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Effects of Disease Causing Point Mutations on Actin's Resilience

2013; Elsevier BV; Volume: 104; Issue: 2 Linguagem: Inglês

10.1016/j.bpj.2012.11.3577

1542-0086

Ashley Brate, Ava Yun Lin, Jonathan Crain, Ewa Próchniewicz, Jamex Ervasti, David D. Thomas,

RNA Research and Splicing

We have used spectroscopic probes to determine the structural dynamics of actin, as affected by point mutations that are known to cause Duchenne muscular dystrophy (DMD). DMD is caused by mutations within the cytoskeletal protein dystrophin. The present study focuses on single amino acid replacements in the N-terminal actin-binding domain (DysABD1), which result in muscular dystrophies with a wide spectrum of severities. Though these point mutations occur in ABD1, the affinity of dystrophin for actin is not substantially perturbed (Henderson et al., PNAS 2010). However, affinity is only one facet of dystrophin's interaction with actin. We have previously shown, using transient phosphorescence anisotropy (TPA), that binding of dystrophin to actin increases its resilience, and we hypothesize that this cytoskeletal resilience is needed to act as a mechanical buffer during contractions. Previous results have shown a correlation between the TPA-measured resilience and the physiological measures of muscle mechanical function in mice (Lin et al., J. Mol Biol 2012). In this project, we expand this area of research by testing several known disease-causing point mutations in DysABD1 and evaluate their effects on actin's resilience. We hypothesize that while affinity is not significantly affected, mutant full length dystrophin loses its natural ability to increase the resilience in actin as determined from TPA. Our findings will provide insight into the pathophysiology of these disease-causing mutations - why some mutations are more devastating than others, and why a single amino acid change can have a large impact on dystrophin's function.