@inbook{14848, abstract = {Regulating protein states is considered the core function of chaperones. However, despite their importance to all major cellular processes, the conformational changes that chaperones impart on polypeptide chains are difficult to study directly due to their heterogeneous, dynamic, and multi-step nature. Here, we review recent advances towards this aim using single-molecule manipulation methods, which are rapidly revealing new mechanisms of conformational control and helping to define a different perspective on the chaperone function.}, author = {Wruck, F. and Avellaneda Sarrió, Mario and Naqvi, M. M. and Koers, E. J. and Till, K. and Gross, L. and Moayed, F. and Roland, A. and Heling, L. W. H. J. and Mashaghi, A. and Tans, S. J.}, booktitle = {Biophysics of Molecular Chaperones}, editor = {Hiller, Sebastian and Liu, Maili and He, Lichun}, isbn = {9781839162824}, pages = {278--318}, publisher = {Royal Society of Chemistry}, title = {{Probing Single Chaperone Substrates}}, doi = {10.1039/bk9781839165986-00278}, volume = {29}, year = {2023}, } @article{9794, abstract = {Lymph nodes (LNs) comprise two main structural elements: fibroblastic reticular cells that form dedicated niches for immune cell interaction and capsular fibroblasts that build a shell around the organ. Immunological challenge causes LNs to increase more than tenfold in size within a few days. Here, we characterized the biomechanics of LN swelling on the cellular and organ scale. We identified lymphocyte trapping by influx and proliferation as drivers of an outward pressure force, causing fibroblastic reticular cells of the T-zone (TRCs) and their associated conduits to stretch. After an initial phase of relaxation, TRCs sensed the resulting strain through cell matrix adhesions, which coordinated local growth and remodeling of the stromal network. While the expanded TRC network readopted its typical configuration, a massive fibrotic reaction of the organ capsule set in and countered further organ expansion. Thus, different fibroblast populations mechanically control LN swelling in a multitier fashion.}, author = {Assen, Frank P and Abe, Jun and Hons, Miroslav and Hauschild, Robert and Shamipour, Shayan and Kaufmann, Walter and Costanzo, Tommaso and Krens, Gabriel and Brown, Markus and Ludewig, Burkhard and Hippenmeyer, Simon and Heisenberg, Carl-Philipp J and Weninger, Wolfgang and Hannezo, Edouard B and Luther, Sanjiv A. and Stein, Jens V. and Sixt, Michael K}, issn = {1529-2916}, journal = {Nature Immunology}, pages = {1246--1255}, publisher = {Springer Nature}, title = {{Multitier mechanics control stromal adaptations in swelling lymph nodes}}, doi = {10.1038/s41590-022-01257-4}, volume = {23}, year = {2022}, } @article{11588, abstract = {Visualizing cell behavior and effector function on a single cell level has been crucial for understanding key aspects of mammalian biology. Due to their small size, large number and rapid recruitment into thrombi, there is a lack of data on fate and behavior of individual platelets in thrombosis and hemostasis. Here we report the use of platelet lineage restricted multi-color reporter mouse strains to delineate platelet function on a single cell level. We show that genetic labeling allows for single platelet and megakaryocyte (MK) tracking and morphological analysis in vivo and in vitro, while not affecting lineage functions. Using Cre-driven Confetti expression, we provide insights into temporal gene expression patterns as well as spatial clustering of MK in the bone marrow. In the vasculature, shape analysis of activated platelets recruited to thrombi identifies ubiquitous filopodia formation with no evidence of lamellipodia formation. Single cell tracking in complex thrombi reveals prominent myosin-dependent motility of platelets and highlights thrombus formation as a highly dynamic process amenable to modification and intervention of the acto-myosin cytoskeleton. Platelet function assays combining flow cytrometry, as well as in vivo, ex vivo and in vitro imaging show unaltered platelet functions of multicolor reporter mice compared to wild-type controls. In conclusion, platelet lineage multicolor reporter mice prove useful in furthering our understanding of platelet and MK biology on a single cell level.}, author = {Nicolai, Leo and Kaiser, Rainer and Escaig, Raphael and Hoffknecht, Marie Louise and Anjum, Afra and Leunig, Alexander and Pircher, Joachim and Ehrlich, Andreas and Lorenz, Michael and Ishikawa-Ankerhold, Hellen and Aird, William C. and Massberg, Steffen and Gärtner, Florian R}, issn = {1592-8721}, journal = {Haematologica}, number = {7}, pages = {1669--1680}, publisher = {Ferrata Storti Foundation}, title = {{Single platelet and megakaryocyte morpho-dynamics uncovered by multicolor reporter mouse strains in vitro and in vivo}}, doi = {10.3324/haematol.2021.278896}, volume = {107}, year = {2022}, } @article{11843, abstract = {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 mouse dendritic cells (DCs) as a 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 the pathogenic strain CFT073 to CD14 reduced DC migration by overactivation of integrins and blunted expression of co-stimulatory molecules by overactivating the NFAT (nuclear factor of activated T-cells) pathway, both rate-limiting factors of T cell activation. This response was binary at the single-cell level, but averaged in larger populations exposed to both piliated and non-piliated pathogens, presumably via the exchange of immunomodulatory cytokines. 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.}, author = {Tomasek, Kathrin and Leithner, Alexander F and Glatzová, Ivana and Lukesch, Michael S. and Guet, Calin C and Sixt, Michael K}, issn = {2050-084X}, journal = {eLife}, publisher = {eLife Sciences Publications}, title = {{Type 1 piliated uropathogenic Escherichia coli hijack the host immune response by binding to CD14}}, doi = {10.7554/eLife.78995}, volume = {11}, year = {2022}, } @article{12085, abstract = {Molecular catch bonds are ubiquitous in biology and essential for processes like leucocyte extravasion1 and cellular mechanosensing2. Unlike normal (slip) bonds, catch bonds strengthen under tension. The current paradigm is that this feature provides ‘strength on demand3’, thus enabling cells to increase rigidity under stress1,4,5,6. However, catch bonds are often weaker than slip bonds because they have cryptic binding sites that are usually buried7,8. Here we show that catch bonds render reconstituted cytoskeletal actin networks stronger than slip bonds, even though the individual bonds are weaker. Simulations show that slip bonds remain trapped in stress-free areas, whereas weak binding allows catch bonds to mitigate crack initiation by moving to high-tension areas. This ‘dissociation on demand’ explains how cells combine mechanical strength with the adaptability required for shape change, and is relevant to diseases where catch bonding is compromised7,9, including focal segmental glomerulosclerosis10 caused by the α-actinin-4 mutant studied here. We surmise that catch bonds are the key to create life-like materials.}, author = {Mulla, Yuval and Avellaneda Sarrió, Mario and Roland, Antoine and Baldauf, Lucia and Jung, Wonyeong and Kim, Taeyoon and Tans, Sander J. and Koenderink, Gijsje H.}, issn = {1476-4660}, journal = {Nature Materials}, number = {9}, pages = {1019--1023}, publisher = {Springer Nature}, title = {{Weak catch bonds make strong networks}}, doi = {10.1038/s41563-022-01288-0}, volume = {21}, year = {2022}, } @article{12119, abstract = {Intravascular neutrophils and platelets collaborate in maintaining host integrity, but their interaction can also trigger thrombotic complications. We report here that cooperation between neutrophil and platelet lineages extends to the earliest stages of platelet formation by megakaryocytes in the bone marrow. Using intravital microscopy, we show that neutrophils “plucked” intravascular megakaryocyte extensions, termed proplatelets, to control platelet production. Following CXCR4-CXCL12-dependent migration towards perisinusoidal megakaryocytes, plucking neutrophils actively pulled on proplatelets and triggered myosin light chain and extracellular-signal-regulated kinase activation through reactive oxygen species. By these mechanisms, neutrophils accelerate proplatelet growth and facilitate continuous release of platelets in steady state. Following myocardial infarction, plucking neutrophils drove excessive release of young, reticulated platelets and boosted the risk of recurrent ischemia. Ablation of neutrophil plucking normalized thrombopoiesis and reduced recurrent thrombosis after myocardial infarction and thrombus burden in venous thrombosis. We establish neutrophil plucking as a target to reduce thromboischemic events.}, author = {Petzold, Tobias and Zhang, Zhe and Ballesteros, Iván and Saleh, Inas and Polzin, Amin and Thienel, Manuela and Liu, Lulu and Ul Ain, Qurrat and Ehreiser, Vincent and Weber, Christian and Kilani, Badr and Mertsch, Pontus and Götschke, Jeremias and Cremer, Sophie and Fu, Wenwen and Lorenz, Michael and Ishikawa-Ankerhold, Hellen and Raatz, Elisabeth and El-Nemr, Shaza and Görlach, Agnes and Marhuenda, Esther and Stark, Konstantin and Pircher, Joachim and Stegner, David and Gieger, Christian and Schmidt-Supprian, Marc and Gärtner, Florian R and Almendros, Isaac and Kelm, Malte and Schulz, Christian and Hidalgo, Andrés and Massberg, Steffen}, issn = {1074-7613}, journal = {Immunity}, keywords = {Infectious Diseases, Immunology, Immunology and Allergy}, number = {12}, pages = {2285--2299.e7}, publisher = {Elsevier}, title = {{Neutrophil “plucking” on megakaryocytes drives platelet production and boosts cardiovascular disease}}, doi = {10.1016/j.immuni.2022.10.001}, volume = {55}, year = {2022}, } @article{12133, abstract = {Social distancing is an effective way to prevent the spread of disease in societies, whereas infection elimination is a key element of organismal immunity. Here, we discuss how the study of social insects such as ants — which form a superorganism of unconditionally cooperative individuals and thus represent a level of organization that is intermediate between a classical society of individuals and an organism of cells — can help to determine common principles of disease defence across levels of organization.}, author = {Cremer, Sylvia and Sixt, Michael K}, issn = {1474-1741}, journal = {Nature Reviews Immunology}, keywords = {Energy Engineering and Power Technology, Fuel Technology}, number = {12}, pages = {713--714}, publisher = {Springer Nature}, title = {{Principles of disease defence in organisms, superorganisms and societies}}, doi = {10.1038/s41577-022-00797-y}, volume = {22}, year = {2022}, } @article{12272, abstract = {Reading, interpreting and crawling along gradients of chemotactic cues is one of the most complex questions in cell biology. In this issue, Georgantzoglou et al. (2022. J. Cell. Biol.https://doi.org/10.1083/jcb.202103207) use in vivo models to map the temporal sequence of how neutrophils respond to an acutely arising gradient of chemoattractant.}, author = {Stopp, Julian A and Sixt, Michael K}, issn = {1540-8140}, journal = {Journal of Cell Biology}, keywords = {Cell Biology}, number = {8}, publisher = {Rockefeller University Press}, title = {{Plan your trip before you leave: The neutrophils’ search-and-run journey}}, doi = {10.1083/jcb.202206127}, volume = {221}, year = {2022}, } @article{10703, abstract = {When crawling through the body, leukocytes often traverse tissues that are densely packed with extracellular matrix and other cells, and this raises the question: How do leukocytes overcome compressive mechanical loads? Here, we show that the actin cortex of leukocytes is mechanoresponsive and that this responsiveness requires neither force sensing via the nucleus nor adhesive interactions with a substrate. Upon global compression of the cell body as well as local indentation of the plasma membrane, Wiskott-Aldrich syndrome protein (WASp) assembles into dot-like structures, providing activation platforms for Arp2/3 nucleated actin patches. These patches locally push against the external load, which can be obstructing collagen fibers or other cells, and thereby create space to facilitate forward locomotion. We show in vitro and in vivo that this WASp function is rate limiting for ameboid leukocyte migration in dense but not in loose environments and is required for trafficking through diverse tissues such as skin and lymph nodes.}, author = {Gaertner, Florian and Reis-Rodrigues, Patricia and De Vries, Ingrid and Hons, Miroslav and Aguilera, Juan and Riedl, Michael and Leithner, Alexander F and Tasciyan, Saren and Kopf, Aglaja and Merrin, Jack and Zheden, Vanessa and Kaufmann, Walter and Hauschild, Robert and Sixt, Michael K}, issn = {1878-1551}, journal = {Developmental Cell}, number = {1}, pages = {47--62.e9}, publisher = {Cell Press ; Elsevier}, title = {{WASp triggers mechanosensitive actin patches to facilitate immune cell migration in dense tissues}}, doi = {10.1016/j.devcel.2021.11.024}, volume = {57}, year = {2022}, } @phdthesis{12401, abstract = {Detachment of the cancer cells from the bulk of the tumor is the first step of metastasis, which is the primary cause of cancer related deaths. It is unclear, which factors contribute to this step. Recent studies indicate a crucial role of the tumor microenvironment in malignant transformation and metastasis. Studying cancer cell invasion and detachments quantitatively in the context of its physiological microenvironment is technically challenging. Especially, precise control of microenvironmental properties in vivo is currently not possible. Here, I studied the role of microenvironment geometry in the invasion and detachment of cancer cells from the bulk with a simplistic and reductionist approach. In this approach, I engineered microfluidic devices to mimic a pseudo 3D extracellular matrix environment, where I was able to quantitatively tune the geometrical configuration of the microenvironment and follow tumor cells with fluorescence live imaging. To aid quantitative analysis I developed a widely applicable software application to automatically analyze and visualize particle tracking data. Quantitative analysis of tumor cell invasion in isotropic and anisotropic microenvironments showed that heterogeneity in the microenvironment promotes faster invasion and more frequent detachment of cells. These observations correlated with overall higher speed of cells at the edge of the bulk of the cells. In heterogeneous microenvironments cells preferentially passed through larger pores, thus invading areas of least resistance and generating finger-like invasive structures. The detachments occurred mostly at the tips of these structures. To investigate the potential mechanism, we established a two dimensional model to simulate active Brownian particles representing the cell nuclei dynamics. These simulations backed our in vitro observations without the need of precise fitting the simulation parameters. Our model suggests the importance of the pore heterogeneity in the direction perpendicular to the orientation of bias field (lateral heterogeneity), which causes the interface roughening.}, author = {Tasciyan, Saren}, issn = {2663-337X}, pages = {105}, publisher = {Institute of Science and Technology Austria}, title = {{Role of microenvironment heterogeneity in cancer cell invasion}}, doi = {10.15479/at:ista:12401}, year = {2022}, }