Program
| MSA3d | |
|---|---|
| Chun, Y. Seow | |
| Department of Pathology and Laboratory Medicine, University of British Columbia | |
| Title | Intermediate filaments in smooth muscle |
| Abstract | Intermediate filaments are abundant in smooth muscle and they can be found in the cytoskeletal network of the cells. It is commonly believed that intermediate filaments are not part of the contractile apparatus, and therefore do not contribute to the generation of active force in the muscle. However, intermediate filaments, together with other cytoskeletal elements, are believed to play an important role in maintaining the shape of the cells and their structural integrity. Details of the structural role played by the intermediate filaments in smooth muscle are nonetheless very sketchy. In this presentation, three-dimensional ultrastructure of aggregates of intermediate filaments and dense bodies in airway smooth muscle is examined. Dense bodies are commonly believed to be the skeletal muscle Z-disks equivalents in smooth muscle. Our 3-D ultrastructure however showed dense bodies strung together by intermediate filaments in a cable-like structure, casting doubts on the role of dense bodies as the "Z-disks". Measurements of the waviness of the intermediate-filament, dense-body cables in the cells revealed an inverse relationship between passive tension borne by the muscle cells and the cable waviness, suggesting that these cables may be able to bear tension in resting muscle. It is known that the passive length-tension relationship in smooth muscle is not elastic, but can be shifted plastically by adapting the muscle at different lengths. Examination of the lengths of the dense-body cables in the muscle cells adapted at different lengths revealed that the cables were able to adjust their lengths rapidly to accommodate the cell length. These length-adjustable cables are therefore likely responsible for the dynamic and plastic length-tension relationship observed in resting smooth muscle and are likely the major regulator of resting smooth muscle length. Because smooth muscle cells are mostly found in the walls of hollow organs, controlling smooth muscle length regulates organ dimension and function, for example, the diameter and resistance of airways. Interaction of intermediate filaments with dense bodies therefore could have an important regulatory role in organ function. Supported by the Canadian Institutes of health Research. |
| Location | Woodward 3 |