TY - JOUR AB - Dendritic cells (DCs) are crucial for the priming of naive T cells and the initiation of adaptive immunity. Priming is initiated at a heterologous cell–cell contact, the immunological synapse (IS). While it is established that F-actin dynamics regulates signaling at the T cell side of the contact, little is known about the cytoskeletal contribution on the DC side. Here, we show that the DC actin cytoskeleton is decisive for the formation of a multifocal synaptic structure, which correlates with T cell priming efficiency. DC actin at the IS appears in transient foci that are dynamized by the WAVE regulatory complex (WRC). The absence of the WRC in DCs leads to stabilized contacts with T cells, caused by an increase in ICAM1-integrin–mediated cell–cell adhesion. This results in lower numbers of activated and proliferating T cells, demonstrating an important role for DC actin in the regulation of immune synapse functionality. AU - Leithner, Alexander F AU - Altenburger, LM AU - Hauschild, R AU - Assen, Frank P AU - Rottner, K AU - TEB, Stradal AU - Diz-Muñoz, A AU - Stein, JV AU - Sixt, Michael K ID - 9094 IS - 4 JF - Journal of Cell Biology SN - 0021-9525 TI - Dendritic cell actin dynamics control contact duration and priming efficiency at the immunological synapse VL - 220 ER - TY - JOUR AB - De novo loss of function mutations in the ubiquitin ligase-encoding gene Cullin3 lead to autism spectrum disorder (ASD). In mouse, constitutive haploinsufficiency leads to motor coordination deficits as well as ASD-relevant social and cognitive impairments. However, induction of Cul3 haploinsufficiency later in life does not lead to ASD-relevant behaviors, pointing to an important role of Cul3 during a critical developmental window. Here we show that Cul3 is essential to regulate neuronal migration and, therefore, constitutive Cul3 heterozygous mutant mice display cortical lamination abnormalities. At the molecular level, we found that Cul3 controls neuronal migration by tightly regulating the amount of Plastin3 (Pls3), a previously unrecognized player of neural migration. Furthermore, we found that Pls3 cell-autonomously regulates cell migration by regulating actin cytoskeleton organization, and its levels are inversely proportional to neural migration speed. Finally, we provide evidence that cellular phenotypes associated with autism-linked gene haploinsufficiency can be rescued by transcriptional activation of the intact allele in vitro, offering a proof of concept for a potential therapeutic approach for ASDs. AU - Morandell, Jasmin AU - Schwarz, Lena A AU - Basilico, Bernadette AU - Tasciyan, Saren AU - Dimchev, Georgi A AU - Nicolas, Armel AU - Sommer, Christoph M AU - Kreuzinger, Caroline AU - Dotter, Christoph AU - Knaus, Lisa AU - Dobler, Zoe AU - Cacci, Emanuele AU - Schur, Florian KM AU - Danzl, Johann G AU - Novarino, Gaia ID - 9429 IS - 1 JF - Nature Communications KW - General Biochemistry KW - Genetics and Molecular Biology TI - Cul3 regulates cytoskeleton protein homeostasis and cell migration during a critical window of brain development VL - 12 ER - TY - THES AB - Bacteria-host interactions represent a continuous trade-off between benefit and risk. Thus, the host immune response is faced with a non-trivial problem – accommodate beneficial commensals and remove harmful pathogens. This is especially difficult as molecular patterns, such as lipopolysaccharide or specific surface organelles such as pili, are conserved in both, commensal and pathogenic bacteria. Type 1 pili, tightly regulated by phase variation, are considered an important virulence factor of pathogenic bacteria as they facilitate invasion into host cells. While invasion represents a de facto passive mechanism for pathogens to escape the host immune response, we demonstrate a fundamental role of type 1 pili as active modulators of the innate and adaptive immune response. AU - Tomasek, Kathrin ID - 10307 SN - 2663-337X TI - Pathogenic Escherichia coli hijack the host immune response ER - TY - GEN AB - A key attribute of persistent or recurring bacterial infections is the ability of the pathogen to evade the host’s immune response. Many Enterobacteriaceae express type 1 pili, a pre-adapted virulence trait, to invade host epithelial cells and establish persistent infections. However, the molecular mechanisms and strategies by which bacteria actively circumvent the immune response of the host remain poorly understood. Here, we identified CD14, the major co-receptor for lipopolysaccharide detection, on dendritic cells as a previously undescribed binding partner of FimH, the protein located at the tip of the type 1 pilus of Escherichia coli. The FimH amino acids involved in CD14 binding are highly conserved across pathogenic and non-pathogenic strains. Binding of pathogenic bacteria to CD14 lead to reduced dendritic cell migration and blunted expression of co-stimulatory molecules, both rate-limiting factors of T cell activation. While defining an active molecular mechanism of immune evasion by pathogens, the interaction between FimH and CD14 represents a potential target to interfere with persistent and recurrent infections, such as urinary tract infections or Crohn’s disease. AU - Tomasek, Kathrin AU - Leithner, Alexander F AU - Glatzová, Ivana AU - Lukesch, Michael S. AU - Guet, Calin C AU - Sixt, Michael K ID - 10316 T2 - bioRxiv TI - Type 1 piliated uropathogenic Escherichia coli hijack the host immune response by binding to CD14 ER - TY - JOUR AB - T lymphocytes utilize amoeboid migration to navigate effectively within complex microenvironments. The precise rearrangement of the actin cytoskeleton required for cellular forward propulsion is mediated by actin regulators, including the actin‐related protein 2/3 (Arp2/3) complex, a macromolecular machine that nucleates branched actin filaments at the leading edge. The consequences of modulating Arp2/3 activity on the biophysical properties of the actomyosin cortex and downstream T cell function are incompletely understood. We report that even a moderate decrease of Arp3 levels in T cells profoundly affects actin cortex integrity. Reduction in total F‐actin content leads to reduced cortical tension and disrupted lamellipodia formation. Instead, in Arp3‐knockdown cells, the motility mode is dominated by blebbing migration characterized by transient, balloon‐like protrusions at the leading edge. Although this migration mode seems to be compatible with interstitial migration in three‐dimensional environments, diminished locomotion kinetics and impaired cytotoxicity interfere with optimal T cell function. These findings define the importance of finely tuned, Arp2/3‐dependent mechanophysical membrane integrity in cytotoxic effector T lymphocyte activities. AU - Obeidy, Peyman AU - Ju, Lining A. AU - Oehlers, Stefan H. AU - Zulkhernain, Nursafwana S. AU - Lee, Quintin AU - Galeano Niño, Jorge L. AU - Kwan, Rain Y.Q. AU - Tikoo, Shweta AU - Cavanagh, Lois L. AU - Mrass, Paulus AU - Cook, Adam J.L. AU - Jackson, Shaun P. AU - Biro, Maté AU - Roediger, Ben AU - Sixt, Michael K AU - Weninger, Wolfgang ID - 7234 IS - 2 JF - Immunology and Cell Biology SN - 08189641 TI - Partial loss of actin nucleator actin-related protein 2/3 activity triggers blebbing in primary T lymphocytes VL - 98 ER - TY - JOUR AB - A two-dimensional mathematical model for cells migrating without adhesion capabilities is presented and analyzed. Cells are represented by their cortex, which is modeled as an elastic curve, subject to an internal pressure force. Net polymerization or depolymerization in the cortex is modeled via local addition or removal of material, driving a cortical flow. The model takes the form of a fully nonlinear degenerate parabolic system. An existence analysis is carried out by adapting ideas from the theory of gradient flows. Numerical simulations show that these simple rules can account for the behavior observed in experiments, suggesting a possible mechanical mechanism for adhesion-independent motility. AU - Jankowiak, Gaspard AU - Peurichard, Diane AU - Reversat, Anne AU - Schmeiser, Christian AU - Sixt, Michael K ID - 7623 IS - 3 JF - Mathematical Models and Methods in Applied Sciences SN - 02182025 TI - Modeling adhesion-independent cell migration VL - 30 ER - TY - JOUR AB - Cells navigating through complex tissues face a fundamental challenge: while multiple protrusions explore different paths, the cell needs to avoid entanglement. How a cell surveys and then corrects its own shape is poorly understood. Here, we demonstrate that spatially distinct microtubule dynamics regulate amoeboid cell migration by locally promoting the retraction of protrusions. In migrating dendritic cells, local microtubule depolymerization within protrusions remote from the microtubule organizing center triggers actomyosin contractility controlled by RhoA and its exchange factor Lfc. Depletion of Lfc leads to aberrant myosin localization, thereby causing two effects that rate-limit locomotion: (1) impaired cell edge coordination during path finding and (2) defective adhesion resolution. Compromised shape control is particularly hindering in geometrically complex microenvironments, where it leads to entanglement and ultimately fragmentation of the cell body. We thus demonstrate that microtubules can act as a proprioceptive device: they sense cell shape and control actomyosin retraction to sustain cellular coherence. AU - Kopf, Aglaja AU - Renkawitz, Jörg AU - Hauschild, Robert AU - Girkontaite, Irute AU - Tedford, Kerry AU - Merrin, Jack AU - Thorn-Seshold, Oliver AU - Trauner, Dirk AU - Häcker, Hans AU - Fischer, Klaus Dieter AU - Kiermaier, Eva AU - Sixt, Michael K ID - 7875 IS - 6 JF - The Journal of Cell Biology TI - Microtubules control cellular shape and coherence in amoeboid migrating cells VL - 219 ER - TY - JOUR AB - In contrast to lymph nodes, the lymphoid regions of the spleen—the white pulp—are located deep within the organ, yielding the trafficking paths of T cells in the white pulp largely invisible. In an intravital microscopy tour de force reported in this issue of Immunity, Chauveau et al. show that T cells perform unidirectional, perivascular migration through the enigmatic marginal zone bridging channels. AU - Sixt, Michael K AU - Lämmermann, Tim ID - 7876 IS - 5 JF - Immunity SN - 10747613 TI - T cells: Bridge-and-channel commute to the white pulp VL - 52 ER - TY - JOUR AB - Cell migration entails networks and bundles of actin filaments termed lamellipodia and microspikes or filopodia, respectively, as well as focal adhesions, all of which recruit Ena/VASP family members hitherto thought to antagonize efficient cell motility. However, we find these proteins to act as positive regulators of migration in different murine cell lines. CRISPR/Cas9-mediated loss of Ena/VASP proteins reduced lamellipodial actin assembly and perturbed lamellipodial architecture, as evidenced by changed network geometry as well as reduction of filament length and number that was accompanied by abnormal Arp2/3 complex and heterodimeric capping protein accumulation. Loss of Ena/VASP function also abolished the formation of microspikes normally embedded in lamellipodia, but not of filopodia capable of emanating without lamellipodia. Ena/VASP-deficiency also impaired integrin-mediated adhesion accompanied by reduced traction forces exerted through these structures. Our data thus uncover novel Ena/VASP functions of these actin polymerases that are fully consistent with their promotion of cell migration. AU - Damiano-Guercio, Julia AU - Kurzawa, Laëtitia AU - Müller, Jan AU - Dimchev, Georgi A AU - Schaks, Matthias AU - Nemethova, Maria AU - Pokrant, Thomas AU - Brühmann, Stefan AU - Linkner, Joern AU - Blanchoin, Laurent AU - Sixt, Michael K AU - Rottner, Klemens AU - Faix, Jan ID - 7909 JF - eLife TI - Loss of Ena/VASP interferes with lamellipodium architecture, motility and integrin-dependent adhesion VL - 9 ER - TY - JOUR AB - The WAVE regulatory complex (WRC) is crucial for assembly of the peripheral branched actin network constituting one of the main drivers of eukaryotic cell migration. Here, we uncover an essential role of the hematopoietic-specific WRC component HEM1 for immune cell development. Germline-encoded HEM1 deficiency underlies an inborn error of immunity with systemic autoimmunity, at cellular level marked by WRC destabilization, reduced filamentous actin, and failure to assemble lamellipodia. Hem1−/− mice display systemic autoimmunity, phenocopying the human disease. In the absence of Hem1, B cells become deprived of extracellular stimuli necessary to maintain the strength of B cell receptor signaling at a level permissive for survival of non-autoreactive B cells. This shifts the balance of B cell fate choices toward autoreactive B cells and thus autoimmunity. AU - Salzer, Elisabeth AU - Zoghi, Samaneh AU - Kiss, Máté G. AU - Kage, Frieda AU - Rashkova, Christina AU - Stahnke, Stephanie AU - Haimel, Matthias AU - Platzer, René AU - Caldera, Michael AU - Ardy, Rico Chandra AU - Hoeger, Birgit AU - Block, Jana AU - Medgyesi, David AU - Sin, Celine AU - Shahkarami, Sepideh AU - Kain, Renate AU - Ziaee, Vahid AU - Hammerl, Peter AU - Bock, Christoph AU - Menche, Jörg AU - Dupré, Loïc AU - Huppa, Johannes B. AU - Sixt, Michael K AU - Lomakin, Alexis AU - Rottner, Klemens AU - Binder, Christoph J. AU - Stradal, Theresia E.B. AU - Rezaei, Nima AU - Boztug, Kaan ID - 8132 IS - 49 JF - Science Immunology TI - The cytoskeletal regulator HEM1 governs B cell development and prevents autoimmunity VL - 5 ER -