In vitro rejuvenation of brain mitochondria by the inhibition of actin polymerization

Area of Science:

• Mitochondrial biology
• Cellular respiration
• Neuroscience

Background:

• Brain mitochondrial function, specifically oxygen consumption rate (OCR) and cytochrome c oxidase (CcO) activity of respiratory complex IV (CIV), declines with age in male mice.
• The regulatory mechanisms of mitochondrial function, particularly involving CIV, are not fully understood.

Purpose of the Study:

• To investigate the role of actin in regulating CIV activity and OCR in brain mitochondria.
• To explore the interaction of actin with cytochrome c (cyt c) and its impact on electron transport chain complexes III (CIII) and CIV.

Main Methods:

• Isolation of brain mitochondria from male mice of different age groups.
• Assessment of OCR and CcO activity.
• Identification and quantification of CIV-associated proteins, including actin.
• Inhibition of actin polymerization using cytochalasin B (CB).
• Analysis of cytochrome c binding to CIV and CIII after CB treatment.
• Evaluation of CIV assembly and activity in supercomplexes and monomers.

Main Results:

• Actin was identified within isolated brain mitochondria.
• Inhibition of actin polymerization with CB significantly enhanced mitochondrial OCR and CIV CcO activity.
• CB treatment led to a significant reduction in CIV-bound cytochrome c and an increase in CIII-bound cytochrome c.
• CB did not alter CIV assembly or CcO activity in CIV-containing supercomplexes or CIV monomers.

Conclusions:

• Mitochondrial actin plays a critical role in regulating CIV activity and OCR in brain mitochondria.
• Actin influences the retention of cytochrome c between CIII and CIV, thereby modulating mitochondrial respiration.
• Targeting mitochondrial actin may offer a therapeutic strategy to improve age-related decline in brain mitochondrial function.