Slow and Fast Myosin Binding Protein-C in Human Skeletal Muscles

ABSTRACT The demographics of the population of developed countries are changing, such that people are living longer. Age-related skeletal muscle weakness represents major concerns for the quality of life in elderly and the growing healthcare burden. Its aetiology is not adequately understood, inevitably meaning that effective preventative or therapeutic strategies are lacking. Similarly, skeletal muscle diseases are largely understudied compared to their cardiac muscle counterparts, which is mirrored in the lack of therapeutic interventions for these debilitating diseases. The fast and slow skeletal paralogs of myosin binding protein-C (MyBP-C) are multi-domain proteins localized to the inner two-thirds of the skeletal muscle sarcomere where they form regulatory interactions with both actin-containing thin and myosin-containing thick filaments. Ablation of MyBP-C paralogs leads to impairment of skeletal muscle development, function and regulation, and mutations in the genes encoding for skeletal MyBP-Cs are frequently associated with myopathies such as distal arthrogryposis and lethal congenital contractural syndrome. Moreover, post-translational modifications of both fast and slow MyBP-C paralogs have been directly linked to the age-related decline in skeletal muscle performance (i.e. dynapenia). However, in contrast to the better studied cardiac cMyBP-C, the molecular mechanisms of control of skeletal muscle function by MyBP-C have remained largely obscure. Our preliminary data show that both slow and fast MyBP-C co-exist in various skeletal muscles but have distinct effects on myofilament contractility and its regulation. This project therefore combines the expertise of three investigators in molecular biochemistry, cell physiology and computational modelling (Thomas Kampourakis, PhD, University of Kentucky; Kenneth S. Campbell, PhD, University of Kentucky; and Kerry S. McDonald, PhD, University of Missouri) to characterize the multi-scale structure-function relationship of skeletal MyBP-C ranging from molecules to cellular and organ-level function. Our project has three specific aims. Aim 1: Define the expression, sub-cellular localization and biochemical state of MyBP-C paralogs in different human skeletal muscles. Aim 2: Quantify the effects of skeletal MyBP-C isoforms and their modifications on the regulatory state of the contractile myofilaments. Aim 3: Test for the effects of myopathy- associated mutations in MyBP-C on molecular and sarcomere-level function. This combined approach is uniquely powerful for elucidating the molecular mechanisms underlying the regulation of striated muscle contraction, and the physiological and pathological factors that control contractility of the skeletal myofilaments. An understanding of these mechanisms will underpin the future development of new drugs and therapies for the wide range of muscle diseases/dysfunction in which contractility is compromised.