Structures and functions of calcium channel β subunits
Structures and functions of calcium channel β subunits
复制标题
DOI：
10.1023/a:1021989622656
复制
发表时间：
1998-08-01
影响因子：
3
通讯作者：
Stefani, E
中科院分区：
文献类型：
--
作者：
Birnbaumer, L;Qin, N;Stefani, E
钙通道β亚基对阿尔法(1)亚基的表现有深远的影响。在这篇文章中，我们总结了我们目前对从cDNA推导出的β亚基一级结构的知识，并说明了它们的不同性质。在与α(1)亚基共表达时，β亚基的作用在L型和非L型通道中有所不同，这主要是因为这两种类型的通道对受β亚基影响的电压有不同的反应，如α(1C)的单脉冲前脉冲促进(α(1E)不存在)和G蛋白对α(1E)的抑制(α(1C)不存在)。一个β亚基，一种棕榈酰化的脑β2a剪接变异体，有几个其他亚基没有见过的影响，这些都是由于棕榈酰化。我们还说明了这一发现，即α(1)在卵母细胞中的功能性表达需要一个β亚基，即使最终的通道没有显示它存在的证据。我们提出了两种钙离子通道的结构模型，以解释在β亚基表达有限的细胞中所见的“单独的α(1)”通道。在一个模型中，在适当的折叠和膜插入后，β与成熟的α(1)解离。在另一种模型中，当高水平的β共同表达时，被调控的通道将具有亚单位组成α(1)β，“陪伴”的β仍然与成熟通道相关，而“单独的阿尔法(1)”通道实际上将是阿尔法(1)β通道。当共表达高水平的β时，受调控的通道将具有组成[α(1)β]β。
Calcium channel beta subunits have profound effects on how alpha(1) subunits perform. In this article we summarize our present knowledge of the primary structures of beta subunits as deduced from cDNAs and illustrate their different properties. Upon co-expression with alpha(1) subunits, the effects of beta subunits vary somewhat between L-type and non-L-type channels mostly because the two types of channels have different responses to voltage which are affected by beta subunits, such as lone-lasting prepulse facilitation of alpha(1C) (absent in alpha(1E)) and inhibition by G protein beta gamma dimer of alpha(1E), absent in alpha(1C). One beta subunit, a brain beta 2a splice variant that is palmitoylated, has several effects not seen with any of the others, and these are due to palmitoylation. We also illustrate the finding that functional expression of alpha(1) in oocytes requires a beta subunit even if the final channel shows no evidence for its presence. We propose two structural models for Ca2+ channels to account for "alpha(1) alone" channels seen in cells with limited beta subunit expression. In one model, beta dissociates from the mature alpha(1) after proper folding and membrane insertion. Regulated channels seen upon co-expression of high levels of beta would then have subunit composition alpha(1)beta In the other model, the "chaperoning" beta remains associated with the mature channel and "alpha(1) alone" channels would in fact be alpha(1)beta channels. Upon co-expression of high levels of beta the regulated channels would have composition [alpha(1)beta]beta.