Twitchin kinase inhibits muscle activity.
Twitchin kinase inhibits muscle activity.
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DOI：
10.1091/mbc.e16-10-0707
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发表时间：
2017-06-15
影响因子：
3.3
通讯作者：
Benian GM
中科院分区：
文献类型：
--
作者：
Matsunaga Y;Hwang H;Franke B;Williams R;Penley M;Qadota H;Yi H;Morran LT;Lu H;Mayans O;Benian GM
肌肉表达具有激酶结构域的巨大多肽，但其催化活性的体内意义尚不清楚。对表达具有催化失活激酶的巨大蛋白质twitchin的突变线虫的分析表明，twitchin激酶抑制肌肉活性，并受到选择的青睐。肌节含有由多个免疫球蛋白和纤连蛋白结构域和一个或两个蛋白激酶结构域组成的巨大多肽。虽然这个家庭的激酶结构域的结合伙伴已经确定，这些激酶结构域的催化必要性仍然未知。此外，该激酶家族的各种成员被怀疑是没有活性或几乎没有活性的假激酶。在这里，我们解决催化的必要性，第一次，使用原型无脊椎动物的代表性tickin（E22）从秀丽隐杆线虫。在体外实验中，参与ATP配位的保守赖氨酸（K）与丙氨酸（A）的变化导致激酶活性的消除，而不影响激酶结构域的整体结构。同样的突变，unc-22（sf 21），在内源性tickin基因中产生。unc-22（sf 21）蠕虫有组织良好的肌节。然而，unc-22（sf 21）突变体比野生型蠕虫移动得更快，并且通过光遗传学实验，收缩得更多。野生型线虫比unc-22（sf 21）突变体表现出更大的竞争适应度。因此，抽搐蛋白激酶的催化活性在体内具有作用，在体内它抑制肌肉活性并可能通过选择来维持。
Muscles express giant polypeptides with kinase domains, but the in vivo significance of their catalytic activity has been unknown. Analysis of a mutant nematode that expresses the giant protein twitchin with a catalytically inactive kinase indicates that twitchin kinase inhibits muscle activity and is favored by selection. Muscle sarcomeres contain giant polypeptides composed of multiple immunoglobulin and fibronectin domains and one or two protein kinase domains. Although binding partners for a number of this family’s kinase domains have been identified, the catalytic necessity of these kinase domains remains unknown. In addition, various members of this kinase family are suspected pseudokinases with no or little activity. Here we address catalytic necessity for the first time, using the prototypic invertebrate representative twitchin (UNC-22) from Caenorhabditis elegans. In in vitro experiments, change of a conserved lysine (K) that is involved in ATP coordination to alanine (A) resulted in elimination of kinase activity without affecting the overall structure of the kinase domain. The same mutation, unc-22(sf21), was generated in the endogenous twitchin gene. The unc-22(sf21) worms have well-organized sarcomeres. However, unc-22(sf21) mutants move faster than wild-type worms and, by optogenetic experiments, contract more. Wild-type nematodes exhibited greater competitive fitness than unc-22(sf21) mutants. Thus the catalytic activity of twitchin kinase has a role in vivo, where it inhibits muscle activity and is likely maintained by selection.