Cardiac myosin binding protein-C palmitoylation is associated with increased myofilament affinity, reduced myofilament Ca²⁺ sensitivity and is increased in ischaemic heart failure

Abstract

Cardiac myosin binding protein-C (cMyBP-C) is an essential regulator of cardiac contractility through its interactions with the thick and thin filament. cMyBP-C is heavily influenced by post-translational modifications, including phosphorylation which improves cardiac inotropy and lusitropy, and S-glutathionylation, which impairs phosphorylation and is increased in heart failure. Palmitoylation is an essential cysteine modification that regulates the activity of cardiac ion channels and soluble proteins, however, its relevance to myofilament proteins has not been investigated. In the present study, we purified palmitoylated proteins from ventricular cardiomyocytes and identified that cardiac actin, myosin and cMyBP-C are palmitoylated. The palmitoylated form of cMyBP-C was more resistant to salt extraction from the myofilament lattice than the non-palmitoylated form. Isometric tension measurements suggest c-MyBP-C palmitoylation reduces myofilament Ca2+ sensitivity, with no change to maximum force or passive tension. Importantly, cMyBP-C palmitoylation levels are reduced at the site of injury in a rabbit model of heart failure but increased in samples from patients with ischaemic heart failure. Identification of cMyBP-C palmitoylation site revealed S-glutathionylated cysteines C635 and C651 are required for cMyBP-C palmitoylation, suggesting an interplay between the modifications at these sites. We conclude that structural and contractile proteins within the myofilament lattice are palmitoylated, with important functional consequences for cardiac contractile performance.

zDHHC5 expression is increased in cardiac hypertrophy and reduced in heart failure but this does not correlate with changes in substrate palmitoylation

“…Increased NCX1 palmitoylation, as observed in human HF, would enhance inactivation and reduce Ca 2+ efflux which, whilst improving systolic function, this would contribute to diastolic impairment, of which NCX1 is a key mediator (Kass et al, 2004). Interestingly, the pattern of NCX1 palmitoylation associated with HF that we report here was recapitulated for cardiac myosin binding protein-C, again suggesting that upstream factors such as a fatty acid and fatty acyl-CoA availability may be regulating the changes of substrate palmitoylation (Main et al, 2022).…”

“…Palmitoylation has emerged over the last decade a crucial regulatory modification for every class of protein, including several involved in cardiac excitation-contraction coupling (Chien et al ., 1996; Tulloch et al ., 2011; Howie et al ., 2013; Gök., 2020; Main et al ., 2022). As many of these proteins are dysregulated in diseases such as HF, palmitoylation may represent a novel mechanism to manipulate their function for therapeutic benefit (Main & Fuller, 2021).…”

Dynamic but discordant alterations in zDHHC5 expression and palmitoylation of its substrates in cardiac pathologies

“…Whilst improving systolic function, this would contribute to diastolic impairment, of which NCX1 is a key mediator ( Kass et al, 2004 ). Interestingly, the pattern of NCX1 palmitoylation associated with HF that we report here was recapitulated for cardiac myosin binding protein-C, again suggesting that upstream factors such as a fatty acid and fatty acyl-CoA availability may be responsible for the changes of substrate palmitoylation ( Main et al, 2022 ).…”

“…Whilst improving systolic function, this would contribute to diastolic impairment, of which NCX1 is a key mediator (Kass et al, 2004). Interestingly, the pattern of NCX1 palmitoylation associated with HF that we report here was recapitulated for Frontiers in Physiology frontiersin.org cardiac myosin binding protein-C, again suggesting that upstream factors such as a fatty acid and fatty acyl-CoA availability may be responsible for the changes of substrate palmitoylation (Main et al, 2022). A significant finding, but also a limitation of this study, is the lack of consistency in the changes in zDHHC5 expression and substrate palmitoylation between different animal models and human HF.…”

“…Palmitoylation has emerged over the last decade a crucial regulatory modification for every class of protein, including several involved in cardiac excitation-contraction coupling ( Chien et al, 1996 ; Tulloch et al, 2011 ; Howie et al, 2013 ; Gök et al, 2020 ; Main et al, 2022 ). As many of these proteins are dysregulated in diseases such as HF, palmitoylation may represent a novel mechanism to manipulate their function for therapeutic benefit ( Main and Fuller, 2021 ).…”