Thue W Schwartz

IT University of Copenhagen, København, Capital Region, Denmark

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Publications (198)1349.45 Total impact

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    ABSTRACT: G protein-coupled receptor 39 (GPR39) is a constitutively active, orphan member of the ghrelin receptor family that is activated by zinc ions. GPR39 is here described to be expressed in a full-length, biologically active seven-transmembrane form, GPR39-1a, as well as in a truncated splice variant five-transmembrane form, GPR39-1b. The 3' exon of the GPR39 gene overlaps with an antisense gene called LYPD1 (Ly-6/PLAUR domain containing 1). Quantitative RT-PCR analysis demonstrated that GPR39-1a is expressed selectively throughout the gastrointestinal tract, including the liver and pancreas as well as in the kidney and adipose tissue, whereas the truncated GPR39-1b form has a more broad expression pattern, including the central nervous system but with highest expression in the stomach and small intestine. In contrast, the LYPD1 antisense gene is highly expressed throughout the central nervous system as characterized with both quantitative RT-PCR and in situ hybridization analysis. A functional analysis of the GPR39 promoter region identified sites for the hepatocyte nuclear factors 1alpha and 4alpha (HNF-1alpha and -4alpha) and specificity protein 1 (SP1) transcription factors as being important for the expression of GPR39. In vivo experiments in rats demonstrated that GPR39 is up-regulated in adipose tissue during fasting and in response to streptozotocin treatment, although its expression is kept constant in the liver from the same animals. GPR39-1a was expressed in white but not brown adipose tissue and was down-regulated during adipocyte differentiation of fibroblasts. It is concluded that the transcriptional control mechanism, the tissue expression pattern, and in vivo response to physiological stimuli all indicate that the GPR39 receptor very likely is of importance for the function of a number of metabolic organs, including the liver, gastrointestinal tract, pancreas, and adipose tissue.
    Molecular Endocrinology 08/2007; 21(7):1685-98. DOI:10.1210/me.2007-0055 · 4.20 Impact Factor
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    ABSTRACT: The glucagon-like peptide (GLP)-1 receptor is a promising target for the treatment of type 2 diabetes and obesity, and there is great interest in characterizing the pharmacology of the GLP-1 receptor and its ligands. In the present report, we have applied bioluminescence resonance energy transfer assays to measure agonist-induced recruitment of betaarrestins and G-protein-coupled receptor kinase (GRK) 2 to the GLP-1 receptor in addition to traditional measurements of second messenger generation. The peptide hormone oxyntomodulin is described in the literature as a full agonist on the glucagon and GLP-1 receptors. Surprisingly, despite being full agonists in GLP-1 receptor-mediated cAMP accumulation, oxyntomodulin and glucagon were observed to be partial agonists in recruiting betaarrestins and GRK2 to the GLP-1 receptor. We suggest that oxyntomodulin and glucagon are biased ligands on the GLP-1 receptor.
    Journal of Pharmacology and Experimental Therapeutics 07/2007; 322(1):148-54. DOI:10.1124/jpet.107.120006 · 3.86 Impact Factor
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    ABSTRACT: Large DNA viruses such as herpesvirus and poxvirus encode proteins that target and exploit the chemokine system of their host. These proteins have the potential to block or change the orchestrated recruitment of leukocytes to sites of viral infection. The genome of Kaposi sarcoma-associated herpes virus (KSHV) encodes three chemokine-like proteins named vCCL1, vCCL2, and vCCL3. In this study vCCL3 was probed in parallel with vCCL1 and vCCL2 against a panel of the 18 classified human chemokine receptors. In calcium mobilization assays vCCL1 acted as a selective CCR8 agonist, whereas vCCL2 was found to act as a broad spectrum chemokine antagonist of human chemokine receptors, including the lymphotactin receptor. In contrast vCCL3 was found to be a highly selective agonist for the human lymphotactin receptor XCR1. The potency of vCCL3 was found to be 10-fold higher than the endogenous human XCL1 chemokine in respect to phosphatidylinositol turnover and calcium mobilization as well as chemotaxis. High expression of XCR1 was found in placenta and neutrophils by real-time PCR. These data are consistent with reports of different expression profiles for vCCL2 and vCCL3 during the life cycle of KSHV, indicate a novel, sophisticated exploitation by the virus of specifically the lymphotactin receptor by both agonist and antagonist mechanisms, and suggest a unique physiological importance of this (somewhat overlooked) chemokine receptor.
    Journal of Biological Chemistry 06/2007; 282(24):17794-805. DOI:10.1074/jbc.M702001200 · 4.60 Impact Factor
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    ABSTRACT: The carboxyamidated wFwLL peptide was used as a core ligand to probe the structural basis for agonism versus inverse agonism in the constitutively active ghrelin receptor. In the ligand, an efficacy switch could be built at the N terminus, as exemplified by AwFwLL, which functioned as a high potency agonist, whereas KwFwLL was an equally high potency inverse agonist. The wFw-containing peptides, agonists as well as inverse agonists, were affected by receptor mutations covering the whole main ligand-binding pocket with key interaction sites being an aromatic cluster in transmembrane (TM)-VI and -VII and residues on the opposing face of TM-III. Gain-of-function in respect of either increased agonist or inverse agonist potency or swap between high potency versions of these properties was obtained by substitutions at a number of positions covering a broad area of the binding pocket on TM-III, -IV, and -V. However, in particular, space-generating substitutions at position III:04 shifted the efficacy of the ligands from inverse agonism toward agonism, whereas similar substitutions at position III: 08, one helical turn below, shifted the efficacy from agonism toward inverse agonism. It is suggested that the relative position of the ligand in the binding pocket between this "efficacy shift region" on TM-III and the opposing aromatic cluster on TM-VI and TM-VII leads either to agonism, i.e. in a superficial binding mode, or it leads to inverse agonism, i.e. in a more profound binding mode. This relationship between different binding modes and opposite efficacy is in accordance with the Global Toggle Switch model for 7TM receptor activation.
    Journal of Biological Chemistry 06/2007; 282(21):15799-811. DOI:10.1074/jbc.M609796200 · 4.60 Impact Factor
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    ABSTRACT: Most non-peptide antagonists for CC-chemokine receptors share a common pharmacophore with a centrally located, positively charged amine that interacts with the highly conserved glutamic acid (Glu) located in position 6 of transmembrane helix VII (VII:06). We present a novel CCR8 non-peptide agonist, LMD-009 that also contains a centrally located, positively charged amine. LMD-009 selectively stimulated CCR8 among the 20 identified human chemokine receptors. It mediated chemotaxis, inositol-phosphate accumulation and calcium release with high potencies (EC50 from 11 to 87 nM) and with efficacies similar to the endogenous agonist CCL1, and competed for (125)I-CCL1 binding with an affinity of 66 nM. A series of 29 mutations targeting 25 amino acids broadly distributed in the minor and major ligand-binding pockets of CCR8 uncovered that the binding of LMD-009 and of four analogs (LMD584, -902, -268, and -174) included several key-residues for non-peptide antagonists targeting CCR1, -2 and -5. Importantly, a nearly 1000-fold decrease in potency was observed for all five compounds for the Ala substitution of the anchor-point GluVII:06 (Glu(286)) and a 19-fold gain-of-function was observed for LMD-009 (but not the four other analogs) for the Ala substitution of PheVI:16 (Phe(254)). These structural hallmarks were particularly important in the generation of a model of the molecular mechanism of action for LMD-009. In conclusion, we present the first molecular mapping of the interaction of a non-peptide agonist with a chemokine receptor, and show that the binding pocket of LMD-009 and of analogs overlaps considerably with the binding pockets of CC-chemokine receptor non-peptide antagonists in general.
    Molecular pharmacology 06/2007; 72(2). DOI:10.1124/mol.107.035543 · 4.12 Impact Factor
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    ABSTRACT: The chemokine receptor CXCR3 can exhibit weak coreceptor function for several human immunodeficiency virus type 1 (HIV-1) and HIV-2 strains and clinical isolates. These viruses produced microscopically visible cytopathicity in U87.CD4.CXCR3 cell cultures, whereas untransfected (CXCR3-negative) U87.CD4 cells remained uninfected. Depending on the particular virus, the coreceptor efficiency of CXCR3 was 100- to >10,000-fold lower compared to that of CXCR4. A CXCR3 variant carrying the CXCR4 binding pocket was constructed by simultaneous lysine-to-alanine and serine-to-glutamate substitutions at positions 300 and 304 of the CXCR3 receptor. This mutant receptor (CXCR3[K300A, S304E]) showed markedly enhanced HIV coreceptor function compared to the wild-type receptor (CXCR3[WT]). Moreover, the CXCR4 antagonist AMD3100 exhibited antagonistic and anti-HIV activities in U87.CD4.CXCR3[K300A, S304E] cells but not in U87.CD4.CXCR3[WT] cells.
    Journal of Virology 05/2007; 81(7):3632-9. DOI:10.1128/JVI.01941-06 · 4.65 Impact Factor
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    ABSTRACT: Seven transmembrane segment (7TM) receptors are activated through a common, still rather unclear molecular mechanism by a variety of chemical messengers ranging from monoamines to large proteins. By introducing a His residue at position III:05 in the CXCR3 receptor a metal ion site was built between the extracellular ends of transmembrane (TM) III and TM-IV to anchor aromatic chelators at a location corresponding to the presumed binding pocket for adrenergic receptor agonists. In this construct, free metal ions had no agonistic effect in accordance with the optimal geometry of the metal ion site in molecular models built over the inactive form of rhodopsin. In contrast, the aromatic chelators bipyridine or phenanthrolene in complex with Zn(II) or Cu(II) acted as potent agonists displaying signaling efficacies similar to or even better than the endogenous chemokine agonists. Molecular modeling and molecular simulations combined with mutational analysis indicated that the metal ion site-anchored chelators act as agonists by establishing an aromatic-aromatic, second-site interaction with TyrVI:16 on the inner face of TM-VI. It is noteworthy that this interaction required that the extracellular segment of TM-VI moves inward in the direction of TM-III, whereby TyrVI:16 together with the chelators complete an "aromatic zipper" also comprising PheIII:08 (corresponding to the monoamine receptor anchoring point) and TyrVII:10 (corresponding to the retinal attachment site in rhodopsin). Chemokine agonism was independent of this aromatic zipper. It is proposed that in rhodopsin-like 7TM receptors, small-molecule compounds in general act as agonists in a similar manner as here demonstrated with the artificial, metal ion site anchored chelators, by holding TM-VI bent inward.
    Molecular Pharmacology 04/2007; 71(3):930-41. DOI:10.1124/mol.106.030031 · 4.12 Impact Factor
  • Birgitte Holst, Kristoffer Egerod, Thue W. Schwartz
    Handbook of Contemporary Neuropharmacology, 03/2007; , ISBN: 9780470101001
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    ABSTRACT: GPR39 is an orphan member of the ghrelin receptor family that recently was suggested to be the receptor for obestatin, a peptide derived from the ghrelin precursor. Here, we compare the effect of obestatin to the effect of Zn(2+) on signal transduction and study the effect of obestatin on food intake. Although Zn(2+) stimulated inositol phosphate turnover, cAMP production, arrestin mobilization, as well as cAMP response element-dependent and serum response element-dependent transcriptional activity in GPR39-expressing cells as opposed to mock-transfected cells, no reproducible effect was obtained with obestatin in the GPR39-expressing cells. Moreover, no specific binding of obestatin could be detected in two different types of GPR39-expressing cells using three different radioiodinated forms of obestatin. By quantitative PCR analysis, GPR39 expression was readily detected in peripheral organs such as duodenum and kidney but not in the pituitary and hypothalamus, i.e. presumed central target organs for obestatin. Obestatin had no significant and reproducible effect on acute food intake in either freely fed or fasted lean mice. It is concluded that GPR39 is probably not the obestatin receptor. In contrast, the potency and efficacy of Zn(2+) in respect of activating signaling indicates that this metal ion could be a physiologically relevant agonist or modulator of GPR39.
    Endocrinology 02/2007; 148(1):13-20. DOI:10.1210/en.2006-0933 · 4.64 Impact Factor
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    ABSTRACT: The extracellular part of transmembrane segment V (TM-V) is expected to be involved in the activation process of 7TM receptors, but its role is far from clear. Here, we study the highly constitutively active CXC-chemokine receptor encoded by human herpesvirus 8 (ORF74-HHV8), in which a metal ion site was introduced at the extracellular end of TM-V by substitution of two arginines at positions V:01 and V:05 with histidines [R208H; R212H]. The metal ion site conferred high-potency inverse agonist properties (EC(50), 1.7 microM) to Zn(II) in addition to agonist and allosteric enhancing properties at concentrations >10 microM. The chemokine interaction with [R208H;R212H]-ORF74 was altered compared with wild-type ORF74-HHV8 with decreased agonist (CXCL1/GROalpha) potency (84-fold), affinity (5.8- and 136-fold in competition against agonist and inverse agonist, respectively), and binding capacity (B(max); 25-fold). Zn(II) in activating concentrations (100 microM) acted as an allosteric enhancer as it increased the B(max) (7.1-fold), the potency (9.9-fold), the affinity (1.7- and 6.1-fold in competition against agonist and inverse agonist, respectively), and the efficacy (2.5-fold) of CXCL1/GROalpha. The activating properties of Zn(II) were not due to a metal ion site between the ligand and the receptor because CXCL1/GROalpha analogs in which the putative metal-ion binding residues had been substituted-[H19A] and [H34A]-acted like wild-type CXCL1/GROalpha. Based on the complex action of Zn(II) and on the chemokine interaction for [R208H;R212H]-ORF74, we conclude that the extracellular end of TM-V is important for the activation of this CXC-chemokine receptor.
    Molecular Pharmacology 01/2007; 70(6):1892-901. DOI:10.1124/mol.106.027425 · 4.12 Impact Factor
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    ABSTRACT: [D-Arg1,D-Phe5,D-Trp7,9,Leu11]Substance P functions as a low-potency antagonist but a high-potency full inverse agonist on the ghrelin receptor. Through a systematic deletion and substitution analysis of this peptide, the C-terminal carboxyamidated pentapeptide wFwLX was identified as the core structure, which itself displayed relatively low inverse agonist potency. Mutational analysis at 17 selected positions in the main ligand-binding crevice of the ghrelin receptor demonstrated that ghrelin apparently interacts only with residues in the middle part of the pocket [i.e., between transmembrane (TM)-III, TM-VI and TM-VII]. In contrast, the inverse agonist peptides bind in a pocket that extends all the way from the extracellular end of TM-II (AspII:20) across between TM-III and TM-VI/VII to TM-V and TM-IV. The potency of the main inverse agonist could be improved up to 20-fold by a number of space-generating mutants located relatively deep in the binding pocket at key positions in TM-III, TM-IV and TM-V. It is proposed that the inverse agonists prevent the spontaneous receptor activation by inserting relatively deeply across the main ligand-binding pocket and sterically blocking the movement of TM-VI and TM-VII into their inward-bend, active conformation. The combined structure-functional analysis of both the ligand and the receptor allowed for the design of a novel, N-terminally Lys-extended analog of wFwLL, which rescued the high-potency, selective inverse agonism that was dependent upon both AspII:20 and GluIII:09. The identified pharmacophore can possibly serve as the basis for targeted discovery of also nonpeptide inverse agonists for the ghrelin receptor.
    Molecular Pharmacology 10/2006; 70(3):936-46. DOI:10.1124/mol.106.024422 · 4.12 Impact Factor
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    ABSTRACT: PYY3-36 is a biopharmaceutical antiobesity agent under development as well as an endogenous satiety hormone, which is generated by dipeptidyl peptidase-IV digestion of polypetide YY (PYY), and in contrast to the parent hormone, PYY is highly selective for the Y2 versus the Y1 receptor. NMR analysis revealed a highly ordered, back-folded structure for human PYY in aqueous solution similar to the classical PP-fold structure of pancreatic polypeptide. The NMR analysis of PYY3-36 also showed a folded structure resembling a PP-fold, which however was characterized by far fewer long distance NOEs than the PP-fold observed in the full-length peptide. This suggests that either a conformational change has occurred in the N-terminal segment of PYY3-36 or that this segments is characterized by larger dynamics. The study supports the notion that the PP-fold is crucial for establishing simultaneous interactions with two subsites in the receptor for binding of, respectively, the N- and C-terminal ends of PYY. The Y2 receptor only requires recognition of the C-terminal segment of the molecule as displayed by the Y2 selective PYY3-36.
    Biochemistry 08/2006; 45(27):8350-7. DOI:10.1021/bi060359l · 3.19 Impact Factor
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    ABSTRACT: Much evidence indicates that, during activation of seven-transmembrane (7TM) receptors, the intracellular segments of the transmembrane helices (TMs) move apart with large amplitude, rigid body movements of especially TM-VI and TM-VII. In this study, AspIII:08 (Asp113), the anchor point for monoamine binding in TM-III, was used as the starting point to engineer activating metal ion sites between the extracellular segments of the beta2-adrenergic receptor. Cu(II) and Zn(II) alone and in complex with aromatic chelators acted as potent (EC50 decreased to 0.5 microm) and efficacious agonists in sites constructed between positions III:08 (Asp or His), VI:16 (preferentially Cys), and/or VII:06 (preferentially Cys). In molecular models built over the backbone conformation of the inactive rhodopsin structure, the heavy atoms that coordinate the metal ion were located too far away from each other to form high affinity metal ion sites in both the bidentate and potential tridentate settings. This indicates that the residues involved in the main ligand-binding pocket will have to move closer to each other during receptor activation. On the basis of the distance constraints from these activating metal ion sites, we propose a global toggle switch mechanism for 7TM receptor activation in which inward movement of the extracellular segments of especially TM-VI and, to some extent, TM-VII is coupled to the well established outward movement of the intracellular segments of these helices. We suggest that the pivots for these vertical seesaw movements are the highly conserved proline bends of the involved helices.
    Journal of Biological Chemistry 07/2006; 281(25):17337-46. DOI:10.1074/jbc.M512510200 · 4.60 Impact Factor
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    ABSTRACT: Epstein-Barr virus (EBV)-induced receptor 2 (EBI2) is an orphan seven-transmembrane (7TM) receptor originally identified as the most up-regulated gene (>200-fold) in EBV-infected cells. Here we show that EBI2 signals with constitutive activity through Galpha(i) as determined by a receptor-mediated inhibition of forskolin-induced cAMP production and an induction of the serum response element-driven transcriptional activity in a pertussis toxin-sensitive manner. Galpha(s) and Galpha(q) were not activated constitutively as determined by the lack of cAMP production, the lack of inositol phosphate turnover, and the lack of activities of the transcription factors: cAMP response element-binding protein and nuclear factor-kappaB. Immunohistochemistry and confocal microscopy of FLAG- and green fluorescent protein-tagged EBI2 revealed cell-surface expression. A putative N-terminal truncated version of EBI2, delta4-EBI2, showed similar expression and signaling through Galpha(i) as full-length EBI2. By using a 32P-labeled EBI2 probe we found a very high expression in lymphoid tissue (spleen and lymph node) and peripheral blood mononuclear cells and a high expression in lung tissue. Real-time PCR of EBV-infected cells showed high expression of EBI2 during latent and lytic infection, in contrast to the EBV-encoded 7TM receptor BILF1, which was induced during lytic infection. EBI2 clustered with the orphan GPR18 by alignment analysis as well as by close proximity in the chromosomal region 13q32.3. Based on the constitutive signaling and cellular expression pattern of EBI2, it is suggested that it may function in conjunction with BILF1 in the reprogramming of the cell during EBV infection.
    Journal of Biological Chemistry 05/2006; 281(19):13199-208. DOI:10.1074/jbc.M602245200 · 4.60 Impact Factor
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    Birgitte Holst, Thue W Schwartz
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    ABSTRACT: The ghrelin receptor is known from in vitro studies to signal in the absence of the hormone ghrelin at almost 50% of its maximal capacity. But, as for many other 7-transmembrane receptors, the in vivo importance of this ligand-independent signaling has remained unclear. In this issue of the JCI, Pantel et al. find that a natural mutation in the ghrelin receptor, Ala204Glu, which is associated with a selective loss of constitutive activity without affecting ghrelin affinity, potency, or efficacy, segregates in 2 families with the development of short stature (see the related article beginning on page 760). By combination of the observations from this study with those related to the phenotype of subjects carrying another natural ghrelin receptor mutation, Phe279Leu, having identical molecular-pharmacological properties, it is proposed that selective lack of ghrelin receptor constitutive signaling leads to a syndrome characterized not only by short stature, but also by obesity that apparently develops during puberty.
    Journal of Clinical Investigation 04/2006; 116(3):637-41. DOI:10.1172/JCI27999 · 13.77 Impact Factor
  • Mette M Rosenkilde, Thue W Schwartz
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    ABSTRACT: A majority of small molecule non-peptide ligands for chemokine receptors in general are characterized by the presence of one or two centrally located, positively charged nitrogen atoms and these compounds are also often of relatively similar elongated overall structure with terminal aromatic moieties. In the corresponding main ligand-binding crevice of the chemokine 7TM receptors is found a centrally located glutamic acid residue in position 6 of transmembrane segment VII in 74% of the chemokine receptors but only in approx. 1% of non-chemokine receptors. GluVII:06 has been demonstrated to be crucially important for the binding and action of a number of non-peptide ligands in for example the CCR1, CCR2 and CCR5 receptors. It is proposed that in chemokine receptors in general GluVII:06 serves as a selective anchor point for the centrally located, positively charged nitrogen of the small molecule ligands and that the two peripheral chemical moieties of the ligands from this central point in the receptor structure explore each of the two halves of the main ligand binding pocket. It is envisioned that knowledge of this binding mode can be exploited in structure-based discovery and design of novel chemokine receptor ligands and especially ligands with specifically optimized properties.
    Current Topics in Medicinal Chemistry 02/2006; 6(13):1319-33. DOI:10.2174/15680266106061319 · 3.45 Impact Factor
  • Thue W Schwartz, Birgitte Holst
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    ABSTRACT: Conventionally, an allosteric modulator is neutral in respect of efficacy and binds to a receptor site distant from the orthosteric site of the endogenous agonist. However, recently compounds being ago-allosteric modulators have been described i.e., compounds acting both as agonists on their own and as enhancers for the endogenous agonists in both increasing agonist potency and providing additive efficacy-superagonism. The additive efficacy can also be observed with agonists, which are neutral or even negative modulators of the potency of the endogenous ligand. Based on the prevailing dimeric concept for 7TM receptors, it is proposed that the ago-allosteric modulators bind in the orthosteric binding site, but-importantly-in the "other" or allosteric protomer of the dimer. Hereby, they can act both as additive co-agonists, and through intermolecular cooperative effects between the protomers, they may influence the potency of the endogenous agonist. It is of interest that at least some endogenous agonists can only occupy one protomer of a dimeric 7TM receptor complex at a time and thereby they leave the orthosteric binding site in the allosteric protomer free, potentially for binding of exogenous, allosteric modulators. If the allosteric modulator is an agonist, it is an ago-allosteric modulator; if it is neutral, it is a classical enhancer. Molecular mapping in hetero-dimeric class-C receptors, where the endogenous agonist clearly binds only in one protomer, supports the notion that allosteric modulators can act through binding in the "other" protomer. It is suggested that for the in vivo, clinical setting a positive ago-allosteric modulator should be the preferred agonist drug.
    Journal of Receptor and Signal Transduction Research 02/2006; 26(1-2):107-28. DOI:10.1080/10799890600567570 · 1.61 Impact Factor
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    ABSTRACT: The multitude of chemically highly different agonists for 7TM receptors apparently do not share a common binding mode or active site but nevertheless act through induction of a common molecular activation mechanism. A global toggle switch model is proposed for this activation mechanism to reconcile the accumulated biophysical data supporting an outward rigid-body movement of the intracellular segments, as well as the recent data derived from activating metal ion sites and tethered ligands, which suggests an opposite, inward movement of the extracellular segments of the transmembrane helices. According to this model, a vertical see-saw movement of TM-VI-and to some degree TM-VII-around a pivot corresponding to the highly conserved prolines will occur during receptor activation, which may involve the outer segment of TM-V in an as yet unclear fashion. Small-molecule agonists can stabilize such a proposed active conformation, where the extracellular segments of TM-VI and -VII are bent inward toward TM-III, by acting as molecular glue deep in the main ligand-binding pocket between the helices, whereas larger agonists, peptides, and proteins can stabilize a similar active conformation by acting as Velcro at the extracellular ends of the helices and the connecting loops.
    Annual Review of Pharmacology 02/2006; 46:481-519. DOI:10.1146/annurev.pharmtox.46.120604.141218 · 18.52 Impact Factor
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    ABSTRACT: Among the rhodopsin-like 7TM receptors, the MC receptors are functionally unique because their high constitutive signaling activity is regulated not only by endogenous peptide agonists—MSH peptides—but also by endogenous inverse agonists, namely, the proteins agouti and AGRP. Moreover, the metal-ion Zn2+ increases the signaling activity of at least the MC1 and MC4 receptors in three distinct ways: (1) by directly functioning as an agonist; (2) by potentiating the action of the endogenous agonist; and (3) by inhibiting the binding of the endogenous inverse agonist. Structurally the MC receptors are part of a small subset of 7TM receptors in which the main ligand-binding crevice, and especially extracellular loops 2 and 3, appear to be specially designed for easy ligand access and bias towards an active state of the receptor—i.e., constitutive activity. Thus, in the MC receptors extracellular loop 2 is ultrashort because TM-IV basically connects directly into TM-V, whereas extracellular loop 3 appears to be held in a particular, constrained conformation by a putative, internal disulfide bridge. The interaction mode for the small and well-defined zinc-ion between a third, free Cys residue in extracellular loop 3 and conceivably an Asp residue located at the inner face of TM-III gives important information concerning the activation mechanism for the MC receptors.
    Annals of the New York Academy of Sciences 01/2006; 994(1):1 - 11. DOI:10.1111/j.1749-6632.2003.tb03156.x · 4.31 Impact Factor
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    ABSTRACT: The chemokine receptors CCR5 and CXCR4 function as coreceptors for human immunodeficiency virus (HIV) and are attractive targets for the development of anti-HIV drugs. The most potent CXCR4 antagonists described until today are the bicyclams. The prototype compound, AMD3100, exhibits potent and selective anti-HIV activity against CXCR4-using (X4) viruses and showed antiviral efficacy in X4 HIV-1-infected persons in a phase II clinical trial. However, AMD3100 lacks oral bioavailability due to its high overall positive charge. Initial structure-activity relationship studies with bicyclam analogues suggested that the bis-macrocyclic structure was a prerequisite for anti-HIV activity. Now, we report that the N-pyridinylmethylene cyclam AMD3465, which lacks the structural constraints mentioned above, fully conserves all the biological properties of AMD3100. Like AMD3100, AMD3465 blocked the cell surface binding of both CXCL12 (the natural CXCR4 ligand), and the specific anti-CXCR4 monoclonal antibody 12G5. AMD3465 dose-dependently inhibited intracellular calcium signaling, chemotaxis, CXCR4 endocytosis and mitogen-activated protein kinase phosphorylation induced by CXCL12. Compared to the bicyclam AMD3100, AMD3465 was even 10-fold more effective as a CXCR4 antagonist, while showing no interaction whatsoever with CCR5. As expected, AMD3465 proved highly potent against X4 HIV strains (IC50: 1-10 nM), but completely failed to inhibit the replication of CCR5-using (R5) viruses. In conclusion, AMD3465 is a novel, monomacrocyclic anti-HIV agent that specifically blocks the interaction of HIV gp120 with CXCR4. Although oral bioavailability is not yet achieved, the monocyclams, with their decreased molecular charge as compared to the bicyclams, embody an important step forward in the design of oral CXCR4 antagonists that can be clinically used as anti-HIV drugs.
    Biochemical Pharmacology 10/2005; 70(5):752-61. DOI:10.1016/j.bcp.2005.05.035 · 4.65 Impact Factor

Publication Stats

9k Citations
1,349.45 Total Impact Points


  • 1990–2015
    • IT University of Copenhagen
      København, Capital Region, Denmark
  • 2012
    • Howard Hughes Medical Institute
      Ashburn, Virginia, United States
  • 2002–2008
    • 7TM Pharma
      Hørsholm, Capital Region, Denmark
    • Universidade Federal de São Paulo
      San Paulo, São Paulo, Brazil
  • 1976–2008
    • Bispebjerg Hospital, Copenhagen University
      København, Capital Region, Denmark
  • 2007
    • University of Ljubljana
      • Institute of Anatomy, Histology and Embryology
      Lubliano, Ljubljana, Slovenia
  • 2006–2007
    • University of Leipzig
      • Institute of Biochemistry
      Leipzig, Saxony, Germany
  • 2005–2006
    • Copenhagen University Hospital Hvidovre
      Hvidovre, Capital Region, Denmark
  • 2003
    • University of British Columbia - Vancouver
      Vancouver, British Columbia, Canada
  • 1990–2003
    • Novo Nordisk
      København, Capital Region, Denmark
  • 2000
    • University of Minnesota Duluth
      • College of Pharmacy
      Duluth, Minnesota, United States
  • 1998
    • Odense University Hospital
      Odense, South Denmark, Denmark
  • 1993
    • Rigshospitalet
      • Department of Clinical Biochemistry
      København, Capital Region, Denmark
    • Kyoto University
      Kioto, Kyōto, Japan
  • 1988
    • Queen's University Belfast
      Béal Feirste, Northern Ireland, United Kingdom
  • 1980–1981
    • Aarhus University
      • Department of Medical Biochemistry
      Aarhus, Central Jutland, Denmark