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First published online August 3, 2005
doi: 10.1242/10.1242/jcs.02461

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Calcium mobilization stimulates Dictyostelium discoideum shear-flow-induced cell motility

¹ Structures et Propriétés des Architectures Moléculaires (UMR 5919 CNRS), Département de Recherche Fondamentale sur la Matière Condensée, CEA-Grenoble, DRFMC/SI3M, 17 rue des Martyrs, 38054 Grenoble Cedex 09, France
² Image Analysis & Computer Graphics, Informatics and Mathematical Modelling, Technical University of Denmark, Richard Petersens Plads, Building 321, DK-2800 Kgs. Lyngby, Denmark
³ Laboratoire de Biochimie et Biophysique des Systèmes Intégrés (UMR 5092 CNRS), Département Réponse et Dynamique Cellulaires, CEA-Grenoble, DRDC/BBSI, 17 rue des Martyrs, 38054 Grenoble Cedex 09, France
⁴ Johns Hopkins University, School of Medicine, 725 N. Wolfe St., 114 WBSB, Baltimore, MD 21205, USA
⁵ Laboratoire des Matériaux et Génie des Procédés, ENS de Physique de Grenoble, Domaine Universitaire, 38402 Saint-Martin d'Hères, France

^* Author for correspondence (e-mail: fbruckert{at}cea.fr)

Accepted 27 April 2005

Application of hydrodynamic mild shear stress to adherent Dictyostelium discoideum vegetative cells triggers active actin cytoskeleton remodeling resulting in net cell movement along the flow. The average cell speed is strongly stimulated by external calcium (Ca²⁺, K_50%=22 µM), but the directionality of the movement is almost unaffected. This calcium concentration is ten times higher than the one promoting cell adhesion to glass surfaces (K_50%=2 µM). Addition of the calcium chelator EGTA or the Ca²⁺-channel blocker gadolinium (Gd³⁺) transiently stops cell movement. Monitoring the evolution of cell-surface contact area with time reveals that calcium stimulates cell speed by increasing the amplitude of both protrusion and retraction events at the cell edge, but not the frequency. As a consequence, with saturating external calcium concentrations, cells are sensitive to very low shear forces (20 pN; =0.1 Pa). Moreover, a null-mutant lacking the unique Gß subunit does not respond to external Ca²⁺ changes (K_50%>1000 µM), although the directionality of the movement is comparable with that of wild-type cells. Furthermore, cells lacking the inositol 1,4,5-trisphosphate receptor (IP₃-receptor) exhibit a markedly reduced Ca²⁺ sensitivity. Thus, calcium release from internal stores and calcium entry through the plasma membrane modulate cell speed in response to shear stress.

Key words: Calcium, Heterotrimeric G proteins, Motility, Hydrodynamic flow, Mechanosensitivity, Dictyostelium discoideum

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