Program in Integrative Molecular and Biomedical Sciences, Baylor College of Medicine, Houston, TX 77030, USA.
Department of Pediatric, Baylor College of Medicine, Houston, TX 77030, USA.
J Cell Sci. 2021 Jan 25;134(2):jcs251140. doi: 10.1242/jcs.251140.
Wnt signaling plays a critical role in development across species and is dysregulated in a host of human diseases. A key step in signal transduction is the formation of Wnt receptor signalosomes, during which a large number of components translocate to the membrane, cluster together and amplify downstream signaling. However, the molecular processes that coordinate these events remain poorly defined. Here, we show that Daam2 regulates canonical Wnt signaling via the PIP-PIP5K axis through its association with Rac1. Clustering of Daam2-mediated Wnt receptor complexes requires both Rac1 and PIP5K, and PIP5K promotes membrane localization of these complexes in a Rac1-dependent manner. Importantly, the localization of Daam2 complexes and Daam2-mediated canonical Wnt signaling is dependent upon actin polymerization. These studies - in chick spinal cord and human and monkey cell lines - highlight novel roles for Rac1 and the actin cytoskeleton in the regulation of canonical Wnt signaling and define Daam2 as a key scaffolding hub that coordinates membrane translocation and signalosome clustering.
Wnt 信号通路在不同物种的发育中起着至关重要的作用,并且在许多人类疾病中失调。信号转导的关键步骤是 Wnt 受体信号小体的形成,在此过程中,大量的成分转移到膜上,聚集在一起并放大下游信号。然而,协调这些事件的分子过程仍未得到很好的定义。在这里,我们通过 Daam2 与 Rac1 的结合,证明 Daam2 通过 PIP-PIP5K 轴调节经典 Wnt 信号通路。Daam2 介导的 Wnt 受体复合物的聚类需要 Rac1 和 PIP5K,并且 PIP5K 以 Rac1 依赖的方式促进这些复合物在膜上的定位。重要的是,Daam2 复合物的定位和 Daam2 介导的经典 Wnt 信号通路依赖于肌动蛋白聚合。这些在鸡脊髓和人及猴细胞系中的研究突出了 Rac1 和肌动蛋白细胞骨架在经典 Wnt 信号通路调节中的新作用,并将 Daam2 定义为协调质膜易位和信号小体聚类的关键支架中心。