FMP Publications

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

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Rapid proton-detected NMR assignment for proteins with fast magic angle spinning
Barbet-Massin(*), E., Pell(*), A. J., Retel, J. S., Andreas(*), L. B., Jaudzems(*), K., Franks, W. T., Nieuwkoop, A. J., Hiller, M., Higman(*), V., Guerry(*), P., Bertarello(*), A., Knight(*), M. J., Felletti(*), M., Le Marchand(*), T., Kotelovica(*), S., Akopjana(*), I., Tars(*), K., Stoppini(*), M., Bellotti(*), V., Bolognesi(*), M., Ricagno(*), S., Chou(*), J. J., Griffin(*), R. G., Oschkinat, H., Lesage(*), A., Emsley(*), L., Herrmann(*), T.; Pintacuda(*), G.
J Am Chem Soc, 136:12489-12497

Tags: NMR-Supported Structural Biology (Oschkinat)

Abstract: Using a set of six (1)H-detected triple-resonance NMR experiments, we establish a method for sequence-specific backbone resonance assignment of magic angle spinning (MAS) nuclear magnetic resonance (NMR) spectra of 5-30 kDa proteins. The approach relies on perdeuteration, amide (2)H/(1)H exchange, high magnetic fields, and high-spinning frequencies (omegar/2pi >/= 60 kHz) and yields high-quality NMR data, enabling the use of automated analysis. The method is validated with five examples of proteins in different condensed states, including two microcrystalline proteins, a sedimented virus capsid, and two membrane-embedded systems. In comparison to contemporary (13)C/(15)N-based methods, this approach facilitates and accelerates the MAS NMR assignment process, shortening the spectral acquisition times and enabling the use of unsupervised state-of-the-art computational data analysis protocols originally developed for solution NMR.

Differences between lutropin-mediated and choriogonadotropin-mediated receptor activation
Grzesik, P., Teichmann, A., Furkert, J., Rutz, C., Wiesner, B., Kleinau(*), G., Schülein, R., Gromoll(*), J.; Krause, G.
Febs J, 281:1479-1492

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

Abstract: The human lutropin/choriogonadotropin receptor (hLHR) for the gonadotropic hormones human luteinizing hormone (hLH; lutropin) and human choriogonadotropin (hCG) is crucial for normal sexual development and fertility. We aimed to unravel differences between the two hLHR hormones in molecular activation mechanisms at hLHR. We utilized a specific hLHR variant that lacks exon 10 (hLHR-delExon10), which maintains full cAMP signaling by hCG, but decreases hLH-induced receptor signaling, resulting in a pathogenic phenotype. Exon 10 encodes 27 amino acids within the hinge region, which is an extracellular segment that is important for signaling and hormone interaction. Initially, we assumed that the lack of exon 10 might disturb intermolecular trans-activation of hLH, a mechanism that has been reported for hCG at hLHR. Coexpression of signaling-deficient hLHR and binding-deficient hLHR can be used to examine the mechanisms of receptor signaling, in particular intermolecular cooperation and intramolecular cis-activation. Therefore, hLHR-delExon10 was combined with the hLHR Lys605-->Glu mutant, in which signaling is abolished, and the hLHR mutant Cys131-->Arg, in which binding is deficient. We found that hCG signaling was partially rescued, indicating trans-activation. However, the hLH signal could not be restored via forced trans-activation with any construct. Fluorescence cross-correlation spectroscopy detected oligomerization in all combinations, indicating that these functional differences cannot be explained by monomerization of hLHR-delExon10. Thus, our data demonstrate not only that the different behavior of hLH at hLHR-delExon10 is unlikely to be related to modified intermolecular receptor activation, but also that hLH may exclusively stimulate the targeted hLHR by cis-activation, whereas hCG is also capable of inducing trans-activation.

Molecular and structural transmembrane determinants critical for embedding claudin-5 into tight junctions reveal a distinct four-helix bundle arrangement
Rossa, J., Protze, J., Kern, C., Piontek, A., Günzel(*), D., Krause, G.; Piontek(*), J.
Biochem J, 464:49-60

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

Abstract: The mechanism of TJ (tight junction) assembly and the structure of TJ strand-forming Cldns (claudins) are unclear. To identify determinants of assembly of blood-brain barrier-related Cldn3 and Cldn5, chimaeric mutants were analysed by cellular reconstitution of TJ strands and live-cell imaging. On the basis of the rescue of mutants deficient for strand formation, we identified Cldn5 residues (Cys128, Ala132, Ile142, Ala163, Ile166 and Leu174) involved in Cldn folding and assembly. Experimental results were combined with structural bioinformatics approaches. Initially the experimentally validated previous model of the ECL2 (extracellular loop 2) of Cldn5 was extended to the flanking transmembrane segments (TM3/TM4). A coiled-coil interface probably caused by alternating small and large residues is supported by concomitant knob-into-hole interactions including Cldn5-specific residues identified in the present paper. To address arrangement of the TMs in a four-helix bundle, data from evolutionary sequence couplings and comparative modelling of intramolecular interfaces in the transmembrane region of Cldns led to a complete Cldn5 model. Our suggested Cldn subtype-specific intramolecular interfaces that are formed by conserved coiled-coil motifs and non-conserved residues in distinct TM positions were confirmed by the recently released crystal structure of Cldn15. The identified molecular and structural determinants essentially contribute to assembly of Cldns into TJ strands.

Stretch-activation of angiotensin II type 1a receptors contributes to the myogenic response of mouse mesenteric and renal arteries
Schleifenbaum(*), J., Kassmann(*), M., Szijarto(*), I. A., Hercule(*), H. C., Tano(*), J. Y., Weinert, S., Heidenreich, M., Pathan(*), A. R., Anistan(*), Y. M., Alenina(*), N., Rusch(*), N. J., Bader(*), M., Jentsch, T. J.; Gollasch(*), M.
Circ Res, 115:263-272

Tags: Physiology and Pathology of Ion Transport (Jentsch)

Abstract: RATIONALE: Vascular wall stretch is the major stimulus for the myogenic response of small arteries to pressure. The molecular mechanisms are elusive, but recent findings suggest that G protein-coupled receptors can elicit a stretch response. OBJECTIVE: To determine whether angiotensin II type 1 receptors (AT1R) in vascular smooth muscle cells exert mechanosensitivity and identify the downstream ion channel mediators of myogenic vasoconstriction. METHODS AND RESULTS: We used mice deficient in AT1R signaling molecules and putative ion channel targets, namely AT1R, angiotensinogen, transient receptor potential channel 6 (TRPC6) channels, or several subtypes of the voltage-gated K+ (Kv7) gene family (KCNQ3, 4, or 5). We identified a mechanosensing mechanism in isolated mesenteric arteries and in the renal circulation that relies on coupling of the AT1R subtype a to a Gq/11 protein as a critical event to accomplish the myogenic response. Arterial mechanoactivation occurs after pharmacological block of AT1R and in the absence of angiotensinogen or TRPC6 channels. Activation of AT1R subtype a by osmotically induced membrane stretch suppresses an XE991-sensitive Kv channel current in patch-clamped vascular smooth muscle cells, and similar concentrations of XE991 enhance mesenteric and renal myogenic tone. Although XE991-sensitive KCNQ3, 4, and 5 channels are expressed in vascular smooth muscle cells, XE991-sensitive K+ current and myogenic contractions persist in arteries deficient in these channels. CONCLUSIONS: Our results provide definitive evidence that myogenic responses of mouse mesenteric and renal arteries rely on ligand-independent, mechanoactivation of AT1R subtype a. The AT1R subtype a signal relies on an ion channel distinct from TRPC6 or KCNQ3, 4, or 5 to enact vascular smooth muscle cell activation and elevated vascular resistance.

Disturbed function of the blood-cerebrospinal fluid barrier aggravates neuro-inflammation
Kooij(*), G., Kopplin(*), K., Blasig, R., Stuiver(*), M., Koning(*), N., Goverse(*), G., van der Pol(*), S. M. A., Hof(*), B. V., Gollasch(*), M., Drexhage(*), J. A. R., Reijerkerk(*), A., Meij(*), I. C., Mebius(*), R., Willnow(*), T. E., Müller(*), D., Blasig, I. E.; de Vries(*), H. E.
Acta Neuropathol, 128:267-277

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

Abstract: Multiple sclerosis (MS) is a chronic neuro-inflammatory disorder, which is marked by the invasion of the central nervous system by monocyte-derived macrophages and autoreactive T cells across the brain vasculature. Data from experimental animal models recently implied that the passage of leukocytes across the brain vasculature is preceded by their traversal across the blood-cerebrospinal fluid barrier (BCSFB) of the choroid plexus. The correlation between the presence of leukocytes in the CSF of patients suffering from MS and the number of inflammatory lesions as detected by magnetic resonance imaging suggests that inflammation at the choroid plexus contributes to the disease, although in a yet unknown fashion. We here provide first insights into the involvement of the choroid plexus in the onset and severity of the disease and in particular address the role of the tight junction protein claudin-3 (CLDN3) in this process. Detailed analysis of human post-mortem brain tissue revealed a selective loss of CLDN3 at the choroid plexus in MS patients compared to control tissues. Importantly, mice that lack CLDN3 have an impaired BCSFB and experience a more rapid onset and exacerbated clinical signs of experimental autoimmune encephalomyelitis, which coincides with enhanced levels of infiltrated leukocytes in their CSF. Together, this study highlights a profound role for the choroid plexus in the pathogenesis of multiple sclerosis, and implies that CLDN3 may be regarded as a crucial and novel determinant of BCSFB integrity.

The specific monomer/dimer equilibrium of the corticotropin-releasing factor receptor type 1 is established in the endoplasmic reticulum
Teichmann, A., Gibert, A., Lampe, A., Grzesik, P., Rutz, C., Furkert, J., Schmoranzer, J., Krause, G., Wiesner, B.; Schülein, R.
J Biol Chem, 289:24250-24262

Tags: Protein Trafficking (Schülein), Cellular Imaging (Wiesner), Structural Bioinformatics and Protein Design (Krause, G.), Molecular Pharmacology and Cell Biology (Haucke)

Abstract: G protein-coupled receptors (GPCRs) represent the most important drug targets. Although the smallest functional unit of a GPCR is a monomer, it became clear in the past decades that the vast majority of the receptors form dimers. Only very recently, however, data were presented that some receptors may in fact be expressed as a mixture of monomers and dimers and that the interaction of the receptor protomers is dynamic. To date, equilibrium measurements were restricted to the plasma membrane due to experimental limitations. We have addressed the question as to where this equilibrium is established for the corticotropin-releasing factor receptor type 1. By developing a novel approach to analyze single molecule fluorescence cross-correlation spectroscopy data for intracellular membrane compartments, we show that the corticotropin-releasing factor receptor type 1 has a specific monomer/dimer equilibrium that is already established in the endoplasmic reticulum (ER). It remains constant at the plasma membrane even following receptor activation. Moreover, we demonstrate for seven additional GPCRs that they are expressed in specific but substantially different monomer/dimer ratios. Although it is well known that proteins may dimerize in the ER in principle, our data show that the ER is also able to establish the specific monomer/dimer ratios of GPCRs, which sheds new light on the functions of this compartment.

Semisynthesis and optimization of G protein-coupled receptor mimics
Abel, S., Geltinger, B., Heinrich, N., Michl, D., Klose, A., Beyermann, M.; Schwarzer(*), D.
J Pept Sci, 20:831-836

Tags: Peptide Chemistry (Beyermann)

Abstract: We have recently developed a soluble mimic of the corticotropin-releasing factor receptor type 1 (CRF1), a membrane-spanning G protein-coupled receptor, which allowed investigations on receptor-ligand interactions. The CRF1 mimic consists of the receptor N-terminus and three synthetic extracellular loops (ECL1-3), which constitute the extracellular receptor domains (ECDs) of CRF1, coupled to a linear peptide template. Here, we report the synthesis of a modified CRF1 mimic, which is more similar to the native receptor possessing a cyclic template that displays the ECDs in a more physiological conformation compared with the initial linear design. In order to facilitate detailed biophysical investigations on CRF1 mimics, we have further established a cost-efficient access to the CRF1 mimic, which is suitable for isotopic labeling for NMR spectroscopy. To this end, the loop-mimicking cyclic peptide of the ECL2 of CRF1 was produced recombinantly and cyclized by expressed protein ligation. Cyclic ECL2 was obtained in milligram scale, and CRF1 mimics synthesized from this material displayed the same binding properties as synthetic CRF1 constructs.

Photoinactivation of glutamate receptors by genetically encoded unnatural amino acids
Klippenstein, V., Ghisi, V., Wietstruk, M.; Plested, A. J.
J Neurosci, 34:980-991

Tags: Molecular Neuroscience and Biophysics (Plested)

Abstract: Ionotropic glutamate receptors (iGluRs) are ubiquitous in the mammalian brain, and the AMPA-subtype is essential for fast, glutamate-activated postsynaptic currents. We incorporated photoactive crosslinkers into AMPA receptors using genetically encoded unnatural amino acid mutagenesis in a mammalian cell line. Receptors rescued by incorporation of unnatural amino acids, including p-benzoyl-l-phenylalanine (BzF, also known as Bpa), had largely similar properties to wild-type channels and were expressed at similar levels. BzF incorporation at subunit interfaces afforded photocrosslinking of subunits, as assessed by biochemical experiments. In electrophysiological recordings, BzF incorporation allowed selective and potent UV-driven photoinactivation of both homomeric (GluA2) and heteromeric (GluA2:GluA1) AMPA receptors. State dependence of trapping at two sites in the lower lobe of the ligand binding domain is consistent with deformation of these domains as well as intersubunit rearrangements during AMPA receptor desensitization.

Activation of Ligand Binding Domains of an AMPA-Type Glutamate Receptor
Baranovic, J., Chebli, M., Salazar, H. P., Faelber(*), K., Ghisi, V., Lau(*), A. Y., Daumke(*), O.; Plested, A. J. R.
Biophys. J., 106:29a-29a

Tags: Molecular Neuroscience and Biophysics (Plested)

Molecular characterization of ubiquitin-specific protease 18 reveals substrate specificity for interferon-stimulated gene 15
Basters(*), A., Geurink(*), P. P., El Oualid(*), F., Ketscher(*), L., Casutt(*), M. S., Krause, E., Ovaa(*), H., Knobeloch(*), K. P.; Fritz(*), G.
Febs J, 281:1918-1928

Tags: Mass Spectrometry (Krause, E.)

Abstract: UNLABELLED: Protein modification by interferon-stimulated gene 15 (ISG15), an ubiquitin-like modifier, affects multiple cellular functions and represents one of the major antiviral effector systems. Covalent linkage of ISG15 to proteins was previously reported to be counteracted by ubiquitin-specific protease 18 (USP18). To date, analysis of the molecular properties of USP18 was hampered by low expression yields and impaired solubility. We established high-yield expression of USP18 in insect cells and purified the protease to homogeneity. USP18 binds with high affinity to ISG15, as shown by microscale thermophoresis with a Kd of 1.3 +/- 0.2 mum. The catalytic properties of USP18 were characterized by a novel assay using ISG15 fused to a fluorophore via an isopeptide bond, giving a Km of 4.6 +/- 0.2 mum and a kcat of 0.23 +/- 0.004 s(-1) , respectively, at pH 7.5. Furthermore, the recombinant enzyme cleaves efficiently ISG15 but not ubiquitin from endogenous cellular substrates. In line with these data, USP18 exhibited neither cross-reactivity with an ubiquitin isopeptide fluorophore substrate, nor with a ubiquitin vinyl sulfone, showing that the enzyme is specific for ISG15. STRUCTURED DIGITAL ABSTRACT: ISG15 and USP18 bind by microscale thermophoresis (View interaction) USP18 cleaves ISG15 by enzymatic study (View interaction).

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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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