Cilenti Lucia, Mahar Rohit, Di Gregorio Jacopo, Ambivero Camilla T, Merritt Matthew E, Zervos Antonis S
Burnett School of Biomedical Sciences, University of Central Florida College of Medicine, Orlando, FL, United States.
Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, FL, United States.
Front Cell Dev Biol. 2022 Jun 29;10:904728. doi: 10.3389/fcell.2022.904728. eCollection 2022.
MUL1 is a multifunctional E3 ubiquitin ligase that is involved in various pathophysiological processes including apoptosis, mitophagy, mitochondrial dynamics, and innate immune response. We uncovered a new function for MUL1 in the regulation of mitochondrial metabolism. We characterized the metabolic phenotype of MUL1(-/-) cells using metabolomic, lipidomic, gene expression profiling, metabolic flux, and mitochondrial respiration analyses. In addition, the mechanism by which MUL1 regulates metabolism was investigated, and the transcription factor HIF-1α, as well as the serine/threonine kinase Akt2, were identified as the mediators of the MUL1 function. MUL1 ligase, through K48-specific polyubiquitination, regulates both Akt2 and HIF-1α protein level, and the absence of MUL1 leads to the accumulation and activation of both substrates. We used specific chemical inhibitors and activators of HIF-1α and Akt2 proteins, as well as Akt2(-/-) cells, to investigate the individual contribution of HIF-1α and Akt2 proteins to the MUL1-specific phenotype. This study describes a new function of MUL1 in the regulation of mitochondrial metabolism and reveals how its downregulation/inactivation can affect mitochondrial respiration and cause a shift to a new metabolic and lipidomic state.
MUL1是一种多功能E3泛素连接酶，参与包括细胞凋亡、线粒体自噬、线粒体动力学和固有免疫反应在内的各种病理生理过程。我们发现了MUL1在调节线粒体代谢方面的新功能。我们使用代谢组学、脂质组学、基因表达谱分析、代谢通量分析和线粒体呼吸分析对MUL1基因敲除（MUL1(-/-)）细胞的代谢表型进行了表征。此外，我们还研究了MUL1调节代谢的机制，并确定转录因子HIF-1α以及丝氨酸/苏氨酸激酶Akt2是MUL1功能的介导因子。MUL1连接酶通过K48特异性多聚泛素化调节Akt2和HIF-1α的蛋白水平，MUL1的缺失会导致这两种底物的积累和激活。我们使用HIF-1α和Akt2蛋白的特异性化学抑制剂和激活剂，以及Akt2基因敲除（Akt2(-/-)）细胞，来研究HIF-1α和Akt2蛋白对MUL1特异性表型的各自贡献。本研究描述了MUL1在调节线粒体代谢方面的新功能，并揭示了其下调/失活如何影响线粒体呼吸并导致向新的代谢和脂质组状态转变。
