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J Cell Biol. 2005 Feb 14;168(4):619-31.

Cell migration without a lamellipodium: translation of actin dynamics into cell movement mediated by tropomyosin.

Author information

1
Department of Cell Biology, The Scripps Research Institute, La Jolla, CA 92037, USA.
2
Johns Hopkins U, Baltimore, MD

Abstract

The actin cytoskeleton is locally regulated for functional specializations for cell motility. Using quantitative fluorescent speckle microscopy (qFSM) of migrating epithelial cells, we previously defined two distinct F-actin networks based on their F-actin-binding proteins and distinct patterns of F-actin turnover and movement. The lamellipodium consists of a treadmilling F-actin array with rapid polymerization-dependent retrograde flow and contains high concentrations of Arp2/3 and ADF/cofilin, whereas the lamella exhibits spatially random punctae of F-actin assembly and disassembly with slow myosin-mediated retrograde flow and contains myosin II and tropomyosin (TM). In this paper, we microinjected skeletal muscle alphaTM into epithelial cells, and using qFSM, electron microscopy, and immunolocalization show that this inhibits functional lamellipodium formation. Cells with inhibited lamellipodia exhibit persistent leading edge protrusion and rapid cell migration. Inhibition of endogenous long TM isoforms alters protrusion persistence. Thus, cells can migrate with inhibited lamellipodia, and we suggest that TM is a major regulator of F-actin functional specialization in migrating cells.

PMID:
15716379
PMCID:
PMC2171771
DOI:
10.1083/jcb.200406063
[Indexed for MEDLINE]
Free PMC Article

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