The residual force enhancement state is structurally distinct from pure isometric contractions, with increased thick filament strain and decreased lattice spacing driven by titin-based forces.
Titin directly contributes to residual force enhancement in muscle through decreased lattice spacing, increased thick filament stiffness, and increased non-cross-bridge forces.
In muscle, titin proteins connect myofilaments together and are thought to be critical for contraction, especially during residual force enhancement (RFE) when steady-state force is elevated after an active stretch. We investigated titin’s function during contraction using small-angle X-ray diffraction to track structural changes before and after 50% titin cleavage and in the RFE-deficient, mdm titin mutant. We report that the RFE state is structurally distinct from pure isometric contractions, with increased thick filament strain and decreased lattice spacing, most likely caused by elevated titin-based forces. Furthermore, no RFE structural state was detected in mdm muscle. We posit that decreased lattice spacing, increased thick filament stiffness, and increased non-cross-bridge forces are the major contributors to RFE. We conclude that titin directly contributes to RFE.
Hessel et al. (Mon,) conducted a other in Muscle contraction / Residual force enhancement. 50% titin cleavage and mdm titin mutant vs. Before cleavage / wild-type was evaluated on Structural changes during residual force enhancement (RFE). The residual force enhancement state is structurally distinct from pure isometric contractions, with increased thick filament strain and decreased lattice spacing driven by titin-based forces.