Cofilin activity downstream of Pak1 regulates cell protrusion efficiency by organizing lamellipodium and lamella actin networks.
Protrusion of the leading edge of migrating epithelial cells requires precise regulation of two actin filament (F-actin) networks, the lamellipodium and the lamella. Cofilin is a downstream target of Rho GTPase signaling that promotes F-actin cycling through its F-actin-nucleating, -severing, and -depolymerizing activity. However, its function in modulating lamellipodium and lamella dynamics, and the implications of these dynamics for protrusion efficiency, has been unclear. Using quantitative fluorescent speckle microscopy, immunofluorescence, and electron microscopy, we establish that the Rac1/Pak1/LIMK1 signaling pathway controls cofilin activity within the lamellipodium. Enhancement of cofilin activity accelerates F-actin turnover and retrograde flow, resulting in widening of the lamellipodium. This is accompanied by increased spatial overlap of the lamellipodium and lamella networks and reduced cell-edge protrusion efficiency. We propose that cofilin functions as a regulator of cell protrusion by modulating the spatial interaction of the lamellipodium and lamella in response to upstream signals.
Delorme
Violaine
V
Department of Immunology, The Scripps Research Institute, La Jolla, CA 92037, USA.
Machacek
Matthias
M
Department of Cell Biology, The Scripps Research Institute, La Jolla, CA 92037, USA.
DerMardirossian
Céline
C
Department of Immunology, The Scripps Research Institute, La Jolla, CA 92037, USA.
Anderson
Karen L
KL
Infectious Diseases Program, The Burnham Institute for Medical Research, La Jolla, CA 92037, USA.
Wittmann
Torsten
T
Department of Cell Biology, The Scripps Research Institute, La Jolla, CA 92037, USA.
Hanein
Dorit
D
Infectious Diseases Program, The Burnham Institute for Medical Research, La Jolla, CA 92037, USA.
Waterman-Storer
Clare
C
Department of Cell Biology, The Scripps Research Institute, La Jolla, CA 92037, USA.
Danuser
Gaudenz
G
Department of Cell Biology, The Scripps Research Institute, La Jolla, CA 92037, USA. Electronic address: gdanuser@scripps.edu.
Bokoch
Gary M
GM
Department of Immunology, The Scripps Research Institute, La Jolla, CA 92037, USA; Department of Cell Biology, The Scripps Research Institute, La Jolla, CA 92037, USA. Electronic address: bokoch@scripps.edu.
D051339:Actin Depolymerizing Factors / Q000502:physiology*; D000199:Actins / Q000502:physiology*; D002460:Cell Line; D002465:Cell Movement; D004847:Epithelial Cells / Q000502:physiology*; D005455:Fluorescent Antibody Technique; D006801:Humans; D054461:Lim Kinases / Q000378:metabolism; D008840:Microfilament Proteins / Q000502:physiology*; D011554:Pseudopodia / Q000502:physiology*; D015398:Signal Transduction; D054462:p21-Activated Kinases / Q000502:physiology*; D020830:rac1 GTP-Binding Protein / Q000378:metabolism
D051339:Actin Depolymerizing Factors; D000199:Actins; D008840:Microfilament Proteins; C515892:LIMK1 protein, human; D054461:Lim Kinases; C515903:PAK1 protein, human; D054462:p21-Activated Kinases; D020830:rac1 GTP-Binding Protein