New physical concepts for cell amoeboid motion

Abstract

Amoeboid motion of cells is an essential mechanism in the function of many biological organisms (e.g., the regiment of scavenger cells in the immune defense system of animals). This process involves rapid chemical polymerization (with numerous protein constituents) to create a musclelike contractile network that advances the cell over the surface. Significant progress has been made in the biology and biochemistry of motile cells, but the physical dynamics of cell spreading and contraction are not well understood. The reason is that general approaches are formulated from complex mass, momentum, and chemical reaction equations for multiphase-multicomponent flow with the nontrivial difficulty of moving boundaries. However, there are strong clues to the dynamics that allow bold steps to be taken in simplifying the physics of motion. First, amoeboid cells often exhibit exceptional kinematics, i.e., steady advance and retraction of local fixed-shape patterns. Second, recent evidence has shown that cell projections "grow" by polymerization along the advancing boundary of the cell. Together, these characteristics represent a local growth process pinned to the interfacial contour of a contractile network. As such, the moving boundary becomes tractable, but subtle features of the motion lead to specific requirements for the chemical nature of the boundary polymerization process. To demonstrate these features, simple examples for limiting conditions of substrate interaction (i.e., "strong" and "weak" adhesion) are compared with data from experimental studies of yeast particle engulfment by blood granulocytes and actin network dynamics in fishscale keratocytes.

Traction forces in locomoting cells

“…As suggested by others [see review by Bereiter-Hahn and Luers, 19941, the tail contraction would also be expected to pull the rear of the cell forward toward the leading lamella and simultaneously drive the cytosolic fluid through the cytoskeletal matrix of the lamella, adding material to the leading edge. Growth of the actin cytoskeleton at the leading edge and simultaneous disassembly throughout the lamella and at the junction between the leading lamella and the nuclear mound complete the processes necessary for operation of a complete causative cycle in this model [Evans, 1993;Condeelis, 19931. The absence of significant tractions under the leading lamella and also near the trailing edge could be explained by invoking the near cancellation of the major contributions acting in these regions (see above).…”

Spatio-temporal analysis of eukaryotic cell motility by improved force cytometry

“…There have been several attempts to model the underlying physical processes in cell motility by using continuum mechanics approaches (23)(24)(25). However, quantitative measurements of the cellular traction forces are still challenging because of the necessary temporal and spatial resolutions.…”

Traction stress analysis and modeling reveal that amoeboid migration in confined spaces is accompanied by expansive forces and requires the structural integrity of the membrane–cortex interactions

“…[10][11][12][13][14][15][16] Recent studies have also shown that cells from multicellular organisms, such as leukocytes, zebrafish primordial germ cells and selected tumor cells, also exhibit amoeboid-like movements. The amoeba migrates via a sterotypic manner by extending its pseudopodia forward and coordinating cytoplasmic streaming.…”