Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States.
California Institute for Quantitative Biosciences (QB3), University of California, Berkeley, Berkeley, United States.
Elife. 2020 Mar 9;9:e53670. doi: 10.7554/eLife.53670.
The many variants of human Ca/calmodulin-dependent protein kinase II (CaMKII) differ in the lengths and sequences of disordered linkers connecting the kinase domains to the oligomeric hubs of the holoenzyme. CaMKII activity depends on the balance between activating and inhibitory autophosphorylation (on Thr 286 and Thr 305/306, respectively, in the human α isoform). Variation in the linkers could alter transphosphorylation rates within a holoenzyme and the balance of autophosphorylation outcomes. We show, using mammalian cell expression and a single-molecule assay, that the balance of autophosphorylation is flipped between CaMKII variants with longer and shorter linkers. For the principal isoforms in the brain, CaMKII-α, with a ~30 residue linker, readily acquires activating autophosphorylation, while CaMKII-β, with a ~200 residue linker, is biased towards inhibitory autophosphorylation. Our results show how the responsiveness of CaMKII holoenzymes to calcium signals can be tuned by varying the relative levels of isoforms with long and short linkers.
人类钙/钙调蛋白依赖性蛋白激酶 II（CaMKII）的多种变体在连接激酶结构域和全酶寡聚中心的无规连接体的长度和序列上存在差异。CaMKII 的活性取决于激活和抑制性自身磷酸化之间的平衡（分别在人类α同工型中的 Thr286 和 Thr305/306 上）。连接体的变异可能会改变全酶内的转磷酸化速率以及自身磷酸化结果的平衡。我们使用哺乳动物细胞表达和单分子测定表明，在具有较长和较短连接体的 CaMKII 变体之间，自身磷酸化的平衡被翻转。对于脑内的主要同工型 CaMKII-α，带有约 30 个残基的连接体，很容易获得激活性自身磷酸化，而带有约 200 个残基的连接体 CaMKII-β 则偏向于抑制性自身磷酸化。我们的结果表明，通过改变具有长和短连接体的同工型的相对水平，可以调节 CaMKII 全酶对钙信号的反应性。
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