Mitochondrial dysfunction in lyssavirus-induced apoptosis

Area of Science:

• Virology
• Cell Biology
• Neuroscience

Background:

• Lyssaviruses are neurotropic viruses known to cause neuronal apoptosis.
• The precise molecular mechanisms by which lyssavirus matrix proteins induce apoptosis remain largely unknown.
• Previous studies suggest matrix proteins of certain lyssaviruses contribute to neuronal cell death.

Purpose of the Study:

• To elucidate the molecular mechanism by which the Mokola virus (MOK) matrix protein (M-MOK) induces neuronal apoptosis.
• To identify the specific viral protein regions and cellular targets involved in M-MOK-mediated apoptosis.
• To compare the apoptotic mechanisms of low-pathogenicity M-MOK with high-pathogenicity lyssavirus matrix proteins.

Main Methods:

• Analysis of truncated M-MOK mutants to map functional domains.
• Yeast two-hybrid assays and coimmunoprecipitation to identify protein interactions.
• Confocal microscopy to assess mitochondrial morphology and protein localization.
• Measurement of cytochrome c oxidase (CcO) activity and assessment of cytochrome c release.

Main Results:

• M-MOK targets mitochondria, disrupts morphology, and induces apoptosis via caspase-9 activation.
• The region between residues 46 and 110 of M-MOK is crucial for mitochondrial targeting and apoptosis induction.
• M-MOK physically associates with cytochrome c oxidase (CcO) subunit I, reducing CcO activity.
• Specific mutations in M-MOK (K77R, N81E) mimicking M-THA reduce apoptosis and restore CcO activity, while reverse mutations in M-THA induce M-MOK-like effects.

Conclusions:

• Mokola virus matrix protein induces apoptosis through mitochondrial targeting and disruption of the respiratory chain.
• Interaction with CcO subunit I and subsequent energy depletion is a novel mechanism for lyssavirus-induced apoptosis.
• Specific amino acid residues (77 and 81) dictate the pathogenic potential and apoptotic mechanism of lyssavirus matrix proteins.