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Nitric oxide synthase-2 regulates mitochondrial Hsp60 chaperone function during bacterial peritonitis in mice
Hagir B Suliman1, Abdelwahid Babiker, Crystal M Withers
1Department of Anesthesiology, Duke University Medical Center, Durham, NC 27710, USA.
Free Radical Biology & Medicine
|January 2, 2010
Summary
Nitric oxide synthase-2 (NOS2) is crucial for mitochondrial biogenesis during bacterial infection. It regulates heat shock protein 60 (Hsp60) function, ensuring mitochondrial DNA transcription and replication.
Area of Science:
- Mitochondrial Biology
- Inflammation and Immunology
- Molecular Mechanisms
Background:
- Nitric oxide synthase-2 (NOS2) generates reactive nitrogen species and modifies cysteine residues, impacting mitochondrial function during inflammation.
- Hepatic mitochondrial biogenesis is vital for cellular energy production and response to infection.
Purpose of the Study:
- To investigate the role of NOS2 in hepatic mitochondrial biogenesis during Escherichia coli peritonitis in mice.
- To elucidate the molecular mechanisms by which NOS2 influences mitochondrial function and gene expression.
Main Methods:
- Comparative analysis of NOS2 knockout (NOS2(-/-)) and wild-type (Wt) mice infected with E. coli.
- Measurement of mRNA and protein levels for key mitochondrial biogenesis factors (PGC-1 alpha, NRF-1, Tfam, Pol gamma).
- Assessment of mitochondrial DNA (mtDNA) transcription, copy number, and respiration rates.
- Investigation of heat shock protein 60 (Hsp60) localization and its interaction with NOS2 using reporter mice and biochemical assays (biotin-switch, immunoprecipitation).
Main Results:
- NOS2(-/-) mice exhibited attenuated mitochondrial biogenesis responses, with lower mRNA levels for PGC-1 alpha, NRF-1, Tfam, and Pol gamma.
- Impaired mitochondrial Tfam and Pol gamma protein accumulation, reduced mtDNA transcription, decreased mtDNA copy number, and lower State 3 respiration rates were observed in NOS2(-/-) mice.
- NOS2 blockade disrupted Hsp60 localization to mitochondria.
- NOS2 directly binds to and S-nitrosylates Hsp60 and Hsp70, with (237)Cys identified as a critical residue in Hsp60.
- NOS2-mediated S-nitrosylation of Hsp60 facilitates Tfam accumulation in mitochondria and supports mtDNA transcription and replication.
Conclusions:
- NOS2 plays a significant role in inflammation-induced hepatic mitochondrial biogenesis.
- The mechanism involves NOS2-dependent S-nitrosylation of Hsp60, which is essential for the import and function of Tfam, thereby regulating mtDNA transcription and replication.
- These findings highlight a novel link between NOS2, chaperone protein modification, and mitochondrial homeostasis during infection.
