性比同聚体Kv4.2或Kv4.3通道更类似于天然I(to,f)。生化研究表明，Kv4.2、Kv4.3和KChIP2可从成年小鼠心室中共免疫沉淀。此外，大多数Kv4.2和KChIP2在原位与Kv4.3相关联。综上所述，这些结果表明功能性小鼠心室I(to,f)通道是异聚体，由Kv4.2/Kv4.3α亚基和KChIP2组成。本文的结果还表明，Kv4.2是成年小鼠心室中I(to,f)表达区域异质性的主要决定因素。
