Macrophages lift off surface-bound bacteria using a filopodium-lamellipodium hook-and-shovel mechanism

Möller, Jens; Lühmann, Tessa; Chabria, Mamta; Hall, Heike; Vogel, Viola

doi:10.1038/srep02884

Cited by 69 publications

(70 citation statements)

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“…Studies of AMP effects on single cells within model biofilms would represent a larger step towards realistic environments [41, 42]. It should also be possible to adapt the methods outlined here to direct, time-resolved imaging of the fate of bacterial cells as they are attacked by neutrophils or macrophages [43]. …”

Section: Discussionmentioning

confidence: 99%

Lights, Camera, Action! Antimicrobial Peptide Mechanisms Imaged in Space and Time

Choi

Rangarajan

Weisshaar

2016

Trends in Microbiology

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Deeper understanding of the bacteriostatic and bactericidal mechanisms of antimicrobial peptides (AMPs) should help in the design of new antibacterial agents. Over several decades, a variety of biochemical assays have been applied to bulk bacterial cultures. While some of these bulk assays provide time resolution on the order of 1 min, they do not capture faster mechanistic events. Nor can they provide subcellular spatial information or discern cell-to-cell heterogeneity within the bacterial population. Single-cell, time-resolved imaging assays bring a completely new spatiotemporal dimension to AMP mechanistic studies. We review recent work that provides new insights into the timing, sequence, and spatial distribution of AMP-induced effects on bacterial cells.

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Section: Discussionmentioning

confidence: 99%

Lights, Camera, Action! Antimicrobial Peptide Mechanisms Imaged in Space and Time

Choi

Rangarajan

Weisshaar

2016

Trends in Microbiology

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“…Similarly, Kress et al (6) reported that filopodia act as "phagocytic tentacles" and pulled IgG-coated beads in an optical trap with discrete steps, suggesting that a motor protein was involved. More recently, Möller et al (7) reported that macrophages can use filopodia to lift membrane-bound bacteria, thereby enabling a lamellipodial protrusion to engulf the target in a so-called hook-and-shovel mechanism.…”

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confidence: 99%

Multiple roles of filopodial dynamics in particle capture and phagocytosis and phenotypes of Cdc42 and Myo10 deletion

Horsthemke

Bachg

Groll

et al. 2017

Journal of Biological Chemistry

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Edited by Velia M. FowlerMacrophage filopodia, finger-like membrane protrusions, were first implicated in phagocytosis more than 100 years ago, but little is still known about the involvement of these actin-dependent structures in particle clearance. Using spinning disk confocal microscopy to image filopodial dynamics in mouse resident Lifeact-EGFP macrophages, we show that filopodia, or filopodia-like structures, support pathogen clearance by multiple means. Filopodia supported the phagocytic uptake of bacterial (Escherichia coli) particles by (i) capturing along the filopodial shaft and surfing toward the cell body, the most common mode of capture; (ii) capturing via the tip followed by retraction; (iii) combinations of surfing and retraction; or (iv) sweeping actions. In addition, filopodia supported the uptake of zymosan (Saccharomyces cerevisiae) particles by (i) providing fixation, (ii) capturing at the tip and filopodia-guided actin anterograde flow with phagocytic cup formation, and (iii) the rapid growth of new protrusions. To explore the role of filopodia-inducing Cdc42, we generated myeloid-restricted Cdc42 knock-out mice. Cdc42-deficient macrophages exhibited rapid phagocytic cup kinetics, but reduced particle clearance, which could be explained by the marked rounded-up morphology of these cells. Macrophages lacking Myo10, thought to act downstream of Cdc42, had normal morphology, motility, and phagocytic cup formation, but displayed markedly reduced filopodia formation. In conclusion, live-cell imaging revealed multiple mechanisms involving macrophage filopodia in particle capture and engulfment. Cdc42 is not critical for filopodia or phagocytic cup formation, but plays a key role in driving macrophage lamellipodial spreading.Phagocytosis is a specialized form of endocytosis, which requires localized actin polymerization to engulf large particles (Ͼ ϳ0.5 m), and initially involves particle binding to phagocytic receptors, which triggers phagocytic cup formation through the activation of kinases, such as Syk, and Rho GTPases, such as the Cdc42 and Rac subfamilies (1). Although phagocytosis has been investigated in-depth, the involvement of filopodia (finger-like projections containing bundled actin filaments (2)) in actually capturing and clearing particles has not been conclusively demonstrated, except for the historical observations of Metschnikoff (3) and more recent work using brightfield microscopy (4 -7).Young et al. (4) observed using time-lapse differential interference contrast (DIC) 2 imaging that Escherichia coli expressing invasin, a transmembrane protein of Yersinia pseudotuberculosis, could enter Hep-2 (HeLa-derived) cells via filopodia. Using another approach, coating of magnetic microbeads with invasin, Vonna et al. (5) found that the adhesion of beads to filopodial tips induced pulling toward the cell body. Similarly, Kress et al. (6) reported that filopodia act as "phagocytic tentacles" and pulled IgG-coated beads in an optical trap with discrete steps, suggesting that a motor pro...

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“…For instance, invadopodia, podosomes, and filopodia are crucial for invasion and migration of cells (1). Filopodia are thin (100 to 300 nm), tube-like, actin-rich structures that function as "antennae" or "tentacles" that cells use to probe and interact with their microenvironment (2)(3)(4). Such structures have been studied in vitro using model systems where the point-like 3D contacts with the extracellular matrix (ECM) have been mimicked by using optically trapped dielectric particles, functionalized with relevant ligands.…”

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confidence: 99%

Helical buckling of actin inside filopodia generates traction

Leijnse

Oddershede

Bendix³

2014

Proc. Natl. Acad. Sci. U.S.A.

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Cells can interact with their surroundings via filopodia, which are membrane protrusions that extend beyond the cell body. Filopodia are essential during dynamic cellular processes like motility, invasion, and cell-cell communication. Filopodia contain crosslinked actin filaments, attached to the surrounding cell membrane via protein linkers such as integrins. These actin filaments are thought to play a pivotal role in force transduction, bending, and rotation. We investigated whether, and how, actin within filopodia is responsible for filopodia dynamics by conducting simultaneous force spectroscopy and confocal imaging of F-actin in membrane protrusions. The actin shaft was observed to periodically undergo helical coiling and rotational motion, which occurred simultaneously with retrograde movement of actin inside the filopodium. The cells were found to retract beads attached to the filopodial tip, and retraction was found to correlate with rotation and coiling of the actin shaft. These results suggest a previously unidentified mechanism by which a cell can use rotation of the filopodial actin shaft to induce coiling and hence axial shortening of the filopodial actin bundle.membrane-cytoskeleton interactions | membrane nanotubes | filopodial retrograde flow | helical buckling | filopodia rotation T ubular membrane remodeling driven by the actin cytoskeleton plays a major role in both pathogenesis and in a healthy immune response. For instance, invadopodia, podosomes, and filopodia are crucial for invasion and migration of cells (1). Filopodia are thin (100 to 300 nm), tube-like, actin-rich structures that function as "antennae" or "tentacles" that cells use to probe and interact with their microenvironment (2-4). Such structures have been studied in vitro using model systems where the point-like 3D contacts with the extracellular matrix (ECM) have been mimicked by using optically trapped dielectric particles, functionalized with relevant ligands. These model systems allow for mechanical and visual control over filopodial dynamics and have significantly advanced the understanding of cellular mechanosensing (5).Extraction of membrane tubes, using optical trapping, has been used to investigate mechanical properties of the membrane-cytoskeleton system (6-10), or membrane cholesterol content (11), and has revealed important insight into the mechanism that peripheral proteins use to shape membranes (12). Motivated by the pivotal role of F-actin in the mechanical behavior of filopodia and other cellular protrusions, special focus has been on revealing the presence of F-actin within extracted membrane tubes (1, 13-16). However, apart from a single study (9), fluorescent visualization of the F-actin was achieved by staining and fixation of the cells, and literature contains conflicting results regarding the presence or absence of actin in membrane tubes pulled from living cells (8,11,17).Filopodia in living cells have the ability to rotate and bend by a so-far unknown mechanism (13,(18)(19)(20). For instance, filopodia ...

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Macrophages lift off surface-bound bacteria using a filopodium-lamellipodium hook-and-shovel mechanism

Cited by 69 publications

References 50 publications

Lights, Camera, Action! Antimicrobial Peptide Mechanisms Imaged in Space and Time

Lights, Camera, Action! Antimicrobial Peptide Mechanisms Imaged in Space and Time

Multiple roles of filopodial dynamics in particle capture and phagocytosis and phenotypes of Cdc42 and Myo10 deletion

Helical buckling of actin inside filopodia generates traction

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