Howard Hughes Medical Institute and Department of Biological Chemistry, University of California, Los Angeles, Los Angeles, CA 90095-1662, USA.
Cell. 2010 Dec 23;143(7):1136-48. doi: 10.1016/j.cell.2010.11.034.
Canonical Wnt signaling requires inhibition of Glycogen Synthase Kinase 3 (GSK3) activity, but the molecular mechanism by which this is achieved remains unclear. Here, we report that Wnt signaling triggers the sequestration of GSK3 from the cytosol into multivesicular bodies (MVBs), so that this enzyme becomes separated from its many cytosolic substrates. Endocytosed Wnt colocalized with GSK3 in acidic vesicles positive for endosomal markers. After Wnt addition, endogenous GSK3 activity decreased in the cytosol, and GSK3 became protected from protease treatment inside membrane-bounded organelles. Cryoimmunoelectron microscopy showed that these corresponded to MVBs. Two proteins essential for MVB formation, HRS/Vps27 and Vps4, were required for Wnt signaling. The sequestration of GSK3 extended the half-life of many other proteins in addition to β-Catenin, including an artificial Wnt-regulated reporter protein containing GSK3 phosphorylation sites. We conclude that multivesicular endosomes are essential components of the Wnt signal-transduction pathway.
经典 Wnt 信号通路需要抑制糖原合成激酶 3（GSK3）的活性，但目前尚不清楚实现这一目标的分子机制。在这里，我们报告称，Wnt 信号触发 GSK3 从细胞质隔离到多泡体（MVBs），使该酶与其许多细胞质底物分离。内吞的 Wnt 与细胞质中的 GSK3 共定位，呈酸性囊泡状，内吞体标志物阳性。Wnt 添加后，细胞质中内源性 GSK3 活性降低，GSK3 在膜结合细胞器内免受蛋白酶处理。冷冻免疫电子显微镜显示，这些对应于多泡体。多泡体形成所必需的两种蛋白质 HRS/Vps27 和 Vps4，对 Wnt 信号也很重要。除了β-连环蛋白之外，GSK3 的隔离还延长了许多其他蛋白质的半衰期，包括含有 GSK3 磷酸化位点的人工 Wnt 调控报告蛋白。我们得出结论，多泡内体是 Wnt 信号转导途径的重要组成部分。
