ANALYSIS AT THE MOLECULAR LEVEL OF THE INTERACTION BETWEEN ALPHA-DYSTROGLYCAN AND BETA-DYSTROGLYCAN

The dystroglycan (DG) is a glycoprotein, associated to dystrophin and sarcoglycans, which anchors the cytoskeleton of muscle fibres to the extracellular matrix. DG is composed of two interacting subunits: alpha-DG, associated to the plasma membrane and forming interactions with the external basement membrane which surrounds the muscle fibres, and beta-DG, crossing the plasma menbrane and interacting with dystrophin. In Duchenne muscular dystrophy, it was observed that the absence of dystrophin is often accompanied by the absence of the DG complex at the sarcolemma, an event dramatically contributing to the reduced stability of muscle and its consequent necrosis. Therefore, it should be considered a very important task to collect new molecular insights about the structural and functional aspects of the DG complex. In particular, the interaction between its two subunits, alpha- and beta-, is likely to play a predominant role for its formation and stability. We have already demonstrated that the interaction is formed between the C-terminal domain of alpha-DG and the N-terminal region of beta-DG, and we have also identified the specific region of alpha-DG involved in the binding (between amino acids 550 and 565). Our research project will focus on the molecular aspects of the interaction between DG subunits. Analyzing a series of recombinant proteins, spanning different regions of alpha-and beta-DG, by sophisticated biophysical techniques, such as nuclear magnetic resonance (NMR), will allow us to identify the specific amino acids involved in the interaction. We will analyze the consequences of mutating such amino acids for the formation of the complex between alpha-DG and beta-DG, and for muscle stability in cells and transgenic mice too.