bims-cytox1 2024-09-15 papers

Issue of 2024‒09‒15
two papers selected by
Gavin McStay, Liverpool John Moores University

Biochim Biophys Acta Bioenerg. 2024 Sep 07. pii: S0005-2728(24)00479-1. [Epub ahead of print] 149509

Stimulation of cytochrome c oxidase activity by detergents.

Irina Smirnova, Fei Wu, Peter Brzezinski.

Cytochrome c oxidase (CytcO) is an integral membrane protein, which catalyzes four-electron reduction of oxygen linked to proton uptake and pumping. Amphipathic molecules bind in sites near the so-called K proton pathway of CytcO to reversibly modulate its activity. However, purification of CytcO for mechanistic studies typically involves the use of detergents, which may interfere with binding of these regulatory molecules. Here, we investigated the CytcO enzymatic activity as well as intramolecular electron transfer linked to proton transfer upon addition of different detergents to bovine heart mitoplasts. The CytcO activity increased upon addition of alkyl glucosides (DDM and DM) and the steroid analog GDN. The maximum stimulating effect was observed for DDM and DM, and the half-stimulating effect correlated with their CMC values. With GDN the stimulation effect was smaller and occurred at a concentration higher than CMC. A kinetic analysis suggests that the stimulation of activity is due to removal of a ligand bound near the K proton pathway, which indicates that in the native membrane this site is occupied to yield a lower than maximal possible CytcO activity. Possible functional consequences are discussed.

Keywords: Kinetics; Membrane protein; Proton pumping; Proton transfer; Respiratory chain

DOI: https://doi.org/10.1016/j.bbabio.2024.149509

Stroke Vasc Neurol. 2024 Sep 11. pii: svn-2024-003099. [Epub ahead of print]

miR-19-3p/GRSF1/COX1 axis attenuates early brain injury via maintaining mitochondrial function after subarachnoid haemorrhage.

Ge Gao, Xiaoyu Sun, Jiajia Xu, Jian Yu, Yang Wang.

BACKGROUND: Guanine-rich RNA sequence binding factor 1 (GRSF1) is an RNA-binding protein, which is eventually localised to mitochondria and promotes the translation of cytochrome C oxidase 1 (COX1) mRNA. However, the role of the miR-19-3p/GRSF1/COX1 axis has not been investigated in an experimental subarachnoid haemorrhage (SAH) model. Thus, we investigated the role of the miR-19-3p/GRSF1/COX1 axis in a SAH-induced early brain injury (EBI) course.METHODS: Primary neurons were treated with oxyhaemoglobin (OxyHb) to simulate in vitro SAH. The rat SAH model was established by injecting autologous arterial blood into the optic chiasma cisterna. The GRSF1 level was downregulated or upregulated by treating the rats and neurons with lentivirus-GRSF1 shRNA (Lenti-GRSF1 shRNA) or lentivirus-GRSF1 (Lenti-GRSF1).
RESULTS: The miR-19-3p level was upregulated and the protein levels of GRSF1 and COX1 were both downregulated in SAH brain tissue. GRSF1 silence decreased and GRSF1 overexpression increased the protein levels of GRSF1 and COX1 in primary neurons and brain tissue, respectively. Lenti-GRSF1 shRNA aggravated, but Lenti-GRSF1 alleviated, the indicators of neuronal injury and neurological impairment in both in vitro and in vivo SAH conditions. In addition, miR-19-3p mimic reduced the protein levels of GRSF1 and COX1 in cultured neurons while miR-19-3p inhibitor increased them. More importantly, Lenti-GRSF1 significantly relieved mitochondrial damage of neurons exposed to OxyHb or induced by SAH and was beneficial to maintaining mitochondrial integrity. Lenti-GRSF1 shRNA treatment, conversely, aggravated mitochondrial damage in neurons.
CONCLUSION: The miR-19-3p/GRSF1/COX1 axis may serve as an underlying target for inhibiting SAH-induced EBI by maintaining mitochondrial integrity.

Keywords: Aneurysm; Cerebrovascular Disorders; Cognitive Dysfunction; Hemorrhage; Stroke

DOI: https://doi.org/10.1136/svn-2024-003099