Department of Biological Sciences, University of Idaho, Moscow, ID 83844, USA.
Department of Microbiology and Molecular Genetics, McGovern Medical School at UTHealth, Houston, TX 77030, USA.
Genetics. 2024 Jun 5;227(2). doi: 10.1093/genetics/iyae057.
Hsp90 is an abundant and essential molecular chaperone that mediates the folding and activation of client proteins in a nucleotide-dependent cycle. Hsp90 inhibition directly or indirectly impacts the function of 10-15% of all proteins due to degradation of client proteins or indirect downstream effects. Due to its role in chaperoning oncogenic proteins, Hsp90 is an important drug target. However, compounds that occupy the ATP-binding pocket and broadly inhibit function have not achieved widespread use due to negative effects. More selective inhibitors are needed; however, it is unclear how to achieve selective inhibition. We conducted a quantitative proteomic analysis of soluble proteins in yeast strains expressing wild-type Hsp90 or mutants that disrupt different steps in the client folding pathway. Out of 2,482 proteins in our sample set (approximately 38% of yeast proteins), we observed statistically significant changes in abundance of 350 (14%) of those proteins (log2 fold change ≥ 1.5). Of these, 257/350 (∼73%) with the strongest differences in abundance were previously connected to Hsp90 function. Principal component analysis of the entire dataset revealed that the effects of the mutants could be separated into 3 primary clusters. As evidence that Hsp90 mutants affect different pools of clients, simultaneous co-expression of 2 mutants in different clusters restored wild-type growth. Our data suggest that the ability of Hsp90 to sample a wide range of conformations allows the chaperone to mediate folding of a broad array of clients and that disruption of conformational flexibility results in client defects dependent on those states.
热休克蛋白 90（Hsp90）是一种丰富且必需的分子伴侣，可在核苷酸依赖性循环中介导客户蛋白的折叠和激活。由于客户蛋白的降解或间接的下游效应，Hsp90 的抑制会直接或间接地影响 10-15%的所有蛋白质的功能。由于其在伴侣致癌蛋白中的作用，Hsp90 是一个重要的药物靶标。然而，由于副作用，占据 ATP 结合口袋并广泛抑制功能的化合物并未得到广泛应用。需要更具选择性的抑制剂；然而，如何实现选择性抑制尚不清楚。我们对表达野生型 Hsp90 或突变体的酵母菌株中的可溶性蛋白进行了定量蛋白质组学分析，这些突变体破坏了客户蛋白折叠途径中的不同步骤。在我们的样本集中的 2482 种蛋白质（约占酵母蛋白的 38%）中，我们观察到其中 350 种蛋白质（log2 倍数变化≥1.5）的丰度发生了统计学上显著的变化（14%）。在这些蛋白质中，有 257/350（∼73%）与 Hsp90 功能的差异最强。对整个数据集的主成分分析表明，突变体的影响可以分为 3 个主要聚类。作为 Hsp90 突变体影响不同客户群体的证据，同时在不同聚类中表达 2 个突变体可以恢复野生型生长。我们的数据表明，Hsp90 能够广泛地取样多种构象的能力允许伴侣介导广泛的客户蛋白折叠，并且构象灵活性的破坏导致依赖于这些状态的客户缺陷。
