title: The actin-based nanomachine at the leading edge of migrating cells.
abstract: Two fundamental parameters of the highly dynamic, ultrathin lamellipodia of migrating fibroblasts have been determined-its thickness in living cells (176 +/- 14 nm), by standing-wave fluorescence microscopy, and its F-actin density (1580 +/- 613 microm of F-actin/microm(3)), via image-based photometry. In combination with data from previous studies, we have computed the density of growing actin filament ends at the lamellipodium margin (241 +/- 100/microm) and the maximum force (1.86 +/- 0.83 nN/microm) and pressure (10.5 +/- 4.8 kPa) obtainable via actin assembly. We have used cell deformability measurements (. J. Cell Sci. 44:187-200;. Proc. Natl. Acad. Sci. USA. 79:5327-5331) and an estimate of the force required to stall the polymerization of a single filament (. Proc. Natl. Acad. Sci. USA. 78:5613-5617;. Biophys. J. 65:316-324) to argue that actin assembly alone could drive lamellipodial extension directly.
authors.affiliation: Center for Light Microscope Imaging and Biotechnology, and Department of Biological Sciences, Carnegie Mellon University, Pittsburgh, Pennsylvania 15213 USA.
authors.forename: V C
authors.initials: VC
authors.lastname: Abraham
authors.forename: V
authors.initials: V
authors.lastname: Krishnamurthi
authors.forename: D L
authors.initials: DL
authors.lastname: Taylor
authors.forename: F
authors.initials: F
authors.lastname: Lanni
mesh_terms: D016475:3T3 Cells; D000199:Actins / Q000502:physiology*; D000818:Animals; D002138:Calibration; D002465:Cell Movement; D048429:Cell Size; D003593:Cytoplasm / Q000502:physiology / Q000648:ultrastructure; D051379:Mice; D008854:Microscopy, Electron; D008856:Microscopy, Fluorescence / Q000379:methods; D008954:Models, Biological
chemical_list: D000199:Actins