Mutations within the C2A domain of dysferlin adopt a molten globule-like conformation in Limb-Girdle muscular dystrophy

Abstract

Limb-Girdle muscular dystrophy (LGMD) is the collective term describing a neuromuscular condition that results from mutation in one of him 16 muscle-related genes. Patients with slowly progressing LGMD may be able to walk for about 30 years after disease onset, but many will become wheelchair bound in their teens. LGMD-2B is a sub-type of this class of muscular dystrophy and involves mutations within the dysferlin gene. Point mutations within one of the seven C2 domains of dysferlin are sufficient to cause disease. Clinical investigation of skeletal muscle from these myopathic patients reveal a lack of dysferlin; however, the mechanism by which dysferlin is removed from the muscle cell is unknown. We have crystallized and solved the X-ray crystal structure of the C2A domain of human dysferlin. Structural, biophysical, and computational analysis of the two known disease-causing mutations the C2A domain of dysferlin shows that while the domain is folded, it has characteristics of a multi-conformation misfolded steady state. This misfolding event would likely interrupt the normal function of the protein and could nucleate intercellular aggregation leading to disease