DNA damage-induced Bcl-xL deamidation is mediated by NHE-1 antiport regulated intracellular pH

Area of Science:

• Molecular Biology
• Cancer Research
• Cell Signaling

Background:

• The pro-survival protein Bcl-xL is crucial for tumor cell resistance to DNA damage.
• Oncogenic tyrosine kinase inhibition of DNA damage-induced Bcl-xL deamidation correlates with T cell transformation.
• The pathway and functional consequences of Bcl-xL deamidation are not fully understood.

Purpose of the Study:

• To elucidate the signaling pathway of DNA damage-induced Bcl-xL deamidation.
• To investigate the functional consequences of Bcl-xL deamidation.
• To explore novel cancer therapeutic strategies based on this pathway.

Main Methods:

• Investigated the effects of DNA damage on Bcl-xL deamidation in mouse cancer models and thymocytes.
• Utilized the NHE-1 Na/H antiport and intracellular pH changes to study the pathway.
• Examined the impact of enforced intracellular alkalinization on tumor cells and leukemia cells.

Main Results:

• Bcl-xL deamidation generates a species unable to sequester pro-apoptotic BH3-only proteins (Bim, Puma).
• DNA damage induces NHE-1 antiport expression, leading to intracellular alkalinization, Bcl-xL deamidation, and apoptosis.
• This cascade is blocked in murine thymocytes and tumor cells with oncogenic tyrosine kinase.
• Enforced alkalinization mimics DNA damage effects, causing deamidation and apoptosis in cancer cells.

Conclusions:

• Defined a novel signaling pathway: DNA damage -> NHE-1 up-regulation -> intracellular alkalinization -> Bcl-xL deamidation -> apoptosis.
• This is the first reported instance of regulated in vivo deamidation of internal asparagine residues.
• Findings suggest potential new avenues for cancer therapy.