How cytoskeletal crosstalk makes cells move: Bridging cell-free and cell studies

Abstract

Cell migration is a fundamental process for life and is highly dependent on the dynamical and mechanical properties of the cytoskeleton. Intensive physical and biochemical crosstalk among actin, microtubules, and intermediate filaments ensures their coordination to facilitate and enable migration. In this review, we discuss the different mechanical aspects that govern cell migration and provide, for each mechanical aspect, a novel perspective by juxtaposing two complementary approaches to the biophysical study of cytoskeletal crosstalk: live-cell studies (often referred to as top-down studies) and cell-free studies (often referred to as bottom-up studies). We summarize the main findings from both experimental approaches, and we provide our perspective on bridging the two perspectives to address the open questions of how cytoskeletal crosstalk governs cell migration and makes cells move.

FIG. 1.

(a) Schematic of the three major cytoskeletal filament types and their distinctive physical properties. (b) Fluorescent confocal microscopy image of human melanoma (MV3) cells stained for α-tubulin (green), F-actin (magenta), and vimentin (cyan). The cell nuclei are shown in blue. (c) An electron microscopy image of an in vitro reconstituted three-component cytoskeletal network showing F-actin (magenta arrows), microtubules (green arrows) and vimentin (cyan arrows). Filaments were pre-polymerized separately at 1 μM. Actin and microtubules were polymerized in MRB0 buffer (80 mM PIPES pH 6.8, 1 mM EGTA and 4 mM MgCl₂) with 50 mM KCl, 1 mM DTT and 0.5 mM ATP, while vimentin was polymerized in V-buffer (40 mM PIPES pH 7, 1 mM EGTA and 4 mM MgCl₂, 100 mM KCl, 1 mM DTT). The filaments were combined in MRB80 buffer (with 50 mM KCl, 1 mM DTT, and 0.5 mM ATP). Scale bar 100 nm.

FIG. 2.

Cytoskeletal crosstalk contributes to every aspect of cell migration including: (1) cell deformability that governs the ability of cells to migrate through confining environments. Red arrows show deformation caused by the cell migrating through the extracellular matrix. (2) Contractility as a major driver of cell motility. Red arrows show actin-myosin contraction. (3) Front-rear polarity for directional migration. (4) Cell–cell adhesions to coordinate collective migration. The leader cell is shown in the dark blue. (5) Plasticity, the ability of cells to interconvert between different migration strategies in response to their environment, for example between mesenchymal and nuclear piston modes. Here, the nucleus is pulled forward (dark blue arrow). Black arrows show the direction of migration. Actin (magenta), vimentin (cyan), nucleus (teal), intercellular adhesions (green linkers), plectin (pink linkers), and extracellular matrix fibers (purple).

FIG. 3.

Schematic of the two general cytoskeletal crosstalk mechanisms and their effect on cytoskeletal biophysics. Entanglements and crosslinks regulate stress stiffening, compressive reinforcement, force distribution and slower stress relaxation. Bundling regulates coupled polymerization and nucleation, guidance and co-alignment, and tip-mediated transport of filaments. Actin (magenta), microtubules (green), intermediate filaments (cyan), and crosslinkers (pink).

FIG. 4.

The proposed route to bridge the gap between live cell (top down) and cell free (bottom up) approaches in the research of cytoskeletal crosstalk in cell migration. Micropatterning and optogenetic tools can be used to manipulate cytoskeletal interactions and help to bridge the gap between the two research approaches. Actin (magenta), microtubules (green), intermediate filaments (cyan), and crosslinkers (pink).