1] Department of Cell and Developmental Biology, University of Michigan, Ann Arbor, MI, USA [2] Life Sciences Institute, University of Michigan, Ann Arbor, MI, USA.
EMBO J. 2012 Aug 15;31(16):3442-56. doi: 10.1038/emboj.2012.200. Epub 2012 Jul 27.
Normal steady-state levels of the signalling lipids PI(3,5)P(2) and PI(5)P require the lipid kinase FAB1/PIKfyve and its regulators, VAC14 and FIG4. Mutations in the PIKfyve/VAC14/FIG4 pathway are associated with Charcot-Marie-Tooth syndrome and amyotrophic lateral sclerosis in humans, and profound neurodegeneration in mice. Hence, tight regulation of this pathway is critical for neural function. Here, we examine the localization and physiological role of VAC14 in neurons. We report that endogenous VAC14 localizes to endocytic organelles in fibroblasts and neurons. Unexpectedly, VAC14 exhibits a pronounced synaptic localization in hippocampal neurons, suggesting a role in regulating synaptic function. Indeed, the amplitude of miniature excitatory postsynaptic currents is enhanced in both Vac14(-/-) and Fig4(-/-) neurons. Re-introduction of VAC14 in postsynaptic Vac14(-/-) cells reverses this effect. These changes in synaptic strength in Vac14(-/-) neurons are associated with enhanced surface levels of the AMPA-type glutamate receptor subunit GluA2, an effect that is due to diminished regulated endocytosis of AMPA receptors. Thus, VAC14, PI(3,5)P(2) and/or PI(5)P play a role in controlling postsynaptic function via regulation of endocytic cycling of AMPA receptors.
正常的信号脂质 PI(3,5)P(2) 和 PI(5)P 的稳态水平需要脂质激酶 FAB1/PIKfyve 及其调节剂 VAC14 和 FIG4。PIKfyve/VAC14/FIG4 途径中的突变与人类的 Charcot-Marie-Tooth 综合征和肌萎缩性侧索硬化症以及小鼠的严重神经退行性变有关。因此，该途径的紧密调节对于神经功能至关重要。在这里，我们研究了 VAC14 在神经元中的定位和生理作用。我们报告内源性 VAC14 定位于成纤维细胞和神经元中的内吞细胞器。出乎意料的是，VAC14 在海马神经元中表现出明显的突触定位，表明其在调节突触功能中的作用。事实上，Vac14(-/-)和 Fig4(-/-)神经元中微小兴奋性突触后电流的幅度增强。在突触后 Vac14(-/-)细胞中重新引入 VAC14 可逆转这种效应。Vac14(-/-)神经元中这种突触强度的变化与 AMPA 型谷氨酸受体亚基 GluA2 的表面水平升高有关，这种效应是由于 AMPA 受体的调节性内吞作用减弱所致。因此，VAC14、PI(3,5)P(2) 和/或 PI(5)P 通过调节 AMPA 受体的内吞循环在控制突触后功能中发挥作用。
