Structure and function of myosin binding protein-C in skeletal muscles - Abstract. The overall goal of this research is to understand how myosin binding protein-C (MyBP-C) regulates skeletal muscle contraction and how mutations in the genes encoding slow and fast MyBP- C (MYBPC1 and MYBPC2, respectively) cause congenital skeletal muscle diseases such as distal limb contractures and myogenic tremors. Until now, cardiac MyBP-C (cMyBP-C, encoded by MYBC3) has received intense research attention because mutations in MYBPC3 account for the majority of mutations leading to hypertrophic cardiomyopathy, however far less is known about the 2 skeletal muscle paralogs of MyBP-C despite their connections to disease. This is in part because slow and fast MyBP-C are co-expressed in most muscle types and MYBPC1 undergoes extensive exon shuffling and post translational modifications that alter its function. Furthermore, the different sMyBP-C and fMyBP- C paralogs, splice variants, and post translational modifications all are thought to differ in their functional effects, but because of overlapping patterns of expression it has proven nearly impossible to disentangle the distinct functional and structural effects of the individual MyBP-C variants in working skeletal muscles. Here, we overcome this challenge by using a novel “cut and paste” method developed exclusively in the PI’s lab that allows us to selectively modify sMyBP-C, fMyBP-C, or both at their native positions in working sarcomeres to systematically determine distinct functional effects of each paralog, splice variant and mutation on contraction and relaxation in any skeletal muscle (Aim 1). In Aim 2 we combine the cut and paste method with X-ray diffraction measurements to determine the unique structural effects of paralogs, variants, and mutations on both thick and thin filament structure in both active and relaxed sarcomeres. Results from this study will give us unprecedented insights into the structural and functional effects of the MyBP-C family of proteins in skeletal muscle, paving the way for the design of therapeutic treatments that selectively target skeletal MyBP-C paralogs to treat inherited contractures and tremors.
