FMP Publications

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

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Optimum levels of exchangeable protons in perdeuterated proteins for proton detection in MAS solid-state NMR spectroscopy
Akbey, Ü., Lange, S., Trent Franks, W., Linser, R., Rehbein, K., Diehl, A., van Rossum, B. J., Reif, B.; Oschkinat, H.
J Biomol NMR, 46:67-73

Tags: Protein Structure (Oschkinat), Solid-State NMR Spectroscopy (Reif)

Abstract: We present a systematic study of the effect of the level of exchangeable protons on the observed amide proton linewidth obtained in perdeuterated proteins. Decreasing the amount of D(2)O employed in the crystallization buffer from 90 to 0%, we observe a fourfold increase in linewidth for both (1)H and (15)N resonances. At the same time, we find a gradual increase in the signal-to-noise ratio (SNR) for (1)H-(15)N correlations in dipolar coupling based experiments for H(2)O concentrations of up to 40%. Beyond 40%, a significant reduction in SNR is observed. Scalar-coupling based (1)H-(15)N correlation experiments yield a nearly constant SNR for samples prepared with < or =30% H(2)O. Samples in which more H(2)O is employed for crystallization show a significantly reduced NMR intensity. Calculation of the SNR by taking into account the reduction in (1)H T (1) in samples containing more protons (SNR per unit time), yields a maximum SNR for samples crystallized using 30 and 40% H(2)O for scalar and dipolar coupling based experiments, respectively. A sensitivity gain of 3.8 is obtained by increasing the H(2)O concentration from 10 to 40% in the CP based experiment, whereas the linewidth only becomes 1.5 times broader. In general, we find that CP is more favorable compared to INEPT based transfer when the number of possible (1)H,(1)H interactions increases. At low levels of deuteration (> or =60% H(2)O in the crystallization buffer), resonances from rigid residues are broadened beyond detection. All experiments are carried out at MAS frequency of 24 kHz employing perdeuterated samples of the chicken alpha-spectrin SH3 domain.

Reciprocal regulation of aquaporin-2 abundance and degradation by protein kinase A and p38-MAP kinase
Nedvetsky, P. I., Tabor, V., Tamma(*), G., Beulshausen, S., Skroblin, P., Kirschner, A., Mutig(*), K., Boltzen, M., Petrucci, O., Vossenkamper, A., Wiesner, B., Bachmann(*), S., Rosenthal(*), W.; Klussmann, E.
Journal of the American Society of Nephrology : JASN, 21:1645-1656

Tags: Anchored Signalling (Klussmann), Cellular Imaging (Wiesner)

Abstract: Arginine-vasopressin (AVP) modulates the water channel aquaporin-2 (AQP2) in the renal collecting duct to maintain homeostasis of body water. AVP binds to vasopressin V2 receptors (V2R), increasing cAMP, which promotes the redistribution of AQP2 from intracellular vesicles into the plasma membrane. cAMP also increases AQP2 transcription, but whether altered degradation also modulates AQP2 protein levels is not well understood. Here, elevation of cAMP increased AQP2 protein levels within 30 minutes in primary inner medullary collecting duct (IMCD) cells, in human embryonic kidney (HEK) 293 cells ectopically expressing AQP2, and in mouse kidneys. Accelerated transcription or translation did not explain this increase in AQP2 abundance. In IMCD cells, cAMP inhibited p38-mitogen-activated protein kinase (p38-MAPK) via activation of protein kinase A (PKA). Inhibition of p38-MAPK associated with decreased phosphorylation (serine 261) and polyubiquitination of AQP2, preventing proteasomal degradation. Our results demonstrate that AVP enhances AQP2 protein abundance by altering its proteasomal degradation through a PKA- and p38-MAPK-dependent pathway.

Distinct Neuropathologic Phenotypes After Disrupting the Chloride Transport Proteins ClC-6 or ClC-7/Ostm1
Pressey(*), S. N. R., O'Donnell(*), K. J., Stauber, T., Fuhrmann, J. C., Tyynela(*), J., Jentsch, T. J.; Cooper(*), J. D.
J Neuropath Exp Neur, 69:1228-1246

Tags: Physiology and Pathology of Ion Transport (Jentsch

Abstract: The proteins ClC-6 and ClC-7 are expressed in the endosomallysosomal system. Because Clcn6-deficient mice display some features of neuronal ceroid lipofuscinosis (NCL), CLCN6 may be a candidate gene for novel forms of NCL. Using landmarks of disease progression from NCL mouse models as a guide, we examined neuropathologic alterations in the central nervous system of Clcn6(-/-), Clcn7(-/-), and gl mice. gl mice bear a mutation in Ostm1, the beta-subunit critical for Clcn7 function. Severely affected Clcn7(-/-) and gl mice have remarkably similar neuropathologic phenotypes, with pronounced reactive changes and neuron loss in the thalamocortical system, similar to findings in early-onset forms of NCL. In contrast, Clcn6(-/-) mice display slowly progressive, milder neuropathologic features with very little thalamic involvement or microglial activation. These findings detail for the first time the markedly different neuropathologic consequences of mutations in these two CLC genes. Clcn7(-/-) and gl mice bear a close resemblance to the progressive neuropathologic phenotypes of early onset forms of NCL, whereas the distinct phenotype of Clcn6-deficient mice suggests that this gene could be a candidate for a later-onset form of mild neurologic dysfunction with some NCL-like features.

TRIM24 links a non-canonical histone signature to breast cancer
Tsai(*), W. W., Wang(*), Z. X., Yiu(*), T. T., Akdemir(*), K. C., Xia(*), W. Y., Winter(*), S., Tsai(*), C. Y., Shi(*), X. B., Schwarzer, D., Plunkett(*), W., Aronow(*), B., Gozani(*), O., Fischle(*), W., Hung(*), M. C., Patel(*), D. J.; Barton(*), M. C.
Nature, 468:927-U320

Tags: Protein Chemistry (Schwarzer)

Abstract: Recognition of modified histone species by distinct structural domains within 'reader' proteins plays a critical role in the regulation of gene expression. Readers that simultaneously recognize histones with multiple marks allow transduction of complex chromatin modification patterns into specific biological outcomes. Here we report that chromatin regulator tripartite motif-containing 24 (TRIM24) functions in humans as a reader of dual histone marks by means of tandem plant homeodomain (PHD) and bromodomain (Bromo) regions. The three-dimensional structure of the PHD-Bromo region of TRIM24 revealed a single functional unit for combinatorial recognition of unmodified H3K4 (that is, histone H3 unmodified at lysine 4, H3K4me0) and acetylated H3K23 (histone H3 acetylated at lysine 23, H3K23ac) within the same histone tail. TRIM24 binds chromatin and oestrogen receptor to activate oestrogen-dependent genes associated with cellular proliferation and tumour development. Aberrant expression of TRIM24 negatively correlates with survival of breast cancer patients. The PHD-Bromo of TRIM24 provides a structural rationale for chromatin activation through a non-canonical histone signature, establishing a new route by which chromatin readers may influence cancer pathogenesis.

Cellular uptake and biological activity of peptide nucleic acids conjugated with peptides with and without cell-penetrating ability
Turner, Y., Wallukat(*), G., Säälik, P., Wiesner, B., Pritz, S.; Oehlke, J.
J Pept Sci, 16:71-80

Tags: Peptide-Lipid-Interaction/ Peptide Transport (Dathe/Oehlke), Cellular Imaging (Wiesner)

Abstract: A 12-mer peptide nucleic acid (PNA) directed against the nociceptin/orphanin FQ receptor mRNA was disulfide bridged with various peptides without and with cell-penetrating features. The cellular uptake and the antisense activity of these conjugates were assessed in parallel. Quantitation of the internalized PNA was performed by using an approach based on capillary electrophoresis with laser-induced fluorescence detection (CE-LIF). This approach enabled a selective assessment of the PNA moiety liberated from the conjugate in the reducing intracellular environment, thus avoiding bias of the results by surface adsorption. The biological activity of the conjugates was studied by an assay based on the downregulation of the nociceptin/orphanin FQ receptor in neonatal rat cardiomyocytes (CM). Comparable cellular uptake was found for all conjugates and for the naked PNA, irrespective of the cell-penetrating properties of the peptide components. All conjugates exhibited a comparable biological activity in the 100 nM range. The naked PNA also exhibited extensive antisense activity, which, however, proved about five times lower than that of the conjugates. The found results suggest cellular uptake and the bioactivity of PNA-peptide conjugates to be not primarily related to the cell-penetrating ability of their peptide components. Likewise from these results it can be inferred that the superior bioactivity of the PNA-peptide conjugates in comparison with that of naked PNA rely on as yet unknown factors rather than on higher membrane permeability. Several hints point to the resistance against cellular export and the aggregation propensity combined with the endocytosis rate to be candidates for such factors.

The KCNQ5 potassium channel mediates a component of the afterhyperpolarization current in mouse hippocampus
Tzingounis(*), A. V., Heidenreich, M., Kharkovets(*), T., Spitzmaul, G., Jensen(*), H. S., Nicoll(*), R. A.; Jentsch, T. J.
P Natl Acad Sci USA, 107:10232-10237

Tags: Physiology and Pathology of Ion Transport (Jentsch

Abstract: Mutations in KCNQ2 and KCNQ3 voltage-gated potassium channels lead to neonatal epilepsy as a consequence of their key role in regulating neuronal excitability. Previous studies in the brain have focused primarily on these KCNQ family members, which contribute to M-currents and afterhyperpolarization conductances in multiple brain areas. In contrast, the function of KCNQ5 (Kv7.5), which also displays widespread expression in the brain, is entirely unknown. Here, we developed mice that carry a dominant negative mutation in the KCNQ5 pore to probe whether it has a similar function as other KCNQ channels. This mutation renders KCNQ5(dn)-containing homomeric and heteromeric channels nonfunctional. We find that Kcnq5(dn/dn) mice are viable and have normal brain morphology. Furthermore, expression and neuronal localization of KCNQ2 and KCNQ3 subunits are unchanged. However, in the CA3 area of hippocampus, a region that highly expresses KCNQ5 channels, the medium and slow afterhyperpolarization currents are significantly reduced. In contrast, neither current is affected in the CA1 area of the hippocampus, a region with low KCNQ5 expression. Our results demonstrate that KCNQ5 channels contribute to the afterhyperpolarization currents in hippocampus in a cell type-specific manner.

Tricellulin forms homomeric and heteromeric tight junctional complexes
Westphal(*), J. K., Dörfel(*), M. J., Krug(*), S. M., Cording, J. D., Piontek, J., Blasig, I. E., Tauber(*), R., Fromm(*), M.; Huber(*), O.
Cellular and Molecular Life Sciences, 67:2057-2068

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

Abstract: Sealing of the paracellular cleft by tight junctions is of central importance for epithelia and endothelia to function as efficient barriers between the extracellular space and the inner milieu. Occludin and claudins represent the major tight junction components involved in establishing this barrier function. A special situation emerges at sites where three cells join together. Tricellulin, a recently identified tetraspan protein concentrated at tricellular contacts, was reported to organize tricellular as well as bicellular tight junctions. Here we show that in MDCK cells, the tricellulin C-terminus is important for the basolateral translocation of tricellulin, whereas the N-terminal domain appears to be involved in directing tricellulin to tricellular contacts. In this respect, identification of homomeric tricellulin-tricellulin and of heteromeric tricellulin-occludin complexes extends a previously published model and suggests that tricellulin and occludin are transported together to the edges of elongating bicellular junctions and get separated when tricellular contacts are formed.

A new phenotype of nongoitrous and nonautoimmune hyperthyroidism caused by a heterozygous thyrotropin receptor mutation in transmembrane helix 6
Winkler(*), F., Kleinau, G., Tarnow(*), P., Rediger(*), A., Grohmann(*), L., Gaetjens(*), I., Krause, G., L'Allemand(*), D., Grüters(*), A., Krude(*), H.; Biebermann(*), H.
The Journal of clinical endocrinology and metabolism, 95:3605-3610

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

Abstract: CONTEXT: Activating mutations in the TSHR gene were found in patients suffering from nonautoimmune hyperthyroidism. In the past, it was assumed that thyroid hyperplasia is due to constitutive activation of the Gs/adenylyl cyclase signaling pathway; however, the physiological role of the Gq/11 pathway in this context remains unclear. OBJECTIVE: In this study, we investigated molecular details of the TSHR in a patient with nonautoimmune and nongoitrous hyperthyroidism. RESULTS: We detected a heterozygous mutation in exon 10 of the TSHR gene leading to an exchange of a cysteine residue for tryptophan at amino acid position 636 in transmembrane helix 6. Functional characterization of the mutant receptor revealed a slight reduction of the cell surface expression and TSH induced cAMP accumulation compared to the wild type. Additional observations included a constitutive activation of the Gs-mediated signaling pathway and a simultaneous nearly complete loss-of-function for the Gq/11 pathway after bovine TSH stimulation. Studies on TSHR models suggest significant changes of important amino acid interactions and the overall helix arrangement caused by mutation C636W. CONCLUSION: We report a patient in whom a TSHR mutation leads to nonautoimmune hyperthyroidism due to a mutation that constitutively activates the Gs signaling pathway but additionally completely inhibits the Gq/11 pathway. The absence of goiter in the patient suggests that the Gq/11 pathway is related to thyroid growth and that different signaling pathways are mediated and regulated by TSH. These functional data could be confirmed by reproducible findings of two siblings with a constitutive activation for both pathways.

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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 
+4930 94793 - 109 (Fax)

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