Abstract 12088: cMyBP-C’S Interaction With Actin is Critical to Maintain Diastolic Function in vivo
Background: cMyBPC’s interaction with actin is critical to maintain diastolic function in vivo
Rationale: Extensive studies demonstrate that cardiac myosin binding protein C (cMyBP-C) is a critical mediator of diastolic function through its interaction with actin, myosin and titin. The precise molecular mechanisms underlying the protein’s function remain elusive as cMyBP-C’s structural domains responsible for actin and/or myosin interaction are ill-defined and the physiological consequences of these filament interactions are unknown.
Objective: In the present study, we made transgenic mice that lacked cMyBP-C’s actin and/or the head region of the myosin heavy chain (S2-MyHC) sites in order to better understand the molecular mechanisms of cMyBPC-mediated regulation of cardiac contraction, particularly diastolic function.
Methods and Results: Using a combination of genetics and functional assays, we defined cMyBP-C’s N-terminal structural domains as well as the critical residues necessary or sufficient to mediate interactions with actin and/or S2-MyHC. Using genetic experiments, we first confirmed that mutation of three lysines to alanines in the C1 domain abolished actin binding (cMyBP-CAct-). Similarly, mutation of three arginines to alanines in the “m” domain abolished S2-MyHC binding (cMyBP-CS2-). To determine the functional roles of these sites in vivo, we generated transgenic lines in which normal cMyBP-C was replaced by either cMyBP-CAct-,S2- or wild type (cMyBP-CWT), transgenically-encoded cMyBP-C. Mutant protein was completely substituted for endogenous cMyBP-C by breeding the transgenes into a cMyBP-C null background. The cMyBP-CAct-,S2- mice developed significant cardiac hypertrophy with myofibrillar disarray and fibrosis. Echocardiographic Doppler measurements showed that cMyBP-CAct-,S2- mice develop both diastolic and systolic dysfunction. In contrast, the cMyBP-CWT Tg line showed normal cardiac structure and function.
Conclusions: These results suggest that the cMyBP-C’s interactions with both actin/S2-MyHC are structurally important to preserve normal cardiac contractility and particularly, cMyBP-C’s interaction with actin is indispensable for normal diastolic function.
Author Disclosures: M. Bhuiyan: None. J. James: None. H. Osinska: None. J. Gulick: None. J. Lorenz: None. J. Robbins: None.
This research has received full or partial funding support from the American Heart Association.
- © 2014 by American Heart Association, Inc.