Department of Chemistry, Oakland University, Rochester, MI, USA.
Department of Genetics, Cell Biology and Development, University of Minnesota, Minneapolis, MN, USA.
Sci Rep. 2022 Feb 2;12(1):1726. doi: 10.1038/s41598-022-05762-2.
Recent structural studies of β-III-spectrin and related cytoskeletal proteins revealed N-terminal sequences that directly bind actin. These sequences are variable in structure, and immediately precede a conserved actin-binding domain composed of tandem calponin homology domains (CH1 and CH2). Here we investigated in Drosophila the significance of the β-spectrin N-terminus, and explored its functional interaction with a CH2-localized L253P mutation that underlies the neurodegenerative disease spinocerebellar ataxia type 5 (SCA5). We report that pan-neuronal expression of an N-terminally truncated β-spectrin fails to rescue lethality resulting from a β-spectrin loss-of-function allele, indicating that the N-terminus is essential to β-spectrin function in vivo. Significantly, N-terminal truncation rescues neurotoxicity and defects in dendritic arborization caused by L253P. In vitro studies show that N-terminal truncation eliminates L253P-induced high-affinity actin binding, providing a mechanistic basis for rescue. These data suggest that N-terminal sequences may be useful therapeutic targets for small molecule modulation of the aberrant actin binding associated with SCA5 β-spectrin and spectrin-related disease proteins.
最近对β-III- spectrin 和相关细胞骨架蛋白的结构研究揭示了直接结合肌动蛋白的 N 端序列。这些序列在结构上是可变的，并且直接位于由串联钙调蛋白同源结构域 (CH1 和 CH2) 组成的保守肌动蛋白结合结构域之前。在这里，我们在果蝇中研究了β- spectrin N 端的重要性，并探索了其与位于 CH2 的 L253P 突变的功能相互作用，该突变是神经退行性疾病脊髓小脑共济失调 5 型 (SCA5) 的基础。我们报告说，神经元泛表达截短的β- spectrin N 端不能挽救因β- spectrin 功能丧失等位基因引起的致死性，这表明 N 端对于β- spectrin 在体内的功能是必需的。重要的是，N 端截断可挽救由 L253P 引起的神经毒性和树突分支缺陷。体外研究表明，N 端截断消除了 L253P 诱导的高亲和力肌动蛋白结合，为挽救提供了机制基础。这些数据表明，N 端序列可能是小分子调节与 SCA5 β- spectrin 和 spectrin 相关疾病蛋白相关的异常肌动蛋白结合的有用治疗靶点。
