F-actin flow drives affinity maturation and spatial organization of LFA-1 at the immunological synapse

Comrie, William A.; Babich, Alexander; Burkhardt, Janis K.

doi:10.1083/jcb.201406121

Cited by 152 publications

(175 citation statements)

References 75 publications

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“…There is now strong evidence for affinity changes (reviewed in Luo et al, 2007), but clustering contributes as well. The talin head alone can shift the integrin conformation towards an active state (Box 1), but there is increasing evidence that forces generated by actin polymerisation and myosin contraction are involved in inducing or stabilising the extended-open conformation (Comrie et al, 2015;Nordenfelt et al, 2016). This additional mechanism fits well with the discovery of other IAPs that cooperate with talin to activate integrins, such as kindlins, although the mechanism is still unclear and kindlins also cluster integrins (Moser et al, 2009;Calderwood et al, 2013;Ye et al, 2013;Rognoni et al, 2016;Georgiadou et al, 2017).…”

Section: Talin In Integrin Activationsupporting

confidence: 48%

Talin – the master of integrin adhesions

Klapholz

Brown

2017

Journal of Cell Science

255

222

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Talin has emerged as the key cytoplasmic protein that mediates integrin adhesion to the extracellular matrix. In this Review, we draw on experiments performed in mammalian cells in culture and Drosophila to present evidence that talin is the most important component of integrin adhesion complexes. We describe how the properties of this adaptor protein enable it to orchestrate integrin adhesions. Talin forms the core of integrin adhesion complexes by linking integrins directly to actin, increasing the affinity of integrin for ligands (integrin activation) and recruiting numerous proteins. It regulates the strength of integrin adhesion, senses matrix rigidity, increases focal adhesion size in response to force and serves as a platform for the building of the adhesion structure. Finally, the mechano-sensitive structure of talin provides a paradigm for how proteins transduce mechanical signals to chemical signals.

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Section: Talin In Integrin Activationsupporting

confidence: 48%

Talin – the master of integrin adhesions

Klapholz

Brown

2017

Journal of Cell Science

255

222

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“…on ICAM-1 substrates (Fig. 3c, Movie 1) as confirmed and consistent with kymographic analysis 9,34 ( Supplementary Fig. 3).…”

Section: Resultssupporting

confidence: 67%

“…Kymographic analysis to determine actin flow velocity was performed as described in Comrie et al 34 , with SIM movies of T cells expressing LifeactmNeonGreen being analyzed using the Fiji image processing package to generate a vertical kymograph traversing the cell leading edge and lamellipodium. The flow rate was calculated based on the slope of deflection of F-actin from the vertical direction 34 (Supplementary Fig.…”

Section: Methodsmentioning

confidence: 99%

Direction of actin flow dictates integrin LFA-1 orientation during leukocyte migration

Nordenfelt

Moore

Mehta

et al. 2016

Preprint

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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, Å-scale structures of cell surface receptors in the context of functional and cellular, μm-scale measurements.

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“…By combining TFM, live-cell imaging, and immunofluorescence, we have shown that Rho-ROCK activity is essential to maintain both pMLC levels and traction forces, linking force generation to MLC phosphorylation and filament assembly. Previous studies (16,17) have examined actin flows during T-cell activation and the role of Rho-kinase activity and myosin IIA on modulation of these flows (16,17). These studies showed that both inhibition of myosin IIA and actin disassembly are required to arrest actin retrograde flows that govern several aspects of signaling, such as microcluster dynamics, Ca 2+ signaling, and PLC-γ1 phosphorylation.…”

Section: Discussionmentioning

confidence: 99%

“…These forces, which peak 5-10 min after stimulation, facilitate T-cell activation, in part, by inducing conformational changes in the TCR-CD3 complex (12)(13)(14)(15). Although actin polymerization/depolymerization dynamics are essential for T cells to maintain dynamic traction stresses and to drive calcium influx and integrin affinity maturation (9,16,17), the regulatory pathways that control these cytoskeletal forces are not completely understood. In particular, whether and how the polarized MT cytoskeleton interacts with the actin cytoskeleton and regulates force generation at the T-cell-APC contact remain open questions.…”

mentioning

confidence: 99%

Dynamic microtubules regulate cellular contractility during T-cell activation

Hui

Upadhyaya

2017

Proc. Natl. Acad. Sci. U.S.A.

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T-cell receptor (TCR) triggering and subsequent T-cell activation are essential for the adaptive immune response. Recently, multiple lines of evidence have shown that force transduction across the TCR complex is involved during TCR triggering, and that the T cell might use its force-generation machinery to probe the mechanical properties of the opposing antigen-presenting cell, giving rise to different signaling and physiological responses. Mechanistically, actin polymerization and turnover have been shown to be essential for force generation by T cells, but how these actin dynamics are regulated spatiotemporally remains poorly understood. Here, we report that traction forces generated by T cells are regulated by dynamic microtubules (MTs) at the interface. These MTs suppress Rho activation, nonmuscle myosin II bipolar filament assembly, and actin retrograde flow at the T-cell-substrate interface. Our results suggest a novel role of the MT cytoskeleton in regulating force generation during T-cell activation.T lymphocytes, central players in the adaptive immune response, are activated when T-cell receptors (TCRs) on their surface recognize cognate peptide-major histocompatibility complex (pMHC) expressed on the surface of antigen-presenting cells (APCs). A burst of actin polymerization is triggered upon TCR stimulation (1), leading to an enhancement of the cell/APC contact area as the T cell spreads over the surface of the APC (2) and the formation of a macromolecular protein assembly known as the immunological synapse (IS) (3, 4). Accompanying IS formation, T cells also undergo a rapid polarization of the microtubule (MT) cytoskeleton, within 1-2 min after initial contact, that facilitates directional secretion of cytokines and cytolytic factors toward the APC (5-7). Therefore, the contact zone between T cells and APCs is a site at which the MT and actin cytoskeletons could potentially interact to regulate signaling.Recent studies have established that T cells generate significant traction stresses at the cell-cell interface, albeit relatively weak compared with adherent cells (8-11). These forces, which peak 5-10 min after stimulation, facilitate T-cell activation, in part, by inducing conformational changes in the TCR-CD3 complex (12-15). Although actin polymerization/depolymerization dynamics are essential for T cells to maintain dynamic traction stresses and to drive calcium influx and integrin affinity maturation (9, 16, 17), the regulatory pathways that control these cytoskeletal forces are not completely understood. In particular, whether and how the polarized MT cytoskeleton interacts with the actin cytoskeleton and regulates force generation at the T-cell-APC contact remain open questions.MTs in the cell exist in two populations: dynamic/tyrosinated MTs and stable MTs that have undergone posttranslational modifications, including detyrosination and acetylation (18). Previous studies of T-cell activation have elucidated that microtubuleorganizing center (MTOC) translocation is associated with the formati...

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F-actin flow drives affinity maturation and spatial organization of LFA-1 at the immunological synapse

Abstract: The T cell actin network generates mechanical forces that regulate LFA-1 activity at the immunological synapse.

Cited by 152 publications

References 75 publications

Talin – the master of integrin adhesions

Talin – the master of integrin adhesions

Direction of actin flow dictates integrin LFA-1 orientation during leukocyte migration

Dynamic microtubules regulate cellular contractility during T-cell activation

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