Institute of Physiology and Pathophysiology, Dept. of Molecular Cell Physiology, Philipps-University Marburg, 35037 Marburg, Germany.
Institute for Neurobiology, University of Münster, 48149 Münster, Germany.
J Cell Sci. 2021 Dec 1;134(23). doi: 10.1242/jcs.258891. Epub 2021 Dec 9.
The WAVE regulatory complex (WRC) is the main activator of the Arp2/3 complex, promoting lamellipodial protrusions in migrating cells. The WRC is basally inactive but can be activated by Rac1 and phospholipids, and through phosphorylation. However, the in vivo relevance of the phosphorylation of WAVE proteins remains largely unknown. Here, we identified casein kinase I alpha (CK1α) as a regulator of WAVE, thereby controlling cell shape and cell motility in Drosophila macrophages. CK1α binds and phosphorylates WAVE in vitro. Phosphorylation of WAVE by CK1α appears not to be required for activation but, rather, regulates its stability. Pharmacologic inhibition of CK1α promotes ubiquitin-dependent degradation of WAVE. Consistently, loss of Ck1α but not ck2 function phenocopies the depletion of WAVE. Phosphorylation-deficient mutations in the CK1α consensus sequences within the VCA domain of WAVE can neither rescue mutant lethality nor lamellipodium defects. By contrast, phosphomimetic mutations rescue all cellular and developmental defects. Finally, RNAi-mediated suppression of 26S proteasome or E3 ligase complexes substantially rescues lamellipodia defects in CK1α-depleted macrophages. Therefore, we conclude that basal phosphorylation of WAVE by CK1α protects it from premature ubiquitin-dependent degradation, thus promoting WAVE function in vivo. This article has an associated First Person interview with the first author of the paper.
WAVE 调节复合物（WRC）是 Arp2/3 复合物的主要激活剂，促进迁移细胞中的片状伪足伸出。WRC 基础上是无活性的，但可以被 Rac1 和磷脂激活，并通过磷酸化。然而，WAVE 蛋白磷酸化在体内的相关性在很大程度上仍然未知。在这里，我们确定了酪蛋白激酶 Iα（CK1α）是 WAVE 的调节剂，从而控制果蝇巨噬细胞的细胞形状和细胞迁移。CK1α 在体外结合并磷酸化 WAVE。CK1α 对 WAVE 的磷酸化似乎不是激活所必需的，而是调节其稳定性。CK1α 的药理学抑制促进 WAVE 的泛素依赖性降解。一致地，Ck1α 的缺失而不是 ck2 功能缺失可模拟 WAVE 的耗竭表型。WAVE 的 VCA 结构域中的 CK1α 共有序列中的磷酸化缺陷突变既不能挽救突变致死性，也不能挽救片状伪足缺陷。相比之下，磷酸化模拟突变可挽救所有细胞和发育缺陷。最后，26S 蛋白酶体或 E3 连接酶复合物的 RNAi 介导抑制可大大挽救 CK1α 耗尽的巨噬细胞中的片状伪足缺陷。因此，我们得出结论，CK1α 对 WAVE 的基础磷酸化可防止其过早发生泛素依赖性降解，从而促进体内 WAVE 功能。本文附有该论文第一作者的相关第一人称采访。
