FMP Publications

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

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The Investigation of cis- and trans-Interactions Between Claudins
Haseloff, R. F., Piontek, J.; Blasig, I. E.
Curr Top Membr, 65:97-112

Tags: Molecular Cell Physiology (Blasig, I.E.)

Abstract: OVERVIEW Claudins control the paracellular permeability of the tight junctions in epithelial and endothelial cells forming single cell layers. Several claudins may constitute a network of strands, establishing a continuous barrier within the intercellular clefts of the monolayer. Depending on the claudin composition of a given tissue, the intracellular space may be tight for any solute or permeable for compounds of different molecular weight or differently charged ions. These functions are largely based on intermolecular claudin claudin interactions. Strand formation between claudins requires two components: a longitudinal association along the plasma membrane of the cell-cis-interaction-and an interplay from one cell surface to the next one-trans-interaction. This chapter is aimed at reviewing methods for the analysis of cis- and trans-interacting claudins.

Short Cationic Antimicrobial Peptides Interact with ATP
Hilpert(*), K., McLeod(*), B., Yu(*), J., Elliott(*), M. R., Rautenbach(*), M., Ruden(*), S., Bürck(*), J., Muhle-Goll(*), C., Ulrich(*), A. S., Keller, S.; Hancock(*), R. E. W.
Antimicrob Agents Ch, 54:4480-4483

Tags: Biophysics of Membrane Proteins (Keller)

Abstract: The mode of action of short, nonhelical antimicrobial peptides is still not well understood. Here we show that these peptides interact with ATP and directly inhibit the actions of certain ATP-dependent enzymes, such as firefly luciferase, DnaK, and DNA polymerase. alpha-Helical and planar or circular antimicrobial peptides did not show such interaction with ATP.

Glycogen synthase kinase 3beta interaction protein functions as an A-kinase anchoring protein
Hundsrucker, C., Skroblin, P., Christian, F., Zenn(*), H. M., Popara, V., Joshi, M., Eichhorst, J., Wiesner, B., Herberg(*), F. W., Reif, B., Rosenthal(*), W.; Klussmann, E.
J Biol Chem, 285:5507-5521

Tags: Anchored Signalling (Klussmann), Solid-State NMR Spectroscopy (Reif), Cellular Imaging (Wiesner)

Abstract: A-kinase anchoring proteins (AKAPs) include a family of scaffolding proteins that target protein kinase A (PKA) and other signaling proteins to cellular compartments and thereby confine the activities of the associated proteins to distinct regions within cells. AKAPs bind PKA directly. The interaction is mediated by the dimerization and docking domain of regulatory subunits of PKA and the PKA-binding domain of AKAPs. Analysis of the interactions between the dimerization and docking domain and various PKA-binding domains yielded a generalized motif allowing the identification of AKAPs. Our bioinformatics and peptide array screening approaches based on this signature motif identified GSKIP (glycogen synthase kinase 3beta interaction protein) as an AKAP. GSKIP directly interacts with PKA and GSK3beta (glycogen synthase kinase 3beta). It is widely expressed and facilitates phosphorylation and thus inactivation of GSK3beta by PKA. GSKIP contains the evolutionarily conserved domain of unknown function 727. We show here that this domain of GSKIP and its vertebrate orthologues binds both PKA and GSK3beta and thereby provides a mechanism for the integration of PKA and GSK3beta signaling pathways.

Cellular structural biology
Ito(*), Y.; Selenko, P.
Curr Opin Struc Biol, 20:640-648

Tags: In-Cell NMR (Selenko)

Abstract: While we appreciate the complexity of the intracellular environment as a general property of every living organism, we collectively lack the appropriate tools to analyze protein structures in a cellular context In-cell NMR spectroscopy represents a novel biophysical tool to investigate the conformational and functional characteristics of biomolecules at the atomic level inside live cells Here, we review recent in-cell NMR developments and provide an outlook towards future applications in prokaryotic and eukaryotic cells We hope to thereby emphasize the usefulness of in-cell NMR techniques for cellular studies of complex biological processes and for structural analyses in native environments

Solid-state NMR and SAXS studies provide a structural basis for the activation of alphaB-crystallin oligomers
Jehle, S., Rajagopal(*), P., Bardiaux, B., Markovic, S., Kühne, R., Stout(*), J. R., Higman, V. A., Klevit(*), R. E., van Rossum, B. J.; Oschkinat, H.
Nat Struct Mol Biol, 17:1037-1042

Tags: Protein Structure (Oschkinat), Computational Chemistry/ Drug Design (Kühne)

Abstract: The small heat shock protein alphaB-crystallin (alphaB) contributes to cellular protection against stress. For decades, high-resolution structural studies on oligomeric alphaB have been confounded by its polydisperse nature. Here, we present a structural basis of oligomer assembly and activation of the chaperone using solid-state NMR and small-angle X-ray scattering (SAXS). The basic building block is a curved dimer, with an angle of approximately 121 degrees between the planes of the beta-sandwich formed by alpha-crystallin domains. The highly conserved IXI motif covers a substrate binding site at pH 7.5. We observe a pH-dependent modulation of the interaction of the IXI motif with beta4 and beta8, consistent with a pH-dependent regulation of the chaperone function. N-terminal region residues Ser59-Trp60-Phe61 are involved in intermolecular interaction with beta3. Intermolecular restraints from NMR and volumetric restraints from SAXS were combined to calculate a model of a 24-subunit alphaB oligomer with tetrahedral symmetry.

Intermolecular protein-RNA interactions revealed by 2D 31P-15N magic angle spinning solid-state NMR spectroscopy
Jehle(*), S., Falb(*), M., Kirkpatrick(*), J. P., Oschkinat, H., van Rossum, B. J., Althoff(*), G.; Carlomagno(*), T.
J Am Chem Soc, 132:3842-3846

Tags: Protein Structure (Oschkinat)

Abstract: The structural investigation of large RNP complexes by X-ray crystallography can be a difficult task due to the flexibility of the RNA and of the protein-RNA interfaces, which may hinder crystallization. In these cases, NMR spectroscopy is an attractive alternative to crystallography, although the large size of typical RNP complexes may limit the applicability of solution NMR. Solid-state NMR spectroscopy, however, is not subject to any intrinsic limitations with respect to the size of the object under investigation, with restrictions imposed solely by the sensitivity of the instrumentation. In addition, it does not require large, well-ordered crystals and can therefore be applied to flexible, partially disordered complexes. Here we show for the first time that solid-state NMR spectroscopy can be used to probe intermolecular interactions at the protein-RNA interface in RNP complexes. Distances between the (15)N nuclei of the protein backbone and the (31)P nuclei of the RNA backbone can be measured in TEDOR experiments and used as restraints in structure calculations. The distance measurement is accurate, as proven for the test case of the L7Ae-box C/D RNA complex, for which a crystal structure is available. The results presented here reveal the as yet unexplored potential of solid-state NMR spectroscopy in the investigation of large RNP complexes.

Modulation of G-protein coupled receptor sample quality by modified cell-free expression protocols: A case study of the human endothelin A receptor
Junge(*), F., Luh(*), L. M., Proverbio(*), D., Schäfer(*), B., Abele(*), R., Beyermann, M., Dötsch(*), V.; Bernhard(*), F.
J Struct Biol, 172:94-106

Tags: Peptide Synthesis (Beyermann)

Abstract: G-protein coupled receptors still represent one of the most challenging targets in membrane protein research. Here we present a strategic approach for the cell-free synthesis of these complex membrane proteins exemplified by the preparative scale production of the human endothelin A receptor. The versatility of the cell-free expression system was used to modulate sample quality by alteration of detergents hence presenting different solubilization environments to the synthesized protein at different stages of the production process. Sample properties after co-translational and post-translational solubilization have been analysed by evaluation of homogeneity, protein stability and receptor ligand binding competence. This is a first quality evaluation of a membrane protein obtained in two different cell-free expression modes and we demonstrate that both can be used for the production of ligand-binding competent endothelin A receptor in quantities sufficient for structural approaches. The presented strategy of cell-free expression protocol development could serve as basic guideline for the production of related receptors in similar systems. (C) 2010 Elsevier Inc. All rights reserved.

Renal ACE2 expression and activity is unaltered during established hypertension in adult SHRSP and TGR(mREN2)27
Kamilic(*), J., Hamming(*), I., Kreutz(*), R., Bolbrinker(*), J., Siems, W. E., Nassar(*), I., Sluimer(*), J. C., Walther(*), T., Navis(*), G. J.; van Goor(*), H.
Hypertens Res, 33:123-128

Tags: Biochemical Neurobiology (Siems)

Abstract: Differential renal expression of a homolog of the angiotensin-converting enzyme (ACE), that is, ACE2, has been implicated as a genetic basis of polygenetic hypertension in the stroke-prone spontaneously hypertensive rat model. However, data on the role of ACE2 in hypertension are still inconclusive. Therefore, we analyzed kidney ACE2 mRNA, ACE2 protein and ACE2 enzyme activities in the adult polygenetic stroke-prone spontaneously hypertensive rat (SHRSP) and the monogenetic TGR(mREN2)27 rat models, in comparison with their normotensive reference strains, Wistar-Kyoto (WKY) and Spraque-Dawley (SD) rats, respectively. Kidney ACE2 mRNA was studied using quantitative real-time reverse transcriptase-PCR (RT-PCR) in cortex and medulla, whereas protein expression was scored semiquantitatively in detail in different renal structures using immunohistochemistry. Furthermore, total renal tissue ACE2 activity was measured using a fluorimetric assay that was specified by the ACE2 inhibitor DX600. In SHRSP and homozygous TGR(mREN2)27 rats with established hypertension, kidney ACE2 mRNA, protein and tissue ACE2 activities were not different from their respective WKY and SD reference strain, respectively. In addition, when we looked at renal localization, we found ACE2 protein to be predominantly present in glomeruli and endothelium with weak staining in distal and negative staining in proximal tubuli. Thus, our data challenge previous work that implicates ACE2 as a candidate gene for hypertension in SHRSP by reporting a significant reduction of ACE2 in the kidneys of SHRSP. Taken together, renal ACE2 is not altered in the SHRSP and TGR(mREN2)27 genetic rat models with established hypertension. Hypertension Research (2010) 33, 123-128; doi: 10.1038/hr.2009.191; published online 20 November 2009

Nonlinear least-squares data fitting in Excel spreadsheets
Kemmer, G.; Keller, S.
Nat Protoc, 5:267-281

Tags: Biophysics of Membrane Proteins (Keller)

Abstract: We describe an intuitive and rapid procedure for analyzing experimental data by nonlinear least-squares fitting (NLSF) in the most widely used spreadsheet program. Experimental data in x/y form and data calculated from a regression equation are inputted and plotted in a Microsoft Excel worksheet, and the sum of squared residuals is computed and minimized using the Solver add-in to obtain the set of parameter values that best describes the experimental data. The confidence of best-fit values is then visualized and assessed in a generally applicable and easily comprehensible way. Every user familiar with the most basic functions of Excel will be able to implement this protocol, without previous experience in data fitting or programming and without additional costs for specialist software. The application of this tool is exemplified using the well-known Michaelis-Menten equation characterizing simple enzyme kinetics. Only slight modifications are required to adapt the protocol to virtually any other kind of dataset or regression equation. The entire protocol takes approximately 1 h.

Effects of ACE2 inhibition in the post-myocardial infarction heart
Kim(*), M. A., Yang(*), D., Kida(*), K., Molotkova(*), N., Yeo(*), S. J., Varki(*), N., Iwata(*), M., Dalton(*), N. D., Peterson(*), K. L., Siems, W. E., Walther(*), T., Cowling(*), R. T., Kjekshus(*), J.; Greenberg(*), B.
Journal of cardiac failure, 16:777-785

Tags: Biochemical Neurobiology (Siems)

Abstract: BACKGROUND: There is evidence that angiotensin-converting enzyme 2 (ACE2) is cardioprotective. To assess this in the post-myocardial infarction (MI) heart, we treated adult male Sprague-Dawley rats with either placebo (PL) or C16, a selective ACE2 inhibitor, after permanent coronary artery ligation or sham operation. METHODS AND RESULTS: Coronary artery ligation resulting in MI between 25% to 50% of the left ventricular (LV) circumference caused substantial cardiac remodeling. Daily C16 administration from postoperative days 2 to 28 at a dose that inhibited myocardial ACE2 activity was associated with a significant increase in MI size and reduction in LV % fractional shortening. Treatment with C16 did not significantly affect post-MI increases in LV end-diastolic dimension but did inhibit increases in wall thickness and fibrosis in non-infarcted LV. On postoperative day 7, C16 had no significant effect on the increased level of apoptosis in the infarct and border zones nor did it significantly affect capillary density surrounding the MI. It did, however, significantly reduce the number of c-kit(+) cells in the border region. CONCLUSIONS: These findings support the notion that ACE2 exerts cardioprotective effects by preserving jeopardized cardiomyocytes in the border zone. The reduction in hypertrophy and fibrosis with C16, however, suggests that ACE2 activity has diverse effects on post-MI remodeling.

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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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