Key Laboratory of Agricultural Environmental Microbiology of Ministry of Agriculture and Rural Affairs, College of Life Sciences, Nanjing Agricultural University, Nanjing 210095, China.
Cell Biol Int. 2019 Aug;43(8):875-889. doi: 10.1002/cbin.11156. Epub 2019 May 20.
Autophagy is an intracellular degradation process involving many Atg proteins, which are recruited hierarchically to regulate this process. Rab/Ypt GTPases and their activators, guanine nucleotide exchange factors (GEFs), which are critical for regulating vesicle trafficking, are also involved in autophagy. Previously, we reported that yeast Vps21 and its GEF Vps9 are required for autophagy. Later, a third yeast VPS9-domain-containing protein, VARP-like 1 (Vrl1), which was identified as a mutant in major laboratory strains, had partially overlapping functions with Vps9 in trafficking. In this study, we showed that Vrl1 performed roles in autophagy, and its VPS9-domain was crucial for its role in autophagy. We found that localization of Vrl1 differed from the other two VPS9-domain-containing proteins, Vps9 and Muk1, and only Vrl1 changed from multipoint to diffusion after starvation. Like Vps9, Vrl1 suppressed autophagic defects caused by the VPS9 deletion. We further showed that these VPS9-domain-containing proteins, Vps9, Muk1, and Vrl1, all co-localized with Atg8 on autophagosomes in cells blocked in any late step of starvation-induced autophagy, with Vrl1 most often co-localizing with Atg8. A small portion (<25%) of these VPS9-domain-containing proteins were degraded through autophagy. However, a large portion (>60%) of Vrl1 decreased independently of autophagy. We propose that Vrl1 may regulate autophagy in a similar way as Vps9, and the level of Vrl1 partly decreases through both autophagy-dependent and -independent routes.
自噬是一种涉及许多 Atg 蛋白的细胞内降解过程，这些蛋白被分层募集以调节这个过程。Rab/Ypt GTPases 和它们的激活因子，鸟嘌呤核苷酸交换因子（GEFs），对于调节囊泡运输至关重要，也参与自噬。之前，我们报道酵母 Vps21 和它的 GEF Vps9 是自噬所必需的。后来，第三种酵母 VPS9 结构域包含蛋白，Vrl1-like 1（Vrl1），它被鉴定为主要实验室菌株中的突变体，在运输中与 Vps9 具有部分重叠的功能。在这项研究中，我们表明 Vrl1 在自噬中发挥作用，并且它的 VPS9 结构域对于其在自噬中的作用至关重要。我们发现 Vrl1 的定位与其他两种含有 VPS9 结构域的蛋白 Vps9 和 Muk1 不同，并且只有 Vrl1 在饥饿后从多点扩散到扩散。与 Vps9 一样，Vrl1 抑制了 VPS9 缺失引起的自噬缺陷。我们进一步表明，这些含有 VPS9 结构域的蛋白，Vps9、Muk1 和 Vrl1，都在饥饿诱导的自噬任何晚期步骤受阻的细胞中与 Atg8 共定位于自噬体上，其中 Vrl1 最常与 Atg8 共定位于自噬体上。这些含有 VPS9 结构域的蛋白的一小部分（<25%）通过自噬降解。然而，大部分（>60%）的 Vrl1 减少不依赖于自噬。我们提出 Vrl1 可能以类似于 Vps9 的方式调节自噬，并且 Vrl1 的水平部分通过自噬依赖和非依赖途径下降。
