Migrasome-driven mitocytosis relieves mitochondrial damage induced by chikungunya virus viroporins TF and 6K

By employing a cell culture model of chikungunya virus (CHIKV) infection, the research team led by Professor Leiliang Zhang (Shandong First Medical University) found that CHIKV induces mitochondrial damage. Transmission electron microscopy (TEM) revealed notable mitochondrial abnormalities in CHIKV-infected Huh7.5.1 cells, characterized by swollen cristae and vacuolar-like damage, indicating that CHIKV infection disrupts normal mitochondrial function. Furthermore, the presence of damaged mitochondria was detected in migrasomes, suggesting that CHIKV infection triggers mitochondrial dysfunction alongside migrasome-mediated mitocytosis.

To further understand the underlying mechanisms of mitochondrial impairment, the researchers evaluated mitochondrial membrane potential (MMP) using the MMP indicator probe MT-1. The results demonstrated a significant decrease in MMP in CHIKV-infected Huh7.5.1 cells compared to controls. Immunofluorescence assays confirmed that migrasomes produced following infection contained mitochondrial membrane protein prohibitin 2 (PHB2). Uninfected cells showed no production of migrasomes containing mitochondria, while CHIKV-infected cells produced a substantial number enriched with damaged mitochondria, further substantiating the role of migrasome-mediated mitocytosis in relieving mitochondrial stress. The study then shifted focus to specific CHIKV proteins contributing to mitochondrial damage. By overexpressing ten CHIKV proteins tagged with green fluorescent protein (GFP), a marked reduction in MMP was observed in cells expressing the structural proteins TF and 6K, implying their role in inducing mitochondrial dysfunction. To validate these findings, the researchers introduced a frameshifting inhibitor, merafloxacin, which reduced TF production during CHIKV infection. Cells treated with merafloxacin showed partial recovery of MMP, indicating that TF and 6K are critical mediators of mitochondrial impairment associated with CHIKV. Exploring the role of nsP1, another CHIKV protein, the team found that nsP1 significantly facilitated migrasome formation, thereby enhancing mitochondrial quality control. In cells co-transfected with nsP1 and either TF or 6K, migrasomes enriched with mitochondria were observed, alongside an observed improvement in MMP, suggesting that nsP1 mitigates TF/6K-induced mitochondrial damage.

The study also identified a conserved arginine residue (R37) in TF and 6K critical for mitochondrial damage. R37S mutant viruses exhibited intact mitochondrial morphology in infected cells compared to wild-type CHIKV, pointing to the importance of this residue in inducing mitochondrial dysfunction. The researchers observed that the R37S mutation resulted in lower cytosolic and mitochondrial calcium levels, further supporting the idea that R37 is essential for viroporin activity, which contributes to mitochondrial impairment. RNA sequencing analysis revealed that genes associated with endoplasmic reticulum (ER) protein processing were upregulated in wild-type CHIKV compared to the R37S mutant, indicating that R37 plays a crucial role in the mitochondrial damage mediated by viroporins.

“These findings elucidate the mechanisms by which CHIKV disrupts mitochondrial integrity and function, highlighting potential therapeutic targets to alleviate virally induced mitochondrial damage,” said Professor Leiliang Zhang, “This study offers critical insights into the role of viroporins as pivotal factors in mitochondrial dysfunction and migrasome formation, enhancing our comprehension of CHIKV biology. It establishes a foundation for exploring viroporin-targeted therapeutic interventions aimed at mitigating the adverse effects of CHIKV on mitochondrial function and overall cellular health.”

Future directions include validating the current findings in an in vivo animal model and extending the conclusions to other alphaviruses. This study establishes mitocytosis as a key function of virus-induced migrasomes, prompting researchers to further investigate the role of migrasomes in other viral infections.

About Author:

Leiliang Zhang earned his B.S. and Ph.D. in Biochemistry and Molecular Biology from Peking University in China. He then completed postdoctoral studies at Harvard Medical School and the University of Florida. Prior to joining Shandong First Medical University and Shandong Academy of Medical Sciences as a professor, he served as a principal investigator at the Institute of Pathogen Biology, Chinese Academy of Medical Sciences, and Peking Union Medical College. His research interests focus on investigating host-virus interactions, and he has made significant contributions to the understanding of various viruses, including Hepatitis C Virus (HCV), Chikungunya Virus (CHIKV), and poxvirus. Notable discoveries from his work include the identification of virus-induced migrasomes, elucidation of how HCV manipulates PI4P, and characterization of how viruses hijack SNX27-mediated endocytosis. Additionally, he serves as an editor for Microbiology Spectrum and Frontiers in Microbiology.