MyoTRIM, an engineered tripartite motif (TRIM) protein, recapitulates canonical phosphatidylserine binding and enhances cell membrane resealing capacity

• Published in: Physiology (Bethesda, Md.) Md.), 2024-05, Vol.39 (S1)
• Main Authors: Lopez Perez, Miguel A., Banford, Kassidy K., Bulgart, Hannah R., Giarrano, Gianni, Weisleder, Noah
• Format: Article
• Language: English
• ISSN: 1548-9213; 1548-9221
• DOI: 10.1152/physiol.2024.39.S1.1462

Abstract only Duchenne Muscular Dystrophy (DMD) is the most prevalent hereditary neuromuscular disease and involves progressive muscle degeneration that contributes to early death. DMD is caused by mutations in the dystrophin gene, which eliminates its expression and leads to compromised structural integrity of the muscle cell plasma membrane. Although there is no cure for DMD, a recently approved gene therapy has shown desirable primary endpoints, including dystrophin expression, but limited secondary functional endpoints. Moreover, this genetic approach is limited to patients within a narrow age range. Therefore, novel therapies addressing the underlying structural cause of the disease remain necessary. The tripartite motif protein 72/mitsugumin 53 (TRIM72/MG53) is integral for an effective membrane repair response after injury. We have reported that overexpression of MG53 or exogenous delivery of recombinant human MG53 protein (rhMG53) can increase membrane repair capacity in many different cell types and improve pathology in multiple muscular dystrophy animal models. MG53 is thought to mediate this effect by binding phosphatidylserine (PS) at membrane injury sites. Yet, the structural basis of this therapeutic interaction is poorly understood. Here, we test the hypothesis that we can recapitulate the therapeutic effects of rhMG53 by engineering a novel TRIM protein, MyoTRIM, that retains PS binding capabilities while eliminating its canonical enzymatic activity. Using molecular, cellular, and physiological methodologies, we tested an engineered catalytic inactive MG53 variant, MyoTRIM. We found that enzymatic activity is dispensable for canonical subcellular localization and improved membrane resealing kinetics when endogenously overexpressed or made available exogenously as a recombinant protein. We report MG53’s propensity to aggregate in the presence or absence of specific canonical protein domains. Additionally, we demonstrate that MyoTRIM can bind PS and establish that carboxy-terminal domains are required for effcient PS binding. Lastly, we show preliminary data highlighting MyoTRIM’s therapeutic potential in dystrophic mouse models, suggesting improved functional outcomes, i.e. increased membrane repair and muscle force production. Taken together, these data suggest that the engineered protein MyoTRIM can recapitulate MG53’s therapeutic effect on membrane resealing while eliminating the canonical E3 ligase catalytic activity, thereby eliminating