Poster abstracts

Poster number 33 submitted by Thomas Kwiatkowski

Downstream regulators that facilitate sarcolemma membrane repair as potential therapeutics for Duchenne muscular dystrophy

Thomas A. Kwiatkowski (OSBP Graduate Student ), Aubrey Rose (Undergraduate ), Kevin Mcelhanon (Graduate Student), Brian Paleo (Graduate Student ), Eric X Beck (Lab Technician), Sayak Bhattacharya (Post Doc )

Abstract:
Duchenne muscular dystrophy (DMD) is a fatal X-linked inherited neuromuscular disorder due to mutations in the dystrophin gene and is the most commonly inherited muscular disease in children. The dystrophin protein normally serves as a shock absorber for mechanical stress and a signaling platform protein in muscle fibers, but when dystrophin is lacking, patients experience an accumulation of membrane damage to which the muscle fibers cannot adequately repair. As result, there is an increase in fiber necrosis that exceed the regenerative capacity of the muscle causing DMD patients to display skeletal muscle deterioration and eventual death in the third decade of life. There is currently no cure for DMD and treatments that stimulate the membrane repair process in muscle fibers have been greatly overlooked and underutilized as a potential therapeutic approach. This project investigates a novel membrane repair signaling cascade in skeletal muscle that utilize glucose storage vesicles (GSVs) and their key regulators Akt Substrate 160 kDa (AS160) and rab G proteins as a means to close membrane wounds. Based on our preliminary data we hypothesize that AS160 phosphorylation and activation of associating rab G proteins facilitate the translocation of intercellular GSVs to disruption sites in the sarcolemma membrane for wound closure. Thus, modulating the function of these proteins may stimulate repair and have therapeutic benefits for DMD. Through the use of mutant plasmids and live cell imaging we have observed that GSVs containing the glucose transport protein Glut4 translocate to injury cites in C2C12 myoblasts and isolated mouse muscle fibers. We have also identified that AS160 phosphorylation from the phosphoinositide-3 kinase (PI3K)/Akt1 signaling axis regulate membrane repair in cultured muscle cells. Importantly, we have screened GSV associating rab G proteins and have found that rab10 and 8A are involved in sarcolemma membrane repair in vivo, and activating rab10 significantly improves membrane resealing in vivo in the muscle of a Duchenne muscular dystrophy mouse model (MDX). This project explores a signaling cascade new to the membrane repair field and can lead to new therapies that target more specific proteins within skeletal muscle to protect against damage in DMD patients.

Keywords: muscular dystrophy, membrane repair, rab G proteins