Biophysical Society Conference | Estes Park 2023

Membrane Budding and Fusion

Poster Abstracts

PROGRESS TOWARDS THE STRUCTURE AND FUNCTION OF DYSFERLIN

Matthew Dominguez 1 ; R. Bryan Sutton 1 ; 1 Texas Tech University Health Sciences Center, Cell Physiology and Molecular Biophysics, Lubbock, TX, USA

Muscular dystrophy is characterized by progressive muscle weakness and atrophy, which eventually results in immobility. Limb-girdle muscular dystrophy (LGMD)-Type 2B/2R, a prominent type of muscular dystrophy, is often called a dysferlinopathy. Unfortunately, there is currently no cure available for dysferlinopathy. LGMD-2B occurs due to mutations in the dysferlin gene. The dysferlin protein is a 237-kDa, type II integral membrane protein that plays a vital role in the repair of damaged plasma membranes (PMR) in skeletal and cardiac muscles. Understanding the structure and function of the dysferlin protein will be crucial for developing potential treatments. Although numerous studies have investigated dysferlin's in vivo membrane fusion activity, the underlying mechanism behind dysferlin-mediated fusion remains unclear. Dysferlin is a large protein composed of eight C2 domains (labeled C2A-C2G), two intertwined DysF domains, and one C-terminal transmembrane helix. Small-angle X-ray scattering (SAXS) experimen ts performed on purified ΔTM -dysferlin indicate that the protein can form homo dimers in a Ca2+-dependent manner. Since Ca2+ initiates dysferlin-mediated fusion, the homo dimerization we observe may be a fundamental aspect of the dysferlin membrane fusion mechanism. Moreover, recent advancements in protein structure prediction have aided in discovering a previously unidentified C2 domain, C2-FerA. This domain incorporates a 4-helix bundle, known as FerA, inserted as an extended loop between β - strand 4 and β -strand 5. Additionally, the Sutton laboratory's domain boundary predictions have facilitated the isolation and crystallization of the C2G domain of human dysferlin. Collectively, these findings have provided valuable insights into the distinct characteristics of dysferlin and the wider ferlin protein family. This knowledge will contribute to developing potential therapeutic interventions for dysferlinopathies, bringing us closer to effective treatments for individuals affected by muscular dystrophy.

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