Like other biological processes, macroautophagy/autophagy must be tightly controlled for maintenance of cellular homeostasis and for proper response to changing cellular conditions. To gain insights into the regulation of autophagy, we recently conducted a genome-wide CRISPR-Cas9 knockout screen using cells expressing endogenous LC3B tagged with GFP-mCherry as a reporter. This approach allowed us to identify the ubiquitin-activating enzyme UBA6 and the hybrid ubiquitin-conjugating enzyme/ubiquitin ligase BIRC6 as novel autophagy regulators. We found that these enzymes cooperate to mediate monoubiquitination and proteasomal degradation of LC3B, thus limiting the pool of LC3B available for autophagy. Depletion of UBA6 or BIRC6 increased the level of cytosolic LC3B, enhancing the degradation of autophagy adaptors and the clearance of intracellular proteins aggregates. This finding could be the basis for the development of pharmacological inhibitors of UBA6 or BIRC6 for the treatment of protein aggregation disorders. Recent work by another group showed that BIRC6 itself is subject to ubiquitination and proteasomal degradation, highlighting the existence of a complex regulatory network for the control of LC3B levels.

中文翻译：

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通过泛素化和蛋白酶体降解调节 LC3B 水平。


与其他生物过程一样，必须严格控制巨自噬/自噬，以维持细胞稳态并对不断变化的细胞条件做出适当反应。为了深入了解自噬的调控，我们最近使用表达带有 GFP-mCherry 标记的内源 LC3B 的细胞作为报告基因，进行了全基因组 CRISPR-Cas9 敲除筛选。这种方法使我们能够将泛素激活酶 UBA6 和混合泛素结合酶/泛素连接酶 BIRC6 鉴定为新型自噬调节剂。我们发现这些酶协同介导 LC3B 的单泛素化和蛋白酶体降解，从而限制了可用于自噬的 LC3B 池。 UBA6 或 BIRC6 的消耗增加了胞质 LC3B 的水平，增强了自噬接头的降解和细胞内蛋白质聚集体的清除。这一发现可能成为开发用于治疗蛋白质聚集疾病的 UBA6 或 BIRC6 药理学抑制剂的基础。另一个小组最近的工作表明，BIRC6 本身会发生泛素化和蛋白酶体降解，强调了控制 LC3B 水平的复杂调控网络的存在。