USP24 is a cross-reactive DUB targeting MOV10 to regulate IFN-I production

Area of Science:

• Immunology
• Molecular Biology
• Virology

Background:

• Type I Interferon (IFN-I) signaling is crucial for innate immunity against viruses.
• Interferon-Stimulated Gene 15 (ISG15) conjugation (ISGylation) is a key post-translational modification in this response.
• Ubiquitin-specific protease 18 (USP18) is the primary deISGylase, but other deubiquitylating enzymes (DUBs) also process ISG15.

Purpose of the Study:

• To identify novel ISG15-cross-reactive DUBs.
• To elucidate the role of USP24 in ISGylation and innate immune responses.
• To investigate USP24's specific targets and regulatory mechanisms in interferon production.

Main Methods:

• Activity-based protein profiling to identify USP24's DUB activity towards ISG15.
• In vitro enzymatic assays using pro-ISG15 and ISG15-conjugated substrates.
• Cellular studies involving USP24 depletion and knockout to assess ISGylation levels and IFN-β production.
• Proteomic analysis to identify USP24's deISGylation targets, including MOV10.
• Co-immunoprecipitation assays to study protein-protein interactions (MOV10-IFIT3).

Main Results:

• USP24 was identified as an ISG15-cross-reactive DUB, processing ISG15 substrates in vitro.
• USP24 depletion or knockout enhanced ISG15 conjugation and IFN-β production upon viral mimicry, without affecting canonical IFN-I signaling.
• Proteomics identified MOV10 as a specific USP24 deISGylation target.
• ISGylation of MOV10 promotes its interaction with IFIT3, enhancing IFN-β production.
• USP24 negatively regulates this pathway by deISGylating MOV10.

Conclusions:

• USP24 plays a significant role in negatively regulating ISGylation of MOV10 and subsequent IFN-β production.
• USP24 acts as a deISGylase for MOV10, modulating the innate immune response to viral stimuli.
• USP24 represents a potential therapeutic target for infectious and inflammatory diseases due to its role in controlling interferon responses.