Communication in Membrane Repair

Abstract

The force generated by muscle cells places a high amount of stress on their plasma membranes creating lesions which must be effectively repaired in order for the cell to survive. Multiple proteins have been implicated in the membrane repair process, one of which is dysferlin, a seven C2 domain containing protein. Of the seven C2 domains within dysferlin, only the C2A domain exists in two isoforms and has been suggested to be the Ca2+ sensor within dysferlin. Mutations within dysferlin have been found to cause several types of muscular dystrophies including Limb-Girdle muscular dystrophy, Myoshi Myopathy and Distal Anterior Compartment Myopathy. In vivo studies have revealed that after membrane rupture, dysferlin interacts with multiple proteins including annexin A2. In order to gain a better understanding of how this system functions, this author used methods including differential scanning calorimetry (DSC) and spectroscopy (fluorescence and circular dichroism) to examine both isoforms of the C2A domain and annexin A2. All three proteins were found to be marginally stable suggestive of a system that is highly capable of information propagation. From this, a picture emerges where mutations within dysferlin could result in a dramatic shift in the conformational ensemble available to the protein, which would interfere with its ability to properly interact and communicate with the other members of the membrane repair machinery. This would result in the loss of the ability to properly repair the membrane.