Related Experiment Video
Updated: Jul 16, 2026

Myosin-Specific Adaptations of In vitro Fluorescence Microscopy-Based Motility Assays
Published on: February 4, 2021
Expression and function of COOH-terminal myosin heavy chain isoforms in mouse smooth muscle
Anne F Martin1, Sunita Bhatti, Gail J Pyne-Geithman
1Dept. of Physiology and Biophysics, University of Illinois at Chicago, 835 S. Wolcott Ave., Chicago, IL 60612, USA. afmartin@uic.edu
Abstract:
Isoforms of the smooth muscle myosin motor, SM1 and SM2, differ in length at the carboxy terminal tail region. Their proportion changes with development, hormonal status and disease, but their function is unknown. We developed mice carrying the myosin heavy chain (MyHC) transgenes SM1, cMyc-tagged SM1, SM2, and V5-tagged SM2, and all transgenes corresponded to the SMa NH(2)-terminal isoform. Transgene expression was targeted to smooth muscle by the smooth muscle alpha-actin promoter. Immunoblot analysis showed substantial expression of the cMyc-tagged SM1 and V5-tagged SM2 MyHC protein in aorta and bladder and transgene mRNA was expressed in mice carrying unlabeled SM1 or SM2 transgenes. Despite significant protein expression of tagged MyHCs we found only small changes in the SM1:SM2 protein ratio. Significant changes in functional phenotype were observed in mice carrying unlabeled SM1 or SM2 transgenes. Force in aorta and bladder was increased (72 +/- 14%, 92 +/- 11%) in SM1 and decreased to 57 +/- 1% and 80 +/- 3% in SM2 transgenic mice. SM1 transgenic bladders had faster (1.8 +/- 0.3 s) and SM2 slower (7.1 +/- 0.5 s) rates of force redevelopment following a rapid step shortening. We hypothesize that small changes in the SM1:SM2 ratio could be amplified if they are associated with changes in thick filament assembly and underlie the altered contractility. These data provide evidence indicating an in vivo function for the COOH-terminal isoforms of smooth muscle myosin and suggest that the SM1:SM2 ratio is tightly regulated in smooth muscle tissues.
More Related Videos
08:12Intact Short, Intermediate, and Long Skeletal Muscle Fibers Obtained by Enzymatic Dissociation of Six Hindlimb Muscles of Mice: Beyond Flexor Digitorum Brevis
Published on: December 1, 2023
09:17MultiBac System-Based Purification and Biophysical Characterization of Human Myosin-7a
Published on: August 23, 2024
Related Concept Videos
Overview of Myosin Structure and Function
Smooth Muscle Contraction
The onset of contraction is triggered by an increase in calcium ions within the sarcoplasm, similar to the process in striated muscle. However, smooth muscles have a relatively smaller reservoir of the sarcoplasmic...
Actin and Myosin in Muscle Contraction
Functions of Smooth Muscles
Function of visceral smooth muscles
Visceral smooth muscle is found in the walls of all hollow organs, except the heart, and is a key player in the involuntary movements that drive the functioning of these internal organs. This tissue is arranged in...
Structure and Organization of Smooth Muscles
Structure of smooth muscle cell
Smooth muscle cells are spindle-shaped with tapering ends and a...
The Role of Actin and Myosin in Non-muscle Cells