Proteomic analysis of laser capture microscopy purified myotendinous junction regions from muscle sections

The myotendinous junction is a specialized structure of the muscle fibre enriched in mechanosensing complexes, including costameric proteins and core elements of the z-disc. Here, laser capture microdissection was applied to purify membrane regions from the myotendinous junctions of mouse skeletal muscles, which were then processed for proteomic analysis. Sarcolemma sections from the longitudinal axis of the muscle fibre were used as control for the specificity of the junctional preparation. Gene ontology term analysis of the combined lists indicated a statistically significant enrichment in membrane-associated proteins. The myotendinous junction preparation contained previously uncharacterized proteins, a number of z-disc costameric ligands (e.g., actinins, capZ, αB cristallin, filamin C, cypher, calsarcin, desmin, FHL1, telethonin, nebulin, titin and an enigma-like protein) and other proposed players of sarcomeric stretch sensing and signalling, such as myotilin and the three myomesin homologs. A subset were confirmed by immunofluorescence analysis as enriched at the myotendinous junction, suggesting that laser capture microdissection from muscle sections is a valid approach to identify novel myotendinous junction players potentially involved in mechanotransduction pathways.