Abstract
Many biological processes are triggered or driven by mechanical forces in the cytoskeletal network, but these transducing forces have rarely been assessed. Striated muscle, with its well-organized structure provides an opportunity to assess intracellular forces using small-angle X-ray fiber diffraction. We present a new methodology using Monte Carlo simulations of muscle contraction in an explicit 3D sarcomere lattice to predict the fiber deformations and length changes along thin filaments during contraction. Comparison of predicted diffraction patterns to experimental meridional X-ray reflection profiles allows assessment of the stepwise changes in intermonomer spacings and forces in the myofilaments within living muscle cells. These changes along the filament length reflect the effect of forces from randomly attached crossbridges. This approach enables correlation of the molecular events, such as the current number of attached crossbridges and the distributions of crossbridge forces to macroscopic measurements of force and length changes during muscle contraction. In addition, assessments of fluctuations in local forces in the myofilaments may reveal how variations in the filament forces acting on signaling proteins in the sarcomere M-bands and Z-discs modulate gene expression, protein synthesis and degradation, and as well to mechanisms of adaptation of muscle in response to changes in mechanical loading.
Highlights
Mechanical forces acting in living cells are extremely important in understanding mechanotransduction, cell migration and cell physiological function [1,2,3,4]
We show that the newly developed MUSICO X-ray diffraction module can predict several orders of actin meridional diffraction reflections where the first order reflection primarily reports the average strains in the filaments, but the higher order meridional reflections report on the non-uniformity of the spacings [14]
The shifts are the measure of average change in spacing from relaxed to contracted state, and the widths of the higher order reflections are the measure of the degree of nonuniformity of the actin monomer spacings
Summary
Mechanical forces acting in living cells are extremely important in understanding mechanotransduction, cell migration and cell physiological function [1,2,3,4]. The simplest method for interpreting the relationship between deformed sarcomere structure, due to developed tension, and meridional reflections in X-ray diffraction patterns, uses the correlation between an average atomic spacing and X-ray patterns along the meridional axis. Using this approach, Huxley et al (1994) and Wakabayashi et al (1994) estimated the elastic characteristics of actin and myosin filaments [12,13] by plotting the changes in the axial spacing of the first order actin meridional reflection as a function of developed force. There is much more information contained in the diffraction patterns if methods can be developed to extract it
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
