The pharmacology of adrenomedullin 2/intermedin

Adrenomedullin 2 (AM2) or intermedin is a member of the calcitonin gene-related peptide (CGRP)/calcitonin family of peptides and was discovered in 2004. Unlike other members of this family, no unique receptor has yet been identified for it. It is extensively distributed throughout the body. It causes hypotension when given peripherally, but when given into the CNS, it increases blood pressure and causes sympathetic activation. It also increases prolactin release, is anti-diuretic and natriuretic and reduces food intake. Whilst its effects resemble those of AM, it is frequently more potent. Some characterization of AM2 has been done on molecularly defined receptors; the existing data suggest that it preferentially activates the AM receptor formed from calcitonin receptor-like receptor and receptor activity modifying protein 3. On this complex, its potency is generally equivalent to that of AM. There is no known receptor-activity where it is more potent than AM. In tissues and in animals it is frequently antagonised by CGRP and AM antagonists; however, situations exist in which an AM2 response is maintained even in the presence of supramaximal concentrations of these antagonists. Thus, there is a partial mismatch between the pharmacology seen in tissues and that on cloned receptors. The only AM2 antagonists are peptide fragments, and these have limited selectivity. It remains unclear as to whether novel AM2 receptors exist or whether the mismatch in pharmacology can be explained by factors such as metabolism. © 2011 The British Pharmacological Society.

Structure-function analysis of amino acid 74 of human RAMP1 and RAMP3 and its role in peptide interactions with adrenomedullin and calcitonin gene-related peptide receptors

The receptors for calcitonin gene-related peptide (CGRP) and adrenomedullin (AM) are complexes of the calcitonin receptor-like receptor (CLR) and receptor activity-modifying proteins (RAMP). The CGRP receptor is a CLR/RAMP1 pairing whereas CLR/RAMP2 and CLR/RAMP3 constitute two subtypes of AM receptor: AM(1) and AM(2), respectively. Previous studies identified Glu74 in RAMP3 to be important for AM binding and potency. To further understand the importance of this residue and its equivalent in RAMP1 (Trp74) we substituted the native amino acids with several others. In RAMP3, these were Trp, Phe, Tyr, Ala, Ser, Thr, Arg and Asn; in RAMP1, Glu, Phe, Tyr, Ala and Asn substitutions were made. The mutant RAMPs were co-expressed with CLR in Cos7 cells; receptor function in response to AM, AM(2)/intermedin and CGRP was measured in a cAMP assay and cell surface expression was determined by ELISA. Phe reduced AM potency in RAMP3 but had no effect in RAMP1. In contrast, Tyr had no effect in RAMP3 but enhanced AM potency in RAMP1. Most other substitutions had a small effect on AM potency in both receptors whereas there was little impact on CGRP or AM(2) potency. Overall, these data suggest that the geometry and charge of the residue at position 74 contribute to how AM interacts with the AM(2) and CGRP receptors and confirms the role of this position in dictating differential AM pharmacology at the AM(2) and CGRP receptors.

Adrenomedullin and calcitonin gene-related peptide receptors in endocrine-related cancers:opportunities and challenges

Adrenomedullin (AM), adrenomedullin 2 (AM2/intermedin) and calcitonin gene-related peptide (CGRP) are members of the calcitonin family of peptides. They can act as growth or survival factors for a number of tumours, including those that are endocrine-related. One mechanism through which this occurs is stimulating angiogenesis and lymphangiogenesis. AM is expressed by numerous tumour types and for some cancers, plasma AM levels can be correlated with the severity of the disease. In cancer models, lowering AM content or blocking AM receptors can reduce tumour mass. AM receptors are complexes formed between a seven transmembrane protein, calcitonin receptor-like receptor and one of the two accessory proteins, receptor activity-modifying proteins (RAMPs) 2 or 3 to give the AM1 and AM2 receptors respectively. AM also has affinity at the CGRP receptor, which uses RAMP1. Unfortunately, due to a lack of selective pharmacological tools or antibodies to distinguish AM and CGRP receptors, the precise receptors and signal transduction pathways used by the peptides are often uncertain. Two other membrane proteins, RDC1 and L1/G10D (the 'ADMR'), are not currently considered to be genuine CGRP or AM receptors. In order to properly evaluate whether AM or CGRP receptor inhibition has a role in cancer therapy, it is important to identify which receptors mediate the effects of these peptides. To effectively distinguish AM1 and AM2 receptors, selective receptor antagonists need to be developed. The development of specific CGRP receptor antagonists suggests that this is now feasible.

Peptidoglycan derived from Staphylococcus epidermidis induces Connexin43 hemichannel activity with consequences on the innate immune response in endothelial cells

Gram-positive bacterial cell wall components including PGN (peptidoglycan) elicit a potent pro-inflammatory response in diverse cell types, including endothelial cells, by activating TLR2 (Toll-like receptor 2) signalling. The functional integrity of the endothelium is under the influence of a network of gap junction intercellular communication channels composed of Cxs (connexins) that also form hemichannels, signalling conduits that are implicated in ATP release and purinergic signalling. PGN modulates Cx expression in a variety of cell types, yet effects in endothelial cells remain unresolved. Using the endothelial cell line b.End5, a 6 h challenge with PGN induced IL-6 (interleukin 6), TLR2 and Cx43 mRNA expression that was associated with enhanced Cx43 protein expression and gap junction coupling. Cx43 hemichannel activity, measured by ATP release from the cells, was induced following 15 min of exposure to PGN. Inhibition of hemichannel activity with carbenoxolone or apyrase prevented induction of IL-6 and TLR2 mRNA expression by PGN, but had no effect on Cx43 mRNA expression levels. In contrast, knockdown of TLR2 expression had no effect on PGN-induced hemichannel activity, but reduced the level of TLR2 and Cx43 mRNA expression following 6 h of PGN challenge. PGN also acutely induced hemichannel activity in HeLa cells transfected to express Cx43, but had no effect in Cx43-deficient HeLa OHIO cells. All ATP responses were blocked with Cx-specific channel blockers. We conclude that acute Cx43 hemichannel signalling plays a role in the initiation of early innate immune responses in the endothelium.

Structure-activity relationships for α-calcitonin gene-related peptide

Calcitonin gene-related peptide (CGRP) is a member of the calcitonin (CT) family of peptides. It is a widely distributed neuropeptide implicated in conditions such as neurogenic inflammation. With other members of the CT family, it shares an N-terminal disulphide-bonded ring which is essential for biological activity, an area of potential α-helix, and a C-terminal amide. CGRP binds to the calcitonin receptor-like receptor (CLR) in complex with receptor activity-modifying protein 1 (RAMP1), a member of the family B (or secretin-like) GPCRs. It can also activate other CLR or calcitonin-receptor/RAMP complexes. This 37 amino acid peptide comprises the N-terminal ring that is required for receptor activation (residues 1-7); an α-helix (residues 8-18), a region incorporating a β-bend (residues 19-26) and the C-terminal portion (residues 27-37), that is characterized by bends between residues 28-30 and 33-34. A few residues have been identified that seem to make major contributions to receptor binding and activation, with a larger number contributing either to minor interactions (which collectively may be significant), or to maintaining the conformation of the bound peptide. It is not clear if CGRP follows the pattern of other family B GPCRs in binding largely as an α-helix. Linked Articles This article is part of a themed section on Neuropeptides. To view the other articles in this section visit http://dx.doi.org/10.1111/bph.2013.170.issue-7 © 2012 The Authors. British Journal of Pharmacology © 2012 The British Pharmacological Society.

Human rhinovirus-induced inflammatory responses are inhibited by phosphatidylserine containing liposomes

Human rhinovirus (HRV) infections are major contributors to the healthcare burden associated with acute exacerbations of chronic airway disease, such as chronic obstructive pulmonary disease and asthma. Cellular responses to HRV are mediated through pattern recognition receptors that may in part signal from membrane microdomains. We previously found Toll-like receptor signaling is reduced, by targeting membrane microdomains with a specific liposomal phosphatidylserine species, 1-stearoyl-2-arachidonoyl-sn-glycero-3-phospho-L-serine (SAPS). Here we explored the ability of this approach to target a clinically important pathogen. We determined the biochemical and biophysical properties and stability of SAPS liposomes and studied their ability to modulate rhinovirus-induced inflammation, measured by cytokine production, and rhinovirus replication in both immortalized and normal primary bronchial epithelial cells. SAPS liposomes rapidly partitioned throughout the plasma membrane and internal cellular membranes of epithelial cells. Uptake of liposomes did not cause cell death, but was associated with markedly reduced inflammatory responses to rhinovirus, at the expense of only modest non-significant increases in viral replication, and without impairment of interferon receptor signaling. Thus using liposomes of phosphatidylserine to target membrane microdomains is a feasible mechanism for modulating rhinovirus-induced signaling, and potentially a prototypic new therapy for viral-mediated inflammation.

Pathogen-Specific Adaptations to Conserved Signaling Pathways in Cryptococcus neoformans

Cryptococcus neoformans is an opportunistic fungal pathogen that causes significant disease worldwide. Even though this fungus has not evolved specifically to cause human disease, it has a remarkable ability to adapt to many different environments within its infected host. C. neoformans adapts by utilizing conserved eukaryotic and fungal-specific signaling pathways to sense and respond to stresses within the host. Upon infection, two of the most significant environmental changes this organism experiences are elevated temperature and high pH.

Conserved Rho and Ras family GTPases are central regulators of thermotolerance in C. neoformans. Many GTPases require prenylation to associate with cellular membranes and function properly. Using molecular genetic techniques, microscopy, and infection models, I demonstrated that the prenyltransferase, geranylgeranyl transferase I (GGTase I) is required for thermotolerance and pathogenesis. Using fluorescence microscopy, I found that only a subset of conserved GGTase I substrates requires this enzyme for membrane localization. Therefore, the C. neoformans GGTase I may recognize its substrate in a slightly different manner than other eukaryotic organisms.

The alkaline response transcription factor, Rim101, is a central regulator of stress-response genes important for adapting to the host environment. In particular, Rim101 regulates cell surface alterations involved in immune avoidance. In other fungi, Rim101 is activated by alkaline pH through a conserved signaling pathway, but this pathway had yet been characterized in C. neoformans. Using molecular genetic techniques, I identified and analyzed the conserved members of the Rim pathway. I found that it was only partially conserved in C. neoformans, missing the components that sense pH and initiate pathway activation. Using a genetic screen, I identified a novel Rim pathway component named Rra1. Structural prediction and genetic epistasis experiments suggest that Rra1 may serve as the Rim pathway pH sensor in C. neoformans and other related basidiomycete fungi.

To explore the relevance of Rim pathway signaling in the interaction of C neoformans with its host, I characterized the Rim101-regulated cell wall changes that prevent immune detection. Using HPLC, enzymatic degradation, and cell wall stains, I found that the rim101Δ mutation resulted in increased cell wall chitin exposure. In vitro co-culture assays demonstrated that increased chitin exposure is associated with enhanced activation of macrophages and dendritic cells. To further test this association, I demonstrated that other mutant strains with increased chitin exposure induce macrophage and dendritic cell responses similar to rim101Δ. We used primary macrophages from mutant mouse lines to demonstrate that members of both the Toll-like receptor and C-type lectin receptor families are involved in detecting strains with increased chitin exposure. Finally, in vivo immunological experiments demonstrated that the rim101Δ strain induced a global inflammatory immune response in infected mouse lungs, expanding upon our previous in vivo rim101Δ studies. These results demonstrate that cell wall organization largely determines how fungal cells are detected by the immune system.

Control of the innate immune response by the mevalonate pathway.

Deficiency in mevalonate kinase (MVK) causes systemic inflammation. However, the molecular mechanisms linking the mevalonate pathway to inflammation remain obscure. Geranylgeranyl pyrophosphate, a non-sterol intermediate of the mevalonate pathway, is the substrate for protein geranylgeranylation, a protein post-translational modification that is catalyzed by protein geranylgeranyl transferase I (GGTase I). Pyrin is an innate immune sensor that forms an active inflammasome in response to bacterial toxins. Mutations in MEFV (encoding human PYRIN) result in autoinflammatory familial Mediterranean fever syndrome. We found that protein geranylgeranylation enabled Toll-like receptor (TLR)-induced activation of phosphatidylinositol-3-OH kinase (PI(3)K) by promoting the interaction between the small GTPase Kras and the PI(3)K catalytic subunit p110δ. Macrophages that were deficient in GGTase I or p110δ exhibited constitutive release of interleukin 1β that was dependent on MEFV but independent of the NLRP3, AIM2 and NLRC4 inflammasomes. In the absence of protein geranylgeranylation, compromised PI(3)K activity allows an unchecked TLR-induced inflammatory responses and constitutive activation of the Pyrin inflammasome.

Btk regulates macrophage polarization in response to lipopolysaccharide

Bacterial Lipopolysaccharide (LPS) is a strong inducer of inflammation and does so by inducing polarization of macrophages to the classic inflammatory M1 population. Given the role of Btk as a critical signal transducer downstream of TLR4, we investigated its role in M1/M2 induction. In Btk deficient (Btk (-\-)) mice we observed markedly reduced recruitment of M1 macrophages following intraperitoneal administration of LPS. Ex vivo analysis demonstrated an impaired ability of Btk(-/-) macrophages to polarize into M1 macrophages, instead showing enhanced induction of immunosuppressive M2-associated markers in response to M1 polarizing stimuli, a finding accompanied by reduced phosphorylation of STAT1 and enhanced STAT6 phosphorylation. In addition to STAT activation, M1 and M2 polarizing signals modulate the expression of inflammatory genes via differential activation of transcription factors and regulatory proteins, including NF-κB and SHIP1. In keeping with a critical role for Btk in macrophage polarization, we observed reduced levels of NF-κB p65 and Akt phosphorylation, as well as reduced induction of the M1 associated marker iNOS in Btk(-/-) macrophages in response to M1 polarizing stimuli. Additionally enhanced expression of SHIP1, a key negative regulator of macrophage polarisation, was observed in Btk(-/-) macrophages in response to M2 polarizing stimuli. Employing classic models of allergic M2 inflammation, treatment of Btk (-/-) mice with either Schistosoma mansoni eggs or chitin resulted in increased recruitment of M2 macrophages and induction of M2-associated genes. This demonstrates an enhanced M2 skew in the absence of Btk, thus promoting the development of allergic inflammation.

Alternative splicing takes control of cytokine signaling

Thesis (Ph.D.)--University of Washington, 2016-08

FROM GENES TO GENOMES: LOCAL ADAPTATION AND ADAPTIVE POTENTIAL IN TWO ARCTIC SEABIRDS

By investigating the mechanisms underlying the evolution and the maintenance of local adaptations we can help predict how species will adapt to future environmental change. In this thesis I investigate local adaptation and adaptive potential in thick-billed and common murres (Uria lomvia and U. aalge), two arctic seabirds of international conservation concern. Thanks to the recent development of new genomic methods, I address three major themes that are relevant for both the development of evolutionary theory and conservation: 1) the role of gene flow in the origin and maintenance of adaptation; 2) levels and distribution of standing genetic variation, and their contribution to adaptive potential; and 3) the genomic mechanisms maintaining an adaptive dimorphism within a single interbreeding population. First, I review the literature on genomics of local adaptation with gene flow and find that adaptation can be maintained despite gene flow, that gene flow itself can promote adaptation, and that genetic architecture is important in the origin and maintenance of local adaptations. Second, I genotype genome-wide markers and toll-like receptor genes (TLRs) to investigate local adaptation and adaptive potential in thick-billed murres. Thick-billed murres do not show signatures of local adaptation to their breeding grounds, but outlier loci group birds according to their non-breeding distributions, suggesting that selection and/or demographic connectivity in the winter may explain patterns of differentiation in this species. Genetic variation at TLRs does not decrease with increasing latitude as predicted, but tests of selection and measures of genetic diversity suggest differences in local selective regimes at most genes. Thick-billed murres show high levels of standing genetic variation and their adaptive potential will mostly depend on rate and magnitude of environmental change. Finally, I improve and annotate the assembly of the highly heterozygous genome of the thick-billed murre. Using this assembly as a reference, I perform whole genome analyses to investigate the genomic basis of an adaptive dimorphism in Atlantic common murres. I show for the first time that a 60 kb complex copy number variant in a non-coding region maintains differences in plumage and cold adaptation despite high gene flow.

Infección por virus sincitial respiratorio y su relación con valores de IGG en niños críticos

Antecedente: La infección por el virus sincitial respiratorio (VSR) representa una elevada morbimortalidad, y en algunos casos necesidad de manejo en unidades de cuidado intensivo pediátrico (UCIP). La respuesta inmunológica influye de manera directa en la expresión de la severidad y pronóstico de los pacientes con infección respiratoria. Metodología: Estudio de una cohorte retrospectiva de pacientes con infección respiratoria grave secundaria a VSR, sin historia de inmunodeficiencia, atendidos en la UCIP del Hospital Universitario Clínica San Rafael. Se realizó análisis descriptivoglobaly de acuerdo a la categorización de las prueba de IgG. Resultados: De 188 pacientes que ingresaron a la UCIP, 13% presentaron infección por VSR (24), con una edad promedio de 7,3 (DE=3,6) meses. Pertenecían al sexo masculino79,83%. Se encontró que 12,5% tenían un valor de IgGbajo para su edad, 58,33% tenían valores en límite inferior y el 29,17% dentro de rangos normales para su edad. En los pacientes con IgG baja, fue mayor la presentación de choque séptico que no responde a líquidos (100 vs 92 vs 86%), la mediana de días de ventilación mecánica fue mayor (8 vs 6 vs 5 respectivamente), así como la mortalidad (67 vs 7,1 vs 0%). Conclusión: Nuestra serie encontró que aquellos pacientes con niveles bajos o valores en el límite inferior de IgG sérica tuvieron mayor compromiso sistémico, mayor duración de ventilación mecánica y mayor mortalidad. Se necesitan estudios prospectivos que relaciones niveles bajos de IgG con severidad y pronostico en estos pacientes con infección grave por VSR.

Genome-Wide Detection of Serpentine Receptor-Like Proteins in Malaria Parasites

Serpentine receptors comprise a large family of membrane receptors distributed over diverse organisms, such as bacteria, fungi, plants and all metazoans. However, the presence of serpentine receptors in protozoan parasites is largely unknown so far. In the present study we performed a genome-wide search for proteins containing seven transmembrane domains (7TM) in the human malaria parasite Plasmodium falciparum and identified four serpentine receptor-like proteins. These proteins, denoted PfSR1, PfSR10, PfSR12 and PfSR25, show membrane topologies that resemble those exhibited by members belonging to different families of serpentine receptors. Expression of the pfsrs genes was detected by Real Time PCR in P. falciparum intraerythrocytic stages, indicating that they potentially code for functional proteins. We also found corresponding homologues for the PfSRs in five other Plasmodium species, two primate and three rodent parasites. PfSR10 and 25 are the most conserved receptors among the different species, while PfSR1 and 12 are more divergent. Interestingly, we found that PfSR10 and PfSR12 possess similarity to orphan serpentine receptors of other organisms. The identification of potential parasite membrane receptors raises a new perspective for essential aspects of malaria parasite host cell infection.

Isolation of a cDNA for an octopamine-like, G-protein coupled receptor from the cattle tick, Boophilus microplus

Octopamine is a biogenic amine neurotransmitter of invertebrates that binds to a G-protein coupled receptor that has seven transmembrane domains. Formamidine pesticides like amitraz are highly specific agonists of the octopamine receptor. Amitraz is used extensively to control the cattle tick, Boophilus microplus, and many other ticks but now there are strains of ticks that are resistant to amitraz. We have isolated a cDNA from the cattle tick, B. miciroplus, that belongs to the biogenic amine family of receptors. The predicted amino acid sequence from this cDNA is most similar to octopamine receptors from insects. The nucleotide sequence of this gene from amitraz-resistant and amitraz-susceptible cattle ticks was identical. Thus, a point mutation/s did not confer resistance to amitraz in the strains we studied. Alternative explanations for resistance to amitraz in B. microplus are discussed. (C) 1999 Elsevier Science Ltd. All rights reserved.

Fms-like tyrosine kinase 3 ligand administration overcomes a genetically determined dendritic cell deficiency in NOD mice and protects against diabetes development

A dendritic cell (DC) imbalance with a marked deficiency in CD4(-)8(+) DC occurs in non-obese diabetic (NOD) mice, a model of human autoimmune diabetes mellitus. Using a NOD congenic mouse strain, we find that this CD4(-)8(+) DC deficiency is associated with a gene segment on chromosome 4, which also encompasses non-MHC diabetes susceptibility loci. Treatment of NOD mice with fms-like tyrosine kinase 3 ligand (FL) enhances the level of CD4(-)8(+) DC, temporarily reversing the DC subtype imbalance. At the same time, fms-like tryosine kinase 3 ligand treatment blocks early stages of the diabetogenic process and with appropriately timed administration can completely prevent diabetes development. This points to a possible clinical use of FL to prevent autoimmune disease.