Sirt3 increases CNPase enzymatic activity through deacetylation and facilitating substrate accessibility

Area of Science:

• Biochemistry
• Molecular Biology
• Cardiovascular Research

Background:

• Myocardial 2',3'-cyclic nucleotide 3'-phosphodiesterase (CNPase) plays a role in heart failure pathophysiology.
• SIRT3 is a key regulator of mitochondrial protein acetylation, but its effect on CNPase is unknown.
• Understanding CNPase regulation is crucial for developing new heart failure therapies.

Purpose of the Study:

• To investigate whether CNPase is regulated by acetylation and deacetylation.
• To determine the effect of acetylation on CNPase enzymatic activity.
• To elucidate the molecular mechanism of SIRT3-mediated regulation of CNPase.

Main Methods:

• Immunofluorescence and cell fractionation to determine CNPase mitochondrial localization.
• Biochemical assays to assess CNPase enzymatic activity after acetylation.
• Co-immunoprecipitation coupled with mass spectrometry to identify acetylation sites.
• Molecular dynamics simulations to analyze the structural impact of acetylation.

Main Results:

• CNPase is localized in mitochondria and co-localizes with SIRT3.
• SIRT3 directly associates with CNPase, and its activity regulates CNPase enzymatic function.
• Acetylation of CNPase, particularly at sites K196, K379, and K128, decreases its enzymatic activity.
• Acetylation suppresses CNPase activity by reducing binding pocket opening and substrate access.

Conclusions:

• SIRT3-mediated acetylation is a novel regulatory mechanism for myocardial CNPase enzymatic activity.
• Acetylation of specific lysine residues (K196, K379, K128) inhibits CNPase function.
• Targeting CNPase post-translational modifications presents a promising therapeutic avenue for heart failure.