Site-specific phosphorylation of myosin binding protein-C coordinates thin and thick filament activation in cardiac muscle

• DOI: 10.1073/pnas.1903033116
• Publication Date: 2019-07-16T00:25:43Z
• Authors: Saraswathi Ponnam; Ivanka Sevrieva; Yin-Biao Sun; Malcolm Irving; Thomas Kampourakis
• Keywords: Myofilament; Cardiac muscle; Phosphorylation cascade

The heart's response to varying demands of the body is regulated by signaling pathways that activate protein kinases which phosphorylate sarcomeric proteins. Although phosphorylation cardiac myosin binding protein-C (cMyBP-C) has been recognized as a key regulator myocardial contractility, little known about its mechanism action. Here, we used kinase A (PKA) and Cε (PKCε), well ribosomal S6 II (RSK2), have different specificities for cMyBP-C's multiple sites, show individual sites are not independent, cMyBP-C controlled positive negative regulatory coupling between those sites. PKA N terminus on 3 conserved serine residues hierarchical antagonizes PKCε, vice versa. In contrast, RSK2 accelerates phosphorylation. We N-terminal domains in defined states protein-protein interaction studies with isolated native thin filaments S2 domain site-specific this region controls both actin-containing myosin-containing thick filaments. also fluorescence probes myosin-associated light chain troponin C monitor structural changes myofilaments intact heart muscle cells associated activation contraction states. Our results suggest acts integrator determines downstream physiological function.