Blaine J T, Ribera A B
Department of Physiology and Biophysics, University of Colorado Health Sciences Center, Denver, Colorado 80262, USA.
J Neurosci. 1998 Dec 1;18(23):9585-93. doi: 10.1523/JNEUROSCI.18-23-09585.1998.
Four alpha-subunits are thought to coassemble and form a voltage-dependent potassium (Kv) channel. Kv alpha-subunits belong to one of four major subfamilies (Kv1, Kv2, Kv3, Kv4). Within a subfamily up to eight different genetic isotypes exist (e.g., Kv1.1, Kv1.2). Different isotypes within the Kv1 or Kv3 subfamily coassemble. It is not known, however, whether the only two members of the vertebrate Kv2 subfamily identified thus far, Kv2.1 and Kv2.2, heteromultimerize. This might account for the lack of detection of heteromultimeric Kv2 channels in situ despite the coexpression of Kv2.1 and Kv2.2 mRNAs within the same cell. To probe whether Kv2 isotypes can form heteromultimers, we developed a dominant-negative mutant Kv2.2 subunit to act as a molecular poison of Kv2 subunit-containing channels. The dominant-negative Kv2.2 suppresses formation of functional channels when it is coexpressed in oocytes with either wild-type Kv2.2 or Kv2.1 subunits. These results indicate that Kv2.1 and Kv2.2 subunits are capable of heteromultimerization. Thus, in native cells either Kv2.1 and Kv2.2 subunits are targeted at an early stage to different biosynthetic compartments or heteromultimerization otherwise is inhibited.
四个α亚基被认为共同组装并形成一个电压依赖性钾（Kv）通道。Kvα亚基属于四个主要亚家族之一（Kv1、Kv2、Kv3、Kv4）。在一个亚家族中存在多达八种不同的基因同种型（例如，Kv1.1、Kv1.2）。Kv1或Kv3亚家族中的不同同种型共同组装。然而，目前尚不清楚迄今为止在脊椎动物中鉴定出的Kv2亚家族仅有的两个成员Kv2.1和Kv2.2是否会形成异源多聚体。这可能解释了尽管Kv2.1和Kv2.2 mRNA在同一细胞中共表达，但原位未检测到异源多聚体Kv2通道的原因。为了探究Kv2同种型是否能形成异源多聚体，我们构建了一个显性负性突变体Kv2.2亚基，作为含Kv2亚基通道的分子毒物。当显性负性Kv2.2与野生型Kv2.2或Kv2.1亚基在卵母细胞中共表达时，它会抑制功能性通道的形成。这些结果表明Kv2.1和Kv2.2亚基能够进行异源多聚化。因此，在天然细胞中，要么Kv2.1和Kv2.2亚基在早期被靶向到不同的生物合成区室，要么异源多聚化在其他方面受到抑制。
