Date of Award
Fall 9-4-2025
Degree Type
Dissertation
Degree Name
Doctor of Philosophy (PhD)
Department
Physiology
First Advisor
Jonathan Kirk
Abstract
Methylglyoxal is a reactive carbonyl species that modifies lysine residues via a process called glycation and is elevated in high-risk conditions for heart failure, like diabetes and aging. Glycation is non-enzymatic and irreversible, thus modified proteins must be removed via degradation. We hypothesized methylglyoxal competes with and blocks protein lysine ubiquitination in a dangerous feed-forward cycle of decreasing protein turnover and increasing glycation. Indeed, mass spectrometry analysis of human and mouse cardiomyocytes confirm these two PTMs share target lysine residues on sarcomeric proteins, including β-myosin heavy chain. To determine whether methylglyoxal and ubiquitination directly compete, we exposed C2C12 myoblasts and neonatal rat ventricular myocytes to methylglyoxal (100μM; 10μM respectively for initial supraphysiological, and more physiological perspectives respectively); both exhibited reduced protein ubiquitination. To test whether reduced protein turnover results in accruing glycation, we utilized BAG3 KO mice (hetero-and-homozygous), which have decreased sarcomere protein turnover. Sarcomere protein glycation was increased in BAG3 KO mice, and residues overlapped with those glycated in diabetic humans, supporting these PTMs’ competition. Further, literature suggests SRX supports myosin turnover, reduces contraction, and increases relaxation. Our data (x-ray; MANT-ATP; cell culture) shows methylglyoxal increases SRX, decreases filament proximity, and impairs autophagy, suggesting methylglyoxal prevents myosin turnover by preventing myosin ubiquitination and interaction with chaperones. We previously showed sarcomere glycation reduced contractile function, so this feed-forward mechanism has the potential to worsen function. Thus, we tested whether increased glycation impacted sarcomere function in BAG3 KO mice. Force-calcium measurements were performed pre- and post-100μM methylglyoxal treatment. As previously, methylglyoxal caused a significant decrease in maximum calcium activated force (Fmax) in wild-type mice, but this effect was reduced in BAG3 KO mice, Indicating elevated protein glycation already impacted these mice. These results underscore the possibility that glycation/ubiquitination crosstalk impacts sarcomere function across multiple high-risk conditions. Breaking this loop therapeutically may be efficacious in treating diseases with increased glycation.
Recommended Citation
Delligatti, Christine Elizabeth, "Methylglyoxal Glycation Competes with Ubiquitination, Disrupting Sarcomere Funciton" (2025). Dissertations. 4247.
https://ecommons.luc.edu/luc_diss/4247
