FMP Publications

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

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Subtype-specific block of voltage-gated K+ channels by mu-conopeptides
Leipold(*), E., Ullrich, F., Thiele(*), M., Tietze(*), A. A., Terlau(*), H., Imhof(*), D.; Heinemann(*), S. H.
Biochem. Biophys. Res. Commun., 482:1135-1140

Tags: Physiology and Pathology of Ion Transport (Jentsch)

Abstract: The neurotoxic cone snail peptide mu-GIIIA specifically blocks skeletal muscle voltage-gated sodium (Na(V)1.4) channels. The related conopeptides mu-PIIIA and mu-SIIIA, however, exhibit a wider activity spectrum by also inhibiting the neuronal Na-V channels Na-V 1.2 and Na-V 1.7. Here we demonstrate that those mu-conopeptides with a broader target range also antagonize select subtypes of voltage-gated potassium channels of the K(v)1 family: mu-PIIIA and mu-SIIIA inhibited K(V)1.1 and K(V)1.6 channels in the nanomolar range, while being inactive on subtypes K(V)1.2-1.5 and K(V)2.1. Construction and electro-physiological evaluation of chimeras between K(V)1.5 and K(V)1.6 revealed that these toxins block K-V channels involving their pore regions; the subtype specificity is determined in part by the sequence close to the selectivity filter but predominantly by the so-called turret domain, i.e. the extracellular loop connecting the pore with transmembrane segment S5. Conopeptides mu-SIIIA and mu-PIIIA thus, are not specific for Na-V channels, and the known structure of some K-V channel subtypes may provide access to structural insight into the molecular interaction between-conopeptides and their target channels. (C) 2016 Elsevier Inc. All rights reserved.

Selective transport of neurotransmitters and modulators by distinct volume-regulated LRRC8 anion channels
Lutter, D., Ullrich, F., Lueck, J. C., Kempa(*), S.; Jentsch, T. J.
J Cell Sci, 130:1122-1133

Tags: Physiology and Pathology of Ion Transport (Jentsch)

Abstract: In response to swelling, mammalian cells release chloride and organic osmolytes through volume-regulated anion channels (VRACs). VRACs are heteromers of LRRC8A and other LRRC8 isoforms (LRRC8B to LRRC8E), which are co-expressed in HEK293 and most other cells. The spectrum of VRAC substrates and its dependence on particular LRRC8 isoforms remains largely unknown. We show that, besides the osmolytes taurine and myo-inositol, LRRC8 channels transport the neurotransmitters glutamate, aspartate and gamma-aminobutyric acid (GABA) and the co-activator D-serine. HEK293 cells engineered to express defined subsets of LRRC8 isoforms were used to elucidate the subunit-dependence of transport. Whereas LRRC8D was crucial for the translocation of overall neutral compounds like myo-inositol, taurine and GABA, and sustained the transport of positively charged lysine, flux of negatively charged aspartate was equally well supported by LRRC8E. Disruption of LRRC8B or LRRC8C failed to decrease the transport rates of all investigated substrates, but their inclusion into LRRC8 heteromers influenced the substrate preference of VRAC. This suggested that individual VRACs can contain three or more different LRRC8 subunits, a conclusion confirmed by sequential co-immunoprecipitations. Our work suggests a composition-dependent role of VRACs in extracellular signal transduction.

Lipid-mediated PX-BAR domain recruitment couples local membrane constriction to endocytic vesicle fission
Schöneberg(*), J., Lehmann, M., Ullrich(*), A., Posor, Y., Lo, W. T., Lichtner, G., Schmoranzer, J., Haucke, V.; Noe(*), F.
Nat Commun, 8:15873

Tags: Molecular Pharmacology and Cell Biology (Haucke)

Abstract: Clathrin-mediated endocytosis (CME) involves membrane-associated scaffolds of the bin-amphiphysin-rvs (BAR) domain protein family as well as the GTPase dynamin, and is accompanied and perhaps triggered by changes in local lipid composition. How protein recruitment, scaffold assembly and membrane deformation is spatiotemporally controlled and coupled to fission is poorly understood. We show by computational modelling and super-resolution imaging that phosphatidylinositol 3,4-bisphosphate [PI(3,4)P2] synthesis within the clathrin-coated area of endocytic intermediates triggers selective recruitment of the PX-BAR domain protein SNX9, as a result of complex interactions of endocytic proteins competing for phospholipids. The specific architecture induces positioning of SNX9 at the invagination neck where its self-assembly regulates membrane constriction, thereby providing a template for dynamin fission. These data explain how lipid conversion at endocytic pits couples local membrane constriction to fission. Our work demonstrates how computational modelling and super-resolution imaging can be combined to unravel function and mechanisms of complex cellular processes.

Evidence for Heterodimerization and Functional Interaction of the Angiotensin Type 2 Receptor and the Receptor MAS
Leonhardt(*), J., Villela(*), D. C., Teichmann, A., Munter(*), L. M., Mayer(*), M. C., Mardahl(*), M., Kirsch(*), S., Namsolleck(*), P., Lucht(*), K., Benz(*), V., Alenina(*), N., Daniell(*), N., Horiuchi(*), M., Iwai(*), M., Multhaup(*), G., Schülein, R., Bader(*), M., Santos(*), R. A., Unger(*), T.; Steckelings(*), U. M.

Tags: Protein Trafficking (Schülein), Cellular Imaging (Wiesner)

Abstract: The angiotensin type 2 receptor (AT2R) and the receptor MAS are receptors of the protective arm of the renin-angiotensin system. They mediate strikingly similar actions. Moreover, in various studies, AT2R antagonists blocked the effects of MAS agonists and vice versa. Such cross-inhibition may indicate heterodimerization of these receptors. Therefore, this study investigated the molecular and functional interplay between MAS and the AT2R. Molecular interactions were assessed by fluorescence resonance energy transfer and by cross correlation spectroscopy in human embryonic kidney-293 cells transfected with vectors encoding fluorophore-tagged MAS or AT2R. Functional interaction of AT2R and MAS was studied in astrocytes with CX3C chemokine receptor-1 messenger RNA expression as readout. Coexpression of fluorophore-tagged AT2R and MAS resulted in a fluorescence resonance energy transfer efficiency of 10.8 +/- 0.8%, indicating that AT2R and MAS are capable to form heterodimers. Heterodimerization was verified by competition experiments using untagged AT2R and MAS. Specificity of dimerization of AT2R and MAS was supported by lack of dimerization with the transient receptor potential cation channel, subfamily C-member 6. Dimerization of the AT2R was abolished when it was mutated at cysteine residue 35. AT2R and MAS stimulation with the respective agonists, Compound 21 or angiotensin-(1-7), significantly induced CX3C chemokine receptor-1 messenger RNA expression. Effects of each agonist were blocked by an AT2R antagonist (PD123319) and also by a MAS antagonist (A-779). Knockout of a single of these receptors made astrocytes unresponsive for both agonists. Our results suggest that MAS and the AT2R form heterodimers and that-at least in astrocytes-both receptors functionally depend on each other.

Direct Experimental Evidence for Halogen-Aryl pi Interactions in Solution from Molecular Torsion Balances
Sun, H., Horatscheck, A., Martos, V., Bartetzko, M., Uhrig, U., Lentz, D., Schmieder, P.; Nazare, M.
Angew Chem Int Ed Engl, 56:6454-6458

Tags: Medicinal Chemistry (Nazare), Solution NMR (Schmieder), Computational Chemistry/ Drug Design (Kühne)

Abstract: We dissected halogen-aryl pi interactions experimentally using a bicyclic N-arylimide based molecular torsion balances system, which is based on the influence of the non-bonded interaction on the equilibria between folded and unfolded states. Through comparison of balances modulated by higher halogens with fluorine balances, we determined the magnitude of the halogen-aryl pi interactions in our unimolecular systems to be larger than -5.0 kJ mol-1 , which is comparable with the magnitude estimated in the biomolecular systems. Our study provides direct experimental evidence of halogen-aryl pi interactions in solution, which until now have only been revealed in the solid state and evaluated theoretically by quantum-mechanical calculations.


VRAC: molecular identification as LRRC8 heteromers with differential functions
Jentsch, T. J., Lutter, D., Planells-Cases, R., Ullrich, F.; Voss, F. K.
Pflugers Arch, 468:385-393

Tags: Physiology and Pathology of Ion Transport (Jentsch)

Abstract: A major player of vertebrate cell volume regulation is the volume-regulated anion channel (VRAC), which conducts halide ions and organic osmolytes to counteract osmotic imbalances. The molecular entity of this channel was unknown until very recently, although its biophysical characteristics and diverse physiological roles have been extensively studied over the last 30 years. On the road to the molecular identification of VRAC, experimental difficulties led to the proposal of a variety of false candidates. In 2014, in a final breakthrough, two groups independently identified LRRC8A as indispensable component of VRAC. LRRC8A is part of the leucine-rich repeat containing 8 family, which is comprised of five members (LRRC8A-E). Of those, LRRC8A is an obligatory subunit of VRAC but it needs at least one of the other family members to mediate the swelling-induced Cl(-) current ICl,vol. This review discusses the remarkable journey which led to the molecular identification of VRAC, evidence for LRRC8 proteins forming the VRAC pore and their heteromeric assembly. Furthermore, first major insights on the role of LRRC8 proteins in cancer drug resistance and apoptosis and the role of LRRC8D in cisplatin and taurine transport will be summarized.

Inactivation and Anion Selectivity of Volume-regulated Anion Channels (VRACs) Depend on C-terminal Residues of the First Extracellular Loop
Ullrich, F., Reincke, S. M., Voss, F. K., Stauber, T.; Jentsch, T. J.
J Biol Chem, 291:17040-17048

Tags: Physiology and Pathology of Ion Transport (Jentsch)

Abstract: Canonical volume-regulated anion channels (VRACs) are crucial for cell volume regulation and have many other important roles, including tumor drug resistance and release of neurotransmitters. Although VRAC-mediated swelling-activated chloride currents (ICl,vol) have been studied for decades, exploration of the structure-function relationship of VRAC has become possible only after the recent discovery that VRACs are formed by differently composed heteromers of LRRC8 proteins. Inactivation of ICl,vol at positive potentials, a typical hallmark of VRACs, strongly varies between native cell types. Exploiting the large differences in inactivation between different LRRC8 heteromers, we now used chimeras assembled from isoforms LRRC8C and LRRC8E to uncover a highly conserved extracellular region preceding the second LRRC8 transmembrane domain as a major determinant of ICl,vol inactivation. Point mutations identified two amino acids (Lys-98 and Asp-100 in LRRC8A and equivalent residues in LRRC8C and -E), which upon charge reversal strongly altered the kinetics and voltage dependence of inactivation. Importantly, charge reversal at the first position also reduced the iodide > chloride permeability of ICl,vol This change in selectivity was stronger when both the obligatory LRRC8A subunit and the other co-expressed isoform (LRR8C or -E) carried such mutations. Hence, the C-terminal part of the first extracellular loop not only determines VRAC inactivation but might also participate in forming its outer pore. Inactivation of VRACs may involve a closure of the extracellular mouth of the permeation pathway.

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

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.

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

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.


Subunit composition of VRAC channels determines substrate specificity and cellular resistance to Pt-based anti-cancer drugs
Planells-Cases, R., Lutter, D., Guyader(*), C., Gerhards(*), N. M., Ullrich, F., Elger, D. A., Kucukosmanoglu(*), A., Xu(*), G., Voss, F. K., Reincke, S. M., Stauber, T., Blomen(*), V. A., Vis(*), D. J., Wessels(*), L. F., Brummelkamp(*), T. R., Borst(*), P., Rottenberg(*), S.; Jentsch, T. J.
EMBO J, 34:2993-3008

Tags: Physiology and Pathology of Ion Transport (Jentsch)

Abstract: Although platinum-based drugs are widely used chemotherapeutics for cancer treatment, the determinants of tumor cell responsiveness remain poorly understood. We show that the loss of subunits LRRC8A and LRRC8D of the heteromeric LRRC8 volume-regulated anion channels (VRACs) increased resistance to clinically relevant cisplatin/carboplatin concentrations. Under isotonic conditions, about 50% of cisplatin uptake depended on LRRC8A and LRRC8D, but neither on LRRC8C nor on LRRC8E. Cell swelling strongly enhanced LRRC8-dependent cisplatin uptake, bolstering the notion that cisplatin enters cells through VRAC. LRRC8A disruption also suppressed drug-induced apoptosis independently from drug uptake, possibly by impairing VRAC-dependent apoptotic cell volume decrease. Hence, by mediating cisplatin uptake and facilitating apoptosis, VRAC plays a dual role in the cellular drug response. Incorporation of the LRRC8D subunit into VRAC substantially increased its permeability for cisplatin and the cellular osmolyte taurine, indicating that LRRC8 proteins form the channel pore. Our work suggests that LRRC8D-containing VRACs are crucial for cell volume regulation by an important organic osmolyte and may influence cisplatin/carboplatin responsiveness of tumors.

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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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