J Biol Chem. 2025 Jul 31. pii: S0021-9258(25)02406-8. [Epub ahead of print] 110555
Runtai Chen,
Seyed Amirhossein Tabatabaei Dakhili,
Rokas Geruskis,
Yuan Yuan Zhao,
Steven Lockhart,
Lusine Tonoyan,
Arno Siraki,
Guocheng Huang,
Adam Kinnaird,
Darren H Freed,
Shelley Minteer,
Evangelos D Michelakis,
John R Ussher,
Gopinath Sutendra.
The mitochondrial Electron Transport Chain (ETC) is a four complex unit that could be considered the most essential infrastructure within the mitochondria, as it primarily functions to generate the mitochondrial membrane potential (ΔΨm, the cells equivalent to battery capacity), which can then be utilized for ATP synthesis or heat production. Another important aspect of ETC function is the generation of mitochondrial reactive oxygen species (mtROS), which are essential physiologic signaling mediators that can be toxic to the cell if their levels become too high. Currently, it remains unresolved how a highly utilized and functioning ETC can sense excessive mtROS generation and adapt, to enhance ΔΨm. Here we identified a redox hub consisting of cysteine (Cys) residues 64, 75, 78 and 92 within Ndufs1 of complex I of the ETC. Oxidation of these Cys residues promotes the incorporation of complex I into the respirasome supercomplex. Mechanistically, oxidation of the redox hub increased the distance between Fe-S clusters N5 and N6a in complex I, compromising complex I activity. This impairment was rescued by integration with complex III2 and IV into the respirasome supercomplex. Compared to parental cells or Ndufs1-KO cells, C92D (an oxidation mimetic) Ndufs1-knockin A549 cells had higher levels of ETC supercomplexes, ΔΨm and oxygen consumption rates, while isolated mitochondrial membranes generated more electrical current when integrated onto a biobattery platform. Knockdown of complex III2 significantly reduced complex I activity (within the respirasome) from C92D Ndufs1-knockin cells, but not parental A549 cells. Finally, disruption of ETC supercomplexes with the small molecule drug MitoTam increased the therapeutic efficacy of mtROS inducing chemotherapeutics in both C92D Ndufs1-knockin or metastatic lung cancer cells. These findings provide new insights into how the ETC can initiate supercomplex transformation.
Keywords: Cancer Resistance; Cysteine Oxidation; Electron Transport Chain; Mitochondria; Reactive Oxygen Species; Supercomplex