Bio

Honors & Awards


  • Stipend of the German Research Foundation (DFG), DFG-Deutsche Forschungsgemeinschaft (2011-2013)
  • Stanford Dean's Fellowship, Stanford (2010-2011)
  • Stanford Dean's Fellowship, Stanford (2009-2010)

Professional Education


  • Doctor of Philosophy, J W Goethe Universitat Frankfurt (2009)

Stanford Advisors


Research & Scholarship

Current Research and Scholarly Interests


My research focus is on the molecular mechanism underlying synaptic vesicle release and replenishment at the afferent fiber synapse of inner hair cells in the mammalian cochlea.

Publications

Journal Articles


  • A simple method for purification of vestibular hair cells and non-sensory cells, and application for proteomic analysis. PloS one Herget, M., Scheibinger, M., Guo, Z., Jan, T. A., Adams, C. M., Cheng, A. G., Heller, S. 2013; 8 (6)

    Abstract

    Mechanosensitive hair cells and supporting cells comprise the sensory epithelia of the inner ear. The paucity of both cell types has hampered molecular and cell biological studies, which often require large quantities of purified cells. Here, we report a strategy allowing the enrichment of relatively pure populations of vestibular hair cells and non-sensory cells including supporting cells. We utilized specific uptake of fluorescent styryl dyes for labeling of hair cells. Enzymatic isolation and flow cytometry was used to generate pure populations of sensory hair cells and non-sensory cells. We applied mass spectrometry to perform a qualitative high-resolution analysis of the proteomic makeup of both the hair cell and non-sensory cell populations. Our conservative analysis identified more than 600 proteins with a false discovery rate of <3% at the protein level and <1% at the peptide level. Analysis of proteins exclusively detected in either population revealed 64 proteins that were specific to hair cells and 103 proteins that were only detectable in non-sensory cells. Statistical analyses extended these groups by 53 proteins that are strongly upregulated in hair cells versus non-sensory cells and vice versa by 68 proteins. Our results demonstrate that enzymatic dissociation of styryl dye-labeled sensory hair cells and non-sensory cells is a valid method to generate pure enough cell populations for flow cytometry and subsequent molecular analyses.

    View details for DOI 10.1371/journal.pone.0066026

    View details for PubMedID 23750277

  • Conformation of peptides bound to the transporter associated with antigen processing (TAP) PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Herget, M., Baldauf, C., Schoelz, C., Parcej, D., Wiesmueller, K., Tampe, R., Abele, R., Bordignon, E. 2011; 108 (4): 1349-1354

    Abstract

    The ATP-binding cassette transporter associated with antigen processing (TAP) plays a key role in the adaptive immune defense against infected or malignantly transformed cells by translocating proteasomal degradation products into the lumen of the endoplasmic reticulum for loading onto MHC class I molecules. The broad substrate spectrum of TAP, rendering peptides from 8 to 40 residues, including even branched or modified molecules, suggests an unforeseen structural flexibility of the substrate-binding pocket. Here we used EPR spectroscopy to reveal conformational details of the bound peptides. Side-chain dynamics and environmental polarity were derived from covalently attached 2,2,5,5-tetramethylpyrrolidine-1-oxyl spin probes, whereas 2,2,6,6-tetramethylpiperidine-1-oxyl-4-amino-4-carboxylic acid spin-labeled peptides were used to detect backbone properties. Dependent on the spin probe's position, striking differences in affinity, dynamics, and polarity were found. The side-chains' mobility was strongly restricted at the ends of the peptide, whereas the central region was flexible, suggesting a central peptide bulge. In the end, double electron electron resonance allowed the determination of intrapeptide distances in doubly labeled peptides bound to TAP. Simulations based on a rotamer library led to the conclusion that peptides bind to TAP in an extended kinked structure, analogous to those bound to MHC class I proteins.

    View details for DOI 10.1073/pnas.1012355108

    View details for Web of Science ID 000286594800030

    View details for PubMedID 21205905

  • Single residue within the antigen translocation complex TAP controls the epitope repertoire by stabilizing a receptive conformation PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA Baldauf, C., Schrodt, S., Herget, M., Koch, J., Tampe, R. 2010; 107 (20): 9135-9140

    Abstract

    The recognition of virus infected or malignantly transformed cells by cytotoxic T lymphocytes critically depends on the transporter associated with antigen processing (TAP), which delivers proteasomal degradation products into the endoplasmic reticulum lumen for subsequent loading of major histocompatibility complex class I molecules. Here we have identified a single cysteinyl residue in the TAP complex that modulates peptide binding and translocation, thereby restricting the epitope repertoire. Cysteine 213 in human TAP2 was found to be part of a newly uncovered substrate-binding site crucial for peptide recognition. This residue contacts the peptide in the binding pocket in an orientated manner. The translocation complex can be reversibly inactivated by thiol modification of this cysteinyl residue. As part of an unexpected mechanism, this residue is crucial in complementing the binding pocket for a given subset of epitopes as well as in maintaining a substrate-receptive conformation of the translocation complex.

    View details for DOI 10.1073/pnas.1001308107

    View details for Web of Science ID 000277822600023

    View details for PubMedID 20439763

  • Purification and Reconstitution of the Antigen Transport Complex TAP A PREREQUISITE FOR DETERMINATION OF PEPTIDE STOICHIOMETRY AND ATP HYDROLYSIS JOURNAL OF BIOLOGICAL CHEMISTRY Herget, M., Kreissig, N., Kolbe, C., Schoelz, C., Tampe, R., Abele, R. 2009; 284 (49): 33740-33749

    Abstract

    The transporter associated with antigen processing (TAP) is an essential machine of the adaptive immune system that translocates antigenic peptides from the cytosol into the endoplasmic reticulum lumen for loading of major histocompatibility class I molecules. To examine this ABC transport complex in mechanistic detail, we have established, after extensive screening and optimization, the solubilization, purification, and reconstitution for TAP to preserve its function in each step. This allowed us to determine the substrate-binding stoichiometry of the TAP complex by fluorescence cross-correlation spectroscopy. In addition, the TAP complex shows strict coupling between peptide binding and ATP hydrolysis, revealing no basal ATPase activity in the absence of peptides. These results represent an optimal starting point for detailed mechanistic studies of the transport cycle of TAP by single molecule experiments to analyze single steps of peptide translocation and the stoichiometry between peptide transport and ATP hydrolysis.

    View details for DOI 10.1074/jbc.M109.047779

    View details for Web of Science ID 000272165200004

    View details for PubMedID 19808685

  • Mechanism of substrate sensing and signal transmission within an ABC transporter - Use of a trojan horse strategy JOURNAL OF BIOLOGICAL CHEMISTRY Herget, M., Oancea, G., Schrodt, S., Karas, M., Tampe, R., Abele, R. 2007; 282 (6): 3871-3880

    Abstract

    By translocating proteasomal degradation products into the endoplasmic reticulum for loading of major histocompatibility complex I molecules, the ABC transporter TAP plays a focal role in the adaptive immunity against infected or malignantly transformed cells. A key question regarding the transport mechanism is how the quality of the incoming peptide is detected and how this information is transmitted to the ATPase domains. To identify residues involved in this process, we evolved a Trojan horse strategy in which a small artificial protease is inserted into antigenic epitopes. After binding, the TAP backbone in contact is cleaved, allowing the peptide sensor site to be mapped by mass spectrometry. Within this sensor site, we identified residues that are essential for tight coupling of peptide binding and transport. This sensor and transmission interface is restructured during the ATP hydrolysis cycle, emphasizing its important function in the cross-talk between the transmembrane and the nucleotide-binding domains. This allocrite sensor may be similarly positioned in other members of the ABC exporter family.

    View details for DOI 10.1074/jbc.M608480200

    View details for Web of Science ID 000244481900051

    View details for PubMedID 17164240

  • Structure and dynamics of membrane-associated ICP47, a viral inhibitor of the MHC I antigen-processing machinery JOURNAL OF BIOLOGICAL CHEMISTRY Aisenbrey, C., Sizun, C., Koch, J., Herget, M., Abele, R., Bechinger, B., Tampe, R. 2006; 281 (41): 30365-30372

    Abstract

    To evade the host's immune response, herpes simplex virus employs the immediate early gene product ICP47 (IE12) to suppress antigen presentation to cytotoxic T-lymphocytes by inhibition of the ATP-binding cassette transporter associated with antigen processing (TAP). ICP47 is a membrane-associated protein adopting an alpha-helical conformation. Its active domain was mapped to residues 3-34 and shown to encode all functional properties of the full-length protein. The active domain of ICP47 was reconstituted into oriented phospholipid bilayers and studied by proton-decoupled 15N and 2H solid-state NMR spectroscopy. In phospholipid bilayers, the protein adopts a helix-loop-helix structure, where the average tilt angle of the helices relative to the membrane surface is approximately 15 degrees (+/- 7 degrees ). The alignment of both structured domains exhibits a mosaic spread of approximately 10 degrees . A flexible dynamic loop encompassing residues 17 and 18 separates the two helices. Refinement of the experimental data indicates that helix 1 inserts more deeply into the membrane. These novel insights into the structure of ICP47 represent an important step toward a molecular understanding of the immune evasion mechanism of herpes simplex virus and are instrumental for the design of new therapeutics.

    View details for DOI 10.1074/jbc.M603000200

    View details for Web of Science ID 000241075900010

    View details for PubMedID 16835230

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