SKELETAL MyBP-C ISOFORMS TUNE THE MOLECULAR CONTRACTILITY OF DIVERGENT SKELETAL MUSCLE SYSTEMS

ABSTRACT Skeletal muscle myosin-binding protein C (MyBP-C) is a myosin thick filament-associated protein; localized through its C terminus to distinct regions (C-zones) of the sarcomere. MyBP-C modulates muscle contractility, presumably through its N terminus extending from the thick filament and interacting with either the myosin head region and/or the actin thin filament. Two isoforms of MyBP-C (fast- and slow-type) are expressed in a muscle-type specific manner. Are the expression, localization, and Ca2+-dependent modulatory capacities of these isoforms different in fast-twitch extensor digitorum longus (EDL) and slow-twitch soleus (SOL) muscles derived from Sprague-Dawley rats? By mass spectrometry, four MyBP-C isoforms (one fast-type MyBP-C and three N-terminally spliced slow-type MyBP-C) were expressed in EDL but only the three slow-type MyBP-C isoforms in SOL. Using EDL and SOL native thick filaments in which the MyBP-C stoichiometry and localization are preserved, native thin filament sliding over these thick filaments showed that only in the C-zone, MyBP-C Ca2+-sensitizes the thin filament and slows thin filament velocity. These modulatory properties depended on MyBP-C’s N-terminus, as N-terminal proteolysis attenuated MyBP-C’s functional capacities. To determine each MyBP-C isoform’s contribution to thin filament Ca2+-sensitization and slowing in the C-zone, we used a combination ofin vitromotility assays using expressed recombinant N-terminal fragments andin silicomechanistic modeling. Our results suggest that each skeletal MyBP-C isoform’s N terminus is functionally distinct and has modulatory capacities that depend on the muscle-type in which they are expressed, providing the potential for molecular tuning of skeletal muscle performance through differential MyBP-C expression.SIGNIFICANCE Myosin-binding protein C (MyBP-C) is a critical component of the skeletal muscle sarcomere, muscle’s smallest contractile unit. MyBP-C’s importance is evident by genetic mutations leading to human myopathies, such as distal arthrogryposis (i.e. club foot). However, the molecular basis of MyBP-C’s functional impact on skeletal muscle contractility is far from certain. Complicating matters further is the expression of fast- and slow-type MyBP-C isoforms that depend on whether the muscle is fast- or slow-twitch. Using multi-scale proteomic, biophysical and mathematical modeling approaches, we define the expression, localization, and modulatory capacities of these distinct skeletal MyBP-C isoforms in rat skeletal muscles. Each MyBP-C isoform appears to modulate muscle contractility differentially; providing the capacity to fine-tune muscle’s mechanical performance as physiological demands arise..

Medienart:	Preprint

Erscheinungsjahr:	2022
Erschienen:	2022

Enthalten in:	bioRxiv.org - (2022) vom: 21. Sept. Zur Gesamtaufnahme - year:2022

Sprache:	Englisch

Beteiligte Personen:	Li, Amy [VerfasserIn] Nelson, Shane [VerfasserIn] Rahmanseresht, Sheema [VerfasserIn] Braet, Filip [VerfasserIn] Cornachione, Anabelle S. [VerfasserIn] Previs, Samantha Beck [VerfasserIn] O’Leary, Thomas S. [VerfasserIn] McNamara, James W. [VerfasserIn] Rassier, Dilson E. [VerfasserIn] Sadayappan, Sakthivel [VerfasserIn] Previs, Michael J. [VerfasserIn] Warshaw, David M. [VerfasserIn]

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Themen:	570 Biology

doi:	10.1101/676601

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PPN (Katalog-ID):	XBI000548545