Previous Article | Next Article ![]()
Infect Immun, August 1998, p. 3775-3782, Vol. 66, No. 8
Division of Infectious Diseases,
Received 27 February 1998/Returned for modification 26 March
1998/Accepted 4 May 1998
The actin-based motility of Listeria monocytogenes
requires the addition of actin monomers to the barbed or plus ends of
actin filaments. Immunofluorescence micrographs have demonstrated that gelsolin, a protein that both caps barbed ends and severs actin filaments, is concentrated directly behind motile bacteria at the
junction between the actin filament rocket tail and the bacterium. In
contrast, CapG, a protein that strictly caps actin filaments, fails to
localize near intracellular Listeria. To explore the effect
of increasing concentrations of gelsolin on bacterial motility, NIH 3T3
fibroblasts stably transfected with gelsolin cDNA were infected with
Listeria. The C5 cell line containing 2.25 times control
levels of gelsolin supported significantly higher velocities of
bacterial movement than did control fibroblasts (mean ± standard error of the mean, 0.09 ± 0.003 µm/s [n = 176] versus 0.05 ± 0.003 µm/s [n = 65]).
The rate of disassembly of the Listeria-induced actin
filament rocket tail was found to be independent of gelsolin content.
Therefore, if increases in gelsolin content result in increases in
Listeria-induced rocket tail assembly rates, a positive correlation between gelsolin content and tail length would be expected.
BODIPY-phalloidin staining of four different stably transfected NIH 3T3
fibroblast cell lines confirmed this expectation (r = 0.92). Rocket tails were significantly longer in cells with a high
gelsolin content. Microinjection of gelsolin 1/2 (consisting of the
amino-terminal half of native gelsolin) also increased bacterial
velocity by more than 2.2 times. Microinjection of CapG had no effect
on bacterial movement. Cultured skin fibroblasts derived from
gelsolin-null mice were capable of supporting intracellular Listeria motility at velocities comparable to those
supported by wild-type skin fibroblasts. These experiments demonstrated that the surface of Listeria contains a polymerization zone
that can block the barbed-end-capping activity of both gelsolin and CapG. The ability of Listeria to uncap actin filaments
combined with the severing activity of gelsolin can accelerate
actin-based motility. However, gelsolin is not absolutely required for
the actin-based intracellular movement of Listeria because
its function can be replaced by other actin regulatory proteins in
gelsolin-null cells, demonstrating the functional redundancy of the
actin system.
0019-9567/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Gelsolin, a Protein That Caps the Barbed Ends and
Severs Actin Filaments, Enhances the Actin-Based Motility of
Listeria monocytogenes in Host Cells
*
Corresponding author. Mailing address: Division of
Infectious Diseases, Box 100277, University of Florida College of
Medicine, Gainesville, FL 32610. Phone: (352) 392-4058. Fax: (352)
392-6481. E-mail: southfs{at}medmac.ufl.edu.
Infect Immun, August 1998, p. 3775-3782, Vol. 66, No. 8
0019-9567/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
This article has been cited by other articles:
Copyright © 2009 by the American Society for Microbiology. For an alternate route to Journals.ASM.org, visit: http://intl-journals.asm.org | More Info»