Investigation of Ca2+-Handling and Glycogen-Related Proteins in Human Skeletal Muscle, and the Effects of Disease, Exercise and Endurance Training

Submission note: A thesis submitted in total fulfilment of the requirements for the degree of Doctor of Philosophy to the School of Molecular Sciences, College of Science, Health and Engineering, La Trobe University, Victoria, Australia.

Thesis with publications.

Skeletal muscle is a dynamic, plastic tissue that has the ability to adapt to functional and metabolic demands, such as disease and/or exercise. Adaptations can result in perturbations to calcium (Ca2 positive) regulation and cellular metabolism, influencing skeletal muscle energy expenditure. In many cases Ca2 positive regulation and energy expenditure are linked. Healthy skeletal muscle maintains regulation of myoplasmic Ca2 positive concentration (Ca2 positive), including the transients that regulate muscle contraction. There are tightly regulated and constant fluctuations of [Ca2 positive] that drive muscle contraction. Ca2 positive movement within skeletal muscle is maintained by coordinated signalling between proteins that are vital to healthy skeletal muscle function. This thesis examines the role of energy metabolism, in particular by way of glycogen availability and use, in the regulation of Ca2 positive - handling. The major aim was to investigate the expression and regulation of key Ca2 positive -handling and glycogen-related proteins in human skeletal muscle. This was achieved using the settings of exercise and muscle disease. Importantly, skeletal muscle heterogeneity, which is inherently present due to the expression of different forms of myosin heavy chain proteins, has been addressed by performing many experiments at the individual fibre level. The results provide greater insight into mechanisms of muscle function, which are currently understood at the broader whole muscle level. The results for this thesis are presented across three experimental result chapters. Firstly, the abundance and subcellular localisation of important sarcoplasmic reticulum Ca2 positive -transport regulatory proteins in resting human skeletal muscle. Secondly, the perturbation of important skeletal muscle Ca2 positive -handling and glycogen-related protein abundance in patients with limb-girdle muscular dystrophy type 2A (LGMD2A). Finally, the effects of different acute exercise bouts and carbohydrate availability on the abundance of proteins involved in glucose/glycogen metabolism in skeletal muscle of competitive endurance-trained cyclists.