Modulation of structure and dynamics of cardiac troponin by phosphorylation and mutations revealed by molecular dynamics simulations

Abstract

Phosphorylation of cardiac muscle troponin I by protein kinase A enhances troponin regulatory dynamics and is an essential part of the’ flight or fight’ response to adrenaline. Elucidating how phosphorylation at serines 22 and 23 modulates structural dynamics has been difficult as key regulatory segments of troponin are unresolved. The effect of phosphorylation on the wild type, obtained from all-atom molecular dynamics simulations of the troponin core, demonstrates a significant rigidification of the structure that involves a rearrangement of the cTnI(1-33) - cTnC interaction, and changes in the distribution of the cTnC helix A/B angle and the interdomain angle, between the regulatory head and ITC arm. The familiar dilated cardiomyopathy cTnC G159D mutation whose Ca2+-sensitivity is not modulated by cTnI phosphorylation exhibits a structure inherently more rigid than WT, with phosphorylation reversing the direction of all metrics relative to WT.

Suppression of lusitropy as a disease mechanism in cardiomyopathies

“…In the case of DCM mutations a case can be made that this is causative of the disease since it is the only mutation-related property that is common to every thin-filament related DCM mutation ( 1 , 33 , 38 ), whereas for HCM, the increase in Ca 2+ -sensitivity is probably the key driver of the cardiomyopathy. Mechanistically, uncoupling usually involves an impaired response of the thin filaments to TnI phosphorylation ( 34 ), however, the cTnI R21C mutation has a mechanism whereby the mutation interferes with the phosphorylation process itself ( 35 ). Another mechanism that could generate impaired lusitropy is if the balance of phosphorylation of TnI and PLB in response to Iso is disturbed as suggested by Najafi et al ( 36 ).…”

“…Studies on the effects of mutations that uncouple TnI phosphorylation from the Ca 2+ -sensitivity shift indicate that they probably act by inducing a subtle, phosphorylation-dependent change in the dynamics of troponin ( 69 – 74 ), most clearly indicated by a recent study on the TnC G159D mutation ( 34 ). Remarkably, it has been found that several small molecules are capable of fully restoring the Ca 2+ -sensitivity shift in vitro and restoring lusitropy to mutated cardiomyocytes ( 7 , 45 , 75 , 76 ).…”

Nutraceuticals Silybin B, resveratrol and epigallocatechin-3 gallate (EGCG) bind to cardiac muscle troponin to restore the loss of lusitropy caused by cardiomyopathy mutationsin vitro, in vivo, andin silico

“…Molecular Dynamics studies 4.3.1 MD simulations of troponin were performed as described by Yang et al [24].…”

Ryanodine receptor‐associated myopathies: What's myosin got to do with it?

“…selected two of the phosphorylated residues in the MYH7 polypeptide (Ser1362 in RYR1‐CM and Tyr1375 in both RYR1‐CM and RYR1‐RM) for closer examination using molecular dynamics (MD) simulations. MD has been widely used to examine molecular processes that are challenging, if not impossible to assess in muscle with current experimental approaches 11,15–19 . Dynamic simulations of portions of MYH7 rod suggest that phosphorylation could negatively impact structural dynamics of the rod—and by implication the thick filament backbone and interaction with IHM—in myopathy patients.…”

“…MD has been widely used to examine molecular processes that are challenging, if not impossible to assess in muscle with current experimental approaches. 11,[15][16][17][18][19] Dynamic simulations of portions of MYH7 rod suggest that phosphorylation could negatively impact structural dynamics of the rod-and by implication the thick filament backbone and interaction with IHM-in myopathy patients.…”