Giordano 2023 MiPschool Obergurgl

Giordano 2023 MiPschool Obergurgl

Mitochondrial cytochrome c oxidase subunit 4 isoform 2 (Cox4i2) promotes the hypoxia-induced reduction of the electron transfer system and fosters superoxide production.

Link: MiPschool Obergurgl 2023

Giordano Luca (2023)

Event: MiPschool Obergurgl 2023

Authors: Giordano Luca, Nolte A, Wittig Ilka, Pak Oleg, Knoepp F, Ramser K, Wahl J, Cabrera A, Huettemann Maik, Grossman Lawrence, Pecina Petr, Ghofrani HA, Seeger W, Weissmann Norbert, Giehl K, Sommer Natascha

Introduction: Hypoxia in the lung alveoli triggers the contraction of the small precapillary pulmonary arteries, i.e., hypoxic pulmonary vasoconstriction (HPV), avoiding life-threatening hypoxemia. Pulmonary arterial smooth muscle cells (PASMCs) are involved in HPV, with the mitochondrial cytochrome c oxidase (COX) subunit 4 isoform 2 (Cox4i2) playing an essential role in the acute oxygen sensing1. Nonetheless, the molecular mechanism by which Cox4i2 sensitizes the whole COX remains unclear.
Methods: We analysed superoxide production by MitoSOX, oxygen consumption by high-resolution respirometry, redox changes of the electron transport system (ETS) by RAMAN spectroscopy, and supercomplex formation by blue native gel analysis of PASMCs isolated from wild type (WT) and Cox4i2 knockout mice (Cox4i2 KO) exposed to normoxia or hypoxia. To figure out the role of Cox4i2-specific cysteine residues we generated mouse epithelial (CMT167) cells overexpressing either Cox4i1, or WT Cox4i2, or Cox4i2 mutants (C41S, C55A, C109S), and we tested their superoxide production and oxygen affinity.
Results: Respiration, abundance, and COX assembly were similar in WT and Cox4i2 KO PASMCs. On the contrary, hypoxia-induced production of superoxide and the reduction of ETS components (NADH, ubiquinol, cytochrome c) was prevented in Cox4i2 KO PASMCs. CMT167 cells expressing either Cox4i1, or Cox4i2 mutants lacked hypoxia-induced superoxide production, which was detected only in cells expressing WT Cox4i2. Overexpression of Cox4i1, or Cox4i2, or Cox4i2 mutants did not affect oxygen affinity. Our findings suggests that Cox4i2 does not alter superoxide production by rearrangement of supercomplexes, but by the reduction of the ETS, likely mediated by the cysteine residues. Sommer N, Hüttemann M, et al. Mitochondrial Complex IV Subunit 4 Isoform 2 Is Essential for Acute Pulmonary Oxygen Sensing. Circ Res. 2017;121(4):424-38.

• Keywords: cytochrome c oxidase, hypoxia, oxygen sensing, Cox4i2

• O2k-Network Lab: DE Giessen Weissmann N

Affiliations and acknowledgements

Giordano L¹, Nolte A¹, Wittig I², Pak O¹, Knoepp F¹, Ramser K³, Wahl J³, Cabrera A², Hüttemann M⁴, Grossman LI⁴, Pecina P⁵, Ghofrani HA¹, Seeger W^1,6, Weissmann N¹, Giehl K⁷, Sommer N¹

1. Dept. of Internal Medicine, Univ. of Giessen and Marburg Lung Center, Member of the German Center for Lung Research, Excellence Cluster Cardio-Pulmonary Institute, Justus-Liebig Univ., Giessen, Germany
2. Institute for Cardiovascular Physiology, Goethe-Univ., Frankfurt, Germany
3. Dept of Engineering Sciences and Mathematics, Luleå Univ. of Technology, Luleå, Sweden
4. Center for Molecular Medicine and Genetics, Wayne State Univ. School of Medicine, Detroit, USA
5. Laboratory of Bioenergetics, Institute of Physiology CAS, Prague, Czech Republic
6. Institute for Lung Health, Justus-Liebig Univ., Giessen, Germany
7. Department of Internal Medicine, Justus-Liebig Univ., Giessen, Germany

Corresponding author: Natascha.Sommer@innere.med.uni-giessen.de

Funding: Supported by the German Research Foundation (DFG) – Project number 268555672 – SFB 1213, Project A06, and by the O2k-Network Award.

Labels:

Stress:Hypoxia 

Enzyme: Complex IV;cytochrome c oxidase 

Event: Poster