title: Rapid suppression of activated Rac1 by cadherins and nectins during de novo cell-cell adhesion.
abstract: Cell-cell adhesion in simple epithelia involves the engagement of E-cadherin and nectins, and the reorganization of the actin cytoskeleton and membrane dynamics by Rho GTPases, particularly Rac1. However, it remains unclear whether E-cadherin and nectins up-regulate, maintain or suppress Rac1 activity during cell-cell adhesion. Roles for Rho GTPases are complicated by cell spreading and integrin-based adhesions to the extracellular matrix that occur concurrently with cell-cell adhesion, and which also require Rho GTPases. Here, we designed a simple approach to examine Rac1 activity upon cell-cell adhesion by MDCK epithelial cells, without cell spreading or integrin-based adhesion. Upon initiation of cell-cell contact in 3-D cell aggregates, we observed an initial peak of Rac1 activity that rapidly decreased by ∼66% within 5 minutes, and further decreased to a low baseline level after 30 minutes. Inhibition of E-cadherin engagement with DECMA-1 Fab fragments or competitive binding of soluble E-cadherin, or nectin2alpha extracellular domain completely inhibited Rac1 activity. These results indicate that cadherins and nectins cooperate to induce and then rapidly suppress Rac1 activity during initial cell-cell adhesion, which may be important in inhibiting the migratory cell phenotype and allowing the establishment of initially weak cell-cell adhesions.
authors.affiliation: Department of Biology, The James H. Clark Center, The Bio-X Program, Stanford University, Stanford, California, United States of America.
authors.forename: Khameeka N
authors.initials: KN
authors.lastname: Kitt
authors.forename: W James
authors.initials: WJ
authors.lastname: Nelson
mesh_terms: D000818:Animals; D015820:Cadherins / Q000494:pharmacology*; D002448:Cell Adhesion / Q000187:drug effects; D015815:Cell Adhesion Molecules / Q000494:pharmacology*; D002449:Cell Aggregation / Q000187:drug effects; D002460:Cell Line; D004285:Dogs; D004789:Enzyme Activation / Q000187:drug effects; D006801:Humans; D007140:Immunoglobulin Fab Fragments / Q000494:pharmacology; D000075983:Nectins; D011993:Recombinant Fusion Proteins / Q000494:pharmacology; D020830:rac1 GTP-Binding Protein / Q000378:metabolism*
chemical_list: D015820:Cadherins; D015815:Cell Adhesion Molecules; D007140:Immunoglobulin Fab Fragments; D000075983:Nectins; D011993:Recombinant Fusion Proteins; D020830:rac1 GTP-Binding Protein