Supramolecular Assembly of GSK3α as a Cellular Response to Amino Acid Starvation

This data submission contains the raw confocal immunofluorescence microscopy and Western blot images for our manuscript, which describes the following: The tolerance of amino acid starvation is fundamental to robust cellular fitness. Asparagine depletion is lethal to some cancer cells, a vulnerability exploited clinically using asparaginase. We report that resistance to asparagine starvation is uniquely dependent on an N-terminal low-complexity domain of GSK3α lacking in its paralog GSK3β. In response to depletion of specific amino acids, including asparagine, leucine or valine, this domain mediates supramolecular assembly of GSK3α with ubiquitin-proteasome system components in spatially sequestered cytoplasmic bodies. This effect is independent of mTORC1 or GCN2. In normal cells, GSK3α promotes survival during essential amino acid starvation. In human leukemia, GSK3α body formation predicts asparaginase resistance, and sensitivity to asparaginase combined with a GSK3α inhibitor. We propose that GSK3α body formation provides a cellular mechanism to maximize the catalytic efficiency of proteasomal protein degradation in response to amino acid starvation, an adaptive response co-opted by cancer cells for asparaginase resistance.

本数据集提交内容包含对应手稿的共聚焦免疫荧光显微镜成像与蛋白质免疫印迹（Western blot）原始图像，该手稿阐述如下内容：氨基酸饥饿耐受性是维持细胞强健生存能力的核心基础。天冬酰胺耗竭会导致部分癌细胞死亡，临床中可通过天冬酰胺酶（asparaginase）靶向利用这一抗癌弱点。我们发现，癌细胞对天冬酰胺饥饿的耐药性，唯一依赖于糖原合成激酶3α（GSK3α）的N端低复杂度结构域，而该结构域在其旁系同源蛋白糖原合成激酶3β（GSK3β）中缺失。当包括天冬酰胺、亮氨酸或缬氨酸在内的特定氨基酸发生耗竭时，该结构域介导GSK3α与泛素-蛋白酶体系统（ubiquitin-proteasome system）组分在空间隔离的细胞质体中形成超分子组装。该效应不依赖于雷帕霉素靶蛋白复合物1（mTORC1）与通用调控非阻遏2蛋白（GCN2）。在正常细胞中，GSK3α可在必需氨基酸饥饿状态下促进细胞存活。在人类白血病中，GSK3α体的形成可预测癌细胞对天冬酰胺酶的耐药性，以及对天冬酰胺酶联合GSK3α抑制剂的敏感性。我们提出，GSK3α体的形成是一种细胞适应性机制：在氨基酸饥饿状态下，该机制可最大化蛋白酶体介导的蛋白质降解催化效率，而癌细胞可劫持这一适应性通路以获得天冬酰胺酶耐药性。