bims-cytox1 2023-10-29 papers

Issue of 2023‒10‒29
two papers selected by
Gavin McStay, Liverpool John Moores University

Int J Mol Sci. 2023 Oct 13. pii: 15144. [Epub ahead of print]24(20):

Mitochondrial sAC-cAMP-PKA Axis Modulates the ΔΨm-Dependent Control Coefficients of the Respiratory Chain Complexes: Evidence of Respirasome Plasticity.

Rosella Scrima, Olga Cela, Michela Rosiello, Ari Qadir Nabi, Claudia Piccoli, Giuseppe Capitanio, Francesco Antonio Tucci, Aldo Leone, Giovanni Quarato, Nazzareno Capitanio.

The current view of the mitochondrial respiratory chain complexes I, III and IV foresees the occurrence of their assembly in supercomplexes, providing additional functional properties when compared with randomly colliding isolated complexes. According to the plasticity model, the two structural states of the respiratory chain may interconvert, influenced by the intracellular prevailing conditions. In previous studies, we suggested the mitochondrial membrane potential as a factor for controlling their dynamic balance. Here, we investigated if and how the cAMP/PKA-mediated signalling influences the aggregation state of the respiratory complexes. An analysis of the inhibitory titration profiles of the endogenous oxygen consumption rates in intact HepG2 cells with specific inhibitors of the respiratory complexes was performed to quantify, in the framework of the metabolic flux theory, the corresponding control coefficients. The attained results, pharmacologically inhibiting either PKA or sAC, indicated that the reversible phosphorylation of the respiratory chain complexes/supercomplexes influenced their assembly state in response to the membrane potential. This conclusion was supported by the scrutiny of the available structure of the CI/CIII2/CIV respirasome, enabling us to map several PKA-targeted serine residues exposed to the matrix side of the complexes I, III and IV at the contact interfaces of the three complexes.

Keywords: cAMP/PKA signaling pathway; metabolic flux theory; mitochondrial membrane potential; mitochondrial respiratory chain complexes; soluble adenylate cyclase; supercomplexes

DOI: https://doi.org/10.3390/ijms242015144

Int J Mol Sci. 2023 Oct 16. pii: 15229. [Epub ahead of print]24(20):

OXPHOS Organization and Activity in Mitochondria of Plants with Different Life Strategies.

Irina V Ukolova, Gennadii B Borovskii.

The study of the supramolecular organization of the mitochondrial oxidative phosphorylation system (OXPHOS) in various eukaryotes has led to the accumulation of a considerable amount of data on the composition, stoichiometry, and architecture of its constituent superstructures. However, the link between the features of system arrangement and the biological characteristics of the studied organisms has been poorly explored. Here, we report a comparative investigation into supramolecular and functional OXPHOS organization in the mitochondria of etiolated shoots of winter wheat (Triticum aestivum L.), maize (Zea mays L.), and pea (Pisum sativum L.). Investigations based on BN-PAGE, in-gel activity assays, and densitometric analysis revealed both similarities and specific OXPHOS features apparently related to the life strategies of each species. Frost-resistant winter wheat was distinguished by highly stable basic I1III2IVa/b respirasomes and V2 dimers, highly active complex I, and labile complex IV, which were probably essential for effective OXPHOS adaptation during hypothermia. Maize, a C4 plant, had the highly stable dimers IV2 and V2, less active complex I, and active alternative NAD(P)H dehydrogenases. The latter fact could contribute to successful chloroplast-mitochondrial cooperation, which is essential for highly efficient photosynthesis in this species. The pea OXPHOS contained detergent-resistant high-molecular respirasomes I1-2III2IVn, highly active complexes IV and V, and stable succinate dehydrogenase, suggesting an active energy metabolism in organelles of this plant. The results and conclusions are in good agreement with the literature data on the respiratory activity of mitochondria from these species and are summarized in a proposed scheme of organization of OXPHOS fragments.

Keywords: BN-PAGE; OXPHOS; maize; pea; plant mitochondria; supercomplexes; winter wheat

DOI: https://doi.org/10.3390/ijms242015229