Single-molecule imaging reveals the concerted release of myosin from regulated thin filaments

Regulated thin filaments (RTFs) tightly control striated muscle contraction through calcium binding to troponin, which enables tropomyosin to expose myosin-binding sites on actin. Myosin binding holds tropomyosin in an open position, exposing more myosin-binding sites on actin, leading to cooperativ...

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Auteurs principaux: Quentin M Smith, Alessio V Inchingolo, Madalina-Daniela Mihailescu, Hongsheng Dai, Neil M Kad
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Langue:EN
Publié: eLife Sciences Publications Ltd 2021
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spelling oai:doaj.org-article:b292140cde184a14b4f0e4ce71ad097e2021-11-26T11:12:14ZSingle-molecule imaging reveals the concerted release of myosin from regulated thin filaments10.7554/eLife.691842050-084Xe69184https://doaj.org/article/b292140cde184a14b4f0e4ce71ad097e2021-09-01T00:00:00Zhttps://elifesciences.org/articles/69184https://doaj.org/toc/2050-084XRegulated thin filaments (RTFs) tightly control striated muscle contraction through calcium binding to troponin, which enables tropomyosin to expose myosin-binding sites on actin. Myosin binding holds tropomyosin in an open position, exposing more myosin-binding sites on actin, leading to cooperative activation. At lower calcium levels, troponin and tropomyosin turn off the thin filament; however, this is antagonised by the high local concentration of myosin, questioning how the thin filament relaxes. To provide molecular details of deactivation, we used single-molecule imaging of green fluorescent protein (GFP)-tagged myosin-S1 (S1-GFP) to follow the activation of RTF tightropes. In sub-maximal activation conditions, RTFs are not fully active, enabling direct observation of deactivation in real time. We observed that myosin binding occurs in a stochastic step-wise fashion; however, an unexpectedly large probability of multiple contemporaneous detachments is observed. This suggests that deactivation of the thin filament is a coordinated active process.Quentin M SmithAlessio V InchingoloMadalina-Daniela MihailescuHongsheng DaiNeil M KadeLife Sciences Publications Ltdarticlecooperativitymuscleactinfluorescence imagingregulationcalciumMedicineRScienceQBiology (General)QH301-705.5ENeLife, Vol 10 (2021)
institution DOAJ
collection DOAJ
language EN
topic cooperativity
muscle
actin
fluorescence imaging
regulation
calcium
Medicine
R
Science
Q
Biology (General)
QH301-705.5
spellingShingle cooperativity
muscle
actin
fluorescence imaging
regulation
calcium
Medicine
R
Science
Q
Biology (General)
QH301-705.5
Quentin M Smith
Alessio V Inchingolo
Madalina-Daniela Mihailescu
Hongsheng Dai
Neil M Kad
Single-molecule imaging reveals the concerted release of myosin from regulated thin filaments
description Regulated thin filaments (RTFs) tightly control striated muscle contraction through calcium binding to troponin, which enables tropomyosin to expose myosin-binding sites on actin. Myosin binding holds tropomyosin in an open position, exposing more myosin-binding sites on actin, leading to cooperative activation. At lower calcium levels, troponin and tropomyosin turn off the thin filament; however, this is antagonised by the high local concentration of myosin, questioning how the thin filament relaxes. To provide molecular details of deactivation, we used single-molecule imaging of green fluorescent protein (GFP)-tagged myosin-S1 (S1-GFP) to follow the activation of RTF tightropes. In sub-maximal activation conditions, RTFs are not fully active, enabling direct observation of deactivation in real time. We observed that myosin binding occurs in a stochastic step-wise fashion; however, an unexpectedly large probability of multiple contemporaneous detachments is observed. This suggests that deactivation of the thin filament is a coordinated active process.
format article
author Quentin M Smith
Alessio V Inchingolo
Madalina-Daniela Mihailescu
Hongsheng Dai
Neil M Kad
author_facet Quentin M Smith
Alessio V Inchingolo
Madalina-Daniela Mihailescu
Hongsheng Dai
Neil M Kad
author_sort Quentin M Smith
title Single-molecule imaging reveals the concerted release of myosin from regulated thin filaments
title_short Single-molecule imaging reveals the concerted release of myosin from regulated thin filaments
title_full Single-molecule imaging reveals the concerted release of myosin from regulated thin filaments
title_fullStr Single-molecule imaging reveals the concerted release of myosin from regulated thin filaments
title_full_unstemmed Single-molecule imaging reveals the concerted release of myosin from regulated thin filaments
title_sort single-molecule imaging reveals the concerted release of myosin from regulated thin filaments
publisher eLife Sciences Publications Ltd
publishDate 2021
url https://doaj.org/article/b292140cde184a14b4f0e4ce71ad097e
work_keys_str_mv AT quentinmsmith singlemoleculeimagingrevealstheconcertedreleaseofmyosinfromregulatedthinfilaments
AT alessiovinchingolo singlemoleculeimagingrevealstheconcertedreleaseofmyosinfromregulatedthinfilaments
AT madalinadanielamihailescu singlemoleculeimagingrevealstheconcertedreleaseofmyosinfromregulatedthinfilaments
AT hongshengdai singlemoleculeimagingrevealstheconcertedreleaseofmyosinfromregulatedthinfilaments
AT neilmkad singlemoleculeimagingrevealstheconcertedreleaseofmyosinfromregulatedthinfilaments
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