Heat shock protein 60 negatively regulates the biological functions of ubiquitin-like protein MNSFβ in macrophages
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Monoclonal nonspecific suppressor factor β (MNSFβ) is a ubiquitously expressed ubiquitin-like protein known to be involved in various biological functions. Previous studies have demonstrated that MNSFβ covalently modify its target proteins including Bcl-G, a proapoptotic protein. In this study, we purified a 65 kDa MNSFβ adduct from mouse liver lysates by sequential chromatography on DEAE and glutathione S-transferase (GST)-fusioned MNSFβ immobilized on glutathione-Sepharose beads in the presence of ATP. MALDI-TOF mass spectrometry fingerprinting revealed that this MNSFβ adduct consists of an 8.5 kDa MNSFβ and heat shock protein 60 (HSP60), a mitochondrial protein involved in protein folding. Fingerprinting analysis of the MNSFβ adduct demonstrates that MNSFβ conjugates to HSP60 with a linkage between the C-terminal Gly74 and Lys481. HSP60 siRNA neutralized the inhibition of apoptosis by MNSFβ siRNA in LPS/IFNγ-stimulated Raw264.7, a murine macrophage cell line. HSP60 siRNA also down-regulated the enhancement of TNFα production by MNSFβ siRNA in LPS-stimulated Raw264.7 cells. Here, we firstly report that MNSFβ activity is negatively regulated by molecular chaperone.
KeywordsUbiquitin-like protein Molecular chaperone Inflammation responses
Monoclonal nonspecific suppressor factor
Heat shock protein 60
This work was supported by a grant-in-aid for scientific research (C) to M.N. (17K07335) from the Ministry of Education, Culture, Sports, Science and Technology of Japan.
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Conflict of interest
All authors declare that they have no competing interest.
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