5-alpha-reductase

2012年8月27日星期一

NF-?B: where did it come from and why?

NF-?B: where did it come from and why?

Immunol Rev. 2012 Mar;246(1):14-35

Authors: Gilmore TD, Wolenski FS

Abstract
The vast majority of research on nuclear factor ?B (NF-?B) signaling in the past 25 years has focused on its roles in normal and disease-related processes in vertebrates, especially mice and humans. Recent genome and transcriptome sequencing efforts have shown that homologs of NF-?B transcription factors, inhibitor of NF-?B (I?B) proteins, and I?B kinases are present in a variety of invertebrates, including several in phyla simpler than Arthropoda, the phylum containing insects such Drosophila. Moreover, many invertebrates also contain genes encoding homologs of upstream signaling proteins in the Toll-like receptor signaling pathway, which is well-known for its downstream activation of NF-?B for innate immunity. This review describes what we now know or can infer and speculate about the evolution of the core elements of NF-?B signaling as well as the biological processes controlled by NF-?B in invertebrates. Further research on NF-?B in invertebrates is likely to uncover information about the evolutionary origins of this key human signaling pathway and may have relevance to our management of the responses of ecologically and economically important organisms to environmental and adaptive pressures.

PMID: 22435545 [PubMed - indexed for MEDLINE]

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Molecular pharmacology of histamine H4 receptors.

Molecular pharmacology of histamine H4 receptors.

Front Biosci. 2012;17:2089-106

Authors: Nijmeijer S, de Graaf C, Leurs R, Vischer HF

Abstract
The histamine H4 receptor (H4R) is the youngest member of the histamine receptor family. Based on its predominant expression pattern in hematopoietic cells, the H4R is considered to be an interesting drug target for inflammatory disorders such as allergy and asthma. Since the identification and cloning of the H4R in 2000, drug discovery programs boosted the development of various H4R (specific) ligands. Differences between H4R orthologs in combination with available three-dimensional G protein-coupled receptor (GPCR) models have guided site-directed mutagenesis studies to gain insight in ligand binding and receptor activation. In addition, ongoing characterization of H4R-mediated signaling in transfected and native cells contributes to further unravel the (patho-) physiological functions of H4Rs.

PMID: 22652766 [PubMed - in process]

G-protein Receptors gpcr pathway NF-κB

An update of novel screening methods for GPCR in drug discovery.

An update of novel screening methods for GPCR in drug discovery.

Expert Opin Drug Discov. 2012 Jun 21;

Authors: Chen L, Jin L, Zhou N

Abstract
Introduction: G protein-coupled receptors (GPCRs) are the largest and most versatile group of cytomembrane receptors, comprising of approximately 300 non-sensory and druggable members. Traditional GPCR drug screening is based on radiometric competition binding assays, which are expensive and hazardous to human health. Furthermore, the paradox of high investment and low output, in terms of new drugs, highlights the need for more efficient and effective drug screening methods. Areas covered: This review summarizes non-radioactive assays assessing the ligand-receptor binding including: the fluorescence polarization assay, the TR-FRET assay and the surface plasmon resonance assay. It also looks at non-radioactive assays that assess receptor activation and signaling including: second messenger-based assays and ?-arrestin recruitment-based assays. This review also looks at assays based on cellular phenotypic change. Expert opinion: GPCR signaling pathways look to be more complicated than previously thought. The existence of receptor allosteric sites and multireceptor downstream effectors restricts the traditional assay methods. The emergence of novel drug screening methods such as those for assessing ?-arrestin recruitment and cellular phenotypic change may provide us with improved drug screening efficiency and effect.

PMID: 22716301 [PubMed - as supplied by publisher]

NF-κB NF-kB signaling pathway NF-kB pathway

2012年8月26日星期日

Receptor-specific regulation of ERK1/2 activation by members of the "free fatty acid receptor" family.

Receptor-specific regulation of ERK1/2 activation by members of the "free fatty acid receptor" family.

J Recept Signal Transduct Res. 2012 Aug;32(4):196-201

Authors: Seljeset S, Siehler S

Abstract
Context: The "free fatty acid receptors" (FFARs) GPR40, GPR41, and GPR43 regulate various physiological homeostases, and are all linked to activation of extracellular signal-regulated kinases (ERK)1/2. Objective: Investigation of coupling of FFARs to two other mitogen-activated protein kinases (MAPKs) sometimes regulated by G protein-coupled receptors (GPCRs), c-Jun N-terminal kinase (JNK) and p38MAPK, and characterization of signaling proteins involved in the regulation of FFAR-mediated ERK1/2 activation. Methods: FFARs were recombinantly expressed, cells challenged with the respective agonist, and MAPK activation quantitatively determined using an AlphaScreen SureFire assay. Inhibitors for signaling proteins were utilized to characterize ERK1/2 pathways. Results: Propionate-stimulated GPR41 strongly coupled to ERK1/2 activation, while the coupling of linoleic acid-activated GPR40 and acetate-activated GPR43 was weaker. JNK and p38MAPK were weakly activated by FFARs. All three receptors activated ERK1/2 fully or partially via G(i/o) and Rac. PI3K was relevant for GPR40- and GPR41-mediated ERK1/2 activation, and Src was essential for GPR40- and GPR43-induced activation. Raf-1 was not involved in the GPR43-triggered activation. Conclusion: The results demonstrate a novel role of Rac in GPCR-mediated ERK1/2 signaling, and that GPCRs belonging to the same family can regulate ERK1/2 activation by different receptor-specific mechanisms.

PMID: 22712802 [PubMed - in process]

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Selection and characterization of DARPins specific for the neurotensin receptor 1.

Selection and characterization of DARPins specific for the neurotensin receptor 1.

Protein Eng Des Sel. 2009 Jun;22(6):357-66

Authors: Milovnik P, Ferrari D, Sarkar CA, Pl�ckthun A

Abstract
We describe here the selection and characterization of designed ankyrin repeat proteins (DARPins) that bind specifically to the rat neurotensin receptor 1 (NTR1), a G-protein coupled receptor (GPCR). The selection procedure using ribosome display and the initial clone analysis required <10 microg of detergent-solubilized, purified NTR1. Complex formation with solubilized GPCR was demonstrated by ELISA and size-exclusion chromatography; additionally, the GPCR could be detected in native membranes of mammalian cells using fluorescence microscopy. The main binding epitope in the GPCR lies within the 33 amino acids following the seventh transmembrane segment, which comprise the putative helix 8, and additional binding interactions are possibly contributed by the cytoplasmic loop 3, thus constituting a discontinuous epitope. Since the selected binders recognize the GPCR both in detergent-solubilized and in membrane-embedded forms, they will be potentially useful both in co-crystallization trials and for signal transduction experiments.

PMID: 19389717 [PubMed - indexed for MEDLINE]

GPCR Signaling G-protein Receptors gpcr pathway

Classification of G-protein coupled receptors at four levels.

Classification of G-protein coupled receptors at four levels.

Protein Eng Des Sel. 2006 Nov;19(11):511-6

Authors: Gao QB, Wang ZZ

Abstract
G-protein coupled receptors (GPCRs) are transmembrane proteins which via G-proteins initiate some of the important signaling pathways in a cell and are involved in various physiological processes. Thus, computational prediction and classification of GPCRs can supply significant information for the development of novel drugs in pharmaceutical industry. In this paper, a nearest neighbor method has been introduced to discriminate GPCRs from non-GPCRs and subsequently classify GPCRs at four levels on the basis of amino acid composition and dipeptide composition of proteins. Its performance is evaluated on a non-redundant dataset consisted of 1406 GPCRs for six families and 1406 globular proteins using the jackknife test. The present method based on amino acid composition achieved an overall accuracy of 96.4% and Matthew's correlation coefficient (MCC) of 0.930 for correctly picking out the GPCRs from globular proteins. The overall accuracy and MCC were further enhanced to 99.8% and 0.996 by dipeptide composition-based method. On the other hand, the present method has successfully classified 1406 GPCRs into six families with an overall accuracy of 89.6 and 98.8% using amino acid composition and dipeptide composition, respectively. For the subfamily prediction of 1181 GPCRs of rhodopsin-like family, the present method achieved an overall accuracy of 76.7 and 94.5% based on the amino acid composition and dipeptide composition, respectively. Finally, GPCRs belonging to the amine subfamily and olfactory subfamily of rhodopsin-like family were further analyzed at the type level. The overall accuracy of dipeptide composition-based method for the classification of amine type and olfactory type of GPCRs reached 94.5 and 86.9%, respectively, while the overall accuracy of amino acid composition-based method was very low for both subfamilies. In comparison with existing methods in the literature, the present method also displayed great competitiveness. These results demonstrate the effectiveness of our method on identifying and classifying GPCRs correctly. GPCRsIdentifier, a corresponding stand-alone executable program for GPCR identification and classification was also developed, which can be acquired freely on request from the authors for academic purposes.

PMID: 17032692 [PubMed - indexed for MEDLINE]

discover more info here find out more info GPCR Signaling

The circadian neuropeptide PDF signals preferentially through a specific adenylate cyclase isoform AC3 in M pacemakers of Drosophila.

The circadian neuropeptide PDF signals preferentially through a specific adenylate cyclase isoform AC3 in M pacemakers of Drosophila.

PLoS Biol. 2012 Jun;10(6):e1001337

Authors: Duvall LB, Taghert PH

Abstract
The neuropeptide Pigment Dispersing Factor (PDF) is essential for normal circadian function in Drosophila. It synchronizes the phases of M pacemakers, while in E pacemakers it decelerates their cycling and supports their amplitude. The PDF receptor (PDF-R) is present in both M and subsets of E cells. Activation of PDF-R stimulates cAMP increases in vitro and in M cells in vivo. The present study asks: What is the identity of downstream signaling components that are associated with PDF receptor in specific circadian pacemaker neurons? Using live imaging of intact fly brains and transgenic RNAi, we show that adenylate cyclase AC3 underlies PDF signaling in M cells. Genetic disruptions of AC3 specifically disrupt PDF responses: they do not affect other Gs-coupled GPCR signaling in M cells, they can be rescued, and they do not represent developmental alterations. Knockdown of the Drosophila AKAP-like scaffolding protein Nervy also reduces PDF responses. Flies with AC3 alterations show behavioral syndromes consistent with known roles of M pacemakers as mediated by PDF. Surprisingly, disruption of AC3 does not alter PDF responses in E cells--the PDF-R(+) LNd. Within M pacemakers, PDF-R couples preferentially to a single AC, but PDF-R association with a different AC(s) is needed to explain PDF signaling in the E pacemakers. Thus critical pathways of circadian synchronization are mediated by highly specific second messenger components. These findings support a hypothesis that PDF signaling components within target cells are sequestered into "circadian signalosomes," whose compositions differ between E and M pacemaker cell types.

PMID: 22679392 [PubMed - in process]

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