King's College London

Research portal

Structural and functional effects of myosin binding protein-C phosphorylation in heart muscle are not mimicked by serine-to-aspartate substitutions

Research output: Contribution to journalLetter

Original languageEnglish
JournalJournal of Biological Chemistry
Early online date6 Aug 2018
DOIs
Publication statusE-pub ahead of print - 6 Aug 2018

Documents

King's Authors

Abstract

Myosin-binding protein-C (cMyBP-C) is a key regulator of contractility in heart muscle, and its regulatory function is controlled in turn by phosphorylation of multiple serines in its m-domain. The structural and functional effects of m-domain phosphorylation have often been inferred from those of the corresponding serine-to-aspartate (S–D) substitutions, in both in vivo and in vitro studies. Here, using a combination of in vitro binding assays and in situ structural and functional assays in ventricular trabeculae of rat heart and the expressed C1mC2 region of cMyBP-C, containing the m-domain flanked by domains C1 and C2, we tested whether these substitutions do in fact mimic the effects of phosphorylation. In situ changes in thin and thick filament structure were determined from changes in polarized fluorescence from bifunctional probes attached to troponin C or myosin regulatory light chain, respectively. We show that both the action of exogenous C1mC2 to activate contraction in the absence of calcium and the accompanying change in thin filament structure are abolished by tris-phosphorylation of the m-domain, but unaffected by the corresponding S–D substitutions. The latter produced an intermediate change in thick filament structure. Both tris-phosphorylation and S–D substitutions abolished the interaction between C1mC2 and myosin sub-fragment 2 (myosin S2) in vitro, but yielded different effects on thin filament binding. These results suggest that some previous inferences from the effects of S–D substitutions in cMyBP-C should be reconsidered and that the distinct effects of tris-phosphorylation and S–D substitutions on cMyBP-C may provide a useful basis for future studies.

Download statistics

No data available

View graph of relations

© 2018 King's College London | Strand | London WC2R 2LS | England | United Kingdom | Tel +44 (0)20 7836 5454