TY - JOUR AB - Although much is known about the physiological framework of T cell motility, and numerous rate-limiting molecules have been identified through loss-of-function approaches, an integrated functional concept of T cell motility is lacking. Here, we used in vivo precision morphometry together with analysis of cytoskeletal dynamics in vitro to deconstruct the basic mechanisms of T cell migration within lymphatic organs. We show that the contributions of the integrin LFA-1 and the chemokine receptor CCR7 are complementary rather than positioned in a linear pathway, as they are during leukocyte extravasation from the blood vasculature. Our data demonstrate that CCR7 controls cortical actin flows, whereas integrins mediate substrate friction that is sufficient to drive locomotion in the absence of considerable surface adhesions and plasma membrane flux. AU - Hons, Miroslav AU - Kopf, Aglaja AU - Hauschild, Robert AU - Leithner, Alexander F AU - Gärtner, Florian R AU - Abe, Jun AU - Renkawitz, Jörg AU - Stein, Jens AU - Sixt, Michael K ID - 15 IS - 6 JF - Nature Immunology TI - Chemokines and integrins independently tune actin flow and substrate friction during intranodal migration of T cells VL - 19 ER - TY - JOUR AB - The actomyosin ring generates force to ingress the cytokinetic cleavage furrow in animal cells, yet its filament organization and the mechanism of contractility is not well understood. We quantified actin filament order in human cells using fluorescence polarization microscopy and found that cleavage furrow ingression initiates by contraction of an equatorial actin network with randomly oriented filaments. The network subsequently gradually reoriented actin filaments along the cell equator. This strictly depended on myosin II activity, suggesting local network reorganization by mechanical forces. Cortical laser microsurgery revealed that during cytokinesis progression, mechanical tension increased substantially along the direction of the cell equator, while the network contracted laterally along the pole-to-pole axis without a detectable increase in tension. Our data suggest that an asymmetric increase in cortical tension promotes filament reorientation along the cytokinetic cleavage furrow, which might have implications for diverse other biological processes involving actomyosin rings. AU - Spira, Felix AU - Cuylen Haering, Sara AU - Mehta, Shalin AU - Samwer, Matthias AU - Reversat, Anne AU - Verma, Amitabh AU - Oldenbourg, Rudolf AU - Sixt, Michael K AU - Gerlich, Daniel ID - 569 JF - eLife SN - 2050084X TI - Cytokinesis in vertebrate cells initiates by contraction of an equatorial actomyosin network composed of randomly oriented filaments VL - 6 ER - TY - JOUR AB - Blood platelets are critical for hemostasis and thrombosis and play diverse roles during immune responses. Despite these versatile tasks in mammalian biology, their skills on a cellular level are deemed limited, mainly consisting in rolling, adhesion, and aggregate formation. Here, we identify an unappreciated asset of platelets and show that adherent platelets use adhesion receptors to mechanically probe the adhesive substrate in their local microenvironment. When actomyosin-dependent traction forces overcome substrate resistance, platelets migrate and pile up the adhesive substrate together with any bound particulate material. They use this ability to act as cellular scavengers, scanning the vascular surface for potential invaders and collecting deposited bacteria. Microbe collection by migrating platelets boosts the activity of professional phagocytes, exacerbating inflammatory tissue injury in sepsis. This assigns platelets a central role in innate immune responses and identifies them as potential targets to dampen inflammatory tissue damage in clinical scenarios of severe systemic infection. In addition to their role in thrombosis and hemostasis, platelets can also migrate to sites of infection to help trap bacteria and clear the vascular surface. AU - Gärtner, Florian R AU - Ahmad, Zerkah AU - Rosenberger, Gerhild AU - Fan, Shuxia AU - Nicolai, Leo AU - Busch, Benjamin AU - Yavuz, Gökce AU - Luckner, Manja AU - Ishikawa Ankerhold, Hellen AU - Hennel, Roman AU - Benechet, Alexandre AU - Lorenz, Michael AU - Chandraratne, Sue AU - Schubert, Irene AU - Helmer, Sebastian AU - Striednig, Bianca AU - Stark, Konstantin AU - Janko, Marek AU - Böttcher, Ralph AU - Verschoor, Admar AU - Leon, Catherine AU - Gachet, Christian AU - Gudermann, Thomas AU - Mederos Y Schnitzler, Michael AU - Pincus, Zachary AU - Iannacone, Matteo AU - Haas, Rainer AU - Wanner, Gerhard AU - Lauber, Kirsten AU - Sixt, Michael K AU - Massberg, Steffen ID - 571 IS - 6 JF - Cell Press SN - 00928674 TI - Migrating platelets are mechano scavengers that collect and bundle bacteria VL - 171 ER - TY - JOUR AB - Migration frequently involves Rac-mediated protrusion of lamellipodia, formed by Arp2/3 complex-dependent branching thought to be crucial for force generation and stability of these networks. The formins FMNL2 and FMNL3 are Cdc42 effectors targeting to the lamellipodium tip and shown here to nucleate and elongate actin filaments with complementary activities in vitro. In migrating B16-F1 melanoma cells, both formins contribute to the velocity of lamellipodium protrusion. Loss of FMNL2/3 function in melanoma cells and fibroblasts reduces lamellipodial width, actin filament density and -bundling, without changing patterns of Arp2/3 complex incorporation. Strikingly, in melanoma cells, FMNL2/3 gene inactivation almost completely abolishes protrusion forces exerted by lamellipodia and modifies their ultrastructural organization. Consistently, CRISPR/Cas-mediated depletion of FMNL2/3 in fibroblasts reduces both migration and capability of cells to move against viscous media. Together, we conclude that force generation in lamellipodia strongly depends on FMNL formin activity, operating in addition to Arp2/3 complex-dependent filament branching. AU - Kage, Frieda AU - Winterhoff, Moritz AU - Dimchev, Vanessa AU - Müller, Jan AU - Thalheim, Tobias AU - Freise, Anika AU - Brühmann, Stefan AU - Kollasser, Jana AU - Block, Jennifer AU - Dimchev, Georgi A AU - Geyer, Matthias AU - Schnittler, Hams AU - Brakebusch, Cord AU - Stradal, Theresia AU - Carlier, Marie AU - Sixt, Michael K AU - Käs, Josef AU - Faix, Jan AU - Rottner, Klemens ID - 659 JF - Nature Communications SN - 20411723 TI - FMNL formins boost lamellipodial force generation VL - 8 ER - TY - JOUR AB - Macrophage filopodia, finger-like membrane protrusions, were first implicated in phagocytosis more than 100 years ago, but little is still known about the involvement of these actin-dependent structures in particle clearance. Using spinning disk confocal microscopy to image filopodial dynamics in mouse resident Lifeact-EGFP macrophages, we show that filopodia, or filopodia-like structures, support pathogen clearance by multiple means. Filopodia supported the phagocytic uptake of bacterial (Escherichia coli) particles by (i) capturing along the filopodial shaft and surfing toward the cell body, the most common mode of capture; (ii) capturing via the tip followed by retraction; (iii) combinations of surfing and retraction; or (iv) sweeping actions. In addition, filopodia supported the uptake of zymosan (Saccharomyces cerevisiae) particles by (i) providing fixation, (ii) capturing at the tip and filopodia-guided actin anterograde flow with phagocytic cup formation, and (iii) the rapid growth of new protrusions. To explore the role of filopodia-inducing Cdc42, we generated myeloid-restricted Cdc42 knock-out mice. Cdc42-deficient macrophages exhibited rapid phagocytic cup kinetics, but reduced particle clearance, which could be explained by the marked rounded-up morphology of these cells. Macrophages lacking Myo10, thought to act downstream of Cdc42, had normal morphology, motility, and phagocytic cup formation, but displayed markedly reduced filopodia formation. In conclusion, live-cell imaging revealed multiple mechanisms involving macrophage filopodia in particle capture and engulfment. Cdc42 is not critical for filopodia or phagocytic cup formation, but plays a key role in driving macrophage lamellipodial spreading. AU - Horsthemke, Markus AU - Bachg, Anne AU - Groll, Katharina AU - Moyzio, Sven AU - Müther, Barbara AU - Hemkemeyer, Sandra AU - Wedlich Söldner, Roland AU - Sixt, Michael K AU - Tacke, Sebastian AU - Bähler, Martin AU - Hanley, Peter ID - 668 IS - 17 JF - Journal of Biological Chemistry SN - 00219258 TI - Multiple roles of filopodial dynamics in particle capture and phagocytosis and phenotypes of Cdc42 and Myo10 deletion VL - 292 ER - TY - JOUR AB - Trafficking cells frequently transmigrate through epithelial and endothelial monolayers. How monolayers cooperate with the penetrating cells to support their transit is poorly understood. We studied dendritic cell (DC) entry into lymphatic capillaries as a model system for transendothelial migration. We find that the chemokine CCL21, which is the decisive guidance cue for intravasation, mainly localizes in the trans-Golgi network and intracellular vesicles of lymphatic endothelial cells. Upon DC transmigration, these Golgi deposits disperse and CCL21 becomes extracellularly enriched at the sites of endothelial cell-cell junctions. When we reconstitute the transmigration process in vitro, we find that secretion of CCL21-positive vesicles is triggered by a DC contact-induced calcium signal, and selective calcium chelation in lymphatic endothelium attenuates transmigration. Altogether, our data demonstrate a chemokine-mediated feedback between DCs and lymphatic endothelium, which facilitates transendothelial migration. AU - Vaahtomeri, Kari AU - Brown, Markus AU - Hauschild, Robert AU - De Vries, Ingrid AU - Leithner, Alexander F AU - Mehling, Matthias AU - Kaufmann, Walter AU - Sixt, Michael K ID - 672 IS - 5 JF - Cell Reports SN - 22111247 TI - Locally triggered release of the chemokine CCL21 promotes dendritic cell transmigration across lymphatic endothelia VL - 19 ER - TY - JOUR AB - Navigation of cells along gradients of guidance cues is a determining step in many developmental and immunological processes. Gradients can either be soluble or immobilized to tissues as demonstrated for the haptotactic migration of dendritic cells (DCs) toward higher concentrations of immobilized chemokine CCL21. To elucidate how gradient characteristics govern cellular response patterns, we here introduce an in vitro system allowing to track migratory responses of DCs to precisely controlled immobilized gradients of CCL21. We find that haptotactic sensing depends on the absolute CCL21 concentration and local steepness of the gradient, consistent with a scenario where DC directionality is governed by the signal-to-noise ratio of CCL21 binding to the receptor CCR7. We find that the conditions for optimal DC guidance are perfectly provided by the CCL21 gradients we measure in vivo. Furthermore, we find that CCR7 signal termination by the G-protein-coupled receptor kinase 6 (GRK6) is crucial for haptotactic but dispensable for chemotactic CCL21 gradient sensing in vitro and confirm those observations in vivo. These findings suggest that stable, tissue-bound CCL21 gradients as sustainable “roads” ensure optimal guidance in vivo. AU - Schwarz, Jan AU - Bierbaum, Veronika AU - Vaahtomeri, Kari AU - Hauschild, Robert AU - Brown, Markus AU - De Vries, Ingrid AU - Leithner, Alexander F AU - Reversat, Anne AU - Merrin, Jack AU - Tarrant, Teresa AU - Bollenbach, Tobias AU - Sixt, Michael K ID - 674 IS - 9 JF - Current Biology SN - 09609822 TI - Dendritic cells interpret haptotactic chemokine gradients in a manner governed by signal to noise ratio and dependent on GRK6 VL - 27 ER - TY - JOUR AB - The INO80 complex (INO80-C) is an evolutionarily conserved nucleosome remodeler that acts in transcription, replication, and genome stability. It is required for resistance against genotoxic agents and is involved in the repair of DNA double-strand breaks (DSBs) by homologous recombination (HR). However, the causes of the HR defect in INO80-C mutant cells are controversial. Here, we unite previous findings using a system to study HR with high spatial resolution in budding yeast. We find that INO80-C has at least two distinct functions during HR—DNA end resection and presynaptic filament formation. Importantly, the second function is linked to the histone variant H2A.Z. In the absence of H2A.Z, presynaptic filament formation and HR are restored in INO80-C-deficient mutants, suggesting that presynaptic filament formation is the crucial INO80-C function during HR. AU - Lademann, Claudio AU - Renkawitz, Jörg AU - Pfander, Boris AU - Jentsch, Stefan ID - 677 IS - 7 JF - Cell Reports SN - 22111247 TI - The INO80 complex removes H2A.Z to promote presynaptic filament formation during homologous recombination VL - 19 ER - TY - JOUR AB - A change regarding the extent of adhesion - hereafter referred to as adhesion plasticity - between adhesive and less-adhesive states of mammalian cells is important for their behavior. To investigate adhesion plasticity, we have selected a stable isogenic subpopulation of human MDA-MB-468 breast carcinoma cells growing in suspension. These suspension cells are unable to re-adhere to various matrices or to contract three-dimensional collagen lattices. By using transcriptome analysis, we identified the focal adhesion protein tensin3 (Tns3) as a determinant of adhesion plasticity. Tns3 is strongly reduced at mRNA and protein levels in suspension cells. Furthermore, by transiently challenging breast cancer cells to grow under non-adherent conditions markedly reduces Tns3 protein expression, which is regained upon re-adhesion. Stable knockdown of Tns3 in parental MDA-MB-468 cells results in defective adhesion, spreading and migration. Tns3-knockdown cells display impaired structure and dynamics of focal adhesion complexes as determined by immunostaining. Restoration of Tns3 protein expression in suspension cells partially rescues adhesion and focal contact composition. Our work identifies Tns3 as a crucial focal adhesion component regulated by, and functionally contributing to, the switch between adhesive and non-adhesive states in MDA-MB-468 cancer cells. AU - Veß, Astrid AU - Blache, Ulrich AU - Leitner, Laura AU - Kurz, Angela AU - Ehrenpfordt, Anja AU - Sixt, Michael K AU - Posern, Guido ID - 694 IS - 13 JF - Journal of Cell Science SN - 00219533 TI - A dual phenotype of MDA MB 468 cancer cells reveals mutual regulation of tensin3 and adhesion plasticity VL - 130 ER - TY - JOUR AB - Coordinated changes of cell shape are often the result of the excitable, wave-like dynamics of the actin cytoskeleton. New work shows that, in migrating cells, protrusion waves arise from mechanochemical crosstalk between adhesion sites, membrane tension and the actin protrusive machinery. AU - Müller, Jan AU - Sixt, Michael K ID - 1161 IS - 1 JF - Current Biology SN - 09609822 TI - Cell migration: Making the waves VL - 27 ER - TY - JOUR AB - Actin filaments polymerizing against membranes power endocytosis, vesicular traffic, and cell motility. In vitro reconstitution studies suggest that the structure and the dynamics of actin networks respond to mechanical forces. We demonstrate that lamellipodial actin of migrating cells responds to mechanical load when membrane tension is modulated. In a steady state, migrating cell filaments assume the canonical dendritic geometry, defined by Arp2/3-generated 70° branch points. Increased tension triggers a dense network with a broadened range of angles, whereas decreased tension causes a shift to a sparse configuration dominated by filaments growing perpendicularly to the plasma membrane. We show that these responses emerge from the geometry of branched actin: when load per filament decreases, elongation speed increases and perpendicular filaments gradually outcompete others because they polymerize the shortest distance to the membrane, where they are protected from capping. This network-intrinsic geometrical adaptation mechanism tunes protrusive force in response to mechanical load. AU - Mueller, Jan AU - Szep, Gregory AU - Nemethova, Maria AU - De Vries, Ingrid AU - Lieber, Arnon AU - Winkler, Christoph AU - Kruse, Karsten AU - Small, John AU - Schmeiser, Christian AU - Keren, Kinneret AU - Hauschild, Robert AU - Sixt, Michael K ID - 727 IS - 1 JF - Cell SN - 00928674 TI - Load adaptation of lamellipodial actin networks VL - 171 ER - TY - DATA AB - Immunological synapse DC-Tcells AU - Leithner, Alexander F ID - 5567 KW - Immunological synapse TI - Immunological synapse DC-Tcells ER - TY - JOUR AB - Immune cells communicate using cytokine signals, but the quantitative rules of this communication aren't clear. In this issue of Immunity, Oyler-Yaniv et al. (2017) suggest that the distribution of a cytokine within a lymphatic organ is primarily governed by the local density of cells consuming it. AU - Assen, Frank P AU - Sixt, Michael K ID - 664 IS - 4 JF - Immunity SN - 10747613 TI - The dynamic cytokine niche VL - 46 ER - TY - JOUR AB - Protective responses against pathogens require a rapid mobilization of resting neutrophils and the timely removal of activated ones. Neutrophils are exceptionally short-lived leukocytes, yet it remains unclear whether the lifespan of pathogen-engaged neutrophils is regulated differently from that in the circulating steady-state pool. Here, we have found that under homeostatic conditions, the mRNA-destabilizing protein tristetraprolin (TTP) regulates apoptosis and the numbers of activated infiltrating murine neutrophils but not neutrophil cellularity. Activated TTP-deficient neutrophils exhibited decreased apoptosis and enhanced accumulation at the infection site. In the context of myeloid-specific deletion of Ttp, the potentiation of neutrophil deployment protected mice against lethal soft tissue infection with Streptococcus pyogenes and prevented bacterial dissemination. Neutrophil transcriptome analysis revealed that decreased apoptosis of TTP-deficient neutrophils was specifically associated with elevated expression of myeloid cell leukemia 1 (Mcl1) but not other antiapoptotic B cell leukemia/ lymphoma 2 (Bcl2) family members. Higher Mcl1 expression resulted from stabilization of Mcl1 mRNA in the absence of TTP. The low apoptosis rate of infiltrating TTP-deficient neutrophils was comparable to that of transgenic Mcl1-overexpressing neutrophils. Our study demonstrates that posttranscriptional gene regulation by TTP schedules the termination of the antimicrobial engagement of neutrophils. The balancing role of TTP comes at the cost of an increased risk of bacterial infections. AU - Ebner, Florian AU - Sedlyarov, Vitaly AU - Tasciyan, Saren AU - Ivin, Masa AU - Kratochvill, Franz AU - Gratz, Nina AU - Kenner, Lukas AU - Villunger, Andreas AU - Sixt, Michael K AU - Kovarik, Pavel ID - 679 IS - 6 JF - The Journal of Clinical Investigation SN - 00219738 TI - The RNA-binding protein tristetraprolin schedules apoptosis of pathogen-engaged neutrophils during bacterial infection VL - 127 ER - TY - JOUR AB - RASGRP1 is an important guanine nucleotide exchange factor and activator of the RAS-MAPK pathway following T cell antigen receptor (TCR) signaling. The consequences of RASGRP1 mutations in humans are unknown. In a patient with recurrent bacterial and viral infections, born to healthy consanguineous parents, we used homozygosity mapping and exome sequencing to identify a biallelic stop-gain variant in RASGRP1. This variant segregated perfectly with the disease and has not been reported in genetic databases. RASGRP1 deficiency was associated in T cells and B cells with decreased phosphorylation of the extracellular-signal-regulated serine kinase ERK, which was restored following expression of wild-type RASGRP1. RASGRP1 deficiency also resulted in defective proliferation, activation and motility of T cells and B cells. RASGRP1-deficient natural killer (NK) cells exhibited impaired cytotoxicity with defective granule convergence and actin accumulation. Interaction proteomics identified the dynein light chain DYNLL1 as interacting with RASGRP1, which links RASGRP1 to cytoskeletal dynamics. RASGRP1-deficient cells showed decreased activation of the GTPase RhoA. Treatment with lenalidomide increased RhoA activity and reversed the migration and activation defects of RASGRP1-deficient lymphocytes. AU - Salzer, Elisabeth AU - Çaǧdaş, Deniz AU - Hons, Miroslav AU - Mace, Emily AU - Garncarz, Wojciech AU - Petronczki, Oezlem AU - Platzer, René AU - Pfajfer, Laurène AU - Bilic, Ivan AU - Ban, Sol AU - Willmann, Katharina AU - Mukherjee, Malini AU - Supper, Verena AU - Hsu, Hsiangting AU - Banerjee, Pinaki AU - Sinha, Papiya AU - Mcclanahan, Fabienne AU - Zlabinger, Gerhard AU - Pickl, Winfried AU - Gribben, John AU - Stockinger, Hannes AU - Bennett, Keiryn AU - Huppa, Johannes AU - Dupré, Loï̈C AU - Sanal, Özden AU - Jäger, Ulrich AU - Sixt, Michael K AU - Tezcan, Ilhan AU - Orange, Jordan AU - Boztug, Kaan ID - 1137 IS - 12 JF - Nature Immunology TI - RASGRP1 deficiency causes immunodeficiency with impaired cytoskeletal dynamics VL - 17 ER - TY - JOUR AB - Hemolysis drives susceptibility to bacterial infections and predicts poor outcome from sepsis. These detrimental effects are commonly considered to be a consequence of heme-iron serving as a nutrient for bacteria. We employed a Gram-negative sepsis model and found that elevated heme levels impaired the control of bacterial proliferation independently of heme-iron acquisition by pathogens. Heme strongly inhibited phagocytosis and the migration of human and mouse phagocytes by disrupting actin cytoskeletal dynamics via activation of the GTP-binding Rho family protein Cdc42 by the guanine nucleotide exchange factor DOCK8. A chemical screening approach revealed that quinine effectively prevented heme effects on the cytoskeleton, restored phagocytosis and improved survival in sepsis. These mechanistic insights provide potential therapeutic targets for patients with sepsis or hemolytic disorders. AU - Martins, Rui AU - Maier, Julia AU - Gorki, Anna AU - Huber, Kilian AU - Sharif, Omar AU - Starkl, Philipp AU - Saluzzo, Simona AU - Quattrone, Federica AU - Gawish, Riem AU - Lakovits, Karin AU - Aichinger, Michael AU - Radic Sarikas, Branka AU - Lardeau, Charles AU - Hladik, Anastasiya AU - Korosec, Ana AU - Brown, Markus AU - Vaahtomeri, Kari AU - Duggan, Michelle AU - Kerjaschki, Dontscho AU - Esterbauer, Harald AU - Colinge, Jacques AU - Eisenbarth, Stephanie AU - Decker, Thomas AU - Bennett, Keiryn AU - Kubicek, Stefan AU - Sixt, Michael K AU - Superti Furga, Giulio AU - Knapp, Sylvia ID - 1142 IS - 12 JF - Nature Immunology TI - Heme drives hemolysis-induced susceptibility to infection via disruption of phagocyte functions VL - 17 ER - TY - JOUR AB - When neutrophils infiltrate a site of inflammation, they have to stop at the right place to exert their effector function. In this issue of Developmental Cell, Wang et al. (2016) show that neutrophils sense reactive oxygen species via the TRPM2 channel to arrest migration at their target site. © 2016 Elsevier Inc. AU - Renkawitz, Jörg AU - Sixt, Michael K ID - 1150 IS - 5 JF - Developmental Cell TI - A Radical Break Restraining Neutrophil Migration VL - 38 ER - TY - JOUR AB - Cellular locomotion is a central hallmark of eukaryotic life. It is governed by cell-extrinsic molecular factors, which can either emerge in the soluble phase or as immobilized, often adhesive ligands. To encode for direction, every cue must be present as a spatial or temporal gradient. Here, we developed a microfluidic chamber that allows measurement of cell migration in combined response to surface immobilized and soluble molecular gradients. As a proof of principle we study the response of dendritic cells to their major guidance cues, chemokines. The majority of data on chemokine gradient sensing is based on in vitro studies employing soluble gradients. Despite evidence suggesting that in vivo chemokines are often immobilized to sugar residues, limited information is available how cells respond to immobilized chemokines. We tracked migration of dendritic cells towards immobilized gradients of the chemokine CCL21 and varying superimposed soluble gradients of CCL19. Differential migratory patterns illustrate the potential of our setup to quantitatively study the competitive response to both types of gradients. Beyond chemokines our approach is broadly applicable to alternative systems of chemo- and haptotaxis such as cells migrating along gradients of adhesion receptor ligands vs. any soluble cue. AU - Schwarz, Jan AU - Bierbaum, Veronika AU - Merrin, Jack AU - Frank, Tino AU - Hauschild, Robert AU - Bollenbach, Mark Tobias AU - Tay, Savaş AU - Sixt, Michael K AU - Mehling, Matthias ID - 1154 JF - Scientific Reports TI - A microfluidic device for measuring cell migration towards substrate bound and soluble chemokine gradients VL - 6 ER - TY - JOUR AB - In this issue of Cell, Skau et al. show that the formin FMN2 organizes a perinuclear actin cytoskeleton that protects the nucleus and its genomic content of migrating cells squeezing through small spaces. AU - Renkawitz, Jörg AU - Sixt, Michael K ID - 1201 IS - 6 JF - Cell TI - Formin’ a nuclear protection VL - 167 ER - TY - JOUR AB - Understanding the regulation of T-cell responses during inflammation and auto-immunity is fundamental for designing efficient therapeutic strategies against immune diseases. In this regard, prostaglandin E 2 (PGE 2) is mostly considered a myeloid-derived immunosuppressive molecule. We describe for the first time that T cells secrete PGE 2 during T-cell receptor stimulation. In addition, we show that autocrine PGE 2 signaling through EP receptors is essential for optimal CD4 + T-cell activation in vitro and in vivo, and for T helper 1 (Th1) and regulatory T cell differentiation. PGE 2 was found to provide additive co-stimulatory signaling through AKT activation. Intravital multiphoton microscopy showed that triggering EP receptors in T cells is also essential for the stability of T cell-dendritic cell (DC) interactions and Th-cell accumulation in draining lymph nodes (LNs) during inflammation. We further demonstrated that blocking EP receptors in T cells during the initial phase of collagen-induced arthritis in mice resulted in a reduction of clinical arthritis. This could be attributable to defective T-cell activation, accompanied by a decline in activated and interferon-γ-producing CD4 + Th1 cells in draining LNs. In conclusion, we prove that T lymphocytes secret picomolar concentrations of PGE 2, which in turn provide additive co-stimulatory signaling, enabling T cells to attain a favorable activation threshold. PGE 2 signaling in T cells is also required for maintaining long and stable interactions with DCs within LNs. Blockade of EP receptors in vivo impairs T-cell activation and development of T cell-mediated inflammatory responses. This may have implications in various pathophysiological settings. AU - Sreeramkumar, Vinatha AU - Hons, Miroslav AU - Punzón, Carmen AU - Stein, Jens AU - Sancho, David AU - Fresno Forcelledo, Manuel AU - Cuesta, Natalia ID - 1217 IS - 1 JF - Immunology and Cell Biology TI - Efficient T-cell priming and activation requires signaling through prostaglandin E2 (EP) receptors VL - 94 ER -