Dichloroacetate stabilizes the mutant E1 alpha subunit in pyruvate dehydrogenase deficiency

Objective: To determine whether dichloroacetate (DCA) treatment can increas e pyruvate dehydrogenase (PDH) activity in PDH-deficient cell lines harbori ng pathogenic mutations in the PDH E1 alpha gene. Background: PDH deficienc y is a nuclear-encoded mitochondrial disorder and a major recognized cause of neonatal encephalomyopathies associated with primary lactic acidosis. Ov er the last decade, DCA has been used therapeutically, but it has not been clear which patients might benefit. Recent studies suggest that chronic DCA treatment may act by increasing the stability of mutant E1 alpha polypepti de. The relative effects of DCA treatment on PDH-deficient cell lines with E1 alpha mutations primarily affecting polypeptide stability or catalytic a ctivity were determined and the mechanism of enhancement of residual PDH ac tivity explored. Methods: The effect of chronic 5-day DCA treatment on PDH activity was assessed in PDH-deficient cell lines containing the R378H, R14 1Q, K387(FS), and R302C E1 alpha mutations. PDH subunit turnover and steady -state E1 alpha levels before and after DCA treatment were measured in the R378H mutant line. Results: Chronic DCA treatment resulted in 25% (p = 0.04 34), 31% (p = 0.0014) increases in PDH activity in the K387(FS) and R378H c ell lines, both of which are associated with decreased mutant polypeptide s tability. In the R378H mutant cell line, chronic DCA treatment increased st eady-state E1 alpha levels and slowed the rate of E1 alpha turnover twofold . In contrast, PDH activity did not change in the chronically DCA-treated R 302C mutant line, in which the mutant polypeptide has normal stability and reduced catalytic activity. Conclusions: Chronic DCA treatment can increase PDH activity in PDH-deficient cell lines harboring mutations that affect E 1 alpha stability, suggesting a biochemical criterion by which DCA-responsi ve patients might be selected.