Dichloroacetate stabilizes the mutant E1alpha subunit in pyruvate dehydrogenase deficiency

Area of Science:

• Biochemistry
• Genetics
• Mitochondrial Disorders

Background:

• Pyruvate dehydrogenase (PDH) deficiency is a severe mitochondrial disorder causing neonatal encephalomyopathies and lactic acidosis.
• Dichloroacetate (DCA) is a therapeutic agent, but its efficacy in PDH deficiency is not fully understood.
• DCA may enhance PDH activity by increasing the stability of mutant E1alpha polypeptides.

Purpose of the Study:

• To investigate if dichloroacetate (DCA) can enhance pyruvate dehydrogenase (PDH) activity in cell lines with PDH deficiency due to E1alpha gene mutations.
• To explore the mechanism by which DCA affects PDH activity in different types of E1alpha mutations.
• To identify potential criteria for selecting patients who may benefit from DCA treatment.

Main Methods:

• Assessed the effect of chronic 5-day DCA treatment on PDH activity in PDH-deficient cell lines with specific E1alpha mutations (R378H, R141Q, K387(FS), R302C).
• Measured PDH subunit turnover and steady-state E1alpha levels in the R378H mutant cell line before and after DCA treatment.

Main Results:

• Chronic DCA treatment significantly increased PDH activity (25-31%) in cell lines with E1alpha mutations affecting polypeptide stability (K387(FS) and R378H).
• In the R378H mutant line, DCA increased steady-state E1alpha levels and reduced E1alpha turnover rate twofold.
• No significant change in PDH activity was observed in the R302C mutant cell line, which has normal E1alpha stability but reduced catalytic activity.

Conclusions:

• Chronic DCA treatment effectively increases PDH activity in PDH-deficient cell lines with E1alpha mutations impacting polypeptide stability.
• These findings suggest that E1alpha polypeptide stability is a key factor in determining responsiveness to DCA.
• A biochemical criterion based on E1alpha stability could aid in selecting PDH-deficient patients who are likely to benefit from DCA therapy.