Human Metapneumovirus Nucleoprotein Impairs Stress-Induced Mitophagy and Mitochondrial Quality Control

Human metapneumovirus (HMPV) is an important respiratory pathogen for which specific antiviral therapies are currently unavailable, and the mechanisms by which HMPV regulates host mitochondrial homeostasis remain poorly understood. Here, we investigated the role of HMPV nucleoprotein (N) in mitophagy regulation and mitochondrial quality control, with a focus on its association with selective autophagy-related factors. Using recombinant protein purification, surface plasmon resonance, co-immunoprecipitation, confocal microscopy, mitochondrial-targeted mitophagy reporter analysis, and immunoblotting, we examined the interaction between HMPV N and host autophagy-associated factors and evaluated its effects on mitophagy. We demonstrated that HMPV N interacts with TAX1BP1 and LC3, two key components of the selective autophagy machinery. HMPV N signals were spatially associated with mitochondrial regions, and HMPV N expression increased the spatial association of TAX1BP1-positive structures with mitochondria, while reducing the spatial association of LC3-positive structures with TOM20-positive mitochondria under stress conditions. Consistently, HMPV N expression reduced CCCP-induced mitochondrial delivery to acidic compartments and attenuated TOM20 degradation, while exerting limited effects on basal mitochondrial turnover. These findings identify HMPV N as a viral regulator of stress-induced mitophagy and suggest that its interactions with selective autophagy-associated factors contribute to altered mitochondrial homeostasis during infection.