@article{1142, abstract = {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.}, author = {Martins, Rui and Maier, Julia and Gorki, Anna and Huber, Kilian and Sharif, Omar and Starkl, Philipp and Saluzzo, Simona and Quattrone, Federica and Gawish, Riem and Lakovits, Karin and Aichinger, Michael and Radic Sarikas, Branka and Lardeau, Charles and Hladik, Anastasiya and Korosec, Ana and Brown, Markus and Vaahtomeri, Kari and Duggan, Michelle and Kerjaschki, Dontscho and Esterbauer, Harald and Colinge, Jacques and Eisenbarth, Stephanie and Decker, Thomas and Bennett, Keiryn and Kubicek, Stefan and Sixt, Michael K and Superti Furga, Giulio and Knapp, Sylvia}, journal = {Nature Immunology}, number = {12}, pages = {1361 -- 1372}, publisher = {Nature Publishing Group}, title = {{Heme drives hemolysis-induced susceptibility to infection via disruption of phagocyte functions}}, doi = {10.1038/ni.3590}, volume = {17}, year = {2016}, } @article{1150, abstract = {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.}, author = {Renkawitz, Jörg and Sixt, Michael K}, journal = {Developmental Cell}, number = {5}, pages = {448 -- 450}, publisher = {Cell Press}, title = {{A Radical Break Restraining Neutrophil Migration}}, doi = {10.1016/j.devcel.2016.08.017}, volume = {38}, year = {2016}, } @article{1154, abstract = {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. }, author = {Schwarz, Jan and Bierbaum, Veronika and Merrin, Jack and Frank, Tino and Hauschild, Robert and Bollenbach, Mark Tobias and Tay, Savaş and Sixt, Michael K and Mehling, Matthias}, journal = {Scientific Reports}, publisher = {Nature Publishing Group}, title = {{A microfluidic device for measuring cell migration towards substrate bound and soluble chemokine gradients}}, doi = {10.1038/srep36440}, volume = {6}, year = {2016}, } @article{1490, abstract = {To induce adaptive immunity, dendritic cells (DCs) migrate through afferent lymphatic vessels (LVs) to draining lymph nodes (dLNs). This process occurs in several consecutive steps. Upon entry into lymphatic capillaries, DCs first actively crawl into downstream collecting vessels. From there, they are next passively and rapidly transported to the dLN by lymph flow. Here, we describe a role for the chemokine CCL21 in intralymphatic DC crawling. Performing time-lapse imaging in murine skin, we found that blockade of CCL21-but not the absence of lymph flow-completely abolished DC migration from capillaries toward collecting vessels and reduced the ability of intralymphatic DCs to emigrate from skin. Moreover, we found that in vitro low laminar flow established a CCL21 gradient along lymphatic endothelial monolayers, thereby inducing downstream-directed DC migration. These findings reveal a role for intralymphatic CCL21 in promoting DC trafficking to dLNs, through the formation of a flow-induced gradient.}, author = {Russo, Erica and Teijeira, Alvaro and Vaahtomeri, Kari and Willrodt, Ann and Bloch, Joël and Nitschké, Maximilian and Santambrogio, Laura and Kerjaschki, Dontscho and Sixt, Michael K and Halin, Cornelia}, journal = {Cell Reports}, number = {7}, pages = {1723 -- 1734}, publisher = {Cell Press}, title = {{Intralymphatic CCL21 promotes tissue egress of dendritic cells through afferent lymphatic vessels}}, doi = {10.1016/j.celrep.2016.01.048}, volume = {14}, year = {2016}, } @article{1597, abstract = {Chemokines are the main guidance cues directing leukocyte migration. Opposed to early assumptions, chemokines do not necessarily act as soluble cues but are often immobilized within tissues, e.g., dendritic cell migration toward lymphatic vessels is guided by a haptotactic gradient of the chemokine CCL21. Controlled assay systems to quantitatively study haptotaxis in vitro are still missing. In this chapter, we describe an in vitro haptotaxis assay optimized for the unique properties of dendritic cells. The chemokine CCL21 is immobilized in a bioactive state, using laser-assisted protein adsorption by photobleaching. The cells follow this immobilized CCL21 gradient in a haptotaxis chamber, which provides three dimensionally confined migration conditions.}, author = {Schwarz, Jan and Sixt, Michael K}, journal = {Methods in Enzymology}, pages = {567 -- 581}, publisher = {Elsevier}, title = {{Quantitative analysis of dendritic cell haptotaxis}}, doi = {10.1016/bs.mie.2015.11.004}, volume = {570}, year = {2016}, } @article{1599, abstract = {The addition of polysialic acid to N- and/or O-linked glycans, referred to as polysialylation, is a rare posttranslational modification that is mainly known to control the developmental plasticity of the nervous system. Here we show that CCR7, the central chemokine receptor controlling immune cell trafficking to secondary lymphatic organs, carries polysialic acid. This modification is essential for the recognition of the CCR7 ligand CCL21. As a consequence, dendritic cell trafficking is abrogated in polysialyltransferase-deficient mice, manifesting as disturbed lymph node homeostasis and unresponsiveness to inflammatory stimuli. Structure-function analysis of chemokine-receptor interactions reveals that CCL21 adopts an autoinhibited conformation, which is released upon interaction with polysialic acid. Thus, we describe a glycosylation-mediated immune cell trafficking disorder and its mechanistic basis. }, author = {Kiermaier, Eva and Moussion, Christine and Veldkamp, Christopher and Gerardy Schahn, Rita and De Vries, Ingrid and Williams, Larry and Chaffee, Gary and Phillips, Andrew and Freiberger, Friedrich and Imre, Richard and Taleski, Deni and Payne, Richard and Braun, Asolina and Förster, Reinhold and Mechtler, Karl and Mühlenhoff, Martina and Volkman, Brian and Sixt, Michael K}, journal = {Science}, number = {6269}, pages = {186 -- 190}, publisher = {American Association for the Advancement of Science}, title = {{Polysialylation controls dendritic cell trafficking by regulating chemokine recognition}}, doi = {10.1126/science.aad0512}, volume = {351}, year = {2016}, } @article{1321, abstract = {Most migrating cells extrude their front by the force of actin polymerization. Polymerization requires an initial nucleation step, which is mediated by factors establishing either parallel filaments in the case of filopodia or branched filaments that form the branched lamellipodial network. Branches are considered essential for regular cell motility and are initiated by the Arp2/3 complex, which in turn is activated by nucleation-promoting factors of the WASP and WAVE families. Here we employed rapid amoeboid crawling leukocytes and found that deletion of the WAVE complex eliminated actin branching and thus lamellipodia formation. The cells were left with parallel filaments at the leading edge, which translated, depending on the differentiation status of the cell, into a unipolar pointed cell shape or cells with multiple filopodia. Remarkably, unipolar cells migrated with increased speed and enormous directional persistence, while they were unable to turn towards chemotactic gradients. Cells with multiple filopodia retained chemotactic activity but their migration was progressively impaired with increasing geometrical complexity of the extracellular environment. These findings establish that diversified leading edge protrusions serve as explorative structures while they slow down actual locomotion.}, author = {Leithner, Alexander F and Eichner, Alexander and Müller, Jan and Reversat, Anne and Brown, Markus and Schwarz, Jan and Merrin, Jack and De Gorter, David and Schur, Florian and Bayerl, Jonathan and De Vries, Ingrid and Wieser, Stefan and Hauschild, Robert and Lai, Frank and Moser, Markus and Kerjaschki, Dontscho and Rottner, Klemens and Small, Victor and Stradal, Theresia and Sixt, Michael K}, journal = {Nature Cell Biology}, pages = {1253 -- 1259}, publisher = {Nature Publishing Group}, title = {{Diversified actin protrusions promote environmental exploration but are dispensable for locomotion of leukocytes}}, doi = {10.1038/ncb3426}, volume = {18}, year = {2016}, } @article{1201, abstract = {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.}, author = {Renkawitz, Jörg and Sixt, Michael K}, journal = {Cell}, number = {6}, pages = {1448 -- 1449}, publisher = {Cell Press}, title = {{Formin’ a nuclear protection}}, doi = {10.1016/j.cell.2016.11.024}, volume = {167}, year = {2016}, } @article{1217, abstract = {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.}, author = {Sreeramkumar, Vinatha and Hons, Miroslav and Punzón, Carmen and Stein, Jens and Sancho, David and Fresno Forcelledo, Manuel and Cuesta, Natalia}, journal = {Immunology and Cell Biology}, number = {1}, pages = {39 -- 51}, publisher = {Nature Publishing Group}, title = {{Efficient T-cell priming and activation requires signaling through prostaglandin E2 (EP) receptors}}, doi = {10.1038/icb.2015.62}, volume = {94}, year = {2016}, } @article{1285, abstract = {Cell migration is central to a multitude of physiological processes, including embryonic development, immune surveillance, and wound healing, and deregulated migration is key to cancer dissemination. Decades of investigations have uncovered many of the molecular and physical mechanisms underlying cell migration. Together with protrusion extension and cell body retraction, adhesion to the substrate via specific focal adhesion points has long been considered an essential step in cell migration. Although this is true for cells moving on two-dimensional substrates, recent studies have demonstrated that focal adhesions are not required for cells moving in three dimensions, in which confinement is sufficient to maintain a cell in contact with its substrate. Here, we review the investigations that have led to challenging the requirement of specific adhesions for migration, discuss the physical mechanisms proposed for cell body translocation during focal adhesion-independent migration, and highlight the remaining open questions for the future.}, author = {Paluch, Ewa and Aspalter, Irene and Sixt, Michael K}, journal = {Annual Review of Cell and Developmental Biology}, pages = {469 -- 490}, publisher = {Annual Reviews}, title = {{Focal adhesion-independent cell migration}}, doi = {10.1146/annurev-cellbio-111315-125341}, volume = {32}, year = {2016}, } @article{1618, abstract = {CCL19 and CCL21 are chemokines involved in the trafficking of immune cells, particularly within the lymphatic system, through activation of CCR7. Concurrent expression of PSGL-1 and CCR7 in naive T-cells enhances recruitment of these cells to secondary lymphoid organs by CCL19 and CCL21. Here the solution structure of CCL19 is reported. It contains a canonical chemokine domain. Chemical shift mapping shows the N-termini of PSGL-1 and CCR7 have overlapping binding sites for CCL19 and binding is competitive. Implications for the mechanism of PSGL-1's enhancement of resting T-cell recruitment are discussed.}, author = {Veldkamp, Christopher and Kiermaier, Eva and Gabel Eissens, Skylar and Gillitzer, Miranda and Lippner, David and Disilvio, Frank and Mueller, Casey and Wantuch, Paeton and Chaffee, Gary and Famiglietti, Michael and Zgoba, Danielle and Bailey, Asha and Bah, Yaya and Engebretson, Samantha and Graupner, David and Lackner, Emily and Larosa, Vincent and Medeiros, Tysha and Olson, Michael and Phillips, Andrew and Pyles, Harley and Richard, Amanda and Schoeller, Scott and Touzeau, Boris and Williams, Larry and Sixt, Michael K and Peterson, Francis}, journal = {Biochemistry}, number = {27}, pages = {4163 -- 4166}, publisher = {American Chemical Society}, title = {{Solution structure of CCL19 and identification of overlapping CCR7 and PSGL-1 binding sites}}, doi = {10.1021/acs.biochem.5b00560}, volume = {54}, year = {2015}, } @article{1676, author = {Sixt, Michael K and Raz, Erez}, journal = {Current Opinion in Cell Biology}, number = {10}, pages = {4 -- 6}, publisher = {Elsevier}, title = {{Editorial overview: Cell adhesion and migration}}, doi = {10.1016/j.ceb.2015.09.004}, volume = {36}, year = {2015}, } @article{1686, author = {Kiermaier, Eva and Sixt, Michael K}, journal = {Science}, number = {6252}, pages = {1055 -- 1056}, publisher = {American Association for the Advancement of Science}, title = {{Fragmented communication between immune cells: Neutrophils blaze a trail with migratory cues for T cells to follow to sites of infection}}, doi = {10.1126/science.aad0867}, volume = {349}, year = {2015}, } @article{1687, abstract = {Guided cell movement is essential for development and integrity of animals and crucially involved in cellular immune responses. Leukocytes are professional migratory cells that can navigate through most types of tissues and sense a wide range of directional cues. The responses of these cells to attractants have been mainly explored in tissue culture settings. How leukocytes make directional decisions in situ, within the challenging environment of a tissue maze, is less understood. Here we review recent advances in how leukocytes sense chemical cues in complex tissue settings and make links with paradigms of directed migration in development and Dictyostelium discoideum amoebae.}, author = {Sarris, Milka and Sixt, Michael K}, journal = {Current Opinion in Cell Biology}, number = {10}, pages = {93 -- 102}, publisher = {Elsevier}, title = {{Navigating in tissue mazes: Chemoattractant interpretation in complex environments}}, doi = {10.1016/j.ceb.2015.08.001}, volume = {36}, year = {2015}, } @article{477, abstract = {Dendritic cells are potent antigen-presenting cells endowed with the unique ability to initiate adaptive immune responses upon inflammation. Inflammatory processes are often associated with an increased production of serotonin, which operates by activating specific receptors. However, the functional role of serotonin receptors in regulation of dendritic cell functions is poorly understood. Here, we demonstrate that expression of serotonin receptor 5-HT7 (5-HT7TR) as well as its downstream effector Cdc42 is upregulated in dendritic cells upon maturation. Although dendritic cell maturation was independent of 5-HT7TR, receptor stimulation affected dendritic cell morphology through Cdc42-mediated signaling. In addition, basal activity of 5-HT7TR was required for the proper expression of the chemokine receptor CCR7, which is a key factor that controls dendritic cell migration. Consistent with this, we observed that 5-HT7TR enhances chemotactic motility of dendritic cells in vitro by modulating their directionality and migration velocity. Accordingly, migration of dendritic cells in murine colon explants was abolished after pharmacological receptor inhibition. Our results indicate that there is a crucial role for 5-HT7TR-Cdc42-mediated signaling in the regulation of dendritic cell morphology and motility, suggesting that 5-HT7TR could be a new target for treatment of a variety of inflammatory and immune disorders.}, author = {Holst, Katrin and Guseva, Daria and Schindler, Susann and Sixt, Michael K and Braun, Armin and Chopra, Himpriya and Pabst, Oliver and Ponimaskin, Evgeni}, journal = {Journal of Cell Science}, number = {15}, pages = {2866 -- 2880}, publisher = {Company of Biologists}, title = {{The serotonin receptor 5-HT7R regulates the morphology and migratory properties of dendritic cells}}, doi = {10.1242/jcs.167999}, volume = {128}, year = {2015}, } @article{1530, abstract = {In growing cells, protein synthesis and cell growth are typically not synchronous, and, thus, protein concentrations vary over the cell division cycle. We have developed a theoretical description of genetic regulatory systems in bacteria that explicitly considers the cell division cycle to investigate its impact on gene expression. We calculate the cell-to-cell variations arising from cells being at different stages in the division cycle for unregulated genes and for basic regulatory mechanisms. These variations contribute to the extrinsic noise observed in single-cell experiments, and are most significant for proteins with short lifetimes. Negative autoregulation buffers against variation of protein concentration over the division cycle, but the effect is found to be relatively weak. Stronger buffering is achieved by an increased protein lifetime. Positive autoregulation can strongly amplify such variation if the parameters are set to values that lead to resonance-like behaviour. For cooperative positive autoregulation, the concentration variation over the division cycle diminishes the parameter region of bistability and modulates the switching times between the two stable states. The same effects are seen for a two-gene mutual-repression toggle switch. By contrast, an oscillatory circuit, the repressilator, is only weakly affected by the division cycle.}, author = {Bierbaum, Veronika and Klumpp, Stefan}, journal = {Physical Biology}, number = {6}, publisher = {IOP Publishing Ltd.}, title = {{Impact of the cell division cycle on gene circuits}}, doi = {10.1088/1478-3975/12/6/066003}, volume = {12}, year = {2015}, } @article{1537, abstract = {3D amoeboid cell migration is central to many developmental and disease-related processes such as cancer metastasis. Here, we identify a unique prototypic amoeboid cell migration mode in early zebrafish embryos, termed stable-bleb migration. Stable-bleb cells display an invariant polarized balloon-like shape with exceptional migration speed and persistence. Progenitor cells can be reversibly transformed into stable-bleb cells irrespective of their primary fate and motile characteristics by increasing myosin II activity through biochemical or mechanical stimuli. Using a combination of theory and experiments, we show that, in stable-bleb cells, cortical contractility fluctuations trigger a stochastic switch into amoeboid motility, and a positive feedback between cortical flows and gradients in contractility maintains stable-bleb cell polarization. We further show that rearward cortical flows drive stable-bleb cell migration in various adhesive and non-adhesive environments, unraveling a highly versatile amoeboid migration phenotype.}, author = {Ruprecht, Verena and Wieser, Stefan and Callan Jones, Andrew and Smutny, Michael and Morita, Hitoshi and Sako, Keisuke and Barone, Vanessa and Ritsch Marte, Monika and Sixt, Michael K and Voituriez, Raphaël and Heisenberg, Carl-Philipp J}, journal = {Cell}, number = {4}, pages = {673 -- 685}, publisher = {Cell Press}, title = {{Cortical contractility triggers a stochastic switch to fast amoeboid cell motility}}, doi = {10.1016/j.cell.2015.01.008}, volume = {160}, year = {2015}, } @article{1553, abstract = {Cell movement has essential functions in development, immunity, and cancer. Various cell migration patterns have been reported, but no general rule has emerged so far. Here, we show on the basis of experimental data in vitro and in vivo that cell persistence, which quantifies the straightness of trajectories, is robustly coupled to cell migration speed. We suggest that this universal coupling constitutes a generic law of cell migration, which originates in the advection of polarity cues by an actin cytoskeleton undergoing flows at the cellular scale. Our analysis relies on a theoretical model that we validate by measuring the persistence of cells upon modulation of actin flow speeds and upon optogenetic manipulation of the binding of an actin regulator to actin filaments. Beyond the quantitative prediction of the coupling, the model yields a generic phase diagram of cellular trajectories, which recapitulates the full range of observed migration patterns.}, author = {Maiuri, Paolo and Rupprecht, Jean and Wieser, Stefan and Ruprecht, Verena and Bénichou, Olivier and Carpi, Nicolas and Coppey, Mathieu and De Beco, Simon and Gov, Nir and Heisenberg, Carl-Philipp J and Lage Crespo, Carolina and Lautenschlaeger, Franziska and Le Berre, Maël and Lennon Duménil, Ana and Raab, Matthew and Thiam, Hawa and Piel, Matthieu and Sixt, Michael K and Voituriez, Raphaël}, journal = {Cell}, number = {2}, pages = {374 -- 386}, publisher = {Cell Press}, title = {{Actin flows mediate a universal coupling between cell speed and cell persistence}}, doi = {10.1016/j.cell.2015.01.056}, volume = {161}, year = {2015}, } @article{1560, abstract = {Stromal cells in the subcapsular sinus of the lymph node 'decide' which cells and molecules are allowed access to the deeper parenchyma. The glycoprotein PLVAP is a crucial component of this selector function.}, author = {Hons, Miroslav and Sixt, Michael K}, journal = {Nature Immunology}, number = {4}, pages = {338 -- 340}, publisher = {Nature Publishing Group}, title = {{The lymph node filter revealed}}, doi = {10.1038/ni.3126}, volume = {16}, year = {2015}, } @article{1561, abstract = {Replication-deficient recombinant adenoviruses are potent vectors for the efficient transient expression of exogenous genes in resting immune cells. However, most leukocytes are refractory to efficient adenoviral transduction as they lack expression of the coxsackie/adenovirus receptor (CAR). To circumvent this obstacle, we generated the R26/CAG-CARΔ1StopF (where R26 is ROSA26 and CAG is CMV early enhancer/chicken β actin promoter) knock-in mouse line. This strain allows monitoring of in situ Cre recombinase activity through expression of CARΔ1. Simultaneously, CARΔ1 expression permits selective and highly efficient adenoviral transduction of immune cell populations, such as mast cells or T cells, directly ex vivo in bulk cultures without prior cell purification or activation. Furthermore, we show that CARΔ1 expression dramatically improves adenoviral infection of in vitro differentiated conventional and plasmacytoid dendritic cells (DCs), basophils, mast cells, as well as Hoxb8-immortalized hematopoietic progenitor cells. This novel dual function mouse strain will hence be a valuable tool to rapidly dissect the function of specific genes in leukocyte physiology.}, author = {Heger, Klaus and Kober, Maike and Rieß, David and Drees, Christoph and De Vries, Ingrid and Bertossi, Arianna and Roers, Axel and Sixt, Michael K and Schmidt Supprian, Marc}, journal = {European Journal of Immunology}, number = {6}, pages = {1614 -- 1620}, publisher = {Wiley}, title = {{A novel Cre recombinase reporter mouse strain facilitates selective and efficient infection of primary immune cells with adenoviral vectors}}, doi = {10.1002/eji.201545457}, volume = {45}, year = {2015}, }