Microsomal glutathione transferase 1 is not S-nitrosylated in rat liver microsomes or in endotoxin challenged rats

Area of Science:

• Biochemistry
• Molecular Biology
• Toxicology

Background:

• S-nitrosylation is a post-translational modification regulating protein function.
• Microsomal glutathione transferase 1 (MGST1) activation by S-nitrosylation in vitro has been previously reported.
• The in vivo relevance of MGST1 S-nitrosylation remains unclear.

Purpose of the Study:

• To investigate the in vivo relevance of MGST1 S-nitrosylation.
• To identify S-nitrosylated proteins in rat liver microsomes under physiological and stress conditions.

Main Methods:

• Treatment of rat liver microsomes with S-nitrosoglutathione (GSNO).
• Induction of nitrosative stress in rats via endotoxin challenge.
• Analysis of protein S-nitrosylation using matrix-assisted laser dissociation/ionization time-of-flight mass spectrometry (MALDI-TOF MS).

Main Results:

• S-nitrosylated MGST1 was not detected in rat liver microsomes, even after GSNO treatment or endotoxin challenge.
• Several other liver microsomal proteins, including retinol dehydrogenase type I (RODH I), aldolase B, cytochrome P4502C11, and peroxiredoxin 1, were identified as S-nitrosylable.
• These findings indicate that MGST1 S-nitrosylation is unlikely to play a role in the defense against endotoxin-induced nitrosative stress.

Conclusions:

• MGST1 S-nitrosylation is not a significant mechanism for protection against nitrosative stress in vivo.
• Novel S-nitrosylable microsomal proteins were identified, warranting further investigation.
• The study highlights the complexity of protein regulation by S-nitrosylation in the liver.