An analysis of splicing, actin-binding properties, heterodimerization and molecular interactions of the non-muscle α-actinins
An analysis of splicing, actin-binding properties, heterodimerization and molecular interactions of the non-muscle α-actinins
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DOI：
10.1042/bj20121824
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发表时间：
2013-06-15
影响因子：
4.1
通讯作者：
Young, Paul W.
中科院分区：
文献类型：
--
作者：
Foley, Kate S.;Young, Paul W.
非肌肉α-辅肌动蛋白亚型（辅肌动蛋白-1和-4）是密切相关的二聚体肌动蛋白丝交联蛋白。尽管序列相似性高，但其独特的性质被特别地归因于辅肌动蛋白-4。例如，辅肌动蛋白-4，而不是辅肌动蛋白-1，对于肾脏中的正常肾小球功能是必需的，在几种癌症中过表达，并且可以易位到细胞核以调节转录。为了了解这种异构体特异性功能的分子基础，我们第一次全面比较了这些蛋白质的选择性剪接，肌动蛋白结合特性，异源二聚体形成和分子相互作用。我们发现，钙不敏感的肌动蛋白-4的变体只在神经系统中表达，因此不能被视为平滑肌亚型，因为是钙不敏感的肌动蛋白-1的变体的情况。肌动蛋白-1和-4的肌动蛋白结合特性相似，不太可能解释亚型特异性功能。令人惊讶的是，我们发现，辅肌动蛋白-1/-4异二聚体，而不是同源二聚体，是最丰富的形式辅肌动蛋白在许多细胞系。最后，我们使用蛋白质组学方法来确定潜在的异构体特异性相互作用。本研究的结果表明，辅肌动蛋白-1和-4可以很容易地形成异二聚体的单体，可能有不同的性质和相互作用的蛋白质组成。这大大改变了我们对非肌肉辅肌动蛋白功能的看法。
The non-muscle alpha-actinin isoforms (actinin-1 and -4) are closely related dimeric actin filament cross-linking proteins. Despite high sequence similarity, unique properties have been ascribed to actinin-4 in particular. For example, actinin-4, but not actinin-1, is essential for normal glomerular function in the kidney, is overexpressed in several cancers and can translocate to the nucleus to regulate transcription. To understand the molecular basis for such isoform-specific functions we have, for the first time, comprehensively compared these proteins in terms of alternative splicing, actin-binding properties, heterodimer formation and molecular interactions. We find that the Ca2+-insensitive variant of actinin-4 is expressed only in the nervous system and thus cannot be regarded as a smooth muscle isoform, as is the case for the Ca2+-insensitive variant of actinin-1. The actin-binding properties of actinin-1 and -4 are similar and are unlikely to explain isoform-specific functions. Surprisingly, we reveal that actinin-1/-4 heterodimers, rather than homodimers, are the most abundant form of actinin in many cell lines. Finally, we use a proteomics approach to identify potential isoform-specific interactions. The results of the present study indicate that actinin-1 and -4 can readily form heterodimers composed of monomers that may have different properties and interacting proteins. This significantly alters our view of non-muscle actinin function.