TY - JOUR
T1 - Cardiac troponin T N-domain variant destabilizes the actin interface resulting in disturbed myofilament function
AU - Landim-Vieira, Maicon
AU - Ma, Weikang
AU - Song, Taejeong
AU - Rastegarpouyani, Hosna
AU - Gong, Henry
AU - Coscarella, Isabella Leite
AU - Bogaards, Sylvia J. P.
AU - Conijn, Stefan P.
AU - Ottenheijm, Coen A. C.
AU - Hwang, Hyun S.
AU - Papadaki, Maria
AU - Knollmann, Bjorn C.
AU - Sadayappan, Sakthivel
AU - Irving, Thomas C.
AU - Galkin, Vitold E.
AU - Chase, P. Bryant
AU - Pinto, Jose Renato
N1 - Funding Information: ACK?OWLEDGME?TS. We would like to acknowledge Dr. Kenneth A. Taylor for the critical review of the manuscript. We would like to thank Elise Wight and Dr. Timothy Megraw for providing the α-tubulin detyrosinated antibody. This work was supported by the National Heart, Lung and Blood Institute HL128683 (to J.R.P.), HL160966 (to V.E. G., P.B.C., and J.R.P.), R35 HL144980 (to B.C.K.), and R01HL12150 (to C.A.C.O.) and the National Institute of Arthritis and Musculoskeletal and Skin Disease R21 AR077802 (to H.R. and J.R.P.). American Heart Association Fellowship training grants supported Funding Information: T.S. (19POST34380448) and M.L.-V. (2021AHAPRE216237). This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357. BioCAT was supported by grant P30 GM138395 (to T.C.I.) from the National Institute of General Medical Sciences of the NIH. S.S. has received support from NIH grants R01 AR079435, R01 AR079477, R01 AR078001, R01 HL130356, R01 HL105826, R38 HL155775, and R01 HL143490; the American Heart Association 2019 Institutional Undergraduate Student (19UFEL34380251) and Transformation (19TPA34830084 and 945748) awards; the Phospholamban (PLN) Foundation (PLN crazy idea); and the Leducq Foundation (Transatlantic Network 18CVD01). Funding Information: We would like to acknowledge Dr. Kenneth A. Taylor for the critical review of the manuscript. We would like to thank Elise Wight and Dr. Timothy Megraw for providing the a-tubulin detyrosinated antibody. This work was supported by the National Heart, Lung and Blood Institute HL128683 (to J.R.P.), HL160966 (to V.E. G., P.B.C., and J.R.P.), R35 HL144980 (to B.C.K.), and R01HL12150 (to C.A.C.O.) and the National Institute of Arthritis and Musculoskeletal and Skin Disease R21 AR077802 (to H.R. and J.R.P.). American Heart Association Fellowship training grants supported T.S. (19POST34380448) and M.L.-V. (2021AHAPRE216237). This research used resources of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357. BioCAT was supported by grant P30 GM138395 (to T.C.I.) from the National Institute of General Medical Sciences of the NIH. S.S. has received support from NIH grants R01 AR079435, R01 AR079477, R01 AR078001, R01 HL130356, R01 HL105826, R38 HL155775, and R01 HL143490; the American Heart Association 2019 Institutional Undergraduate Student (19UFEL34380251) and Transformation (19TPA34830084 and 945748) awards; the Phospholamban (PLN) Foundation (PLN crazy idea); and the Leducq Foundation (Transatlantic Network 18CVD01). Publisher Copyright: Copyright © 2023 the Author(s).
PY - 2023/6/6
Y1 - 2023/6/6
N2 - Missense variant Ile79Asn in human cardiac troponin T (cTnT-I79N) has been associated with hypertrophic cardiomyopathy and sudden cardiac arrest in juveniles. cTnT-I79N is located in the cTnT N-terminal (TnT1) loop region and is known for its pathological and prognostic relevance. A recent structural study revealed that I79 is part of a hydrophobic interface between the TnT1 loop and actin, which stabilizes the relaxed (OFF) state of the cardiac thin filament. Given the importance of understanding the role of TnT1 loop region in Ca2+ regulation of the cardiac thin filament along with the underlying mechanisms of cTnT-I79N-linked pathogenesis, we investigated the effects of cTnT-I79N on cardiac myofilament function. Transgenic I79N (Tg-I79N) muscle bundles displayed increased myofilament Ca2+ sensitivity, smaller myofilament lattice spacing, and slower crossbridge kinetics. These findings can be attributed to destabilization of the cardiac thin filament's relaxed state resulting in an increased number of crossbridges during Ca2+ activation. Additionally, in the low Ca2+-relaxed state (pCa8), we showed that more myosin heads are in the disordered-relaxed state (DRX) that are more likely to interact with actin in cTnT-I79N muscle bundles. Dysregulation of the myosin super-relaxed state (SRX) and the SRX/DRX equilibrium in cTnT-I79N muscle bundles likely result in increased mobility of myosin heads at pCa8, enhanced actomyosin interactions as evidenced by increased active force at low Ca2+, and increased sinusoidal stiffness. These findings point to a mechanism whereby cTnT-I79N weakens the interaction of the TnT1 loop with the actin filament, which in turn destabilizes the relaxed state of the cardiac thin filament.
AB - Missense variant Ile79Asn in human cardiac troponin T (cTnT-I79N) has been associated with hypertrophic cardiomyopathy and sudden cardiac arrest in juveniles. cTnT-I79N is located in the cTnT N-terminal (TnT1) loop region and is known for its pathological and prognostic relevance. A recent structural study revealed that I79 is part of a hydrophobic interface between the TnT1 loop and actin, which stabilizes the relaxed (OFF) state of the cardiac thin filament. Given the importance of understanding the role of TnT1 loop region in Ca2+ regulation of the cardiac thin filament along with the underlying mechanisms of cTnT-I79N-linked pathogenesis, we investigated the effects of cTnT-I79N on cardiac myofilament function. Transgenic I79N (Tg-I79N) muscle bundles displayed increased myofilament Ca2+ sensitivity, smaller myofilament lattice spacing, and slower crossbridge kinetics. These findings can be attributed to destabilization of the cardiac thin filament's relaxed state resulting in an increased number of crossbridges during Ca2+ activation. Additionally, in the low Ca2+-relaxed state (pCa8), we showed that more myosin heads are in the disordered-relaxed state (DRX) that are more likely to interact with actin in cTnT-I79N muscle bundles. Dysregulation of the myosin super-relaxed state (SRX) and the SRX/DRX equilibrium in cTnT-I79N muscle bundles likely result in increased mobility of myosin heads at pCa8, enhanced actomyosin interactions as evidenced by increased active force at low Ca2+, and increased sinusoidal stiffness. These findings point to a mechanism whereby cTnT-I79N weakens the interaction of the TnT1 loop with the actin filament, which in turn destabilizes the relaxed state of the cardiac thin filament.
KW - TnT1 loop region
KW - cardiac thin filament
KW - cardiac troponin T tail domain
KW - cardiomyopathy
KW - myosin SRX/DRX
UR - http://www.scopus.com/inward/record.url?scp=85160594107&partnerID=8YFLogxK
U2 - https://doi.org/10.1073/pnas.2221244120
DO - https://doi.org/10.1073/pnas.2221244120
M3 - Article
C2 - 37252999
SN - 0027-8424
VL - 120
SP - e2221244120
JO - PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
JF - PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
IS - 23
M1 - e2221244120
ER -