HIF-1 alpha protein as a target for S-nitrosation

Area of Science:

• Biochemistry
• Cellular Biology
• Physiology

Background:

• Hypoxia-inducible factor-1 alpha (HIF-1 alpha) regulates cellular responses to low oxygen.
• Nitric oxide (NO) is increasingly recognized for its role in stabilizing HIF-1 alpha.
• Reactive nitrogen species, like those involved in S-nitrosation, are known protein modifiers.

Purpose of the Study:

• To investigate whether HIF-1 alpha is a direct target of S-nitrosation.
• To determine the extent and conditions of HIF-1 alpha S-nitrosation.
• To explore the functional consequences of HIF-1 alpha S-nitrosation on its stability.

Main Methods:

• In vitro S-nitrosation assays using purified HIF-1 alpha and various NO donors (GSNO, SNAP, spermine-NONOate).
• Cellular S-nitrosation experiments in RCC4 and HEK293 cells treated with NO donors or stimulated endogenous NO production.
• Assessment of HIF-1 alpha stability and S-nitrosation levels following treatment with N-acetyl-cysteine and inhibitors of NO synthesis.

Main Results:

• Purified HIF-1 alpha underwent extensive S-nitrosation of all 15 free thiol groups with NO+ donors.
• Cellular S-nitrosation of HIF-1 alpha was less extensive, modifying 3-4 thiols, but was inducible by endogenous NO.
• S-nitrosation of HIF-1 alpha correlated with its stability, and N-acetyl-cysteine treatment destabilized S-nitrosated HIF-1 alpha.

Conclusions:

• HIF-1 alpha is a direct target for S-nitrosation by both exogenous and endogenous nitric oxide.
• S-nitrosation represents a novel post-translational modification of HIF-1 alpha.
• This modification influences HIF-1 alpha stability and cellular oxygen sensing mechanisms.