INTEGRIN BINDING AND MECHANICAL TENSION INDUCE MOVEMENT OF MESSENGER-RNA AND RIBOSOMES TO FOCAL ADHESIONS

The extracellular matrix (ECM) activates signalling pathways that cont rol cell behaviour by binding to cell-surface integrin receptors and i nducing the formation of focal adhesion complexes (FACs)(1,2). In addi tion to clustered integrins, FACs contain proteins that mechanically c ouple the integrins to the cytoskeleton(3) and to immobilized signal-t ransducing molecules(1,2). Cell adhesion to the ECM also induces a rap id increase in the translation of preexisting messenger RNAs4,5. Gene expression can be controlled locally by targeting mRNAs to specialized cytoskeletal domains(6). Here we investigate whether cell binding to the ECM promotes formation of a cytoskeletal microcompartment speciali zed for translational control at the site of integrin binding. High-re solution in situ hybridization revealed that mRNA and ribosomes rapidl y and specifically localized to FACs that form when cells bind to ECM- coated microbeads, Relocation of these protein synthesis components to the FAC depended on the ability of integrins to mechanically couple t he ECM to the contractile cytoskeleton and on associated tension-mould ing of the actin lattice. Our results suggest a new type of gene regul ation by integrins and by mechanical stress which may involve translat ion of mRNAs into proteins near the sites of signal reception.