Dataset Information

Skeletal Muscle Fibers Inspired Polymeric Actuator by Assembly of Triblock Polymers.

ABSTRACT: Inspired by the striated structure of skeletal muscle fibers, a polymeric actuator by assembling two symmetric triblock copolymers, namely, polystyrene-b-poly(acrylic acid)-b-polystyrene (SAS) and polystyrene-b-poly(ethylene oxide)-b-polystyrene (SES) is developed. Owing to the microphase separation of the triblock copolymers and hydrogen-bonding complexation of their middle segments, the SAS/SES assembly forms a lamellar structure with alternating vitrified S and hydrogen-bonded A/E association layers. The SAS/SES strip can be actuated and operate in response to environmental pH. The contraction ratio and working density of the SAS/SES actuator are approximately 50% and 90 kJ m^-3 , respectively; these values are higher than those of skeletal muscle fibers. In addition, the SAS/SES actuator shows a "catch-state", that is, it can maintain force without energy consumption, which is a feature of mollusc muscle but not skeletal muscle. This study provides a biomimetic approach for the development of artificial polymeric actuators with outstanding performance.

SUBMITTER: Wang W

PROVIDER: S-EPMC9069194 | biostudies-literature | 2022 May

REPOSITORIES: biostudies-literature

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Skeletal Muscle Fibers Inspired Polymeric Actuator by Assembly of Triblock Polymers.

Wang Weijie W Xu Xian X Zhang Caihong C Huang Hao H Zhu Liping L Yue Kan K Zhu Meifang M Yang Shuguang S

Advanced science (Weinheim, Baden-Wurttemberg, Germany) 20220306 13

Inspired by the striated structure of skeletal muscle fibers, a polymeric actuator by assembling two symmetric triblock copolymers, namely, polystyrene-b-poly(acrylic acid)-b-polystyrene (SAS) and polystyrene-b-poly(ethylene oxide)-b-polystyrene (SES) is developed. Owing to the microphase separation of the triblock copolymers and hydrogen-bonding complexation of their middle segments, the SAS/SES assembly forms a lamellar structure with alternating vitrified S and hydrogen-bonded A/E association ...[more]

PMID: 35253397

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Project description:BackgroundMuscle stem cells (MuSCs) undergo numerous state transitions throughout life, which are critical for supporting normal muscle growth and regeneration. Epigenetic modifications in skeletal muscle play a significant role in influencing the niche and cellular states of MuSCs. Mixed-lineage leukemia 4 (Mll4) is a histone methyltransferase critical for activating the transcription of various target genes and is highly expressed in skeletal muscle. This raises the question of whether Mll4 has a regulatory function in modulating the state transitions of MuSCs, warranting further investigation.MethodsTo assess if myofiber-expressed Mll4, a histone methyltransferase, contributes to the maintenance of MuSCs, we crossed MCKCre/+ or HSAMerCreMer/+ mice to Mll4f/f mice to generate myofiber-specific Mll4-deleted mice. Investigations were conducted using 8-week-old and 4-week-old MCKCre/+;Mll4f/f mice, and adult HSAMerCreMer/+;Mll4f/f mice between the ages of 3 months and 6 months.ResultsDuring postnatal myogenesis, Mll4 deleted muscles were observed with increased number of cycling MuSCs that proceeded to a differentiation state, leading to MuSC deprivation. This phenomenon occurred independently of gender. When Mll4 was ablated in adult muscles using the inducible method, adult MuSCs lost their quiescence and differentiated into myoblasts, also causing the depletion of MuSCs. Such roles of Mll4 in myofibers coincided with decreased expression levels of distinct Notch ligands: Jag1 and Dll1 in pubertal and Jag2 and Dll4 in adult muscles.ConclusionsOur study suggests that Mll4 is crucial for maintaining MuSCs in both pubertal and adult muscles, which may be accomplished through the modulation of distinct Notch ligand expressions in myofibers. These findings offer new insights into the role of myofiber-expressed Mll4 as a master regulator of MuSCs, highlighting its significance not only in developmental myogenesis but also in adult muscle, irrespective of sex.

Project description:In skeletal muscle, excitation-contraction (EC) coupling requires depolarization-induced conformational rearrangements in L-type Ca(2+) channel (Ca(V)1.1) to be communicated to the type 1 ryanodine-sensitive Ca(2+) release channel (RYR1) of the sarcoplasmic reticulum (SR) via transient protein-protein interactions. Although the molecular mechanism that underlies conformational coupling between Ca(V)1.1 and RYR1 has been investigated intensely for more than 25 years, the question of whether such signaling occurs via a direct interaction between the principal, voltage-sensing α(1S) subunit of Ca(V)1.1 and RYR1 or through an intermediary protein persists. A substantial body of evidence supports the idea that the auxiliary β(1a) subunit of Ca(V)1.1 is a conduit for this intermolecular communication. However, a direct role for β(1a) has been difficult to test because β(1a) serves two other functions that are prerequisite for conformational coupling between Ca(V)1.1 and RYR1. Specifically, β(1a) promotes efficient membrane expression of Ca(V)1.1 and facilitates the tetradic ultrastructural arrangement of Ca(V)1.1 channels within plasma membrane-SR junctions. In this paper, we demonstrate that overexpression of the RGK protein Rem, an established β subunit-interacting protein, in adult mouse flexor digitorum brevis fibers markedly reduces voltage-induced myoplasmic Ca(2+) transients without greatly affecting Ca(V)1.1 targeting, intramembrane gating charge movement, or releasable SR Ca(2+) store content. In contrast, a β(1a)-binding-deficient Rem triple mutant (R200A/L227A/H229A) has little effect on myoplasmic Ca(2+) release in response to membrane depolarization. Thus, Rem effectively uncouples the voltage sensors of Ca(V)1.1 from RYR1-mediated SR Ca(2+) release via its ability to interact with β(1a). Our findings reveal Rem-expressing adult muscle as an experimental system that may prove useful in the definition of the precise role of the β(1a) subunit in skeletal-type EC coupling.

Dataset Information

Skeletal Muscle Fibers Inspired Polymeric Actuator by Assembly of Triblock Polymers.

Publications

Skeletal Muscle Fibers Inspired Polymeric Actuator by Assembly of Triblock Polymers.

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