Protective effect of a Protein Epitope Mimetic CCR10 antagonist, POL7085, in a model of allergic eosinophilic airway inflammation.

BACKGROUND: Potential involvement of the CCR10/CCL28 axis was recently reported in murine models of allergic asthma. If confirmed, blockade of the CCR10 receptor would represent an alternative to current asthma therapies. We evaluated the effect of a novel Protein Epitope Mimetic CCR10 antagonist, POL7085, in a murine model of allergic eosinophilic airway inflammation. METHODS: Mice were sensitized and challenged to ovalbumin. POL7085, a CCR10 antagonist (7.5 and 15 mg/kg), dexamethasone (1 mg/kg) or vehicle were administered intranasally once daily 1h before each allergen challenge. On day 21, airway hyperresponsiveness, bronchoalveolar lavage inflammatory cells and Th2 cytokines, and lung tissue mucus and collagen were measured. RESULTS: Allergen challenge induced airway hyperresponsiveness in vehicle-treated animals as measured by whole body barometric plethysmography, and eosinophilia in bronchoalveolar lavage. POL7085 dose-dependently and significantly decreased airway hyperresponsiveness (34 ± 16 %) and eosinophil numbers in bronchoalveolar lavage (66 ± 6 %). In addition, the highest dose of POL7085 used significantly inhibited lung IL-4 (85 ± 4 %), IL-5 (87 ± 2 %) and IL-13 (190 ± 19 %) levels, and lung collagen (43 ± 11 %). CONCLUSIONS: The Protein Epitope Mimetic CCR10 antagonist, POL7085, significantly and dose-dependently decreased allergen-induced airway hyperresponsiveness and airway inflammation after once daily local treatment. Our data give strong support for further investigations with CCR10 antagonists in asthmatic disease.

Nematode and arthropod genomes provide new insights into the evolution of class 2 B1 GPCRs.

Nematodes and arthropods are the most speciose animal groups and possess Class 2 B1 G-protein coupled receptors (GPCRs). Existing models of invertebrate Class 2 B1 GPCR evolution are mainly centered on Caenorhabditis elegans and Drosophila melanogaster and a few other nematode and arthropod representatives. The present study reevaluates the evolution of metazoan Class 2 B1 GPCRs and orthologues by exploring the receptors in several nematode and arthropod genomes and comparing them to the human receptors. Three novel receptor phylogenetic clusters were identified and designated cluster A, cluster B and PDF-R-related cluster. Clusters A and B were identified in several nematode and arthropod genomes but were absent from D. melanogaster and Culicidae genomes, whereas the majority of the members of the PDF-R-related cluster were from nematodes. Cluster A receptors were nematode and arthropod-specific but shared a conserved gene environment with human receptor loci. Cluster B members were orthologous to human GCGR, PTHR and Secretin members with which they probably shared a common origin. PDF-R and PDF-R related clusters were present in representatives of both nematodes and arthropods. The results of comparative analysis of GPCR evolution and diversity in protostomes confirm previous notions that C. elegans and D. melanogaster genomes are not good representatives of nematode and arthropod phyla. We hypothesize that at least four ancestral Class 2 B1 genes emerged early in the metazoan radiation, which after the protostome-deuterostome split underwent distinct selective pressures that resulted in duplication and deletion events that originated the current Class 2 B1 GPCRs in nematode and arthropod genomes.

Review: Structure-function and biological properties of the atypical chemokine receptor D6.

The atypical chemokine receptor D6 was initially called "silent" on the basis of lack of conventional signaling events that lead to directional cell migration. It has emerged that D6 is able to bind and drive to degradative compartments most inflammatory CC chemokines and that is able to convey G-protein independent signaling events to optimize its scavenging activity. We here summarize the knowledge available today on D6 structural and signaling properties and its essential role for the control of inflammatory cells traffic and proper development of the adaptive immune response.

Regulation of the immune and inflammatory responses by the 'atypical' chemokine receptor D6.

Chemokines and their receptors are key regulators of leukocyte migration and intra-tissue accumulation under both homeostatic and inflammatory conditions. Regulation of chemokine-dependent responses, particularly those relating to inflammation, is essential to avoid the development of inflammatory and autoimmune pathologies. Recently, a new subfamily of chemokine receptors referred to as the 'atypical' chemokine receptors has emerged, members of which have been shown to play important roles in controlling in vivo chemokine biology. Here we review the basic biology of the chemokine and chemokine receptor family, introduce the topic of 'atypical' chemokine receptor biology and focus specifically on the best-characterized of the 'atypical' chemokine receptors, D6. D6 is a 'scavenging' receptor for inflammatory CC chemokines and plays a central role in the resolution of in vivo inflammatory responses. We describe the biology, biochemistry and pathological relevance of D6 and outline emerging data suggesting that it has additional important roles in integrating innate and adaptive immune responses.

Structure-function dissection of D6, an atypical scavenger receptor.

Chemokines direct leukocyte migration by activating intracellular signalling pathways through G-protein coupled chemokine receptors. However, they also bind to other surface proteins, including a group of molecules which we refer to as 'atypical' chemokine receptors. One such molecule is D6. D6 is structurally-related to other chemokine receptors, and binds specific pro-inflammatory chemokines with high affinity, but surprisingly, when expressed in heterologous cell lines, it is unable to transduce signals after chemokine engagement. Instead, by using the approaches outlined in this chapter, evidence has emerged that D6 acts as a chemokine scavenger which uses unique intracellular trafficking properties to continuously sequester extracellular chemokines into cells. It is envisaged that this suppresses inflammation in vivo by limiting pro-inflammatory chemokine bioavailability, and indeed, D6 deficient mice show exaggerated inflammatory responses to a variety of challenges. In addition to the in vitro functional studies, we also describe the methods we have used to express, purify and analyse large quantities of D6 protein. The unusually high stability of D6 and its broad subcellular distribution enables D6 to be expressed to very high levels in transfected cells, making it possible, at least in principal, to produce enough D6 to allow for purification of quantities suitable for crystallisation. This is a key step on the path towards generating a three-dimensional structure of the molecule. Thus, the protocols we outline have helped establish chemokine scavenging as a novel paradigm in chemokine biology, and may also ultimately provide unprecedented insight into the structure of D6 and other chemokine receptors.

A short amino acid sequence containing tyrosine in the N-terminal region of G protein-coupled receptors is critical for their potential use as co-receptors for human and simian immunodeficiency viruses.

Various G protein-coupled receptors (GPCRs) have the potential to work as co-receptors for human and simian immunodeficiency virus (HIV/SIV). HIV/SIV co-receptors have several tyrosines in their extracellular N-terminal region (NTR) as a common feature. However, the domain structure of the NTR that is critical for GPCRs to have co-receptor activity has not been identified. Comparative studies of different HIV/SIV co-receptors are an effective way to clarify the domain. These studies have been carried out only for the major co-receptors, CCR5 and CXCR4. A chemokine receptor, D6, has been shown to mediate infection of astrocytes with HIV-1. Recently, it was also found that an orphan GPCR, GPR1, and a formyl peptide receptor, FPRL1, work as potent HIV/SIV co-receptors in addition to CCR5 and CXCR4. To elucidate more about the domain of the NTR critical for HIV/SIV co-receptor activity, this study analysed the effects of mutations in the NTR on the co-receptor activity of D6, FPRL1 and GPR1 in addition to CCR5. The results identified a number of tyrosines that are indispensable for the activity of these co-receptors. The number and positions of those tyrosines varied among co-receptors and among HIV-1 strains. Moreover, it was found that a small domain of a few amino acids containing a tyrosine is critical for the co-receptor activity of GPR1. These findings will be useful in elucidating the mechanism that allows GPCRs to have the potential to act as HIV/SIV co-receptors.