The Role of Reversible Protein Phosphorylation in Regulation of the Mitochondrial Electron Transport System During Hypoxia and Reoxygenation Stress in Marine Bivalves

• Published in: Frontiers in Marine Science
• Main Authors: Halina I. Falfushynska, Eugene Sokolov, Helen Piontkivska, Inna M. Sokolova
• Format: Article in Journal/Newspaper
• Language: English
• Published: Frontiers Media S.A. 2020
• Subjects: hypoxia; reoxygenation; post-translational modification (PTM); mitochondrial electron transport chain (ETC); Mollusca; respiratory complexes; Science; Q; General. Including nature conservation; geographical distribution; QH1-199.5; Arctic; Pacific; Arctica islandica; Crassostrea gigas; Pacific oyster
• Online Access: https://doi.org/10.3389/fmars.2020.00467; https://doaj.org/article/d850af1683ba4090b8155e3374eb0c10

Fluctuations in the ambient oxygen concentrations represent a major stressor for aerobic organisms causing ATP deficiency during hypoxia and excessive production of reactive oxygen species during reoxygenation. Modulation of the mitochondrial electron transport system activity was proposed as a major mechanism involved in both the mitochondrial injury and adaptive response, but the mechanisms of ETS regulation during hypoxia/reoxygenation (H/R) stress remain poorly understood in hypoxia-tolerant organisms. To address this gap, we focused on the effects of H/R on activities of the mitochondrial Complexes I and IV in hypoxia-tolerant marine bivalves, the blue mussel Mytilus edulis, the Arctic quahog Arctica islandica and the Pacific oyster Crassostrea gigas, exposing them for 1 or 6 days to extreme hypoxia (<0.1% O2) followed by 1 h of reoxygenation. We used a combination of bioinformatics analysis, biochemical and molecular studies to examine the potential role of the reversible protein phosphorylation in regulation of the Complex I and IV activities and in the mitochondrial responses to H/R stress. Our results showed a strong species-specific modulation of two important kinases, the serine/threonine protein kinase A (PKA) and protein kinase C (PKC) by H/R stress in the studied bivalves. The mitochondrial Complexes I and IV emerged as important targets for modulation by H/R stress, mediated in part through reversible phosphorylation by PKA and PKC. The effects of the reversible phosphorylation on the enzyme activities were species- and condition-specific. In mussels and quahogs, phosphorylation by PKA and PKC led to a strong increase in activity of Complexes I and IV. In oysters, Complexes I and IV were insensitive to PKA and PKC activation except after prolonged hypoxia and reoxygenation when elevated sensitivity to PKA and PKC activation indicated a change in the configuration and/or isoform composition of these enzymes. Non-site-specific dephosphorylation strongly suppressed the activity of Complex I and IV ...