@article{EhmannSauerKittel2015,
  author    = {Ehmann, Nadine and Sauer, Markus and Kittel, Robert J.},
  title     = {Super-resolution microscopy of the synaptic active zone},
  series = {Frontiers in Cellular Neuroscience},
  volume    = {9},
  journal   = {Frontiers in Cellular Neuroscience},
  number    = {7},
  doi       = {10.3389/fncel.2015.00007},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-148997},
  year      = {2015},
  abstract  = {Brain function relies on accurate information transfer at chemical synapses. At the presynaptic active zone (AZ) a variety of specialized proteins are assembled to complex architectures, which set the basis for speed, precision and plasticity of synaptic transmission. Calcium channels are pivotal for the initiation of excitation-secretion coupling and, correspondingly, capture a central position at the AZ. Combining quantitative functional studies with modeling approaches has provided predictions of channel properties, numbers and even positions on the nanometer scale. However, elucidating the nanoscopic organization of the surrounding protein network requires direct ultrastructural access. Without this information, knowledge of molecular synaptic structure-function relationships remains incomplete. Recently, super-resolution microscopy (SRM) techniques have begun to enter the neurosciences. These approaches combine high spatial resolution with the molecular specificity of fluorescence microscopy. Here, we discuss how SRM can be used to obtain information on the organization of AZ proteins},
  language  = {en}
}
@article{EiringMcLaughlinMatikondaetal.2021,
  author    = {Eiring, Patrick and McLaughlin, Ryan and Matikonda, Siddharth S. and Han, Zhongying and Grabenhorst, Lennart and Helmerich, Dominic A. and Meub, Mara and Beliu, Gerti and Luciano, Michael and Bandi, Venu and Zijlstra, Niels and Shi, Zhen-Dan and Tarasov, Sergey G. and Swenson, Rolf and Tinnefeld, Philip and Glembockyte, Viktorija and Cordes, Thorben and Sauer, Markus and Schnermann, Martin J.},
  title     = {Targetable conformationally restricted cyanines enable photon-count-limited applications},
  series = {Angewandte Chemie Internationale Edition},
  volume    = {60},
  journal   = {Angewandte Chemie Internationale Edition},
  number    = {51},
  doi       = {10.1002/anie.202109749},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-256559},
  pages     = {26685-26693},
  year      = {2021},
  abstract  = {Cyanine dyes are exceptionally useful probes for a range of fluorescence-based applications, but their photon output can be limited by trans-to-cis photoisomerization. We recently demonstrated that appending a ring system to the pentamethine cyanine ring system improves the quantum yield and extends the fluorescence lifetime. Here, we report an optimized synthesis of persulfonated variants that enable efficient labeling of nucleic acids and proteins. We demonstrate that a bifunctional sulfonated tertiary amide significantly improves the optical properties of the resulting bioconjugates. These new conformationally restricted cyanines are compared to the parent cyanine derivatives in a range of contexts. These include their use in the plasmonic hotspot of a DNA-nanoantenna, in single-molecule F{\"o}rster-resonance energy transfer (FRET) applications, far-red fluorescence-lifetime imaging microscopy (FLIM), and single-molecule localization microscopy (SMLM). These efforts define contexts in which eliminating cyanine isomerization provides meaningful benefits to imaging performance.},
  language  = {en}
}
@article{LukešGlatzovaKvičalovaetal.2017,
  author    = {Lukeš, Tom{\´a}š and Glatzov{\´a}, Daniela and Kv{\´i}čalov{\´a}, Zuzana and Levet, Florian and Benda, Aleš and Letschert, Sebastian and Sauer, Markus and Brdička, Tom{\´a}š and Lasser, Theo and Cebecauer, Marek},
  title     = {Quantifying protein densities on cell membranes using super-resolution optical fluctuation imaging},
  series = {Nature Communications},
  volume    = {8},
  journal   = {Nature Communications},
  doi       = {10.1038/s41467-017-01857-x},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-172993},
  year      = {2017},
  abstract  = {Quantitative approaches for characterizing molecular organization of cell membrane molecules under physiological and pathological conditions profit from recently developed super-resolution imaging techniques. Current tools employ statistical algorithms to determine clusters of molecules based on single-molecule localization microscopy (SMLM) data. These approaches are limited by the ability of SMLM techniques to identify and localize molecules in densely populated areas and experimental conditions of sample preparation and image acquisition. We have developed a robust, model-free, quantitative clustering analysis to determine the distribution of membrane molecules that excels in densely labeled areas and is tolerant to various experimental conditions, i.e. multiple-blinking or high blinking rates. The method is based on a TIRF microscope followed by a super-resolution optical fluctuation imaging (SOFI) analysis. The effectiveness and robustness of the method is validated using simulated and experimental data investigating nanoscale distribution of CD4 glycoprotein mutants in the plasma membrane of T cells.},
  language  = {en}
}
@article{MarkertBritzProppertetal.2016,
  author    = {Markert, Sebastian Matthias and Britz, Sebastian and Proppert, Sven and Lang, Marietta and Witvliet, Daniel and Mulcahy, Ben and Sauer, Markus and Zhen, Mei and Bessereau, Jean-Louis and Stigloher, Christian},
  title     = {Filling the gap: adding super-resolution to array tomography for correlated ultrastructural and molecular identification of electrical synapses at the C. elegans connectome},
  series = {Neurophotonics},
  volume    = {3},
  journal   = {Neurophotonics},
  number    = {4},
  doi       = {10.1117/1.NPh.3.4.041802},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-187292},
  pages     = {041802},
  year      = {2016},
  abstract  = {Correlating molecular labeling at the ultrastructural level with high confidence remains challenging. Array tomography (AT) allows for a combination of fluorescence and electron microscopy (EM) to visualize subcellular protein localization on serial EM sections. Here, we describe an application for AT that combines near-native tissue preservation via high-pressure freezing and freeze substitution with super-resolution light microscopy and high-resolution scanning electron microscopy (SEM) analysis on the same section. We established protocols that combine SEM with structured illumination microscopy (SIM) and direct stochastic optical reconstruction microscopy (dSTORM). We devised a method for easy, precise, and unbiased correlation of EM images and super-resolution imaging data using endogenous cellular landmarks and freely available image processing software. We demonstrate that these methods allow us to identify and label gap junctions in Caenorhabditis elegans with precision and confidence, and imaging of even smaller structures is feasible. With the emergence of connectomics, these methods will allow us to fill in the gap-acquiring the correlated ultrastructural and molecular identity of electrical synapses.},
  language  = {en}
}
@article{MrestaniPauliKollmannsbergeretal.2021,
  author    = {Mrestani, Achmed and Pauli, Martin and Kollmannsberger, Philip and Repp, Felix and Kittel, Robert J. and Eilers, Jens and Doose, S{\"o}ren and Sauer, Markus and Sir{\´e}n, Anna-Leena and Heckmann, Manfred and Paul, Mila M.},
  title     = {Active zone compaction correlates with presynaptic homeostatic potentiation},
  series = {Cell Reports},
  volume    = {37},
  journal   = {Cell Reports},
  number    = {1},
  doi       = {10.1016/j.celrep.2021.109770},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-265497},
  pages     = {109770},
  year      = {2021},
  abstract  = {Neurotransmitter release is stabilized by homeostatic plasticity. Presynaptic homeostatic potentiation (PHP) operates on timescales ranging from minute- to life-long adaptations and likely involves reorganization of presynaptic active zones (AZs). At Drosophila melanogaster neuromuscular junctions, earlier work ascribed AZ enlargement by incorporating more Bruchpilot (Brp) scaffold protein a role in PHP. We use localization microscopy (direct stochastic optical reconstruction microscopy [dSTORM]) and hierarchical density-based spatial clustering of applications with noise (HDBSCAN) to study AZ plasticity during PHP at the synaptic mesoscale. We find compaction of individual AZs in acute philanthotoxin-induced and chronic genetically induced PHP but unchanged copy numbers of AZ proteins. Compaction even occurs at the level of Brp subclusters, which move toward AZ centers, and in Rab3 interacting molecule (RIM)-binding protein (RBP) subclusters. Furthermore, correlative confocal and dSTORM imaging reveals how AZ compaction in PHP translates into apparent increases in AZ area and Brp protein content, as implied earlier.},
  language  = {en}
}
@article{SchlegelPetersDooseetal.2019,
  author    = {Schlegel, Jan and Peters, Simon and Doose, S{\"o}ren and Schubert-Unkmeir, Alexandra and Sauer, Markus},
  title     = {Super-resolution microscopy reveals local accumulation of plasma membrane gangliosides at Neisseria meningitidis Invasion Sites},
  series = {Frontiers in Cell and Developmental Biology},
  volume    = {7},
  journal   = {Frontiers in Cell and Developmental Biology},
  number    = {194},
  doi       = {10.3389/fcell.2019.00194},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-201639},
  year      = {2019},
  abstract  = {Neisseria meningitidis (meningococcus) is a Gram-negative bacterium responsible for epidemic meningitis and sepsis worldwide. A critical step in the development of meningitis is the interaction of bacteria with cells forming the blood-cerebrospinal fluid barrier, which requires tight adhesion of the pathogen to highly specialized brain endothelial cells. Two endothelial receptors, CD147 and the β2-adrenergic receptor, have been found to be sequentially recruited by meningococci involving the interaction with type IV pilus. Despite the identification of cellular key players in bacterial adhesion the detailed mechanism of invasion is still poorly understood. Here, we investigated cellular dynamics and mobility of the type IV pilus receptor CD147 upon treatment with pili enriched fractions and specific antibodies directed against two extracellular Ig-like domains in living human brain microvascular endothelial cells. Modulation of CD147 mobility after ligand binding revealed by single-molecule tracking experiments demonstrates receptor activation and indicates plasma membrane rearrangements. Exploiting the binding of Shiga (STxB) and Cholera toxin B (CTxB) subunits to the two native plasma membrane sphingolipids globotriaosylceramide (Gb3) and raft-associated monosialotetrahexosylganglioside GM1, respectively, we investigated their involvement in bacterial invasion by super-resolution microscopy. Structured illumination microscopy (SIM) and direct stochastic optical reconstruction microscopy (dSTORM) unraveled accumulation and coating of meningococci with GM1 upon cellular uptake. Blocking of CTxB binding sites did not impair bacterial adhesion but dramatically reduced bacterial invasion efficiency. In addition, cell cycle arrest in G1 phase induced by serum starvation led to an overall increase of GM1 molecules in the plasma membrane and consequently also in bacterial invasion efficiency. Our results will help to understand downstream signaling events after initial type IV pilus-host cell interactions and thus have general impact on the development of new therapeutics targeting key molecules involved in infection.},
  language  = {en}
}
@article{TrinksReinhardDrobnyetal.2021,
  author    = {Trinks, Nora and Reinhard, Sebastian and Drobny, Matthias and Heilig, Linda and L{\"o}ffler, J{\"u}rgen and Sauer, Markus and Terpitz, Ulrich},
  title     = {Subdiffraction-resolution fluorescence imaging of immunological synapse formation between NK cells and A. fumigatus by expansion microscopy},
  series = {Communications Biology},
  volume    = {4},
  journal   = {Communications Biology},
  number    = {1},
  doi       = {10.1038/s42003-021-02669-y},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-264996},
  year      = {2021},
  abstract  = {Expansion microscopy (ExM) enables super-resolution fluorescence imaging on standard microscopes by physical expansion of the sample. However, the investigation of interactions between different organisms such as mammalian and fungal cells by ExM remains challenging because different cell types require different expansion protocols to ensure identical, ideally isotropic expansion of both partners. Here, we introduce an ExM method that enables super-resolved visualization of the interaction between NK cells and Aspergillus fumigatus hyphae. 4-fold expansion in combination with confocal fluorescence imaging allows us to resolve details of cytoskeleton rearrangement as well as NK cells' lytic granules triggered by contact with an RFP-expressing A. fumigatus strain. In particular, subdiffraction-resolution images show polarized degranulation upon contact formation and the presence of LAMP1 surrounding perforin at the NK cell-surface post degranulation. Our data demonstrate that optimized ExM protocols enable the investigation of immunological synapse formation between two different species with so far unmatched spatial resolution.},
  language  = {en}
}