Department of Biology, McGill University, Montreal, Quebec, Canada.
PLoS One. 2020 Jul 2;15(7):e0232137. doi: 10.1371/journal.pone.0232137. eCollection 2020.
In sarcomeres, α-actinin crosslinks thin filaments and anchors them at the Z-disc. Drosophila melanogaster Zasp52 also localizes at Z-discs and interacts with α-actinin via its extended PDZ domain, thereby contributing to myofibril assembly and maintenance, yet the detailed mechanism of Zasp52 function is unknown. Here we show a strong genetic interaction between actin and Zasp52 during indirect flight muscle assembly, indicating that this interaction plays a critical role during myofibril assembly. Our results suggest that Zasp52 contains an actin-binding site, which includes the extended PDZ domain and the ZM region. Zasp52 binds with micromolar affinity to monomeric actin. A co-sedimentation assay indicates that Zasp52 can also bind to F-actin. Finally, we use in vivo rescue assays of myofibril assembly to show that the α-actinin-binding domain of Zasp52 is not sufficient for a full rescue of Zasp52 mutants suggesting additional contributions of Zasp52 actin-binding to myofibril assembly.
在肌节中，α-辅肌动蛋白交联细肌丝，并将其锚定在 Z 盘上。果蝇 Zasp52 也定位于 Z 盘，并通过其扩展 PDZ 结构域与 α-辅肌动蛋白相互作用，从而有助于肌原纤维的组装和维持，但 Zasp52 功能的详细机制尚不清楚。在这里，我们在间接飞行肌组装过程中显示了肌动蛋白和 Zasp52 之间的强烈遗传相互作用，表明这种相互作用在肌原纤维组装过程中起着关键作用。我们的结果表明，Zasp52 包含一个肌动蛋白结合位点，该位点包含扩展 PDZ 结构域和 ZM 区域。Zasp52 以微摩尔亲和力与单体肌动蛋白结合。共沉淀测定表明 Zasp52 也可以与 F-肌动蛋白结合。最后，我们使用肌原纤维组装的体内挽救实验表明，Zasp52 的 α-辅肌动蛋白结合域不足以完全挽救 Zasp52 突变体，这表明 Zasp52 肌动蛋白结合对肌原纤维组装的额外贡献。
