title: Immediate-early signaling induced by E-cadherin engagement and adhesion.
abstract: Epithelial cell-cell interactions require localized adhesive interactions between E-cadherin on opposing membranes and the activation of downstream signaling pathways that affect membrane and actin dynamics. However, it is not known whether E-cadherin engagement and activation of these signaling pathways are locally coordinated or whether signaling is sustained or locally down-regulated like other receptor-mediated pathways. To obtain high spatiotemporal resolution of immediate-early signaling events upon E-cadherin engagement, we used laser tweezers to place beads coated with functional E-cadherin extracellular domain on cells. We show that cellular E-cadherin accumulated rapidly around beads, reaching a sustained plateau level in 1-3 min. Phosphoinositides and Rac1 co-accumulated with E-cadherin, reached peak levels with E-cadherin, but then rapidly dispersed. Both E-cadherin and Rac1 accumulated independently of Rac1 GTP binding/hydrolysis, but these activities were required for Rac1 dispersal. E-cadherin accumulation was dependent on membrane dynamics and actin polymerization, but actin did not stably co-accumulate with E-cadherin; mathematical modeling showed that diffusion-mediated trapping could account for the initial E-cadherin accumulation. We propose that initial E-cadherin accumulation requires active membrane dynamics and involves diffusion-mediated trapping at contact sites; to propagate further contacts, phosphatidylinositol 3-kinase and Rac1 are transiently activated by E-cadherin engagement and initiate a new round of membrane dynamics, but they are subsequently suppressed at that site to allow maintenance of weak E-cadherin mediated adhesion.
authors: Department of Molecular and Cellular Physiology, Stanford University, Stanford, California 94305-5430, USA.
authors: Tomas D
authors: TD
authors: Perez
authors: Masako
authors: M
authors: Tamada
authors: Michael P
authors: MP
authors: Sheetz
authors: W James
authors: WJ
authors: Nelson
mesh_terms: D000199:Actins / Q000378:metabolism; D000818:Animals; D015820:Cadherins / Q000378:metabolism*; D002448:Cell Adhesion / Q000502:physiology; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism*; D004285:Dogs; D004847:Epithelial Cells / Q000166:cytology / Q000378:metabolism*; D008863:Microspheres; D052898:Optical Tweezers; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism*; D010716:Phosphatidylinositols / Q000378:metabolism; D021381:Protein Transport / Q000502:physiology; D015398:Signal Transduction / Q000502:physiology*; D020830:rac1 GTP-Binding Protein / Q000378:metabolism*
chemical_list: D000199:Actins; D015820:Cadherins; D010716:Phosphatidylinositols; D019869:Phosphatidylinositol 3-Kinases; D020830:rac1 GTP-Binding Protein