Cytochrome c Oxidase Subunit 4 Isoform Exchange Results in Modulation of Oxygen Affinity

0524126 - FGÚ 2021 RIV CH eng J - Journal Article
Pajuelo-Reguera, David - Čunátová, Kristýna - Vrbacký, Marek - Pecinová, Alena - Houštěk, Josef - Mráček, Tomáš - Pecina, Petr
Cytochrome c Oxidase Subunit 4 Isoform Exchange Results in Modulation of Oxygen Affinity.
Cells. Roč. 9, č. 2 (2020), č. článku 443. E-ISSN 2073-4409
R&D Projects: GA ČR(CZ) GA16-13671S; GA MZd(CZ) NV17-28784A
Institutional support: RVO:67985823
Keywords : mitochondria * OXPHOS * respiratory chain * cytochrome c oxidase * COX * COX4 isoforms * COX4i2 * oxygen affinity * p(50) * oxygen sensing
OECD category: Biochemistry and molecular biology
Impact factor: 6.600, year: 2020
Method of publishing: Open access
https://www.mdpi.com/2073-4409/9/2/443

Cytochrome c oxidase (COX) is regulated through tissue-, development- or environment-controlled expression of subunit isoforms. The COX4 subunit is thought to optimize respiratory chain function according to oxygen-controlled expression of its isoforms COX4i1 and COX4i2. However, biochemical mechanisms of regulation by the two variants are only partly understood. We created an HEK293-based knock-out cellular model devoid of both isoforms (COX4i1/2 KO). Subsequent knock-in of COX4i1 or COX4i2 generated cells with exclusive expression of respective isoform. Both isoforms complemented the respiratory defect of COX4i1/2 KO. The content, composition, and incorporation of COX into supercomplexes were comparable in COX4i1- and COX4i2-expressing cells. Also, COX activity, cytochrome c affinity, and respiratory rates were undistinguishable in cells expressing either isoform. Analysis of energy metabolism and the redox state in intact cells uncovered modestly increased preference for mitochondrial ATP production, consistent with the increased NADH pool oxidation and lower ROS in COX4i2-expressing cells in normoxia. Most remarkable changes were uncovered in COX oxygen kinetics. The p(50) (partial pressure of oxygen at half-maximal respiration) was increased twofold in COX4i2 versus COX4i1 cells, indicating decreased oxygen affinity of the COX4i2-containing enzyme. Our finding supports the key role of the COX4i2-containing enzyme in hypoxia-sensing pathways of energy metabolism.
Permanent Link: http://hdl.handle.net/11104/0308474