Amy is a PhD Candidate in Chemical Engineering. She works with Prof. William Weis and Prof. Alexander Dunn to study mechanosensitive proteins, using techniques in single molecule force spectroscopy and physics-based simulation.
Education & Certifications
Ph.D., Stanford University, Chemical Engineering (In Progress)
B.S., Massachusetts Institute of Technology, Chemical Engineering
Multi-level force-dependent allosteric enhancement of alphaE-catenin binding to F-actin by vinculin.
Journal of molecular biology
Classical cadherins are transmembrane proteins whose extracellular domains link neighboring cells, and whose intracellular domains connect to the actin cytoskeleton via beta-catenin and alpha-catenin. The cadherin-catenin complex transmits forces that drive tissue morphogenesis and wound healing. In addition, tension-dependent changes in alphaE-catenin conformation enables it to recruit the actin-binding protein vinculin to cell-cell junctions, which contributes to junctional strengthening. How and whether multiple cadherin-complexes cooperate to reinforce cell-cell junctions in response to load remains poorly understood. Here, we used single-molecule optical trap measurements to examine how multiple cadherin-catenin complexes interact with F-actin under load, and how this interaction is influenced by the presence of vinculin. We show that force oriented toward the (-) end of the actin filament results in mean lifetimes 3-fold longer than when force was applied towards the barbed (+) end. We also measured force-dependent actin binding by a quaternary complex comprising the cadherin-catenin complex and the vinculin head region, which cannot itself bind actin. Binding lifetimes of this quaternary complex increased as additional complexes bound F-actin, but only when load was oriented toward the (-) end. In contrast, the cadherin-catenin complex alone did not show this form of cooperativity. These findings reveal multi-level, force-dependent regulation that enhances the strength of the association of multiple cadherin/catenin complexes with F-actin, conferring positive feedback that may strengthen the junction and polarize F-actin to facilitate the emergence of higher-order cytoskeletal organization.
View details for DOI 10.1016/j.jmb.2023.167969
View details for PubMedID 36682678
Mechanism of the cadherin-catenin F-actin catch bond interaction.
Mechanotransduction at cell-cell adhesions is crucial for the structural integrity, organization, and morphogenesis of epithelia. At cell-cell junctions, ternary E-cadherin/beta-catenin/alphaE-catenin complexes sense and transmit mechanical load by binding to F-actin. The interaction with F-actin, described as a two-state catch bond, is weak in solution but is strengthened by applied force due to force-dependent transitions between weak and strong actin-binding states. Here, we provide direct evidence from optical trapping experiments that the catch bond property principally resides in the alphaE-catenin actin-binding domain (ABD). Consistent with our previously proposed model, deletion of the first helix of the five-helix ABD bundle enables stable interactions with F-actin under minimal load that are well-described by a single-state slip bond, even when alphaE-catenin is complexed with beta-catenin and E-cadherin. Our data argue for a conserved catch bond mechanism for adhesion proteins with structurally similar ABDs. We also demonstrate that a stably bound ABD strengthens load-dependent binding interactions between a neighboring complex and F-actin, but the presence of the other alphaE-catenin domains weakens this effect. These results provide mechanistic insight to the cooperative binding of the cadherin-catenin complex to F-actin, which regulate dynamic cytoskeletal linkages in epithelial tissues.
View details for DOI 10.7554/eLife.80130
View details for PubMedID 35913118
Structure and mechanism of the cation-chloride cotransporter NKCC1.
Cation-chloride cotransporters (CCCs) mediate the electroneutral transport of chloride, potassium and/or sodium across the membrane. They have critical roles in regulating cell volume, controlling ion absorption and secretion across epithelia, and maintaining intracellular chloride homeostasis. These transporters are primary targets for some of the most commonly prescribed drugs. Here we determined the cryo-electron microscopy structure of the Na-K-Cl cotransporter NKCC1, an extensively studied member of the CCC family,from Danio rerio. The structure defines the architecture of this protein family and reveals how cytosolic and transmembrane domains are strategically positioned for communication. Structural analyses, functional characterizations and computational studies reveal the ion-translocation pathway, ion-binding sites and key residues for transport activity. These results provide insights into ion selectivity, coupling and translocation, and establish a framework for understanding the physiological functions of CCCs and interpreting disease-related mutations.
View details for DOI 10.1038/s41586-019-1438-2
View details for PubMedID 31367042