FMP Publications

Our publications are recorded in a searchable database since 2010, updates will be added regularly.

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References

2015

Differences in Signal Activation by LH and hCG are Mediated by the LH/CG Receptor's Extracellular Hinge Region
Grzesik, P., Kreuchwig, A., Rutz, C., Furkert, J., Wiesner, B., Schülein, R., Kleinau(*), G., Gromoll(*), J.; Krause, G.
Front Endocrinol (Lausanne), 6:140
(2015)

Tags: Structural Bioinformatics and Protein Design (Krause, G.), Protein Trafficking (Schülein), Cellular Imaging (Wiesner)

Abstract: The human lutropin (hLH)/choriogonadotropin (hCG) receptor (LHCGR) can be activated by binding two slightly different gonadotropic glycoprotein hormones, choriogonadotropin (CG) - secreted by the placenta, and lutropin (LH) - produced by the pituitary. They induce different signaling profiles at the LHCGR. This cannot be explained by binding to the receptor's leucine-rich-repeat domain (LRRD), as this binding is similar for the two hormones. We therefore speculate that there are previously unknown differences in the hormone/receptor interaction at the extracellular hinge region, which might help to understand functional differences between the two hormones. We have therefore performed a detailed study of the binding and action of LH and CG at the LHCGR hinge region. We focused on a primate-specific additional exon in the hinge region, which is located between LRRD and the serpentine domain. The segment of the hinge region encoded by exon10 was previously reported to be only relevant to hLH signaling, as the exon10-deletion receptor exhibits decreased hLH signaling, but unchanged hCG signaling. We designed an advanced homology model of the hormone/LHCGR complex, followed by experimental characterization of relevant fragments in the hinge region. In addition, we examined predictions of a helical exon10-encoded conformation by block-wise polyalanine (helix supporting) mutations. These helix preserving modifications showed no effect on hormone-induced signaling. However, introduction of a structure-disturbing double-proline mutant LHCGR-Q303P/E305P within the exon10-helix has, in contrast to exon10-deletion, no impact on hLH, but only on hCG signaling. This opposite effect on signaling by hLH and hCG can be explained by distinct sites of hormone interaction in the hinge region. In conclusion, our analysis provides details of the differences between hLH- and hCG-induced signaling that are mainly determined in the L2-beta loop of the hormones and in the hinge region of the receptor.

KCNQ5 K(+) channels control hippocampal synaptic inhibition and fast network oscillations
Fidzinski, P., Korotkova, T., Heidenreich, M., Maier(*), N., Schütze, S., Kobler(*), O., Zuschratter(*), W., Schmitz(*), D., Ponomarenko, A.; Jentsch, T. J.
Nat Commun, 6:6254
(2015)

Tags: Physiology and Pathology of Ion Transport (Jentsch), Behavioral Neurodynamics (Korotkova/Ponomarenko)

Abstract: KCNQ2 (Kv7.2) and KCNQ3 (Kv7.3) K(+) channels dampen neuronal excitability and their functional impairment may lead to epilepsy. Less is known about KCNQ5 (Kv7.5), which also displays wide expression in the brain. Here we show an unexpected role of KCNQ5 in dampening synaptic inhibition and shaping network synchronization in the hippocampus. KCNQ5 localizes to the postsynaptic site of inhibitory synapses on pyramidal cells and in interneurons. Kcnq5(dn/dn) mice lacking functional KCNQ5 channels display increased excitability of different classes of interneurons, enhanced phasic and tonic inhibition, and decreased electrical shunting of inhibitory postsynaptic currents. In vivo, loss of KCNQ5 function leads to reduced fast (gamma and ripple) hippocampal oscillations, altered gamma-rhythmic discharge of pyramidal cells and impaired spatial representations. Our work demonstrates that KCNQ5 controls excitability and function of hippocampal networks through modulation of synaptic inhibition.

Analysis of phosphorylation-dependent protein-protein interactions of histone h3
Klingberg(*), R., Jost(*), J. O., Schümann, M., Gelato(*), K. A., Fischle(*), W., Krause, E.; Schwarzer(*), D.
ACS Chem Biol, 10:138-145
(2015)

Tags: Mass Spectrometry (Krause, E.)

Abstract: Multiple posttranslational modifications (PTMs) of histone proteins including site-specific phosphorylation of serine and threonine residues govern the accessibility of chromatin. According to the histone code theory, PTMs recruit regulatory proteins or block their access to chromatin. Here, we report a general strategy for simultaneous analysis of both of these effects based on a SILAC MS scheme. We applied this approach for studying the biochemical role of phosphorylated S10 of histone H3. Differential pull-down experiments with H3-tails synthesized from l- and d-amino acids uncovered that histone acetyltransferase 1 (HAT1) and retinoblastoma-binding protein 7 (RBBP7) are part of the protein network, which interacts with the unmodified H3-tail. An additional H3-derived bait containing the nonhydrolyzable phospho-serine mimic phosphonomethylen-alanine (Pma) at S10 recruited several isoforms of the 14-3-3 family and blocked the recruitment of HAT1 and RBBP7 to the unmodified H3-tail. Our observations provide new insights into the many functions of H3S10 phosphorylation. In addition, the outlined methodology is generally applicable for studying specific binding partners of unmodified histone tails.

The GYF domain protein CD2BP2 is critical for embryogenesis and podocyte function
Albert(*), G. I., Schell(*), C., Kirschner(*), K. M., Schäfer(*), S., Naumann(*), R., Müller(*), A., Kretz(*), O., Kuropka, B., Girbig(*), M., Hübner(*), N., Krause, E., Scholz(*), H., Huber(*), T. B., Knobeloch(*), K. P.; Freund(*), C.
Journal of molecular cell biology, 7:402-414
(2015)

Tags: Mass Spectrometry (Krause, E.)

Abstract: Scaffolding proteins play pivotal roles in the assembly of macromolecular machines such as the spliceosome. The adaptor protein CD2BP2, originally identified as a binding partner of the adhesion molecule CD2, is a pre-spliceosomal assembly factor that utilizes its glycine-tyrosine-phenylalanine (GYF) domain to co-localize with spliceosomal proteins. So far, its function in vertebrates is unknown. Using conditional gene targeting in mice, we show that CD2BP2 is crucial for embryogenesis, leading to growth retardation, defects in vascularization, and premature death at embryonic day 10.5 when absent. Ablation of the protein in bone marrow-derived macrophages indicates that CD2BP2 is involved in the alternative splicing of mRNA transcripts from diverse origins. At the molecular level, we identified the phosphatase PP1 to be recruited to the spliceosome via the N-terminus of CD2BP2. Given the strong expression of CD2BP2 in podocytes of the kidney, we use selective depletion of CD2BP2, in combination with next-generation sequencing, to monitor changes in exon usage of genes critical for podocyte functions, including VEGF and actin regulators. CD2BP2-depleted podocytes display foot process effacement, and cause proteinuria and ultimately lethal kidney failure in mice. Collectively, our study defines CD2BP2 as a non-redundant splicing factor essential for embryonic development and podocyte integrity.

Exploring monovalent and multivalent peptides for the inhibition of FBP21-tWW
Henning(*), L. M., Bhatia(*), S., Bertazzon(*), M., Marczynke(*), M., Seitz(*), O., Volkmer, R., Haag(*), R.; Freund(*), C.
Beilstein J Org Chem, 11:701-706
(2015)

Tags: Peptide Synthesis (Hackenberger/Volkmer)

Abstract: The coupling of peptides to polyglycerol carriers represents an important route towards the multivalent display of protein ligands. In particular, the inhibition of low affinity intracellular protein-protein interactions can be addressed by this design. We have applied this strategy to develop binding partners for FBP21, a protein which is important for the splicing of pre-mRNA in the nucleus of eukaryotic cells. Firstly, by using phage display the optimized sequence WPPPPRVPR was derived which binds with K Ds of 80 muM and 150 microM to the individual WW domains and with a K D of 150 muM to the tandem-WW1-WW2 construct. Secondly, this sequence was coupled to a hyperbranched polyglycerol (hPG) that allowed for the multivalent display on the surface of the dendritic polymer. This novel multifunctional hPG-peptide conjugate displayed a K D of 17.6 microM which demonstrates that the new carrier provides a venue for the future inhibition of proline-rich sequence recognition by FBP21 during assembly of the spliceosome.

Sortase A mediated site-specific immobilization for identification of protein interactions in affinity purification-mass spectrometry experiments
Kuropka, B., Royla, N., Freund(*), C.; Krause, E.
Proteomics, 15:1230-1234
(2015)

Tags: Mass Spectrometry (Krause, E.)

Abstract: Proteomics approaches using MS in combination with affinity purification have emerged as powerful tools to study protein-protein interactions. Here we make use of the specificity of sortase A transpeptidation reaction to prepare affinity matrices in which a protein bait is covalently linked to the matrix via a short C-terminal linker region. As a result of this site-directed immobilization, the bait remains functionally accessible to protein interactions. To apply this approach, we performed SILAC-based pull-down experiments and demonstrate the suitability of the approach.

Analysis of Phosphorylation-dependent Protein Interactions of Adhesion and Degranulation Promoting Adaptor Protein (ADAP) Reveals Novel Interaction Partners Required for Chemokine-directed T cell Migration
Kuropka, B., Witte, A., Sticht(*), J., Waldt(*), N., Majkut, P., Hackenberger, C. P., Schraven(*), B., Krause, E., Kliche(*), S.; Freund(*), C.
Mol Cell Proteomics, 14:2961-2972
(2015)

Tags: Mass Spectrometry (Krause, E.), Chemical Biology II (Hackenberger), Molecular Imaging (Schröder)

Abstract: Stimulation of T cells leads to distinct changes of their adhesive and migratory properties. Signal propagation from activated receptors to integrins depends on scaffolding proteins such as the adhesion and degranulation promoting adaptor protein (ADAP)(1). Here we have comprehensively investigated the phosphotyrosine interactome of ADAP in T cells and define known and novel interaction partners of functional relevance. While most phosphosites reside in unstructured regions of the protein, thereby defining classical SH2 domain interaction sites for master regulators of T cell signaling such as SLP76, Fyn-kinase, and NCK, other binding events depend on structural context. Interaction proteomics using different ADAP constructs comprising most of the known phosphotyrosine motifs as well as the structured domains confirm that a distinct set of proteins is attracted by pY571 of ADAP, including the zeta-chain-associated protein kinase of 70 kDa (ZAP70). The interaction of ADAP and ZAP70 is inducible upon stimulation either of the T cell receptor (TCR) or by chemokine. NMR spectroscopy reveals that the N-terminal SH2 domains within a ZAP70-tandem-SH2 construct is the major site of interaction with phosphorylated ADAP-hSH3(N) and microscale thermophoresis (MST) indicates an intermediate binding affinity (Kd = 2.3 mum). Interestingly, although T cell receptor dependent events such as T cell/antigen presenting cell (APC) conjugate formation and adhesion are not affected by mutation of Y571, migration of T cells along a chemokine gradient is compromised. Thus, although most phospho-sites in ADAP are linked to T cell receptor related functions we have identified a unique phosphotyrosine that is solely required for chemokine induced T cell behavior.

Quantitative analysis of the human T cell palmitome
Morrison(*), E., Kuropka, B., Kliche(*), S., Brügger(*), B., Krause, E.; Freund(*), C.
Sci Rep, 5:11598
(2015)

Tags: Mass Spectrometry (Krause, E.)

Abstract: Palmitoylation is a reversible post-translational modification used to inducibly compartmentalize proteins in cellular membranes, affecting the function of receptors and intracellular signaling proteins. The identification of protein "palmitomes" in several cell lines raises the question to what extent this modification is conserved in primary cells. Here we use primary T cells with acyl-biotin exchange and quantitative mass spectrometry to identify a pool of proteins previously unreported as palmitoylated in vivo.

A modular toolkit to inhibit proline-rich motif-mediated protein-protein interactions
Opitz, R., Müller, M., Reuter, C., Barone, M., Soicke(*), A., Roske(*), Y., Piotukh, K., Huy(*), P., Beerbaum, M., Wiesner, B., Beyermann, M., Schmieder, P., Freund(*), C., Volkmer, R., Oschkinat, H., Schmalz(*), H. G.; Kühne, R.
Proc Natl Acad Sci U S A, 112:5011-5016
(2015)

Tags: Computational Chemistry and Protein Design (Kühne), NMR-Supported Structural Biology (Oschkinat), Peptide Chemistry (Hackenberger/ Volkmer), Solution NMR (Schmieder), Peptide Chemistry (Beyermann), Cellular Imaging (Wiesner)

Abstract: Small-molecule competitors of protein-protein interactions are urgently needed for functional analysis of large-scale genomics and proteomics data. Particularly abundant, yet so far undruggable, targets include domains specialized in recognizing proline-rich segments, including Src-homology 3 (SH3), WW, GYF, and Drosophila enabled (Ena)/vasodilator-stimulated phosphoprotein (VASP) homology 1 (EVH1) domains. Here, we present a modular strategy to obtain an extendable toolkit of chemical fragments (ProMs) designed to replace pairs of conserved prolines in recognition motifs. As proof-of-principle, we developed a small, selective, peptidomimetic inhibitor of Ena/VASP EVH1 domain interactions. Highly invasive MDA MB 231 breast-cancer cells treated with this ligand showed displacement of VASP from focal adhesions, as well as from the front of lamellipodia, and strongly reduced cell invasion. General applicability of our strategy is illustrated by the design of an ErbB4-derived ligand containing two ProM-1 fragments, targeting the yes-associated protein 1 (YAP1)-WW domain with a fivefold higher affinity.

Vesicle uncoating regulated by SH3-SH3 domain-mediated complex formation between endophilin and intersectin at synapses
Pechstein, A., Gerth(*), F., Milosevic(*), I., Jäpel, M., Eichhorn-Grünig, M., Vorontsova(*), O., Bacetic, J., Maritzen, T., Shupliakov(*), O., Freund(*), C.; Haucke, V.
Embo Rep, 16:232-239
(2015)

Tags: Molecular Pharmacology and Cell Biology (Haucke), Membrane Traffic and Cell Motility (Maritzen)

Abstract: Neurotransmission involves the exo-endocytic cycling of synaptic vesicle (SV) membranes. Endocytic membrane retrieval and clathrin-mediated SV reformation require curvature-sensing and membrane-bending BAR domain proteins such as endophilin A. While their ability to sense and stabilize curved membranes facilitates membrane recruitment of BAR domain proteins, the precise mechanisms by which they are targeted to specific sites of SV recycling has remained unclear. Here, we demonstrate that the multi-domain scaffold intersectin 1 directly associates with endophilin A to facilitate vesicle uncoating at synapses. Knockout mice deficient in intersectin 1 accumulate clathrin-coated vesicles at synapses, a phenotype akin to loss of endophilin function. Intersectin 1/endophilin A1 complex formation is mediated by direct binding of the SH3B domain of intersectin to a non-canonical site on the SH3 domain of endophilin A1. Consistent with this, intersectin-binding defective mutant endophilin A1 fails to rescue clathrin accumulation at neuronal synapses derived from endophilin A1-3 triple knockout (TKO) mice. Our data support a model in which intersectin aids endophilin A recruitment to sites of clathrin-mediated SV recycling, thereby facilitating vesicle uncoating.

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Leibniz-Forschungsinstitut für Molekulare Pharmakologie im Forschungsverbund Berlin e.V. (FMP)
Campus Berlin-Buch
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13125 Berlin, Germany
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info(at)fmp-berlin.de

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