Journal Article

αE-catenin is an autoinhibited molecule that coactivates vinculin

Pokutta, Sabine, Choi, Hee-Jung, Bankston, Laurie A, Weis, William I, Cadwell, Gregory W, Bobkov, Andrey A, Liddington, Robert C

2012

Overview

αE-catenin, an essential component of the adherens junction, interacts with the classical cadherin–β-catenin complex and with F-actin, but its precise role is unknown. αE-catenin also binds to the F-actin-binding protein vinculin, which also appears to be important in junction assembly. Vinculin and αE-catenin are homologs that contain a series of helical bundle domains, D1–D5. We mapped the vinculin-binding site to a sequence in D3a comprising the central two helices of a four-helix bundle. The crystal structure of this peptide motif bound to vinculin D1 shows that the two helices adopt a parallel, colinear arrangement suggesting that the αE-catenin D3a bundle must unfold in order to bind vinculin. We show that αE-catenin D3 binds strongly to vinculin, whereas larger fragments and full-length αE-catenin bind approximately 1,000-fold more weakly. Thus, intramolecular interactions within αE-catenin inhibit binding to vinculin. The actin-binding activity of vinculin is inhibited by an intramolecular interaction between the head (D1–D4) and the actin-binding D5 tail. In the absence of F-actin, there is no detectable binding of αE-catenin D3 to full-length vinculin; however, αE-catenin D3 promotes binding of vinculin to F-actin whereas full-length αE-catenin does not. These findings support the combinatorial or \"coincidence\" model of activation in which binding of high-affinity proteins to the vinculin head and tail is required to shift the conformational equilibrium of vinculin from a closed, autoinhibited state to an open, stable F-actin-binding state. The data also imply that αE-catenin must be activated in order to bind to vinculin.

• Publisher: National Academy of Sciences,National Acad Sciences
• Subject: actin / Actins / Actins - chemistry / Actins - genetics / Actins - metabolism / alpha Catenin / alpha Catenin - chemistry / alpha Catenin - genetics / alpha Catenin - metabolism / Amino Acid Sequence / Animals / beta Catenin / beta Catenin - chemistry / beta Catenin - genetics / beta Catenin - metabolism / binding proteins / Binding Sites / Binding Sites - genetics / Biological Sciences / Cadherins / Cadherins - chemistry / Cadherins - genetics / Cadherins - metabolism / Calorimetry / Calorimetry - methods / Catenins / Cell adhesion / chemistry / Chickens / Circular Dichroism / Crystal structure / Crystallography, X-Ray / Dimers / genetics / Ligands / metabolism / methods / Mice / Models, Molecular / Molecular Sequence Data / Monomers / Mutation / Protein Binding / Protein Structure, Secondary / Protein Structure, Tertiary / Proteins / Recombinant Fusion Proteins / Recombinant Fusion Proteins - chemistry / Recombinant Fusion Proteins - metabolism / Sequence Homology, Amino Acid / Vinculin / Vinculin - chemistry / Vinculin - genetics / Vinculin - metabolism