TY - JOUR
T1 - Cooling intact and demembranated trabeculae from rat heart releases myosin motors from their inhibited conformation
AU - Garcia Ovejero, Jesus
AU - Fusi, Luca
AU - Holohan, So-Jin
AU - Ghisleni, Andrea
AU - Narayanan, Theyencheri
AU - Irving, Malcolm
AU - Brunello, Elisabetta
N1 - Funding Information:
This work and the investigators were supported by the British Heart Foundation (King’s British Heart Foundation Centre of Research Excellence, RE/13/2/30182 and RE/18/2/ 34213; Intermediate Basic Science Research Fellowship FS/17/3/ 32604, awarded to E. Brunello, and PG/16/19/32072, awarded to M. Irving), and European Synchrotron Radiation Facility. L. Fusi was funded by a Sir Henry Dale Fellowship awarded by the Wellcome Trust and the Royal Society (210464/Z/18/Z). A. Ghisleni thanks Wellcome Trust Collaborative Award in Science (UK; 201543/Z/16/Z, awarded to Mathias Gautel) and Fondazione Umberto Veronesi (Italy) for financial support. This research was funded in part by the Wellcome Trust (grant no. 210464/Z/ 18/Z). For the purpose of open access, the author has applied a CC BY public copyright license to any Author Accepted Manuscript version arising from this submission.
Publisher Copyright:
© 2022 Ovejero et al.
PY - 2022/3/7
Y1 - 2022/3/7
N2 - Myosin filament-based regulation supplements actin filament-based regulation to control the strength and speed of contraction in heart muscle. In diastole, myosin motors form a folded helical array that inhibits actin interaction; during contraction, they are released from that array. A similar structural transition has been observed in mammalian skeletal muscle, in which cooling below physiological temperature has been shown to reproduce some of the structural features of the activation of myosin filaments during active contraction. Here, we used small-angle x-ray diffraction to characterize the structural changes in the myosin filaments associated with cooling of resting and relaxed trabeculae from the right ventricle of rat hearts from 39°C to 7°C. In intact quiescent trabeculae, cooling disrupted the folded helical conformation of the myosin motors and induced extension of the filament backbone, as observed in the transition from diastole to peak systolic force at 27°C. Demembranation of trabeculae in relaxing conditions induced expansion of the filament lattice, but the structure of the myosin filaments was mostly preserved at 39°C. Cooling of relaxed demembranated trabeculae induced changes in motor conformation and filament structure similar to those observed in intact quiescent trabeculae. Osmotic compression of the filament lattice to restore its spacing to that of intact trabeculae at 39°C stabilized the helical folded state against disruption by cooling. The myosin filament structure and motor conformation of intact trabeculae at 39°C were largely preserved in demembranated trabeculae at 27°C or above in the presence of Dextran, allowing the physiological mechanisms of myosin filament-based regulation to be studied in those conditions.
AB - Myosin filament-based regulation supplements actin filament-based regulation to control the strength and speed of contraction in heart muscle. In diastole, myosin motors form a folded helical array that inhibits actin interaction; during contraction, they are released from that array. A similar structural transition has been observed in mammalian skeletal muscle, in which cooling below physiological temperature has been shown to reproduce some of the structural features of the activation of myosin filaments during active contraction. Here, we used small-angle x-ray diffraction to characterize the structural changes in the myosin filaments associated with cooling of resting and relaxed trabeculae from the right ventricle of rat hearts from 39°C to 7°C. In intact quiescent trabeculae, cooling disrupted the folded helical conformation of the myosin motors and induced extension of the filament backbone, as observed in the transition from diastole to peak systolic force at 27°C. Demembranation of trabeculae in relaxing conditions induced expansion of the filament lattice, but the structure of the myosin filaments was mostly preserved at 39°C. Cooling of relaxed demembranated trabeculae induced changes in motor conformation and filament structure similar to those observed in intact quiescent trabeculae. Osmotic compression of the filament lattice to restore its spacing to that of intact trabeculae at 39°C stabilized the helical folded state against disruption by cooling. The myosin filament structure and motor conformation of intact trabeculae at 39°C were largely preserved in demembranated trabeculae at 27°C or above in the presence of Dextran, allowing the physiological mechanisms of myosin filament-based regulation to be studied in those conditions.
KW - Heart muscle
KW - muscle regulation
KW - X-ray diffraction
KW - myosin motors
UR - http://www.scopus.com/inward/record.url?scp=85123815186&partnerID=8YFLogxK
U2 - 10.1085/jgp.202113029
DO - 10.1085/jgp.202113029
M3 - Article
SN - 0022-1295
VL - 154
JO - Journal of General Physiology
JF - Journal of General Physiology
IS - 3
M1 - e202113029
ER -