@article {131936, title = {An E-cadherin-actin clutch translates the mechanical force of cortical flow for cell-cell contact to inhibit epithelial cell locomotion.}, journal = {Dev Cell}, year = {2023}, month = {2023 Jul 17}, abstract = {

Adherens junctions (AJs) allow cell contact to inhibit epithelial migration yet\ also permit epithelia to move as coherent sheets. How, then, do cells identify which contacts will inhibit locomotion? Here, we show that in human epithelial cells this arises from the orientation of cortical flows at AJs. When the leader cells from different migrating sheets make head-on contact with one another, they assemble AJs that couple together oppositely directed cortical flows. This applies a tensile signal to the actin-binding domain (ABD) of α-catenin, which provides a clutch to promote lateral adhesion growth and inhibit the lamellipodial activity necessary for migration. In contrast, AJs found between leader cells in the same migrating sheet have cortical flows aligned in the same direction, and no such mechanical inhibition takes place. Therefore, α-catenin mechanosensitivity in the clutch between E-cadherin and cortical F-actin allows cells to interpret the direction of motion via cortical flows and signal for contact to inhibit locomotion.

}, issn = {1878-1551}, doi = {10.1016/j.devcel.2023.06.011}, author = {Noordstra, Ivar and Hermoso, Mario D{\'\i}ez and Schimmel, Lilian and Bonfim-Melo, Alexis and Currin-Ross, Denni and Duong, Cao Nguyen and Kalappurakkal, Joseph Mathew and Morris, Richard G and Vestweber, Dietmar and Mayor, Satyajit and Gordon, Emma and Roca-Cusachs, Pere and Yap, Alpha S} } @article {77439, title = {Toward a new picture of the living plasma membrane.}, journal = {Protein Sci}, volume = {29}, year = {2020}, month = {2020 Jun}, pages = {1355-1365}, abstract = {

Our understanding of the plasma membrane structure has undergone a major change since the proposal of the fluid mosaic model of Singer and Nicholson in the 1970s. In this model, the membrane, composed of over thousand lipid and protein species, is organized as a well-equilibrated two-dimensional fluid. Here, the distribution of lipids is largely expected to reflect a multicomponent system, and proteins are expected to be surrounded by an annulus of specialized lipid species. With the recognition that a multicomponent lipid membrane is capable of phase segregation, the membrane is expected to appear as patchwork quilt pattern of membrane domains. However, the constituents of a living membrane are far from being well equilibrated. The living cell membrane actively maintains a trans-bilayer asymmetry of composition, and its constituents are subject to a number of dynamic processes due to synthesis, lipid transfer as well as membrane traffic and turnover. Moreover, membrane constituents engage with the dynamic cytoskeleton of a living cell, and are both passively as well as actively manipulated by this engagement. The extracellular matrix and associated elements also interact with membrane proteins contributing to another layer of interaction. At the nano- and mesoscale, the organization of lipids and proteins emerge from these encounters, as well as from protein-protein, protein-lipid, and lipid-lipid interactions in the membrane. New methods to study the organization of membrane components at these scales have also been developed, and provide an opportunity to synthesize a new picture of the living cell surface as an active membrane composite.

}, issn = {1469-896X}, doi = {10.1002/pro.3874}, author = {Kalappurakkal, Joseph Mathew and Sil, Parijat and Mayor, Satyajit} } @article {59720, title = {Integrin Mechano-chemical Signaling Generates Plasma Membrane Nanodomains that Promote Cell Spreading.}, journal = {Cell}, volume = {177}, year = {2019}, month = {2019 Jun 13}, pages = {1738-1756.e23}, abstract = {

Glycosylphosphatidylinositol-anchored proteins (GPI-APs) are a major class of lipid-anchored plasma membrane proteins. GPI-APs form nanoclusters generated by cortical acto-myosin activity. While our understanding of the physical principles governing this process is emerging, the molecular machinery and functional relevance of GPI-AP nanoclustering are unknown. Here, we first show that a membrane receptor signaling pathway directs nanocluster formation. Arg-Gly-Asp motif-containing ligands bound to the β1-integrin receptor activate src and focal adhesion kinases, resulting in RhoA signaling. This cascade triggers actin-nucleation via specific formins, which, along with myosin activity, drive the nanoclustering of membrane proteins with actin-binding domains. Concurrently, talin-mediated activation of the mechano-transducer vinculin is required for the coupling of the acto-myosin machinery to inner-leaflet lipids, thereby generating GPI-AP nanoclusters. Second, we show that these nanoclusters are functional; disruption of their formation either in GPI-anchor remodeling mutants or in vinculin mutants impairs cell spreading and migration, hallmarks of integrin function.

}, issn = {1097-4172}, doi = {10.1016/j.cell.2019.04.037}, author = {Kalappurakkal, Joseph Mathew and Anilkumar, Anupama Ambika and Patra, Chandrima and van Zanten, Thomas S and Sheetz, Michael P and Mayor, Satyajit} } @article {25251, title = {Actin retrograde flow actively aligns and orients ligand-engaged integrins in focal adhesions.}, journal = {Proc Natl Acad Sci U S A}, volume = {114}, year = {2017}, month = {2017 Oct 03}, pages = {10648-10653}, abstract = {

Integrins are transmembrane receptors that, upon activation, bind extracellular ligands and link them to the actin filament (F-actin) cytoskeleton to mediate cell adhesion and migration. Cytoskeletal forces in migrating cells generated by polymerization- or contractility-driven "retrograde flow" of F-actin from the cell leading edge have been hypothesized to mediate integrin activation for ligand binding. This predicts that these forces should align and orient activated, ligand-bound integrins at the leading edge. Here, polarization-sensitive fluorescence microscopy of GFP-αVβ3 integrins in fibroblasts shows that integrins are coaligned in a specific orientation within focal adhesions (FAs) in a manner dependent on binding immobilized ligand and a talin-mediated linkage to the F-actin cytoskeleton. These findings, together with Rosetta modeling, suggest that integrins in FA are coaligned and may be highly tilted by cytoskeletal forces. Thus, the F-actin cytoskeleton sculpts an anisotropic molecular scaffold in FAs, and this feature may underlie the ability of migrating cells to sense directional extracellular cues.

}, issn = {1091-6490}, doi = {10.1073/pnas.1701136114}, author = {Swaminathan, Vinay and Kalappurakkal, Joseph Mathew and Mehta, Shalin B and Nordenfelt, Pontus and Moore, Travis I and Koga, Nobuyasu and Baker, David A and Oldenbourg, Rudolf and Tani, Tomomi and Mayor, Satyajit and Springer, Timothy A and Waterman, Clare M} } @article {28246, title = {Direction of actin flow dictates integrin LFA-1 orientation during leukocyte migration.}, journal = {Nat Commun}, volume = {8}, year = {2017}, month = {2017 Dec 11}, pages = {2047}, abstract = {

Integrin αβ heterodimer cell surface receptors mediate adhesive interactions that provide traction for cell migration. Here, we test whether the integrin, when engaged to an extracellular ligand and the cytoskeleton, adopts a specific orientation dictated by the direction of actin flow on the surface of migrating cells. We insert GFP into the rigid, ligand-binding head of the integrin, model with Rosetta the orientation of GFP and its transition dipole relative to the integrin head, and measure orientation with fluorescence polarization microscopy. Cytoskeleton and ligand-bound integrins orient in the same direction as retrograde actin flow with their cytoskeleton-binding β-subunits tilted by applied force. The measurements demonstrate that intracellular forces can orient cell surface integrins and support a molecular model of integrin activation by cytoskeletal force. Our results place atomic, {\r A}-scale structures of cell surface receptors in the context of functional and cellular, μm-scale measurements.

}, issn = {2041-1723}, doi = {10.1038/s41467-017-01848-y}, author = {Nordenfelt, Pontus and Moore, Travis I and Mehta, Shalin B and Kalappurakkal, Joseph Mathew and Swaminathan, Vinay and Koga, Nobuyasu and Lambert, Talley J and Baker, David and Waters, Jennifer C and Oldenbourg, Rudolf and Tani, Tomomi and Mayor, Satyajit and Waterman, Clare M and Springer, Timothy A} }