Department of Biological Sciences, University of Denver, Denver, CO 80210, USA.
Molecular and Cellular Biophysics Program, University of Denver, Denver, CO 80210, USA.
Biol Open. 2020 Aug 25;9(8):bio053421. doi: 10.1242/bio.053421.
Vps54 is a subunit of the Golgi-associated retrograde protein (GARP) complex, which is involved in tethering endosome-derived vesicles to the -Golgi network (TGN). In the wobbler mouse, a model for human motor neuron (MN) disease, reduction in the levels of Vps54 causes neurodegeneration. However, it is unclear how disruption of the GARP complex leads to MN dysfunction. To better understand the role of Vps54 in MNs, we have disrupted expression of the ortholog in and examined the impact on the larval neuromuscular junction (NMJ). Surprisingly, we show that both null mutants and MN-specific knockdown of leads to NMJ overgrowth. Reduction of partially disrupts localization of the t-SNARE, Syntaxin-16, to the TGN but has no visible impact on endosomal pools. MN-specific knockdown of in MNs combined with overexpression of the small GTPases Rab5, Rab7, or Rab11 suppresses the NMJ phenotype. Conversely, knockdown of combined with overexpression of dominant negative Rab7 causes NMJ and behavioral abnormalities including a decrease in postsynaptic Dlg and GluRIIB levels without any effect on GluRIIA. Taken together, these data suggest that controls larval MN axon development and postsynaptic density composition through a mechanism that requires Rab7.
Vps54 是高尔基体相关逆行蛋白 (GARP) 复合物的一个亚基，该复合物参与将内体衍生的囊泡与 -高尔基体网络 (TGN) 连接。在 wobbler 小鼠中，Vps54 水平的降低导致神经退行性变，这是一种人类运动神经元 (MN) 疾病的模型。然而，目前尚不清楚 GARP 复合物的破坏如何导致 MN 功能障碍。为了更好地了解 Vps54 在 MNs 中的作用，我们敲除了其同源物在中的表达，并研究了其对幼虫神经肌肉接头 (NMJ) 的影响。令人惊讶的是，我们发现 null 突变体和 MN 特异性敲低都会导致 NMJ 过度生长。 的减少部分破坏了 T 型 SNAP 受体 Syntaxin-16 向 TGN 的定位，但对内体池没有明显影响。MN 特异性敲低与小 GTPases Rab5、Rab7 或 Rab11 的过表达在 MNs 中结合可抑制 NMJ 表型。相反，与显性负性 Rab7 的过表达结合的 敲低会导致 NMJ 和行为异常，包括突触后 Dlg 和 GluRIIB 水平降低，而对 GluRIIA 没有任何影响。综上所述，这些数据表明 通过需要 Rab7 的机制控制幼虫 MN 轴突发育和突触后密度组成。
