@article{AlizadehradKruegerEngstleretal.2015,
  author    = {Alizadehrad, Davod and Kr{\"u}ger, Timothy and Engstler, Markus and Stark, Holger},
  title     = {Simulating the complex cell design of Trypanosoma brucei and its motility},
  series = {PLOS Computational Biology},
  volume    = {11},
  journal   = {PLOS Computational Biology},
  number    = {1},
  doi       = {10.1371/journal.pcbi.1003967},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-144610},
  pages     = {e1003967},
  year      = {2015},
  abstract  = {The flagellate Trypanosoma brucei, which causes the sleeping sickness when infecting a mammalian host, goes through an intricate life cycle. It has a rather complex propulsion mechanism and swims in diverse microenvironments. These continuously exert selective pressure, to which the trypanosome adjusts with its architecture and behavior. As a result, the trypanosome assumes a diversity of complex morphotypes during its life cycle. However, although cell biology has detailed form and function of most of them, experimental data on the dynamic behavior and development of most morphotypes is lacking. Here we show that simulation science can predict intermediate cell designs by conducting specific and controlled modifications of an accurate, nature-inspired cell model, which we developed using information from live cell analyses. The cell models account for several important characteristics of the real trypanosomal morphotypes, such as the geometry and elastic properties of the cell body, and their swimming mechanism using an eukaryotic flagellum. We introduce an elastic network model for the cell body, including bending rigidity and simulate swimming in a fluid environment, using the mesoscale simulation technique called multi-particle collision dynamics. The in silico trypanosome of the bloodstream form displays the characteristic in vivo rotational and translational motility pattern that is crucial for survival and virulence in the vertebrate host. Moreover, our model accurately simulates the trypanosome's tumbling and backward motion. We show that the distinctive course of the attached flagellum around the cell body is one important aspect to produce the observed swimming behavior in a viscous fluid, and also required to reach the maximal swimming velocity. Changing details of the flagellar attachment generates less efficient swimmers. We also simulate different morphotypes that occur during the parasite's development in the tsetse fly, and predict a flagellar course we have not been able to measure in experiments so far.},
  language  = {en}
}
@article{AlsheimerLinkLeubneretal.2014,
  author    = {Alsheimer, Manfred and Link, Jana and Leubner, Monika and Schmitt, Johannes and G{\"o}b, Eva and Benavente, Ricardo and Jeang, Kuan-Teh and Xu, Rener},
  title     = {Analysis of Meiosis in SUN1 Deficient Mice Reveals a Distinct Role of SUN2 in Mammalian Meiotic LINC Complex Formation and Function},
  doi       = {10.1371/journal.pgen.1004099},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-111355},
  year      = {2014},
  abstract  = {LINC complexes are evolutionarily conserved nuclear envelope bridges, composed of SUN (Sad-1/UNC-84) and KASH (Klarsicht/ANC-1/Syne/homology) domain proteins. They are crucial for nuclear positioning and nuclear shape determination, and also mediate nuclear envelope (NE) attachment of meiotic telomeres, essential for driving homolog synapsis and recombination. In mice, SUN1 and SUN2 are the only SUN domain proteins expressed during meiosis, sharing their localization with meiosis-specific KASH5. Recent studies have shown that loss of SUN1 severely interferes with meiotic processes. Absence of SUN1 provokes defective telomere attachment and causes infertility. Here, we report that meiotic telomere attachment is not entirely lost in mice deficient for SUN1, but numerous telomeres are still attached to the NE through SUN2/KASH5-LINC complexes. In Sun12/2 meiocytes attached telomeres retained the capacity to form bouquetlike clusters. Furthermore, we could detect significant numbers of late meiotic recombination events in Sun12/2 mice. Together, this indicates that even in the absence of SUN1 telomere attachment and their movement within the nuclear envelope per se can be functional. Author summary: Correct genome haploidization during meiosis requires tightly regulated chromosome movements that follow a highly conserved choreography during prophase I. Errors in these movements cause subsequent meiotic defects, which typically lead to infertility. At the beginning of meiotic prophase, chromosome ends are tethered to the nuclear envelope (NE). This attachment of telomeres appears to be mediated by well-conserved membrane spanning protein complexes within the NE (LINC complexes). In mouse meiosis, the two main LINC components SUN1 and SUN2 were independently described to localize at the sites of telomere attachment. While SUN1 has been demonstrated to be critical for meiotic telomere attachment, the precise role of SUN2 in this context, however, has been discussed controversially in the field. Our current study was targeted to determine the factual capacity of SUN2 in telomere attachment and chromosome movements in SUN1 deficient mice. Remarkably, although telomere attachment is impaired in the absence of SUN1, we could find a yet undescribed SUN1-independent telomere attachment, which presumably is mediated by SUN2 and KASH5. This SUN2 mediated telomere attachment is stable throughout prophase I and functional in moving telomeres within the NE. Thus, our results clearly indicate that SUN1 and SUN2, at least partially, fulfill redundant meiotic functions.},
  language  = {en}
}
@article{AvotaGassertSchneiderSchaulies2011,
  author    = {Avota, Elita and Gassert, Evelyn and Schneider-Schaulies, Sibylle},
  title     = {Cytoskeletal Dynamics: Concepts in Measles Virus Replication and Immunomodulation},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-69092},
  year      = {2011},
  abstract  = {In common with most viruses, measles virus (MV) relies on the integrity of the cytoskeleton of its host cells both with regard to efficient replication in these cells, but also retention of their motility which favors viral dissemination. It is, however, the surface interaction of the viral glycoprotein (gp) complex with receptors present on lymphocytes and dendritic cells (DCs), that signals effective initiation of host cell cytoskeletal dynamics. For DCs, these may act to regulate processes as diverse as viral uptake and sorting, but also the ability of these cells to successfully establish and maintain functional immune synapses (IS) with T cells. In T cells, MV signaling causes actin cytoskeletal paralysis associated with a loss of polarization, adhesion and motility, which has been linked to activation of sphingomyelinases and subsequent accumulation of membrane ceramides. MV modulation of both DC and T cell cytoskeletal dynamics may be important for the understanding of MV immunosuppression at the cellular level.},
  subject      = {Virologie},
  language  = {en}
}
@article{BogdanSchultzGrosshans2013,
  author    = {Bogdan, Sven and Schultz, J{\"o}rg and Grosshans, J{\"o}rg},
  title     = {Formin' cellular structures: Physiological roles of Diaphanous (Dia) in actin dynamics},
  series = {Communicative \& Integrative Biology},
  volume    = {6},
  journal   = {Communicative \& Integrative Biology},
  number    = {e27634},
  doi       = {10.4161/cib.27634},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-121305},
  year      = {2013},
  abstract  = {Members of the Diaphanous (Dia) protein family are key regulators of fundamental actin driven cellular processes, which are conserved from yeast to humans. Researchers have uncovered diverse physiological roles in cell morphology, cell motility, cell polarity, and cell division, which are involved in shaping cells into tissues and organs. The identification of numerous binding partners led to substantial progress in our understanding of the differential functions of Dia proteins. Genetic approaches and new microscopy techniques allow important new insights into their localization, activity, and molecular principles of regulation.},
  language  = {en}
}
@article{BrosterReixFlorimondCayreletal.2021,
  author    = {Broster Reix, Christine E. and Florimond, C{\´e}lia and Cayrel, Anne and Mailh{\´e}, Am{\´e}lie and Agnero-Rigot, Corentin and Landrein, Nicolas and Dacheux, Denis and Havlicek, Katharina and Bonhivers, M{\´e}lanie and Morriswood, Brooke and Robinson, Derrick R.},
  title     = {Bhalin, an essential cytoskeleton-associated protein of Trypanosoma brucei linking TbBILBO1 of the flagellar pocket collar with the hook complex},
  series = {Microorganisms},
  volume    = {9},
  journal   = {Microorganisms},
  number    = {11},
  issn      = {2076-2607},
  doi       = {10.3390/microorganisms9112334},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-250301},
  year      = {2021},
  abstract  = {Background: In most trypanosomes, endo and exocytosis only occur at a unique organelle called the flagellar pocket (FP) and the flagellum exits the cell via the FP. Investigations of essential cytoskeleton-associated structures located at this site have revealed a number of essential proteins. The protein TbBILBO1 is located at the neck of the FP in a structure called the flagellar pocket collar (FPC) and is essential for biogenesis of the FPC and parasite survival. TbMORN1 is a protein that is present on a closely linked structure called the hook complex (HC) and is located anterior to and overlapping the collar. TbMORN1 is essential in the bloodstream form of T. brucei. We now describe the location and function of BHALIN, an essential, new FPC-HC protein. Methodology/Principal Findings: Here, we show that a newly characterised protein, BHALIN (BILBO1 Hook Associated LINker protein), is localised to both the FPC and HC and has a TbBILBO1 binding domain, which was confirmed in vitro. Knockdown of BHALIN by RNAi in the bloodstream form parasites led to cell death, indicating an essential role in cell viability. Conclusions/Significance: Our results demonstrate the essential role of a newly characterised hook complex protein, BHALIN, that influences flagellar pocket organisation and function in bloodstream form T. brucei parasites.},
  language  = {en}
}
@article{ButtHowardRaman2022,
  author    = {Butt, Elke and Howard, Cory M. and Raman, Dayanidhi},
  title     = {LASP1 in cellular signaling and gene expression: more than just a cytoskeletal regulator},
  series = {Cells},
  volume    = {11},
  journal   = {Cells},
  number    = {23},
  issn      = {2073-4409},
  doi       = {10.3390/cells11233817},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-297447},
  year      = {2022},
  abstract  = {LIM and SH3 protein 1 was originally identified as a structural cytoskeletal protein with scaffolding function. However, recent data suggest additional roles in cell signaling and gene expression, especially in tumor cells. These novel functions are primarily regulated by the site-specific phosphorylation of LASP1. This review will focus on specific phosphorylation-dependent interaction between LASP1 and cellular proteins that orchestrate primary tumor progression and metastasis. More specifically, we will describe the role of LASP1 in chemokine receptor, and PI3K/AKT signaling. We outline the nuclear role for LASP1 in terms of epigenetics and transcriptional regulation and modulation of oncogenic mRNA translation. Finally, newly identified roles for the cytoskeletal function of LASP1 next to its known canonical F-actin binding properties are included.},
  language  = {en}
}
@article{FehrholzChristianPKunzmann2014,
  author    = {Fehrholz, Markus and Christian P., Speer and Kunzmann, Steffen},
  title     = {Caffeine and Rolipram Affect Smad Signalling and TGFβ1 Stimulated CTGF and Transgelin Expression in Lung Epithelial Cells},
  series = {PLoS One},
  volume    = {9},
  journal   = {PLoS One},
  number    = {5},
  doi       = {10.1371/journal.pone.0097357},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-118406},
  pages     = {e97357},
  year      = {2014},
  abstract  = {Caffeine administration is an important part of the therapeutic treatment of bronchopulmonary dysplasia (BPD) in preterm infants. However, caffeine mediated effects on airway remodelling are still undefined. The TGF-β/Smad signalling pathway is one of the key pathways involved in airway remodelling. Connective tissue growth factor (CTGF), a downstream mediator of TGF-β, and transgelin, a binding and stabilising protein of the cytoskeleton, are both regulated by TGF-b1 and play an important role in airway remodelling. Both have also been implicated in the pathogenesis of BPD. The aim of the present study was to clarify whether caffeine, an unspecific phosphodiesterase (PDE) inhibitor, and rolipram, a prototypical PDE-4 selective inhibitor, were both able to affect TGF-β1-induced Smad signalling and CTGF/transgelin expression in lung epithelial cells. Furthermore, the effect of transgelin knock-down on Smad signalling was studied. The pharmacological effect of caffeine and rolipram on Smad signalling was investigated by means of a luciferase assay via transfection of a TGFβ1- inducible reporter plasmid in A549 cells. The regulation of CTGF and transgelin expression by caffeine and rolipram were studied by promoter analysis, real-time PCR and Western blot. Endogenous transgelin expression was down-regulated by lentiviral transduction mediating transgelin-specific shRNA expression. The addition of caffeine and rolipram inhibited TGFβ1 induced reporter gene activity in a concentration-related manner. They also antagonized the TGF-b1 induced upregulation of CTGF and transgelin on the promoter-, the mRNA-, and the protein-level. Functional analysis showed that transgelin silencing reduced TGF-β1 induced Smad-signalling and CTGF induction in lung epithelial cells. The present study highlights possible new molecular mechanisms of caffeine and rolipram including an inhibition of Smad signalling and of TGF-β1 regulated genes involved in airway remodelling. An understanding of these mechanisms might help to explain the protective effects of caffeine in prevention of BPD and suggests rolipram to be a potent replacement for caffeine.},
  language  = {en}
}
@article{FoertschHuppMaetal.2011,
  author    = {F{\"o}rtsch, Christina and Hupp, Sabrina and Ma, Jiangtao and Mitchell, Timothy J. and Maier, Elke and Benz, Roland and Iliev, Asparouh I.},
  title     = {Changes in Astrocyte Shape Induced by Sublytic Concentrations of the Cholesterol-Dependent Cytolysin Pneumolysin Still Require Pore-Forming Capacity},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-69084},
  year      = {2011},
  abstract  = {Streptococcus pneumoniae is a common pathogen that causes various infections, such as sepsis and meningitis. A major pathogenic factor of S. pneumoniae is the cholesterol-dependent cytolysin, pneumolysin. It produces cell lysis at high concentrations and apoptosis at lower concentrations. We have shown that sublytic amounts of pneumolysin induce small GTPase-dependent actin cytoskeleton reorganization and microtubule stabilization in human neuroblastoma cells that are manifested by cell retraction and changes in cell shape. In this study, we utilized a live imaging approach to analyze the role of pneumolysin's pore-forming capacity in the actin-dependent cell shape changes in primary astrocytes. After the initial challenge with the wild-type toxin, a permeabilized cell population was rapidly established within 20-40 minutes. After the initial rapid permeabilization, the size of the permeabilized population remained unchanged and reached a plateau. Thus, we analyzed the non-permeabilized (non-lytic) population, which demonstrated retraction and shape changes that were inhibited by actin depolymerization. Despite the non-lytic nature of pneumolysin treatment, the toxin's lytic capacity remained critical for the initiation of cell shape changes. The non-lytic pneumolysin mutants W433F-pneumolysin and delta6-pneumolysin, which bind the cell membrane with affinities similar to that of the wild-type toxin, were not able to induce shape changes. The initiation of cell shape changes and cell retraction by the wild-type toxin were independent of calcium and sodium influx and membrane depolarization, which are known to occur following cellular challenge and suggested to result from the ion channel-like properties of the pneumolysin pores. Excluding the major pore-related phenomena as the initiation mechanism of cell shape changes, the existence of a more complex relationship between the pore-forming capacity of pneumolysin and the actin cytoskeleton reorganization is suggested.},
  subject      = {Toxikologie},
  language  = {en}
}
@article{JanevskiChohStopperetal.1993,
  author    = {Janevski, J. and Choh, V. and Stopper, Helga and Schiffmann, D. and De Boni, U.},
  title     = {Diethylstilbestrol alters the morphology and calcium levels of growth cones of PC12 cells in vitro},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-86858},
  year      = {1993},
  abstract  = {Diethylstilbestrol (DES) is a synthetic estrogen with carcinogenic properties. DES is known to alter cytoskeletal components, including the organization of actin stress fibres in C6 rat glioma cells. ln a test of the hypothesis that DES disrupts actin Filaments of growth cones in neuron-like cells, DES-induced changes in filopodial lengths were quantified in rat pheochromocytoma (PC12) cells in vitro. DES significantly altered growth cone morphology, with collapse of growth cone filopodia and neurite retraction invariably occurring at a concentration of 10 MikroM. At 5 MikroM DES, transient reductions in total filopodiallengths occurred. At DES concentrations of 0.1 nM and 1 nM, reductions in total filopodiallengths occurred in a fraction of growth cones. Evidence exists which shows that growth cone activity and morphology are intimately linked to Ieveis of intracellular, free calcium and that DES increases such levels. Measurements of free intracellular calcium levels by fluorescence microscopy, at times concurrent with the DES-induced reduction in total filopodial lengths, showed that calcium levels were indeed significantly increased by 10 MirkoM DES. Labelling of filamentaus actin (f-actin) with FITC-phalloidin showed that the f-actin distribution in growth cones exposed to DES could not be differentiated from the distribution found in spontaneously retracting growth cones. Tagether with evidence which showed that growth cone motility was not affected, the results are taken to indicate that DES, rather than acting directly on the cytoskeleton, exerts its effects indirectly, by a calcium-induced destabilization of actin filaments in the growth cone.},
  subject      = {Calcium},
  language  = {en}
}
@article{JesaitisKlotz1993,
  author    = {Jesaitis, A. J. and Klotz, Karl-Norbert},
  title     = {Cytoskeletal regulation of chemotactic receptors: Molecular complexation of N-formyl peptide receptors with G proteins and actin},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-79673},
  year      = {1993},
  abstract  = {Signal transduction via receptors for N-formylmethionyl peptide chemoattractants (FPR) on human neutrophils is a highly regulated process. It involves direct interaction of receptors with heterotrimeric G-proteins and may be under thc control of cytoskeletal clemcnts. Evidencc exists suggesting that thc cytoskeleton and/or the membrane ske1eton determines the distribution of FPR in the plane of the plasma membrane, thus controlling FPR accessibility to different protcins in functionally distinct membrane domains. In desensitized cells, FPR are restricted to domains which are depleted of G proteins but enriched in cytoskeletal proteins such as actin and fodrin. Thus, the G protein signal transduction partners of FPR become inacccssible to the agonist-occupied receptor, preventing cell activation. We are investigating the molecular basis for the interaction of FPR with the membrane skeleton, and our results suggest that FPR, and possibly other receptors, may directly bind to cytoskeletal proteins such as actin.},
  subject      = {Immunologie},
  language  = {en}
}
@article{Morriswood2015,
  author    = {Morriswood, Brooke},
  title     = {Form, fabric, and function of a flagellum-associated cytoskeletal structure.},
  series = {Cells},
  volume    = {4},
  journal   = {Cells},
  number    = {4},
  doi       = {10.3390/cells4040726},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-149467},
  pages     = {726-747},
  year      = {2015},
  abstract  = {Trypanosoma brucei is a uniflagellated protist and the causative agent of African trypanosomiasis, a neglected tropical disease. The single flagellum of T. brucei is essential to a number of cellular processes such as motility, and has been a longstanding focus of scientific enquiry. A number of cytoskeletal structures are associated with the flagellum in T. brucei, and one such structure—a multiprotein complex containing the repeat motif protein TbMORN1—is the focus of this review. The TbMORN1-containing complex, which was discovered less than ten years ago, is essential for the viability of the mammalian-infective form of T. brucei. The complex has an unusual asymmetric morphology, and is coiled around the flagellum to form a hook shape. Proteomic analysis using the proximity-dependent biotin identification (BioID) technique has elucidated a number of its components. Recent work has uncovered a role for TbMORN1 in facilitating protein entry into the cell, thus providing a link between the cytoskeleton and the endomembrane system. This review summarises the extant data on the complex, highlights the outstanding questions for future enquiry, and provides speculation as to its possible role in a size-exclusion mechanism for regulating protein entry. The review additionally clarifies the nomenclature associated with this topic, and proposes the adoption of the term "hook complex" to replace the former name "bilobe" to describe the complex.},
  language  = {en}
}
@article{NieswandtMorowskiBrachsetal.2014,
  author    = {Nieswandt, Bernhard and Morowski, Martina and Brachs, Sebastian and Mielenz, Dirk and D{\"u}tting, Sebastian},
  title     = {The Adaptor Protein Swiprosin-1/EFhd2 Is Dispensable for Platelet Function in Mice},
  doi       = {10.1371/journal.pone.0107139},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-113316},
  year      = {2014},
  abstract  = {Background Platelets are anuclear cell fragments derived from bone marrow megakaryocytes that safeguard vascular integrity, but may also cause pathological vessel occlusion. Reorganizations of the platelet cytoskeleton and agonist-induced intracellular Ca2+-mobilization are crucial for platelet hemostatic function. EF-hand domain containing 2 (EFhd2, Swiprosin-1) is a Ca2+-binding cytoskeletal adaptor protein involved in actin remodeling in different cell types, but its function in platelets is unknown. Objective Based on the described functions of EFhd2 in immune cells, we tested the hypothesis that EFhd2 is a crucial adaptor protein for platelet function acting as a regulator of Ca2+-mobilization and cytoskeletal rearrangements. Methods and Results We generated EFhd2-deficient mice and analyzed their platelets in vitro and in vivo. Efhd2-/- mice displayed normal platelet count and size, exhibited an unaltered in vivo life span and showed normal Ca2+-mobilization and activation/aggregation responses to classic agonists. Interestingly, upon stimulation of the immunoreceptor tyrosine-based activation motif-coupled receptor glycoprotein (GP) VI, Efhd2-/- platelets showed a slightly increased coagulant activity. Furthermore, absence of EFhd2 had no significant impact on integrin-mediated clot retraction, actomyosin rearrangements and spreading of activated platelets on fibrinogen. In vivo EFhd2-deficiency resulted in unaltered hemostatic function and unaffected arterial thrombus formation. Conclusion These results show that EFhd2 is not essential for platelet function in mice indicating that other cytoskeletal adaptors may functionally compensate its loss.},
  language  = {en}
}
@phdthesis{SchellergebBirkholz2020,
  author    = {Scheller [geb. Birkholz], Inga},
  title     = {Studies on the role of actin-binding proteins in platelet production and function in mice},
  doi       = {10.25972/OPUS-16858},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-168582},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2020},
  abstract  = {Platelet activation and aggregation at sites of vascular injury involves massive cytoskeletal re-organization, which is required for proper platelet function. Moreover, the cytoskeleton plays central roles in megakaryo- and thrombopoiesis. Thus, cytoskeletal protein aberrations can be the underlying reason for many pathological phenotypes. Although intensive research is carried out to identify the key players involved in cytoskeletal reorganization, the signaling cascades orchestrating these complex processes are still poorly understood. This thesis investigates the role of three actin-binding proteins, Coactosin-like (Cotl) 1, Profilin (Pfn) 1 and Thymosin (T) β4, in platelet formation and function using genetically modified mice. ADF-H-containing proteins such as Twinfilin or Cofilin are well characterized as regulators of thrombopoesis and cytoskeletal reorganization. Although Cotl1 belongs to the ADF-H protein family, lack of Cotl1 did not affect platelet count or cytoskeletal dynamics. However, Cotl1-deficiency resulted in significant protection from arterial thrombus formation and ischemic stroke in vivo. Defective GPIb-vWF interactions and altered second wave mediator release present potential reasons for the beneficial effect of Cotl1-deficiency. These results reveal an unexpected function of Cotl1 as a regulator of thrombosis and hemostasis, establishing it as a potential target for a safe therapeutic therapy to prevent arterial thrombosis or ischemic stroke. Recent studies showed that the organization of the circumferential actin cytoskeleton modulates calpain-mediated αIIbβ3 integrin closure, thereby also controlling αIIbβ3 integrin localization. The second part of this thesis identified the actin-sequestering protein Pfn1 as a central regulator of platelet integrin function as Pfn1-deficient platelets displayed almost abolished αIIbβ3 integrin signaling. This translated into a profound protection from arterial thrombus formation and prolonged tail bleeding times in vivo which was caused by enhanced calpain-dependent integrin closure. These findings further emphasize the importance of a functional actin cytoskeleton for intact platelet function in vitro and in vivo. Tβ4 is a moonlighting protein, acting as one of the major actin-sequestering proteins in cells of higher eukaryotes and exerting various paracrine functions including anti-inflammatory, immunomodulatory and pro-angiogenic effects. Although excessively studied, its role for cytoskeletal dynamics, the distinction between endo- and exogenous protein function and its uptake and release mechanisms are still poorly understood. Constitutive Tβ4-deficiency resulted in thrombocytopenia accompanied by a largely diminished G-actin pool in platelets and divergent effects on platelet reactivity. Pre-incubation of platelets with recombinant Tβ4 will help to understand the function of endo- and exogenous protein, which is under current investigation.},
  subject      = {Thrombozyt},
  language  = {en}
}
@article{ShirakashiSisarioTabanetal.2023,
  author    = {Shirakashi, Ryo and Sisario, Dmitri and Taban, Danush and Korsa, Tessa and Wanner, Sophia B. and Neubauer, Julia and Djuzenova, Cholpon S. and Zimmermann, Heiko and Sukhorukov, Vladimir L.},
  title     = {Contraction of the rigor actomyosin complex drives bulk hemoglobin expulsion from hemolyzing erythrocytes},
  series = {Biomechanics and Modeling in Mechanobiology},
  volume    = {22},
  journal   = {Biomechanics and Modeling in Mechanobiology},
  number    = {2},
  doi       = {10.1007/s10237-022-01654-6},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-325107},
  pages     = {417-432},
  year      = {2023},
  abstract  = {Erythrocyte ghost formation via hemolysis is a key event in the physiological clearance of senescent red blood cells (RBCs) in the spleen. The turnover rate of millions of RBCs per second necessitates a rapid efflux of hemoglobin (Hb) from RBCs by a not yet identified mechanism. Using high-speed video-microscopy of isolated RBCs, we show that electroporation-induced efflux of cytosolic ATP and other small solutes leads to transient cell shrinkage and echinocytosis, followed by osmotic swelling to the critical hemolytic volume. The onset of hemolysis coincided with a sudden self-propelled cell motion, accompanied by cell contraction and Hb-jet ejection. Our biomechanical model, which relates the Hb-jet-driven cell motion to the cytosolic pressure generation via elastic contraction of the RBC membrane, showed that the contributions of the bilayer and the bilayer-anchored spectrin cytoskeleton to the hemolytic cell motion are negligible. Consistent with the biomechanical analysis, our biochemical experiments, involving extracellular ATP and the myosin inhibitor blebbistatin, identify the low abundant non-muscle myosin 2A (NM2A) as the key contributor to the Hb-jet emission and fast hemolytic cell motion. Thus, our data reveal a rapid myosin-based mechanism of hemolysis, as opposed to a much slower diffusive Hb efflux.},
  language  = {en}
}
@phdthesis{Spindler2020,
  author    = {Spindler, Markus},
  title     = {The role of the adhesion and degranulation promoting adapter protein (ADAP) in platelet production},
  doi       = {10.25972/OPUS-20097},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-200977},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2020},
  abstract  = {Bone marrow (BM) megakaryocytes (MKs) produce platelets by extending proplatelets into sinusoidal blood vessels. Although this process is fundamental to maintain normal platelet counts in circulation only little is known about the regulation of directed proplatelet formation. As revealed in this thesis, ADAP (adhesion and degranulation promoting adapter protein) deficiency (constitutive as well as MK and platelet-specific) resulted in a microthrombocytopenia in mice, recapitulating the clinical hallmark of patients with mutations in the ADAP gene. The thrombocytopenia was caused by a combination of an enhanced removal of platelets from the circulation by macrophages and a platelet production defect. This defect led to an ectopic release of (pro)platelet-like particles into the bone marrow compartment, with a massive accumulation of such fragments around sinusoids. In vitro studies of cultured BM cell-derived MKs revealed a polarization defect of the demarcation membrane system, which is dependent on F-actin dynamics. ADAP-deficient MKs spread on collagen and fibronectin displayed a reduced F-actin content and podosome density in the lowest confocal plane. In addition, ADAP-deficient MKs exhibited a reduced capacity to adhere on Horm collagen and in line with that the activation of beta1-integrins in the lowest confocal plane of spread MKs was diminished. These results point to ADAP as a novel regulator of terminal platelet formation. Beside ADAP-deficient mice, three other knockout mouse models (deficiency for profilin1 (PFN1), Wiskott-Aldrich-syndrome protein (WASP) and Actin-related protein 2/3 complex subunit 2 (ARPC2)) exist, which display ectopic release of (pro)platelet-like particles. As shown in the final part of the thesis, the pattern of the ectopic release of (pro)platelet-like particles in these genetically modified mice (PFN1 and WASP) was comparable to ADAP-deficient mice. Furthermore, all tested mutant MKs displayed an adhesion defect as well as a reduced podosome density on Horm collagen. These results indicate that similar mechanisms might apply for ectopic release.},
  language  = {en}
}
@article{TarauBerlinCurcioetal.2019,
  author    = {Tarau, Ioana-Sandra and Berlin, Andreas and Curcio, Christine A. and Ach, Thomas},
  title     = {The cytoskeleton of the retinal pigment epithelium: from normal aging to age-related macular degeneration},
  series = {International Journal of Molecular Science},
  volume    = {20},
  journal   = {International Journal of Molecular Science},
  number    = {14},
  issn      = {1422-0067},
  doi       = {10.3390/ijms20143578},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-201781},
  year      = {2019},
  abstract  = {The retinal pigment epithelium (RPE) is a unique epithelium, with major roles which are essential in the visual cycle and homeostasis of the outer retina. The RPE is a monolayer of polygonal and pigmented cells strategically placed between the neuroretina and Bruch membrane, adjacent to the fenestrated capillaries of the choriocapillaris. It shows strong apical (towards photoreceptors) to basal/basolateral (towards Bruch membrane) polarization. Multiple functions are bound to a complex structure of highly organized and polarized intracellular components: the cytoskeleton. A strong connection between the intracellular cytoskeleton and extracellular matrix is indispensable to maintaining the function of the RPE and thus, the photoreceptors. Impairments of these intracellular structures and the regular architecture they maintain often result in a disrupted cytoskeleton, which can be found in many retinal diseases, including age-related macular degeneration (AMD). This review article will give an overview of current knowledge on the molecules and proteins involved in cytoskeleton formation in cells, including RPE and how the cytoskeleton is affected under stress conditions — especially in AMD.},
  language  = {en}
}
@article{VolceanovHerbstBiniosseketal.2014,
  author    = {Volceanov, Larisa and Herbst, Katharina and Biniossek, Martin and Schilling, Oliver and Haller, Dirk and N{\"o}lke, Thilo and Subbarayal, Prema and Rudel, Thomas and Zieger, Barbara and H{\"a}cker, Georg},
  title     = {Septins Arrange F-Actin-Containing Fibers on the Chlamydia trachomatis Inclusion and Are Required for Normal Release of the Inclusion by Extrusion},
  series = {MBIO},
  volume    = {5},
  journal   = {MBIO},
  number    = {5},
  issn      = {2150-7511},
  doi       = {10.1128/mBio.01802-14},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-115421},
  pages     = {e01802-14},
  year      = {2014},
  abstract  = {Chlamydia trachomatis is an obligate intracellular human pathogen that grows inside a membranous, cytosolic vacuole termed an inclusion. Septins are a group of 13 GTP-binding proteins that assemble into oligomeric complexes and that can form higher-order filaments. We report here that the septins SEPT2, -9, -11, and probably -7 form fibrillar structures around the chlamydial inclusion. Colocalization studies suggest that these septins combine with F actin into fibers that encase the inclusion. Targeting the expression of individual septins by RNA interference (RNAi) prevented the formation of septin fibers as well as the recruitment of actin to the inclusion. At the end of the developmental cycle of C. trachomatis, newly formed, infectious elementary bodies are released, and this release occurs at least in part through the organized extrusion of intact inclusions. RNAi against SEPT9 or against the combination of SEPT2/7/9 substantially reduced the number of extrusions from a culture of infected HeLa cells. The data suggest that a higher-order structure of four septins is involved in the recruitment or stabilization of the actin coat around the chlamydial inclusion and that this actin recruitment by septins is instrumental for the coordinated egress of C. trachomatis from human cells. The organization of F actin around parasite-containing vacuoles may be a broader response mechanism of mammalian cells to the infection by intracellular, vacuole-dwelling pathogens. IMPORTANCE Chlamydia trachomatis is a frequent bacterial pathogen throughout the world, causing mostly eye and genital infections. C. trachomatis can develop only inside host cells; it multiplies inside a membranous vacuole in the cytosol, termed an inclusion. The inclusion is covered by cytoskeletal "coats" or "cages," whose organization and function are poorly understood. We here report that a relatively little-characterized group of proteins, septins, is required to organize actin fibers on the inclusion and probably through actin the release of the inclusion. Septins are a group of GTP-binding proteins that can organize into heteromeric complexes and then into large filaments. Septins have previously been found to be involved in the interaction of the cell with bacteria in the cytosol. Our observation that they also organize a reaction to bacteria living in vacuoles suggests that they have a function in the recognition of foreign compartments by a parasitized human cell.},
  language  = {en}
}
@phdthesis{Wagner2021,
  author    = {Wagner, Rabea Marie},
  title     = {The Bacterial Exo- and Endo-Cytoskeleton Spatially Confines Functional Membrane Microdomain Dynamics in \(Bacillus\) \(subtilis\)},
  doi       = {10.25972/OPUS-21745},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-217458},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2021},
  abstract  = {Cellular membranes form a boundary to shield the inside of a cell from the outside. This is of special importance for bacteria, unicellular organisms whose membranes are in direct contact with the environment. The membrane needs to allow the reception of information about beneficial and harmful environmental conditions for the cell to evoke an appropriate response. Information gathering is mediated by proteins that need to be correctly organized in the membrane to be able to transmit information. Several principles of membrane organization are known that show a heterogeneous distribution of membrane lipids and proteins. One of them is functional membrane microdomains (FMM) which are platforms with a distinct lipid and protein composition. FMM move within the membrane and their integrity is important for several cellular processes like signal transduction, membrane trafficking and cellular differentiation. FMM harbor the marker proteins flotillins which are scaffolding proteins that act as chaperones in tethering protein cargo to FMM. This enhances the efficiency of cargo protein oligomerization or complex formation which in turn is important for their functionality. The bacterium Bacillus subtilis contains two flotillin proteins, FloA and FloT. They form different FMM assemblies which are structurally similar, but differ in the protein cargo and thus in the specific function. In this work, the mobility of FloA and FloT assemblies in the membrane was dissected using live-cell fluorescence microscopy techniques coupled to genetic, biochemical and molecular biological methods. A characteristic mobility pattern was observed which revealed that the mobility of both flotillins was spatially restricted. Restrictions were bigger for FloT resulting in a decreased diffusion coefficient compared to FloA. Flotillin mobility depends on the interplay of several factors. Firstly, the intrinsic properties of flotillins determine the binding of different protein interaction partners. These proteins directly affect the mobility of flotillins. Additionally, binding of interaction partners determines the assembly size of FloA and FloT. This indirectly affects the mobility, as the endo-cytoskeleton spatially restricts flotillin mobility in a size-dependent manner. Furthermore, the extracellular cell wall plays a dual role in flotillin mobility: its synthesis stimulates flotillin mobility, while at the same time its presence restricts flotillin mobility. As the intracellular flotillins do not have spatial access to the exo-cytoskeleton, this connection is likely mediated indirectly by their cell wall-associated protein interaction partners. Together the exo- and the endo-cytoskeleton restrict the mobility of FloA and FloT. Similar structural restrictions of flotillin mobility have been reported for plant cells as well, where the actin cytoskeleton and the cell wall restrict flotillin mobility. These similarities between eukaryotic and prokaryotic cells indicate that the restriction of flotillin mobility might be a conserved mechanism.},
  subject      = {Heubacillus},
  language  = {en}
}
@phdthesis{Wenzel2014,
  author    = {Wenzel, Jens},
  title     = {Regulation of TLR-induced macrophage responses by cytoskeleton-associated phosphoproteins},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-98843},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2014},
  abstract  = {Toll-like receptors (TLR) are pattern recognition receptors (PRR) by which macrophages (M{\O}) sense pathogen-associated molecular patterns (PAMPs). The recognition of lipopolysaccharide (LPS), the PAMP of gram negative bacteria, by TLR4 triggers signaling cascades and leads to the pro-inflammatory activation of the cells. A recent quantitative and kinetic analysis of the phosphoproteome of LPS-activated primary macrophages highlighted the cytoskeleton as a cell compartment with an enriched protein phosphorylation. In total 44 cytoskeleton-associated proteins were regulated by this post-translational modification and thus might be involved in the control and regulation of key macrophage functions like spreading, motility and phagocytosis. To investigate the control of cytoskeleton-associated cell functions by TLR4 activation, we first developed a method to quantitatively measure the spreading response of bone marrow M{\O} after stimulation with LPS. Fluorescence microscopy was used for cell imaging and visualisation of the M{\O} contact area. In collaboration with the Fraunhofer Institute Erlangen, we developed and validated a software tool for the semi-automated segmentation and quantitation of M{\O} fluorescence microscopy data, which allowed fast, robust and objective image analysis. Using this method, we observed that LPS caused time-dependent spreading, which was detectable after 1-2 h and maximal after 24 h. Next, the impact of genetic or pharmacological inhibition of known TLR signaling components was investigated. Deficiency in the adapter protein MYD88 strongly reduced spreading activity at the late time points, but had no impact early after LPS-stimulation. A similar effect was observed upon pharmacological inhibition of ERK1/2 signaling, indicating that ERK1/2 mediates MYD88-dependent M{\O} spreading. In contrast, M{\O} lacking the MAPK p38 were impaired in the initial spreading response but responded normally 8-24 h after stimulation. The genetic deletion of the MAPK phosphatases DUSP1 and DUSP16 resulted in impaired late spreading, corroborating the essential role for functional MAPK signaling in TLR4-driven M{\O} spreading. To identify the contribution of other cytoskeletal phosphoproteins to M{\O} spreading, siRNA knockdown of selected candidate genes in primary murine M{\O} was employed and combined with automated quantitative image analysis. These experiments revealed a functional role for the Myosins MYO1e and MYO1f in M{\O} spreading. These motor proteins are strongly phosphorylated in LPS-activated M{\O}. Because of their ability to simultaneously bind to actin filaments and cell membrane or other proteins, we investigated their role in phagocytosis, cytokine production and antigen presentation. Phagocytosis and killing of bacteria were not affected in Myo1e-/- macrophages. However, MYO1e plays a role in chemokine secretion and antigen presentation processes. MCP1 (CCL2) release was selectively increased in Myo1e-deficient M{\O} and dendritic cells (DC), while cytokine secretion was unaffected. Furthermore, macrophages and DCs lacking MYO1e showed lower levels of MHC-II on the cell surface. However, mRNA levels of CCL2 and of MHC-II were unaltered. These data suggest a role for MYO1e in the transport of selected chemokines and of MHC-II molecules to the cell surface. MHC-II-restricted antigen presentation assays revealed an impaired capacity of macrophages and DC lacking MYO1e to stimulate antigen-specific T cells, suggesting that the reduced MHC-II expression is functionally relevant. Taken together, in this study first a quantitative image analysis method was developed which allows the unbiased, robust and efficient investigation of the macrophage spreading response. Combination of this method with siRNA knockdown of selected cytoskeleton-associated phosphoproteins led to the identification of MYO1e and MYO1f as regulators of macrophage spreading. Furthermore, we identified MYO1e in M{\O} and DC to be essential for the intracellular transport of CCL2 and MHC-II to the cell surface and for optimal stimulation of antigen-specific CD4 T cells.},
  subject      = {Toll-like-Rezeptoren},
  language  = {en}
}