FMP Publications

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

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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

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.

Muscular Dystrophy Mutations Impair the Nuclear Envelope Emerin Self-assembly Properties
Herrada(*), I., Samson(*), C., Velours(*), C., Renault(*), L., Ostlund(*), C., Chervy(*), P., Puchkov, D., Worman(*), H. J., Buendia(*), B.; Zinn-Justin(*), S.
ACS Chem Biol, 10:2733-2742

Tags: Molecular Pharmacology and Cell Biology (Haucke)

Abstract: More than 100 genetic mutations causing X-linked Emery-Dreifuss muscular dystrophy have been identified in the gene encoding the integral inner nuclear membrane protein emerin. Most mutations are nonsense or frameshift mutations that lead to the absence of emerin in cells. Only very few cases are due to missense or short in-frame deletions. Molecular mechanisms explaining the corresponding emerin variants' loss of function are particularly difficult to identify because of the mostly intrinsically disordered state of the emerin nucleoplasmic region. We now demonstrate that this EmN region can be produced as a disordered monomer, as revealed by nuclear magnetic resonance, but rapidly self-assembles in vitro. Increases in concentration and temperature favor the formation of long curvilinear filaments with diameters of approximately 10 nm, as observed by electron microscopy. Assembly of these filaments can be followed by fluorescence through Thioflavin-T binding and by Fourier-transform Infrared spectrometry through formation of beta-structures. Analysis of the assembly properties of five EmN variants reveals that del95-99 and Q133H impact filament assembly capacities. In cells, these variants are located at the nuclear envelope, but the corresponding quantities of emerin-emerin and emerin-lamin proximities are decreased compared to wild-type protein. Furthermore, variant P183H favors EmN aggregation in vitro, and variant P183T provokes emerin accumulation in cytoplasmic foci in cells. Substitution of residue Pro183 might systematically favor oligomerization, leading to emerin aggregation and mislocalization in cells. Our results suggest that emerin self-assembly is necessary for its proper function and that a loss of either the protein itself or its ability to self-assemble causes muscular dystrophy.

Structural insights into thyroid hormone transport mechanisms of the L-type amino acid transporter 2
Hinz, K. M., Meyer, K., Kinne, A., Schülein, R., Köhrle(*), J.; Krause, G.
Mol Endocrinol, 29:933-942

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

Abstract: Thyroid hormones (THs) are transported across cell membranes by different transmembrane transporter proteins. In previous studies, we showed marked 3,3'-diiodothyronine (3,3'-T2) but moderate T3 uptake by the L-type amino acid transporter 2 (Lat2). We have now studied the structure-function relationships of this transporter and TH-like molecules. Our Lat2 homology model is based on 2 crystal structures of the homologous 12-transmembrane helix transporters arginine/agmatine antiporter and amino acid/polyamine/organocation transporter. Model-driven mutagenesis of residues lining an extracellular recognition site and a TH-traversing channel identified 9 sensitive residues. Using Xenopus laevis oocytes as expression system, we found that side chain shortening (N51S, N133S, N248S, and Y130A) expanded the channel and increased 3,3'-T2 transport. Side chain enlargements (T140F, Y130R, and I137M) decreased 3,3'-T2 uptake, indicating channel obstructions. The opposite results with mutations maintaining (F242W) or impairing (F242V) uptake suggest that F242 may have a gating function. Competitive inhibition studies of 14 TH-like compounds revealed that recognition by Lat2 requires amino and carboxylic acid groups. The size of the adjacent hydrophobic group is restricted. Bulky substituents in positions 3 and 5 of the tyrosine ring are allowed. The phenolic ring may be enlarged, provided that the whole molecule is flexible enough to fit into the distinctly shaped TH-traversing channel of Lat2. Taken together, the next Lat2 features were identified 1) TH recognition site; 2) TH-traversing channel in the center of Lat2; and 3) switch site that potentially facilitates intracellular substrate release. Together with identified substrate features, these data help to elucidate the molecular mechanisms and role of Lat2 in T2 transport.

DOTAM derivatives as active cartilage-targeting drug carriers for the treatment of osteoarthritis
Hu(*), H. Y., Lim(*), N. H., Ding-Pfennigdorff(*), D., Saas(*), J., Wendt(*), K. U., Ritzeler(*), O., Nagase(*), H., Plettenburg(*), O., Schultz(*), C.; Nazare, M.
Bioconjug Chem, 26:383-388

Tags: Medicinal Chemistry (Nazare)

Abstract: Targeted drug-delivery methods are crucial for effective treatment of degenerative joint diseases such as osteoarthritis (OA). Toward this goal, we developed a small multivalent structure as a model drug for the attenuation of cartilage degradation. The DOTAM (1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid amide)-based model structure is equipped with the cathepsin D protease inhibitor pepstatin A, a fluorophore, and peptide moieties targeting collagen II. In vivo injection of these soluble probes into the knee joints of mice resulted in 7-day-long local retention, while the drug carrier equipped with a scrambled peptide sequence was washed away within 6-8 h. The model drug conjugate successfully reduced the cathepsin D protease activity as measured by release of GAG peptide. Therefore, these conjugates represent a promising first drug conjugate for the targeted treatment of degenerative joint diseases.

In vivo visualization of osteoarthritic hypertrophic lesions
Hu(*), H. Y., Lim(*), N. H., Juretschke(*), H. P., Ding-Pfennigdorff(*), D., Florian(*), P., Kohlmann(*), M., Kandira(*), A., von Kries(*), J. P., Saas(*), J., Rudolphi(*), K. A., Wendt(*), K. U., Nagase(*), H., Plettenburg(*), O., Nazare, M.; Schultz(*), C.
Chem Sci, 6:6256-6261

Tags: Medicinal Chemistry (Nazare)

Abstract: Osteoarthritis (OA) is one of the most common diseases in the aging population. While disease progress in humans is monitored indirectly by X-ray or MRI, small animal OA lesions detection always requires surgical intervention and histology. Here we introduce bimodal MR/NIR probes based on cartilage-targeting 1,4,7,10-tetraazacyclododecane 1,4,7,10-tetraacetic acid amide (DOTAM) that are directly administered to the joint cavity. We demonstrate applications in healthy and diseased rat joints by MRI in vivo. The same joints are inspected post-mortem by fluorescence microscopy, showing not only the precise location of the reagents but also revealing details such as focal cartilage damage and chondrophyte or osteophyte formation. This allows for determining the distinct pathological state of the disease and the regeneration capability of the animal model and will help to correctly assess the effect of potential disease modifying OA drugs (DMOADs) in the future.

Discovery of CLC transport proteins: cloning, structure, function and pathophysiology
Jentsch, T. J.
J Physiol, 593:4091-4109

Tags: Physiology and Pathology of Ion Transport (Jentsch)

Abstract: After providing a personal description of the convoluted path leading 25 years ago to the molecular identification of the Torpedo Cl(-) channel ClC-0 and the discovery of the CLC gene family, I succinctly describe the general structural and functional features of these ion transporters before giving a short overview of mammalian CLCs. These can be categorized into plasma membrane Cl(-) channels and vesicular Cl(-) /H(+) -exchangers. They are involved in the regulation of membrane excitability, transepithelial transport, extracellular ion homeostasis, endocytosis and lysosomal function. Diseases caused by CLC dysfunction include myotonia, neurodegeneration, deafness, blindness, leukodystrophy, male infertility, renal salt loss, kidney stones and osteopetrosis, revealing a surprisingly broad spectrum of biological roles for chloride transport that was unsuspected when I set out to clone the first voltage-gated chloride channel.

Departure gate of acidic Ca(2)(+) confirmed
Jentsch, T. J., Hoegg-Beiler, M. B.; Vogt, J.
EMBO J, 34:1737-1739

Tags: Physiology and Pathology of Ion Transport (Jentsch)

Disruption of adaptor protein 2mu (AP-2mu) in cochlear hair cells impairs vesicle reloading of synaptic release sites and hearing
Jung(*), S., Maritzen, T., Wichmann(*), C., Jing(*), Z., Neef(*), A., Revelo(*), N. H., Al-Moyed(*), H., Meese(*), S., Wojcik(*), S. M., Panou(*), I., Bulut(*), H., Schu(*), P., Ficner(*), R., Reisinger(*), E., Rizzoli(*), S. O., Neef(*), J., Strenzke(*), N., Haucke, V.; Moser(*), T.
EMBO J, 34:2686-2702

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

Abstract: Active zones (AZs) of inner hair cells (IHCs) indefatigably release hundreds of vesicles per second, requiring each release site to reload vesicles at tens per second. Here, we report that the endocytic adaptor protein 2mu (AP-2mu) is required for release site replenishment and hearing. We show that hair cell-specific disruption of AP-2mu slows IHC exocytosis immediately after fusion of the readily releasable pool of vesicles, despite normal abundance of membrane-proximal vesicles and intact endocytic membrane retrieval. Sound-driven postsynaptic spiking was reduced in a use-dependent manner, and the altered interspike interval statistics suggested a slowed reloading of release sites. Sustained strong stimulation led to accumulation of endosome-like vacuoles, fewer clathrin-coated endocytic intermediates, and vesicle depletion of the membrane-distal synaptic ribbon in AP-2mu-deficient IHCs, indicating a further role of AP-2mu in clathrin-dependent vesicle reformation on a timescale of many seconds. Finally, we show that AP-2 sorts its IHC-cargo otoferlin. We propose that binding of AP-2 to otoferlin facilitates replenishment of release sites, for example, via speeding AZ clearance of exocytosed material, in addition to a role of AP-2 in synaptic vesicle reformation.

Overlapping functions of stonin 2 and SV2 in sorting of the calcium sensor synaptotagmin 1 to synaptic vesicles
Kaempf, N., Kochlamazashvili, G., Puchkov, D., Maritzen, T., Bajjalieh(*), S. M., Kononenko, N. L.; Haucke, V.
Proc Natl Acad Sci U S A, 112:7297-7302

Tags: Molecular Pharmacology and Cell Biology (Haucke), Membrane Traffic and Cell Motility (Maritzen), Behavioral Neurodynamics (Korotkova/Ponomarenko)

Abstract: Neurotransmission involves the calcium-regulated exocytic fusion of synaptic vesicles (SVs) and the subsequent retrieval of SV membranes followed by reformation of properly sized and shaped SVs. An unresolved question is whether each SV protein is sorted by its own dedicated adaptor or whether sorting is facilitated by association between different SV proteins. We demonstrate that endocytic sorting of the calcium sensor synaptotagmin 1 (Syt1) is mediated by the overlapping activities of the Syt1-associated SV glycoprotein SV2A/B and the endocytic Syt1-adaptor stonin 2 (Stn2). Deletion or knockdown of either SV2A/B or Stn2 results in partial Syt1 loss and missorting of Syt1 to the neuronal surface, whereas deletion of both SV2A/B and Stn2 dramatically exacerbates this phenotype. Selective missorting and degradation of Syt1 in the absence of SV2A/B and Stn2 impairs the efficacy of neurotransmission at hippocampal synapses. These results indicate that endocytic sorting of Syt1 to SVs is mediated by the overlapping activities of SV2A/B and Stn2 and favor a model according to which SV protein sorting is guarded by both cargo-specific mechanisms as well as association between SV proteins.

Involvement of the L-Type Amino Acid Transporter Lat2 in the Transport of 3,3'-Diiodothyronine across the Plasma Membrane
Kinne, A., Wittner, M., Wirth(*), E. K., Hinz, K. M., Schülein, R., Köhrle(*), J.; Krause, G.
Eur Thyroid J, 4:42-50

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

Abstract: Thyroid hormones are transported across cell membranes by transmembrane transporter proteins, for example by members of the monocarboxylate transporter (MCT) and the L-type amino acid transporter (LAT) families. LATs consist of a light chain (e.g. LAT2) and a heavy chain (CD98), which is essential for their cell surface expression and functionality. The specificity of Lat2 for thyroid hormones and their metabolites and its role in their transport was not fully clear. This fact motivated us to establish a cell system to elucidate the uptake of thyroid hormones and their metabolites by mouse Lat2. The coinjection of cRNA coding for Lat2 and CD98 into Xenopus laevis oocytes resulted in a markedly increased level of 3,3'-diiodo-L-thyronine (3,3'-T2) and to some extent also enhanced T3 transport. To gain insight into properties of thyroid hormones and their metabolites transported by Lat2, we inhibited 3,3'-T2 uptake by various iodothyronine derivatives. T1 and T2 derivatives as well as 2-aminobicyclo-[2, 2,1]-heptane-2-carboxylic acid strongly competed with 3,3'-T2 uptake. In addition, we performed T2 uptake measurements with the thyroid hormone-specific transporter MCT8. For both Lat2 and MCT8, Km values in a low micromolar range were calculated. We demonstrated that oocytes are a suitable system for thyroid hormone transport studies mediated by Lat2. Our data indicates that Lat2 compared to other thyroid hormone transporters prefers 3,3'-T2 as the substrate. Thus, Lat2 might contribute to the availability of thyroid hormone by importing and/or exporting 3,3'-T2, which is generated either by T3 inactivation or by rapid deiodinase 1-mediated rT3 degradation.

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Leibniz-Forschungsinstitut für Molekulare Pharmakologie im Forschungsverbund Berlin e.V. (FMP)
Campus Berlin-Buch
Robert-Roessle-Str. 10
13125 Berlin, Germany
+4930 94793 - 100 
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