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Shigella flexneri-Encoded E3 Ubiquitin Ligase IpaH2 Reveals Plakophilin-2 as a Host Restriction Factor for Sindbis
Aaron Embry1, Emily A Rex1, David F Schad1
1Department of Microbiology, University of Texas Southwestern Medical Center, Dallas, TX 75390, USA.
Abstract:
Arthropod-borne viruses (arboviruses) cause a wide range of acute and chronic diseases and represent a growing global health burden. Although some vaccines exist, antiviral therapies remain limited. Identifying host restriction factors may enable new therapeutic strategies. We previously showed that bacterial effector proteins can serve as tools to uncover innate immune defenses. Here, we used a bacterial effector screen in bat cells to identify host factors restricting the arboviruses Sindbis virus (SINV) and O'nyong'nyong virus (ONNV). Several effectors enhanced infection by both viruses. However, we found the Shigella flexneri-encoded E3 ubiquitin ligase IpaH2 to selectively promote SINV replication. IpaH2 enhanced SINV infection across multiple mammalian cell lines, suggesting that it targets a conserved antiviral mechanism, and this effect required IpaH2 E3 ubiquitin ligase activity. Screening of putative IpaH2 host targets identified via ubiquitin-activated interaction trap (UBAIT) assays revealed the host factors ATP-binding cassette sub-family F member 3 (ABCF3) and Plakophilin-2 (PKP2) to play roles in restricting SINV infection. While ABCF3 broadly restricted multiple viruses, PKP2 specifically limited SINV replication, indicating a virus-specific restriction factor. These findings demonstrate that bacterial effector screening can identify both broadly acting and virus-specific host defenses, providing insight into antiviral mechanisms and potential therapeutic targets.
Insights
Bacterial proteins reveal how cells fight arboviruses like Sindbis virus (SINV). Researchers identified host factors, ABCF3 and Plakophilin-2 (PKP2), that restrict SINV, offering new antiviral therapy targets.
Area of Science:
- Virology
- Immunology
- Microbiology
Background:
- Arthropod-borne viruses (arboviruses) pose a significant global health threat with limited antiviral treatments.
- Host restriction factors are crucial for innate immunity against viral infections.
- Bacterial effector proteins can be used as tools to identify host antiviral mechanisms.
Purpose of the Study:
- To identify host factors that restrict arboviruses using a bacterial effector screen.
- To investigate the role of bacterial E3 ubiquitin ligase IpaH2 in arbovirus replication.
- To discover novel antiviral targets for therapeutic strategies.
Main Methods:
- Bacterial effector screen in bat cells to identify host restriction factors for Sindbis virus (SINV) and O'nyong'nyong virus (ONNV).
- Assessed the effect of *Shigella flexneri* IpaH2 on SINV replication across mammalian cell lines.
- Utilized ubiquitin-activated interaction trap (UBAIT) assays to identify IpaH2 host targets.
Main Results:
- The bacterial effector IpaH2 selectively promoted SINV replication, requiring its E3 ubiquitin ligase activity.
- Identified ATP-binding cassette sub-family F member 3 (ABCF3) and Plakophilin-2 (PKP2) as host factors restricting SINV infection.
- ABCF3 showed broad antiviral activity, while PKP2 specifically restricted SINV, indicating a virus-specific factor.
Conclusions:
- Bacterial effector screening is effective in identifying both broad and virus-specific host antiviral defenses.
- ABCF3 and PKP2 are key host factors involved in restricting arbovirus infection, particularly SINV.
- These findings provide insights into antiviral mechanisms and potential therapeutic targets for arboviruses.
