The Huxley crossbridge model as the basic mechanism for airway smooth muscle contraction.

The Huxley crossbridge model as the basic mechanism for airway smooth muscle contraction.
Am J Physiol Lung Cell Mol Physiol. 2019 May 22;:
Authors: Luo L, Wang L, Paré PD, Seow CY, Chitano P
Abstract
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 (Vmax), 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 Vmax on MLC20 phosphorylation could be explained by the presence of an internal load in the muscle preparation....

Source: American Journal of Physiology. Lung Cellular and Molecular Physiology - May 21, 2019 Category: Cytology Authors: Luo L, Wang L, Paré PD, Seow CY, Chitano P Tags: Am J Physiol Lung Cell Mol Physiol Source Type: research