Molecular mechanism for direct actin force-sensing by α-catenin

Mei, Lin; Reyes, Santiago Espinosa de los; Reynolds, Matthew J.; Leicher, Rachel; Liu, Shixin; Alushin, Gregory M.

doi:10.7554/elife.62514

Cited by 74 publications

(97 citation statements)

References 91 publications

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“…Actin-binding proteins have also been shown to modulate filament structural conformations either as part of their regulatory activity or as a means for allosteric cooperative binding to actin 30 – 32 . In addition to effects of protein binding, mechanical perturbations to actin filaments such as torques, tension 33 , 34 and bending have been suggested to influence protein interactions with filaments, including the binding activity of the Arp2/3 complex 21 and severing activity of the protein cofilin 20 , 35 , 36 . Together, these observations suggest that different conformations of F-actin, induced either mechanically or biochemically, could impact the affinity of actin-binding proteins for F-actin.…”

Section: Introductionmentioning

confidence: 99%

Biased localization of actin binding proteins by actin filament conformation

et al. 2020

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The assembly of actin filaments into distinct cytoskeletal structures plays a critical role in cell physiology, but how proteins localize differentially to these structures within a shared cytoplasm remains unclear. Here, we show that the actin-binding domains of accessory proteins can be sensitive to filament conformational changes. Using a combination of live cell imaging and in vitro single molecule binding measurements, we show that tandem calponin homology domains (CH1–CH2) can be mutated to preferentially bind actin networks at the front or rear of motile cells. We demonstrate that the binding kinetics of CH1–CH2 domain mutants varies as actin filament conformation is altered by perturbations that include stabilizing drugs and other binding proteins. These findings suggest that conformational changes of actin filaments in cells could help to direct accessory binding proteins to different actin cytoskeletal structures through a biophysical feedback loop.

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Section: Introductionmentioning

confidence: 99%

Biased localization of actin binding proteins by actin filament conformation

et al. 2020

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“…This suggests that this region is flexible and in various conformations. Recently, the cryogenic electron microscopy structure to 2.9 Å resolution was reported of MVt residues 879–1134 bound to F-actin, but the N-terminus residues 879–980 that include the first α-helix (that we originally named H1’ to emphasize its distinction from the equivalent α-helix H1 of the vinculin isoform) of this five-helix bundle were disordered and could not be modeled [ 70 ]. This is consistent with an earlier 8.2 Å reconstruction of MVt (residues 858–1129) that also showed that α-helix H1’ was displaced from the five-helix bundle domain [ 22 ].…”

Section: Resultsmentioning

confidence: 99%

“…Unfolding of the vinculin tail domain upon binding to filamentous actin or acidic phospholipids has been suggested before [ 15 ], resulting in the release of the coiled coil region preceding α-helix H1’ (or α-helix H1 in vinculin). The recent electron microscopy structures of the F-actin binding domains of vinculin, metavinculin, or αE-catenin have their first α-helices released from their five-helix bundles as a consequence of binding to F-actin as documented by the isolated F-actin binding domains bound to the actin filament [ 70 , 73 ]. Our cryogenic electron microscopy structure of human full-length metavinculin provides a first glimpse of the α-helix H1’ being released even within the auto-inhibited state as a part of its conformational flexibility.…”

Section: Discussionmentioning

confidence: 99%

“…However, our observed pre-release of α-helix H1 suggests that this probably occurs prior to binding to F-actin rather than as a consequence of the interaction leading to the bundling difference observed between the isoforms. The rearrangement of the N-terminal α-helix has been proposed to be a general mechanism for F-actin binding to metavinculin, vinculin, and α-catenin family of proteins [ 70 ]. It has also been observed that the C-terminal region of the five-helix bundle of the F-actin binding tail domain is flexible.…”

Section: Discussionmentioning

confidence: 99%

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The Cryogenic Electron Microscopy Structure of the Cell Adhesion Regulator Metavinculin Reveals an Isoform-Specific Kinked Helix in Its Cytoskeleton Binding Domain

Rangarajan

Izard

2021

IJMS

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Vinculin and its heart-specific splice variant metavinculin are key regulators of cell adhesion processes. These membrane-bound cytoskeletal proteins regulate the cell shape by binding to several other proteins at cell–cell and cell–matrix junctions. Vinculin and metavinculin link integrin adhesion molecules to the filamentous actin network. Loss of both proteins prevents cell adhesion and cell spreading and reduces the formation of stress fibers, focal adhesions, or lamellipodia extensions. The binding of talin at cell–matrix junctions or of α-catenin at cell–cell junctions activates vinculin and metavinculin by releasing their autoinhibitory head–tail interaction. Once activated, vinculin and metavinculin bind F-actin via their five-helix bundle tail domains. Unlike vinculin, metavinculin has a 68-amino-acid insertion before the second α-helix of this five-helix F-actin–binding domain. Here, we present the full-length cryogenic electron microscopy structure of metavinculin that captures the dynamics of its individual domains and unveiled a hallmark structural feature, namely a kinked isoform-specific α-helix in its F-actin-binding domain. Our identified conformational landscape of metavinculin suggests a structural priming mechanism that is consistent with the cell adhesion functions of metavinculin in response to mechanical and cellular cues. Our findings expand our understanding of metavinculin function in the heart with implications for the etiologies of cardiomyopathies.

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“…The central 3 four-helix bundles form the middle (M)-region that functions as a mechanosensor ( 20 , 21 , 22 , 23 , 24 , 25 ). The C-terminal five-helix bundle forms the F-actin-binding domain (ABD) ( 11 , 13 , 26 , 27 ). F-actin binding is allosterically regulated: αE-catenin can bind F-actin readily as a homodimer, but when in complex with β-catenin, mechanical force is required for strong F-actin binding ( 9 , 10 , 11 , 26 ).…”

mentioning

confidence: 99%

Distinct intramolecular interactions regulate autoinhibition of vinculin binding in αT-catenin and αE-catenin

Heier

Pokutta

Dale

et al. 2021

Journal of Biological Chemistry

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Edited by Enrique De La Cruz α-Catenin binds directly to β-catenin and connects the cadherin-catenin complex to the actin cytoskeleton. Tension regulates α-catenin conformation. Actomyosin-generated force stretches the middle (M)-region to relieve autoinhibition and reveal a binding site for the actin-binding protein vinculin. It is not known whether the intramolecular interactions that regulate epithelial (αE)-catenin binding are conserved across the αcatenin family. Here, we describe the biochemical properties of testes (αT)-catenin, an α-catenin isoform critical for cardiac function and how intramolecular interactions regulate vinculin-binding autoinhibition. Isothermal titration calorimetry showed that αT-catenin binds the β-catenin-N-cadherin complex with a similar low nanomolar affinity to that of αEcatenin. Limited proteolysis revealed that the αT-catenin Mregion adopts a more open conformation than αE-catenin. The αT-catenin M-region binds the vinculin N-terminus with low nanomolar affinity, indicating that the isolated αT-catenin Mregion is not autoinhibited and thereby distinct from αE-catenin. However, the αT-catenin head (N-and M-regions) binds vinculin 1000-fold more weakly (low micromolar affinity), indicating that the N-terminus regulates the M-region binding to vinculin. In cells, αT-catenin recruitment of vinculin to cellcell contacts requires the actin-binding domain and actomyosin-generated tension, indicating that force regulates vinculin binding. Together, our results show that the αT-catenin N-terminus is required to maintain M-region autoinhibition and modulate vinculin binding. We postulate that the unique molecular properties of αT-catenin allow it to function as a scaffold for building specific adhesion complexes.

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Molecular mechanism for direct actin force-sensing by α-catenin

Cited by 74 publications

References 91 publications

Biased localization of actin binding proteins by actin filament conformation

Biased localization of actin binding proteins by actin filament conformation

The Cryogenic Electron Microscopy Structure of the Cell Adhesion Regulator Metavinculin Reveals an Isoform-Specific Kinked Helix in Its Cytoskeleton Binding Domain

Distinct intramolecular interactions regulate autoinhibition of vinculin binding in αT-catenin and αE-catenin

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