Department of Biochemistry and Molecular Biology, The Pennsylvania State University, University Park, Pennsylvania, United States of America.
Department of Pathology, Stanford University School of Medicine, Stanford, California, United States of America.
PLoS Biol. 2020 Mar 12;18(3):e3000647. doi: 10.1371/journal.pbio.3000647. eCollection 2020 Mar.
Dendrite microtubules are polarized with minus-end-out orientation in Drosophila neurons. Nucleation sites concentrate at dendrite branch points, but how they localize is not known. Using Drosophila, we found that canonical Wnt signaling proteins regulate localization of the core nucleation protein γTubulin (γTub). Reduction of frizzleds (fz), arrow (low-density lipoprotein receptor-related protein [LRP] 5/6), dishevelled (dsh), casein kinase Iγ, G proteins, and Axin reduced γTub-green fluorescent protein (GFP) at branch points, and two functional readouts of dendritic nucleation confirmed a role for Wnt signaling proteins. Both dsh and Axin localized to branch points, with dsh upstream of Axin. Moreover, tethering Axin to mitochondria was sufficient to recruit ectopic γTub-GFP and increase microtubule dynamics in dendrites. At dendrite branch points, Axin and dsh colocalized with early endosomal marker Rab5, and new microtubule growth initiated at puncta marked with fz, dsh, Axin, and Rab5. We propose that in dendrites, canonical Wnt signaling proteins are housed on early endosomes and recruit nucleation sites to branch points.
树突微管呈负端到出的极化状态，在果蝇神经元中。成核位点集中在树突分支点，但它们如何定位尚不清楚。利用果蝇，我们发现经典 Wnt 信号蛋白调节核心成核蛋白γ微管蛋白（γTub）的定位。减少 frizzleds（fz）、arrow（低密度脂蛋白受体相关蛋白 [LRP] 5/6）、dishevelled（dsh）、酪蛋白激酶 Iγ、G 蛋白和 Axin 减少分支点处的γTub-绿色荧光蛋白（GFP），并且两个树突核形成的功能读数证实了 Wnt 信号蛋白的作用。dsh 和 Axin 都定位在分支点上，dsh 在 Axin 的上游。此外，将 Axin 固定在线粒体上足以募集异位γTub-GFP 并增加树突中的微管动力学。在树突分支点，Axin 和 dsh 与早期内体标记 Rab5 共定位，并且新的微管生长在以 fz、dsh、Axin 和 Rab5 标记的斑点处起始。我们提出，在树突中，经典 Wnt 信号蛋白位于早期内体上，并将成核位点募集到分支点。
