Activation of skeletal muscle is controlled by a dual-filament mechano-sensing mechanism

• DOI: 10.1073/pnas.2302837120
• Publication Date: 2023-05-22T19:02:10Z
• Authors: Elisabetta Brunello; Lorenzo Marcucci; Malcolm Irving; Luca Fusi
• Keywords: Calcium, Dietary; 570; 500; Calcium; muscle regulation; myosin; skeletal muscle; troponin;; Biological Sciences; Myosins; Muscle, Skeletal; Actins; Cytoskeleton; Muscle Contraction

Contraction of skeletal muscle is triggered by a transient rise in intracellular calcium concentration leading to structural change the actin-containing thin filaments that allows binding myosin motors from thick filaments. Most are unavailable for actin resting because they folded back against filament backbone. Release stress, implying positive feedback loop However, it was unclear how and activation mechanisms coordinated, partly most previous studies regulation were conducted at low temperatures where inhibited. Here, we use probes on both troponin monitor states near-physiological conditions. We characterize those steady state, using conventional titrations with buffers, during physiological timescale, jumps produced photolysis caged calcium. The results reveal three intact lattice cell analogous proposed previously isolated proteins. rates transitions between these relation mechano-sensing show thin- thick-filament-based coupled two loops switch achieve rapid cooperative muscle.