title: Coordination of contractility, adhesion and flow in migrating Physarum amoebae.
abstract: This work examines the relationship between spatio-temporal coordination of intracellular flow and traction stress and the speed of amoeboid locomotion of microplasmodia of Physarum polycephalum. We simultaneously perform particle image velocimetry and traction stress microscopy to measure the velocity of cytoplasmic flow and the stresses applied to the substrate by migrating Physarum microamoebae. In parallel, we develop a mathematical model of a motile cell which includes forces from the viscous cytosol, a poro-elastic, contractile cytoskeleton and adhesive interactions with the substrate. Our experiments show that flow and traction stress exhibit back-to-front-directed waves with a distinct phase difference. The model demonstrates that the direction and speed of locomotion are determined by this coordination between contraction, flow and adhesion. Using the model, we identify forms of coordination that generate model predictions consistent with experiments. We demonstrate that this coordination produces near optimal migration speed and is insensitive to heterogeneity in substrate adhesiveness. While it is generally thought that amoeboid motility is robust to changes in extracellular geometry and the nature of extracellular adhesion, our results demonstrate that coordination of adhesive forces is essential to producing robust migration.
authors.affiliation: Department of Mathematics, University of Utah, Salt Lake City, UT, USA olewis@math.utah.edu.
authors.forename: Owen L
authors.initials: OL
authors.lastname: Lewis
authors.affiliation: Mechanical and Aerospace Engineering Department, University of California San Diego, La Jolla, CA, USA.
authors.forename: Shun
authors.initials: S
authors.lastname: Zhang
authors.affiliation: Department of Mathematics, University of California Davis, Davis, CA, USA.
authors.forename: Robert D
authors.initials: RD
authors.lastname: Guy
authors.affiliation: Mechanical and Aerospace Engineering Department, University of California San Diego, La Jolla, CA, USA.
authors.forename: Juan C
authors.initials: JC
authors.lastname: del Álamo
mesh_terms: D002448:Cell Adhesion / Q000502:physiology*; D002465:Cell Movement / Q000502:physiology*; D003198:Computer Simulation; D003285:Contractile Proteins / Q000502:physiology*; D040542:Mechanotransduction, Cellular / Q000502:physiology*; D044085:Microfluidics / Q000379:methods*; D008954:Models, Biological; D033081:Shear Strength / Q000502:physiology
chemical_list: D003285:Contractile Proteins
keywords: amoeboid motility; cell locomotion; cytoplasmic streaming; particle image velocimetry; traction force microscopy