Reorganization of actin filament bundles in living fibroblasts.
Open Access
- 1 October 1984
- journal article
- research article
- Published by Rockefeller University Press in The Journal of cell biology
- Vol. 99 (4) , 1478-1485
- https://doi.org/10.1083/jcb.99.4.1478
Abstract
How actin bundles assemble, disassemble and reorganize during cell movement was investigated. Living chick embryonic fibroblasts were microinjected with actin molecules that were fluorescently labeled with tetramethylrhodamine. The fluorescent analog of actin can be used successfully by both existing and newly formed cellular structures. Time-lapse photography coupled to image-intensified fluorescence microscopy detects various patterns of reorganization in motile cells. Assembly of stress fibers occurred near both the leading and the trailing ends of the cell. The initial structure appeared as discrete spots that subsequently extended into stress fibers. The extension occurred unidirectionally. The site of initiation near the leading edge remained stationary relative to the substrate during subsequent cell advancement. The orientation of the fiber could change according to the direction of cell movement. Existing stress fibers could merge or fragment. The shortening of stress fibers can occur from either end of the fiber. Shortening from the proximal end (centrifugal shortening) was accompanied by a decrease in fluorescence intensity, as if the bundle were disassembling and usually led to the total disappearance of the bundle. Shortening from the distal end (centripetal shortening) is usually accompanied by an increase in fluorescence intensity at the distal end of the bundle, as if this end had pulled loose from its attachment and retracted toward the center of the cell. Besides stress fibers, arc-like actin bundles were also detected in spreading cells. These observations can explain how the organization of actin bundles coordinates with cell movement, and how stress fibers reach a highly regular pattern in static cells.Keywords
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