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Stat6-protease but not Stat5-protease is inhibited by an elastase inhibitor ONO-5046
Kotaro Suzuki1, Hiroshi Nakajima, Kei Ikeda
1Department of Internal Medicine II, Graduate School of Medicine, Chiba University, Chiba 260-8670, Japan.
Abstract:
A short isoform of Stat6 (65-kDa Stat6), a product of proteolytic processing by an undefined protease (Stat6-protease) in the nucleus, downregulates Stat6-mediated signaling in mast cells. Similarly, Stat5-mediated signaling is downregulated by Stat5-protease in myeloid progenitors. These proteases share a number of characteristics, including their nuclear localization and susceptibility to protease inhibitors. Here, we further investigated these Stat proteases. Interestingly, the activity of Stat6-protease but not of Stat5-protease was inhibited by ONO-5046, an elastase inhibitor that inhibits the activity of neutrophil elastase (NE) and NE-related protease proteinase 3 (PR3). Although both NE and PR3 were able to cleave Stat6 in vitro, the cleavage sites of Stat6 by NE or PR3 differed from that by Stat6-protease in mast cells. In addition, both NE and PR3 could also cleave Stat5, but they differed from Stat5-protease in myeloid progenitors. These results suggest that Stat6-protease may belong to the elastase family but differs from NE or PR3.
Insights
Proteolytic processing of Signal transducer and activator of transcription (Stat) proteins by nuclear proteases downregulates their signaling. Stat6-protease activity is inhibited by elastase inhibitors, suggesting it belongs to the elastase family.
Area of Science:
- Molecular Biology
- Cell Signaling
- Protease Biochemistry
Background:
- Signal transducer and activator of transcription (Stat) proteins play crucial roles in cellular signaling pathways.
- Proteolytic processing of Stat proteins by nuclear proteases generates short isoforms that downregulate signaling.
- Stat6 signaling in mast cells and Stat5 signaling in myeloid progenitors are negatively regulated by specific proteases.
Purpose of the Study:
- To further investigate the characteristics of nuclear Stat proteases involved in Stat protein regulation.
- To determine the identity and specificity of the protease responsible for Stat6 processing in mast cells.
- To compare the properties of Stat6-protease and Stat5-protease.
Main Methods:
- In vitro cleavage assays using purified Stat6 and Stat5 proteins.
- Treatment with protease inhibitors, including ONO-5046 (an elastase inhibitor).
- Analysis of cleavage sites and comparison with known protease activities.
Main Results:
- Stat6-protease activity was inhibited by ONO-5046, suggesting a link to the elastase family.
- Neutrophil elastase (NE) and proteinase 3 (PR3) could cleave Stat6 and Stat5 in vitro.
- However, the cleavage sites by NE and PR3 differed from those generated by Stat6-protease and Stat5-protease in their respective cellular contexts.
- Stat5-protease activity was not affected by ONO-5046.
Conclusions:
- Stat6-protease likely belongs to the elastase family but is distinct from NE and PR3.
- The specificities of Stat proteases differ from canonical elastases like NE and PR3, indicating unique roles in Stat protein regulation.
- Further characterization of these Stat proteases is needed to fully elucidate their functions in cellular signaling.