Huntingtin protein maintains balanced energetics in mouse cardiomyocytes

Abstract

Huntingtin (HTT) is a multifunctional protein crucial for proper embryogenesis and nervous system development. Mutation of a single allele in gene coded this protein results in the Huntington׳s disease (HD). There is growing evidence of cardiovascular system pathologies coexisting with the neurological symptoms in HD patients. Thus, this study aims to establish the role of huntingtin protein in cardiomyocytes cellular energy and nucleotides metabolism. We used HTT KO mice embryonic stem cells (ESC) obtained with CRISPR method, wild type mice ESC treated by CRISPR with Scramble control sequence (SCR) as well as wild type (WT) mice ESC and differentiate it into cardiomyocytes. Analysis of intracellular concentration of ATP, ADP, and NAD+, as well as nucleotide catabolites were performed with HPLC. We noted that HTT null cardiomyocytes showed diminished intracellular ATP (4.9 ± 0.5; 6.7 ± 0.4 nmol/mg protein HTT KO vs. SCR) and NAD+ (0.9 ± 0.1; 1.6 ± 0.1 nmol/mg HTT KO vs. SCR). We noted also reduced cellular medium concentration of total purines pool (17.1 ± 1.7; 24.7 ± 2.7 nmol/ml HTT KO vs. SCR) as well as IMP concentration (7.7 ± 0.6; 10.2 ± 0.4 nmol/ml HTT KO vs. SCR). This study indicates that HTT plays an important role in cellular energy balance as well as in nucleotide metabolism in cardiomyocytes. Furthermore, our findings underline that the deterioration in energy metabolism observed in HD may be caused not only by cellular mutant HTT accumulation but also by the loss of HTT function.