FMP Publications

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

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References
Insight into the Modification of Polymeric Micellar and Liposomal Nanocarriers by Fluorescein-Labeled Lipids and Uptake-Mediating Lipopeptides
Draffehn(*), S., Eichhorst, J., Wiesner, B.; Kumke(*), M. U.
Langmuir, 32:6928-6939
(2016)

Tags: Cellular Imaging (Wiesner)

Abstract: Encapsulation of diagnostic and therapeutic compounds in transporters improves their delivery to the point of need. An even more efficient treatment of diseases can be achieved using carriers with targeting or protecting moieties. In the present work, we investigated micellar and liposomal nanocarriers modified with fluorescein, peptides, and polymers that are covalently bound to fatty acids or phospholipids to ensure a self-driven incorporation into the micelles or liposomes. First, we characterized the photophysics of the fluorescent probes in the absence and in the presence of nanocarriers. Changes in the fluorescence decay time, quantum yield, and intensity of a fluorescein-labeled fatty acid (fluorescein-labeled palmitic acid [fPA]) and a fluorescein-labeled lipopeptide (P2fA2) were found. By exploiting these changes, we investigated a lipopeptide (P2A2 as an uptake-mediating unit) in combination with different nanocarriers (micelles and liposomes) and determined the corresponding association constant Kass values, which were found to be very high. In addition, the mobility of fPA was exploited using fluorescence correlation spectroscopy (FCS) and fluorescence depolarization (FD) experiments to characterize the nanocarriers. Cellular uptake experiments with mouse brain endothelial cells provided information on the uptake behavior of liposomes modified by uptake-mediating P2A2 and revealed differences in the uptake behavior between pH-sensitive and pH-insensitive liposomes.

Urolinin: The First Linear Peptidic Urotensin-II Receptor Agonist
Bandholtz(*), S., Erdmann(*), S., von Hacht(*), J. L., Exner(*), S., Krause, G., Kleinau(*), G.; Grotzinger(*), C.
Journal of medicinal chemistry, 59:10100-10112
(2016)

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

Abstract: This study investigated the role of individual U-II amino acid positions and side chain characteristics important for U-IIR activation. A complete permutation library of 209 U-II variants was studied in an activity screen that contained single substitution variants of each position with one of the other 19 proteinogenic amino acids. Receptor activation was measured using a cell-based high-throughput fluorescence calcium mobilization assay. We generated the first complete U-II substitution map for U-II receptor activation, resulting in a detailed view into the structural features required for receptor activation, accompanied by complementary information from receptor modeling and ligand docking studies. On the basis of the systematic SAR study of U-II, we created 33 further short and linear U-II variants from eight to three amino acids in length, including d- and other non-natural amino acids. We identified the first high-potency linear U-II analogues. Urolinin, a linear U-II agonist (nWWK-Tyr(3-NO2)-Abu), shows low nanomolar potency as well as improved metabolic stability.

Bimodal antagonism of PKA signalling by ARHGAP36
Eccles(*), R. L., Czajkowski(*), M. T., Barth(*), C., Müller(*), P. M., McShane(*), E., Grunwald(*), S., Beaudette(*), P., Mecklenburg(*), N., Volkmer, R., Zühlke(*), K., Dittmar(*), G., Selbach(*), M., Hammes(*), A., Daumke(*), O., Klussmann(*), E., Urbe(*), S.; Rocks(*), O.
Nat Commun, 7:12963
(2016)

Tags: Peptide Synthesis (Hackenberger/Volkmer)

Abstract: Protein kinase A is a key mediator of cAMP signalling downstream of G-protein-coupled receptors, a signalling pathway conserved in all eukaryotes. cAMP binding to the regulatory subunits (PKAR) relieves their inhibition of the catalytic subunits (PKAC). Here we report that ARHGAP36 combines two distinct inhibitory mechanisms to antagonise PKA signalling. First, it blocks PKAC activity via a pseudosubstrate motif, akin to the mechanism employed by the protein kinase inhibitor proteins. Second, it targets PKAC for rapid ubiquitin-mediated lysosomal degradation, a pathway usually reserved for transmembrane receptors. ARHGAP36 thus dampens the sensitivity of cells to cAMP. We show that PKA inhibition by ARHGAP36 promotes derepression of the Hedgehog signalling pathway, thereby providing a simple rationale for the upregulation of ARHGAP36 in medulloblastoma. Our work reveals a new layer of PKA regulation that may play an important role in development and disease.

RIM-binding protein 2 regulates release probability by fine-tuning calcium channel localization at murine hippocampal synapses
Grauel(*), M. K., Maglione, M., Reddy-Alla(*), S., Willmes(*), C. G., Brockmann(*), M. M., Trimbuch(*), T., Rosenmund(*), T., Pangalos(*), M., Vardar(*), G., Stumpf(*), A., Walter, A. M., Rost(*), B. R., Eickholt(*), B. J., Haucke, V., Schmitz(*), D., Sigrist(*), S. J.; Rosenmund(*), C.
Proc Natl Acad Sci U S A, 113:11615-11620
(2016)

Tags: Molecular Pharmacology and Cell Biology (Haucke), Molecular and Theoretical Neuroscience (Walter)

Abstract: The tight spatial coupling of synaptic vesicles and voltage-gated Ca2+ channels (CaVs) ensures efficient action potential-triggered neurotransmitter release from presynaptic active zones (AZs). Rab-interacting molecule-binding proteins (RIM-BPs) interact with Ca2+ channels and via RIM with other components of the release machinery. Although human RIM-BPs have been implicated in autism spectrum disorders, little is known about the role of mammalian RIM-BPs in synaptic transmission. We investigated RIM-BP2-deficient murine hippocampal neurons in cultures and slices. Short-term facilitation is significantly enhanced in both model systems. Detailed analysis in culture revealed a reduction in initial release probability, which presumably underlies the increased short-term facilitation. Superresolution microscopy revealed an impairment in CaV2.1 clustering at AZs, which likely alters Ca2+ nanodomains at release sites and thereby affects release probability. Additional deletion of RIM-BP1 does not exacerbate the phenotype, indicating that RIM-BP2 is the dominating RIM-BP isoform at these synapses.

X-exome sequencing of 405 unresolved families identifies seven novel intellectual disability genes
Hu(*), H., Haas(*), S. A., Chelly(*), J., Van Esch(*), H., Raynaud(*), M., de Brouwer(*), A. P., Weinert, S., Froyen(*), G., Frints(*), S. G., Laumonnier, F., Zemojtel(*), T., Love(*), M. I., Richard(*), H., Emde(*), A. K., Bienek(*), M., Jensen(*), C., Hambrock(*), M., Fischer(*), U., Langnick(*), C., Feldkamp(*), M., Wissink-Lindhout(*), W., Lebrun(*), N., Castelnau(*), L., Rucci(*), J., Montjean(*), R., Dorseuil(*), O., Billuart(*), P., Stuhlmann, T., Shaw(*), M., Corbett(*), M. A., Gardner(*), A., Willis-Owen(*), S., Tan(*), C., Friend(*), K. L., Belet(*), S., van Roozendaal(*), K. E., Jimenez-Pocquet(*), M., Moizard(*), M. P., Ronce(*), N., Sun(*), R., O'Keeffe(*), S., Chenna(*), R., van Bommel(*), A., Goke(*), J., Hackett(*), A., Field(*), M., Christie(*), L., Boyle(*), J., Haan(*), E., Nelson(*), J., Turner(*), G., Baynam(*), G., Gillessen-Kaesbach(*), G., Müller, U., Steinberger(*), D., Budny(*), B., Badura-Stronka(*), M., Latos-Bielenska(*), A., Ousager(*), L. B., Wieacker(*), P., Rodriguez Criado(*), G., Bondeson(*), M. L., Anneren(*), G., Dufke(*), A., Cohen(*), M., Van Maldergem(*), L., Vincent-Delorme(*), C., Echenne(*), B., Simon-Bouy(*), B., Kleefstra(*), T., Willemsen(*), M., Fryns(*), J. P., Devriendt(*), K., Ullmann(*), R., Vingron(*), M., Wrogemann(*), K., Wienker(*), T. F., Tzschach(*), A., van Bokhoven(*), H., Gecz(*), J., Jentsch, T. J., Chen(*), W., Ropers(*), H. H.; Kalscheuer(*), V. M.
Molecular psychiatry, 21:133-148
(2016)

Tags: Physiology and Pathology of Ion Transport (Jentsch

Abstract: X-linked intellectual disability (XLID) is a clinically and genetically heterogeneous disorder. During the past two decades in excess of 100 X-chromosome ID genes have been identified. Yet, a large number of families mapping to the X-chromosome remained unresolved suggesting that more XLID genes or loci are yet to be identified. Here, we have investigated 405 unresolved families with XLID. We employed massively parallel sequencing of all X-chromosome exons in the index males. The majority of these males were previously tested negative for copy number variations and for mutations in a subset of known XLID genes by Sanger sequencing. In total, 745 X-chromosomal genes were screened. After stringent filtering, a total of 1297 non-recurrent exonic variants remained for prioritization. Co-segregation analysis of potential clinically relevant changes revealed that 80 families (20%) carried pathogenic variants in established XLID genes. In 19 families, we detected likely causative protein truncating and missense variants in 7 novel and validated XLID genes (CLCN4, CNKSR2, FRMPD4, KLHL15, LAS1L, RLIM and USP27X) and potentially deleterious variants in 2 novel candidate XLID genes (CDK16 and TAF1). We show that the CLCN4 and CNKSR2 variants impair protein functions as indicated by electrophysiological studies and altered differentiation of cultured primary neurons from Clcn4(-/-) mice or after mRNA knock-down. The newly identified and candidate XLID proteins belong to pathways and networks with established roles in cognitive function and intellectual disability in particular. We suggest that systematic sequencing of all X-chromosomal genes in a cohort of patients with genetic evidence for X-chromosome locus involvement may resolve up to 58% of Fragile X-negative cases.

Modulation of Hexadecyl-LPA-Mediated Activation of Mast Cells and Microglia by a Chemical Probe for LPA5
Kozian(*), D. H., von Haeften(*), E., Joho(*), S., Czechtizky(*), W., Anumala, U. R., Roux(*), P., Dudda(*), A., Evers(*), A.; Nazare, M.
Chembiochem, 17:861-865
(2016)

Tags: Medicinal Chemistry (Nazare)

Abstract: Mast cells and microglia play a critical role in innate immunity and inflammation and can be activated by a wide range of endogenous and exogenous stimuli. Lysophosphatidic acid (LPA) has recently been reported to activate mast cells and microglia. Using the human mast cell line HMC-1 and the mouse microglia cell line BV-2, we show that LPA-mediated activation can be prevented by blockade of the LPA receptor 5 (LPA5) in both cell lines. The identification of new LPA5-specific antagonists as tool compounds to probe and modulate the LPA5/LPA axis in relevant in vitro and in vivo assays should contribute to better understanding of the underlying role of LPAs in the development and progression of (neuro-) inflammatory diseases.

Specific binding of a mutated fragment of Clostridium perfringens enterotoxin to endothelial claudin-5 and its modulation of cerebral vascular permeability
Liao(*), Z., Yang(*), Z., Piontek, A., Eichner(*), M., Krause, G., Li(*), L., Piontek(*), J.; Zhang(*), J.
Neuroscience, 327:53-63
(2016)

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

Abstract: The vertebrate blood-brain barrier (BBB) creates an obstacle for central nervous system-related drug delivery. Claudin-5 (Cldn5), expressed in large quantities in BBB, plays a vital role in restricting BBB permeability. The C-terminal domain of Clostridium perfringens enterotoxin (cCPE) has been verified as binding to a subset of claudins (Cldns). The Cldn5-binding cCPE194-319 variant cCPEY306W/S313H was applied in this study to investigate its ability to modulate the permeability of zebrafish larval BBB. In vitro results showed that cCPEY306W/S313H is able to bind specifically to Cldn5 in murine brain vascular endothelial (bEnd.3) cells, and is transported along with Cldn5 from the cell membrane to the cytoplasm, which in turn results in a reduction in transendothelial electrical resistance (TEER). Conversely, this effect can be reversed by removal of cCPEY306W/S313H. In an in vivo experiment, this study estimates the capability of cCPEY306W/S313H to modulate Cldn5 using a rhodamine B-Dextran dye diffusion assay in zebrafish larval BBB. The results show that cCPEY306W/S313H co-localized with Cldn5 in zebrafish cerebral vascular cells and modulated BBB permeability, resulting in dye leakage. Taken together, this study suggests that cCPEY306W/S313H has the capability - both in vitro and in vivo - to modulate BBB permeability temporarily by specific binding to Cldn5.

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