Objectives: Protein phosphatase 2A (PP2A), a major serine/threonine phosphatase, is also known to be a target of ROS. The methylation of PP2A can be catalyzed by leucine carboxyl methyltransferase-1 (LCMT1), which regulates PP2A activity and substrate specificity.

Methods: In the previous study, we have showed that LCMT1-dependent PP2Ac methylation arrests H₂O₂-induced cell oxidative stress damage. To explore the possible protective mechanism, we performed iTRAQ-based comparative quantitative proteomics and phosphoproteomics studies of H₂O₂-treated vector control and LCMT1-overexpressing cells.

Results: A total of 4480 non-redundant proteins and 3801 unique phosphopeptides were identified by this means. By comparing the H₂O₂-regulated proteins in LCMT1-overexpressing and vector control cells, we found that these differences were mainly related to protein phosphorylation, gene expression, protein maturation, the cytoskeleton and cell division. Further investigation of LCMT1 overexpression-specific regulated proteins under H₂O₂ treatment supported the idea that LCMT1 overexpression induced ageneral dephosphorylation of proteins and indicated increased expression of non-erythrocytic hemoglobin, inactivation of MAPK3 and regulation of proteins related to Rho signal transduction, which were known to be linked to the regulation of the cytoskeleton.

Discussion: These data provide proteomics and phosphoproteomics insights into the association of LCMT1-dependent PP2Ac methylation and oxidative stress and indirectly indicate that the methylation of PP2A plays an important role against oxidative stress.

目的：蛋白磷酸酶 2A (PP2A) 是一种主要的丝氨酸/苏氨酸磷酸酶，也是 ROS 的靶标。PP2A 的甲基化可由亮氨酸羧基甲基转移酶-1 (LCMT1) 催化，其调节 PP2A 活性和底物特异性。

方法：在之前的研究中，我们已经表明 LCMT1 依赖性 PP2Ac 甲基化阻止了 H ₂ O ₂诱导的细胞氧化应激损伤。为了探索可能的保护机制，我们对 H ₂ O ₂处理的载体对照和 LCMT1 过表达细胞进行了基于 iTRAQ 的比较定量蛋白质组学和磷酸蛋白质组学研究。

结果：共鉴定出4480个非冗余蛋白和3801个独特的磷酸肽。通过比较LCMT1 过表达和载体对照细胞中H ₂ O ₂调节的蛋白质，我们发现这些差异主要与蛋白质磷酸化、基因表达、蛋白质成熟、细胞骨架和细胞分裂有关。H ₂ O ₂下LCMT1过表达特异性调控蛋白的进一步研究 治疗支持 LCMT1 过表达诱导蛋白质普遍去磷酸化的观点，并表明非红细胞血红蛋白的表达增加、MAPK3 失活和与 Rho 信号转导相关的蛋白质的调节，这些已知与细胞骨架的调节有关。

讨论：这些数据提供了蛋白质组学和磷酸蛋白质组学对 LCMT1 依赖性 PP2Ac 甲基化与氧化应激之间关联的见解，并间接表明 PP2A 的甲基化在对抗氧化应激方面发挥着重要作用。