Molecular mechanism of infectious spleen and kidney necrosis virus in manipulating the hypoxia-inducible factor pathway to augment virus replication

ABSTRACT

Infectious spleen and kidney necrosis virus (ISKNV), a member of the genus Megalocytivirus in the family Iridoviridae, can infect over 50 fish species and cause significant economic losses in Asia. Our previous study showed that hypoxia triggers the hypoxia-inducible factor pathway (HIF-pathway), leading to increased replication of ISKNV through promoting the upregulation of viral hypoxic response genes like orf077r. This study delved into the molecular mechanism of how ISKNV manipulates the HIF-pathway to enhance its replication. In vitro and in vivo experiments confirmed that ISKNV infection activated the HIF-pathway, which in turn promoted ISKNV replication. These findings suggest that ISKNV actively manipulates the HIF-pathway. Co-immunoprecipitation experiments revealed that the ISKNV-encoded protein VP077R interacts with the Von Hippel−Lindau (VHL) protein at the HIF-binding region, competitively inhibiting the interaction of HIF-1α with VHL. This prevents HIF degradation and activates the HIF-pathway. Furthermore, VP077R interacts with factor-inhibiting HIF (FIH), recruiting FIH and S-phase kinase-associated protein 1 (Skp1) to form an FIH – VP077R – Skp1 complex. This complex promotes FIH protein degradation via ubiquitination, further activating the HIF-pathway. These findings indicated that ISKNV takes over the HIF-pathway by releasing two “brakes” on this pathway (VHL and FIH) via VP077R, facilitating virus replication. We speculate that hypoxia initiates a positive feedback loop between ISKNV VP077R and the HIF pathway, leading to the outbreak of ISKNV disease. This work offers valuable insights into the complex interactions between the environment, host, and virus.

KEYWORDS:

• HIF-pathway
• FIH
• VHL
• hypoxia
• iridovirus

Acknowledgements

We grateful to Dr. Dong CF for kindly providing the monoclonal antibody of ISKNV VP101L (mAb2D8, unpublished data).

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data Availability statement

The data that support the findings of this study are openly available in figshare at https://figshare.com/, reference number [10.6084/m9.figshare.25565820].

Ethics statement

The ARRIVE guidelines were followed during your study involving laboratory animals. All animal experiments were performed in accordance with the regulation for animal experimentation of Guangdong Province, China, and were permitted by the Ethics Committee of Sun Yat-sen University (No. 2017080101).

Authorship contribution

Jian He and Yang Yu conducted the experiments. Shaoping Weng and Zhang Qi provided the mandarin fish and ISKNV samples. Jian He, Yang Yu, Wenhui Liu, and Zhimin Li performed the data and laboratory analyses. Changjun Guo and Jian He wrote the article. Changjun Guo conceived the study. Changjun Guo and Jianguo He provided Funding acquisition. All authors contributed to the discussion of the results and provided feedback on the manuscript.

Additional information

Funding

This work was funded by the National Key Research and Development Program of China [grant no. 2022YFE0203900], the China Agriculture Research System [grant no. CARS-46], the Guangdong Key Research and Development Program [grant nos. 2021B0202040002 and 2022B1111030001], the Guangdong Basic and Applied Basic Research Foundation [grant no. 2021A1515010647], the Basic and Applied Basic Research Project of Guangzhou Science and Technology Plan Project [grant no. 202102020299], the Zhuhai basic and applied basic research project [grant no. ZH22017003200008PWC], the Guangdong Laboratory for Lingnan Modern Agriculture [grant no. NZ2021018], and the Science and Technology Planning Project of Guangdong Province [grant no. 2023B1212060023].