Rapamycin insensitive companion of mechanistic target of Rapamycin (Rictor), the key component of mTOR complex 2 (mTORC2), controls both β-cell proliferation and function. We sought to study whether long chain acyl-CoA synthetase 4 (Acsl4) worked downstream of Rictor/mTORC2 to maintain β-cell functional mass. We found Acsl4 was positively regulated by Rictor at transcriptional and posttranslational levels in mouse β-cell. Infecting adenovirus expressing Acsl4 in β-cell-specific-Rictor-knockout (βRicKO) islets and Min6 cells knocking down Rictor with lentivirus-expressing siRNA-oligos targeting Rictor(siRic), recovered the β-cell dysplasia but not dysfunction. Cell bioenergetic experiment performed with Seahorse XF showed that Acsl4 could not rescue the dampened glucose oxidation in Rictor-lacking β-cell, but further promoted lipid oxidation. Transposase-Accessible Chromatin (ATAC) and H3K27Ac chromatin immunoprecipitation (ChIP) sequencing studies reflected the epigenetic elevated molecular signature for β-cell dedifferentiation and mitigated oxidative defense/response. These results were confirmed by the observations of elevated acetylation and ubiquitination of FoxO1, increased protein levels of Gpx1 and Hif1an, excessive reactive oxygen species (ROS) production and diminished MafA in Acsl4 overexpressed Rictor-lacking β-cells. In these cells, antioxidant treatment significantly recovered MafA level and insulin content. Inducing lipid oxidation alone could not mimic the effect of Acsl4 in Rictor lacking β-cell. Our study suggested that Acsl4 function in β-cell was context dependent and might facilitate β-cell dedifferentiation with attenuated Rictor/mTORC2 activity or insulin signaling via posttranslational inhibiting FoxO1 and epigenetically enhancing ROS induced MafA degradation.

雷帕霉素 (Rictor) 是 mTOR 复合物 2 (mTORC2) 的关键成分，它是雷帕霉素机械靶标的不敏感伴侣，控制 β 细胞增殖和功能。我们试图研究长链酰基辅酶 A 合成酶 4 (Acsl4) 是否在 Rictor/mTORC2 下游起作用以维持 β 细胞功能质量。我们发现 Acsl4 在小鼠 β 细胞中的转录和翻译后水平受到 Rictor 的正调控。在 β 细胞特异性 Rictor 敲除 (β Ric KO) 胰岛和 Min6 细胞中感染表达 Acsl4 的腺病毒，用靶向Rictor (si Ric ) 的慢病毒表达 siRNA 寡核苷酸敲低 Rictor ，恢复了 β 细胞发育不良但没有功能障碍。使用 Seahorse XF 进行的细胞生物能实验表明，Acsl4 无法挽救Rictor 中抑制的葡萄糖氧化-缺乏β细胞，但进一步促进脂质氧化。转座酶可及染色质 (ATAC) 和 H3K27Ac 染色质免疫沉淀 (ChIP) 测序研究反映了 β 细胞去分化和减轻氧化防御/反应的表观遗传升高的分子特征。FoxO1 乙酰化和泛素化升高、Gpx1 和 Hif1an 蛋白水平升高、Acsl4 过表达缺乏 Rictor 的 β 细胞中活性氧 (ROS) 产生过多和 MafA 减少，证实了这些结果。在这些细胞中，抗​​氧化剂处理显着恢复了 MafA 水平和胰岛素含量。单独诱导脂质氧化不能模拟 Acsl4 在Rictor 中的作用缺乏β细胞。我们的研究表明，Acsl4 在 β 细胞中的功能是上下文相关的，并且可能通过翻译后抑制 FoxO1 和表观遗传增强 ROS 诱导的 MafA 降解，通过减弱的 Rictor/mTORC2 活性或胰岛素信号促进 β 细胞去分化。