Cell migration without a lamellipodium: translation of actin dynamics into cell movement mediated by tropomyosin.
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.
Gupton
Stephanie L
SL
Department of Cell Biology, The Scripps Research Institute, La Jolla, CA 92037, USA.
Anderson
Karen L
KL
Kole
Thomas P
TP
Fischer
Robert S
RS
Ponti
Aaron
A
Hitchcock-DeGregori
Sarah E
SE
Danuser
Gaudenz
G
Fowler
Velia M
VM
Wirtz
Denis
D
Hanein
Dorit
D
Waterman-Storer
Clare M
CM
D051339:Actin Depolymerizing Factors; D051378:Actin-Related Protein 3; D000199:Actins / Q000378:metabolism*; D000818:Animals; D002448:Cell Adhesion / Q000502:physiology; D002465:Cell Movement / Q000502:physiology*; D002478:Cells, Cultured; D003598:Cytoskeletal Proteins / Q000378:metabolism; D004847:Epithelial Cells / Q000378:metabolism / Q000502:physiology*; D006801:Humans; D008840:Microfilament Proteins / Q000378:metabolism; D008855:Microscopy, Electron, Scanning; D018482:Muscle, Skeletal / Q000378:metabolism; D009218:Myosins / Q000378:metabolism; D011554:Pseudopodia / Q000378:metabolism / Q000502:physiology*; D014335:Tropomyosin / Q000378:metabolism*
C495928:ACTR3 protein, human; D051339:Actin Depolymerizing Factors; D051378:Actin-Related Protein 3; D000199:Actins; D003598:Cytoskeletal Proteins; D008840:Microfilament Proteins; D014335:Tropomyosin; D009218:Myosins
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