Biology subjects

Lee, Y. i.

Publications and source records attributed to Lee, Y. i..

4 recordsLinked to original sources

bioRxiv2023

How Myosin VI Traps its Off-State, is Activated and Dimerizes

Myosin VI (Myo6) is the only minus-end directed nanomotor on actin, allowing it to uniquely contribute to numerous cellular functions. As for other nanomotors, proper functioning of Myo6 relies on precise spatio-temporal control of motor activity via a poorly defined off-state and interactions with partners. Our structural, functional, and cellular studies reveal key features of myosin regulation and indicate that not all partners can activate Myo6. TOM1 and Dab2 cannot bind the off-state while, GIPC1 binds Myo6, releases its auto-inhibition and triggers proximal dimerization. Myo6 partners thus differentially recruit Myo6. We solved a crystal structure of the proximal dimerization domain, and show that its disruption compromises endocytosis in HeLa cells, emphasizing the importance of Myo6 dimerization. Finally, we show that the L926Q deafness mutation disrupts Myo6 auto-inhibition and indirectly impairs proximal dimerization. Our study thus demonstrates the importance of partners in the control of Myo6 auto-inhibition, localization, and activation.

biochemistry↗

bioRxiv2022

Potential limitations of micro-dystrophin gene therapy for Duchenne muscular dystrophy

Adeno-associated viruses (AAVs) expressing versions of truncated dystrophin (micro-dystrophins) are being delivered at high doses to patients with Duchenne muscular dystrophy (DMD) in clinical trials. We examined this strategy with two different micro-dystrophins, similar to those currently in clinical trials, in a severe mouse model of DMD, the D2.mdx mouse, using doses of AAV comparable to those used in the clinical trials. We achieved high levels of micro-dystrophin expression in striated muscle with cardiac expression [~]10 fold higher than that observed in skeletal muscle. Significant, albeit incomplete, correction of the skeletal muscle disease is observed. Surprisingly, a lethal acceleration of cardiac disease progression occurs with one of the micro-dystrophins, while the second appears to benefit the heart. The detrimental impact on the heart in the first case appears to be caused by the high levels of micro-dystrophin in the heart resulting in competition between micro-dystrophin and utrophin at the cardiomyocyte membrane. While the significance of these observations for patients currently being treated with AAV-micro-dystrophin therapies is unclear since the levels of expression being achieved in the DMD hearts are unknown, it suggests that micro-dystrophin treatments may need to be carefully titrated to avoid high levels of expression in the heart.

pharmacology and toxicology↗

bioRxiv2022

Evaluation of the DBA/2J mouse as a potential background strain for genetic models of cardiomyopathy

The potential use of the D2.mdx mouse (the mdx mutation on the DBA/2J genetic background) as a preclinical model of the cardiac aspects of Duchenne muscular dystrophy (DMD) has been criticized based on speculation that the DBA/2J genetic background displays an inherent hypertrophic cardiomyopathy phenotype. Accordingly, the goal of the current study was to further examine the cardiac status of this mouse strain over a 12-month period. DBA/2J mice have been scrutinized for the presence of cardiac lesions, however, in the current study we find that DBA/2J mice contain equivalent amounts of left ventricular collagen as healthy canine and human samples. In a longitudinal echocardiography study, neither sedentary or exercised DBA/2J mice demonstrated left ventricular wall thickening or cardiac functional deficits. In summary, we find no evidence of hypertrophic cardiomyopathy, or any other cardiac pathology, and thus propose that it is an appropriate background strain for genetic modeling of cardiac diseases, including the cardiomyopathy associated with DMD.

physiology↗

bioRxiv2021

Filopodia powered by class X myosin promote fusion of mammalian myoblasts

Skeletal muscle fibers are multinucleated cellular giants formed by the fusion of mononuclear myoblasts. Several molecules involved in myoblast fusion have been discovered, and finger-like projections coincident with myoblast fusion have also been implicated in the fusion process. The role of these cellular projections in muscle cell fusion was investigated herein. We demonstrate that these projections are filopodia generated by class X myosin (Myo10), an unconventional myosin motor protein specialized for filopodia. We further show that Myo10 is highly expressed by differentiating myoblasts, and Myo10 ablation inhibits both filopodia formation and myoblast fusion in vitro. In vivo, Myo10 labels regenerating muscle fibers associated with Duchenne muscular dystrophy and acute muscle injury. Conditional loss of Myo10 from muscle-resident stem cells, known as satellite cells, severely impairs postnatal muscle regeneration. Furthermore, the muscle fusion proteins Myomaker and Myomixer are detected in myoblast filopodia. These data demonstrate that Myo10-driven filopodia facilitate multi-nucleated mammalian muscle formation.

cell biology↗