Key result
MLC20 phosphorylation was directly and linearly correlated with the active stress, stiffness, and power of airway smooth muscle, consistent with the Huxley crossbridge model.
Why the study?
During smooth muscle contraction, changes in protein phosphorylation and signaling enzyme activation alter mechanical manifestations over time, complicating the study of crossbridge relationships.
The study demonstrates that the basic crossbridge mechanism in airway smooth muscle is identical to that in striated muscle and can be explained by the Huxley crossbridge model when time-dependent variables are controlled.
May refine models of smooth muscle contraction; leaves open how dynamic MLC20 phosphorylation affects Vmax in lung tissue.
The cyclic interaction between myosin crossbridges and actin filaments underlies smooth muscle contraction. Phosphorylation of the 20-kDa myosin light chain (MLC20) is a crucial step in activating the crossbridge cycle. Our current understanding of smooth muscle contraction is based on observed correlations among MLC20 phosphorylation, maximal shortening velocity ( V max ), and isometric force over the time course of contraction. However, during contraction there are changes in the extent of phosphorylation of many additional proteins as well as changes in activation of enzymes associated with the signaling pathways. As a consequence, the mechanical manifestation of muscle contraction is likely to change with time. To simplify the study of these relationships, we measured the mechanical properties of airway smooth muscle at different levels of MLC20 phosphorylation at a fixed time during contraction. A simple correlation emerged when time-dependent variables were fixed. MLC20 phosphorylation was found to be directly and linearly correlated with the active stress, stiffness, and power of the muscle; the observed weak dependence of V max on MLC20 phosphorylation could be explained by the presence of an internal load in the muscle preparation. These results can be entirely explained by the Huxley crossbridge model. We conclude that when the influence of time-dependent events during contraction is held constant, the basic crossbridge mechanism in smooth muscle is the same as that in striated muscle.
No takes yet. Share an insight, caveat, or question.
Luo et al. (2019) studied Airway smooth muscle contraction. MLC20 phosphorylation was evaluated on Mechanical properties (active stress, stiffness, power, and Vmax). MLC20 phosphorylation was directly and linearly correlated with the active stress, stiffness, and power of airway smooth muscle, consistent with the Huxley crossbridge model.
Synapse has enriched 5 closely related papers on similar clinical questions. Consider them for comparative context: