Myosin II filament assemblies in the active lamella of fibroblasts: their morphogenesis and role in the formation of actin filament bundles.
Open Access
- 15 November 1995
- journal article
- Published by Rockefeller University Press in The Journal of cell biology
- Vol. 131 (4), 989-1002
- https://doi.org/10.1083/jcb.131.4.989
Abstract
The morphogenesis of myosin II structures in active lamella undergoing net protrusion was analyzed by correlative fluorescence and electron microscopy. In rat embryo fibroblasts (REF 52) microinjected with tetramethylrhodamine-myosin II, nascent myosin spots formed close to the active edge during periods of retraction and then elongated into wavy ribbons of uniform width. The spots and ribbons initially behaved as distinct structural entities but subsequently aligned with each other in a sarcomeric-like pattern. Electron microscopy established that the spots and ribbons consisted of bipolar minifilaments associated with each other at their head-containing ends and arranged in a single row in an "open" zig-zag conformation or as a "closed" parallel stack. Ribbons also contacted each other in a nonsarcomeric, network-like arrangement as described previously (Verkhovsky and Borisy, 1993. J. Cell Biol. 123:637-652). Myosin ribbons were particularly pronounced in REF 52 cells, but small ribbons and networks were found also in a range of other mammalian cells. At the edge of the cell, individual spots and open ribbons were associated with relatively disordered actin filaments. Further from the edge, myosin filament alignment increased in parallel with the development of actin bundles. In actin bundles, the actin cross-linking protein, alpha-actinin, was excluded from sites of myosin localization but concentrated in paired sites flanking each myosin ribbon, suggesting that myosin filament association may initiate a pathway for the formation of actin filament bundles. We propose that zig-zag assemblies of myosin II filaments induce the formation of actin bundles by pulling on an actin filament network and that co-alignment of actin and myosin filaments proceeds via folding of myosin II filament assemblies in an accordion-like fashion.Keywords
This publication has 43 references indexed in Scilit:
- Structure and function of the cytoskeleton of a Dictyostelium myosin-defective mutant.The Journal of cell biology, 1990
- Capping of surface receptors and concomitant cortical tension are generated by conventional myosinNature, 1989
- Formation and movement of myosin-containing structures in living fibroblasts.The Journal of cell biology, 1989
- Direct visualization of bipolar myosin filaments in stress fibers of cultured fibroblastsCell Motility, 1989
- Modulation of cellular morphology and locomotory activity by antibodies against myosin.The Journal of cell biology, 1988
- The dynamic distribution of fluorescent analogues of actin and myosin in protrusions at the leading edge of migrating Swiss 3T3 fibroblasts.The Journal of cell biology, 1988
- Cell motility and chemotaxis in Dictyostelium amebae lacking myosin heavy chainDevelopmental Biology, 1988
- Regulation of actin microfilament integrity in living nonmuscle cells by the cAMP-dependent protein kinase and the myosin light chain kinase.The Journal of cell biology, 1988
- Disruption of the Dictyostelium Myosin Heavy Chain Gene by Homologous RecombinationScience, 1987
- Antisense RNA Inactivation of Myosin Heavy Chain Gene Expression in Dictyostelium discoideumScience, 1987