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Immune receptors are omnipresent in multicellular organisms and comprise a vast array of molecular structures that serve to detect and eliminate pathogenic threats. The immunoglobulin (Ig) domain, a central structural feature of the antigen binding receptors that mediate adaptive immunity in jawed vertebrates, appears to play a particularly widespread role in metazoan immunity. Recent reports also have implicated Ig domains in the immune responses of protostomes such as flies and snails. Our research has focused on understanding the utilization of the Ig domain in the immunity of chordates and has identified numerous multigene families of Ig domain-containing receptors that appear to serve roles distinct from the adaptive antigen-binding receptors. Three families have received particular focus: novel immune-type receptors (NITRs) of bony fish, modular domain immune-type receptors (MDIRs) of cartilaginous fish and variable region-containing chitin-binding proteins (VCBPs) of amphioxus. NITRs and MDIRs are encoded in large multigene families of highly diversified forms and exhibit a striking dichotomy of an apparently ubiquitous presence but extensive diversification of sequence both within and among the particular taxonomic groups in which they are found. Crystal structures of VCBPs and NITRs demonstrate significant similarity to those of antigen-binding receptors but at the same time exhibit key differences that imply acquisition of separate and distinct ligand-binding functions. The tremendous plasticity of the Ig domain makes it a strong focus for studies of evolutionary events that have shaped modern integrated immune systems. Current data are consistent with a model of extremely rapid emergence and divergence of immune receptors, perhaps specific to individual species, as organisms contend with environments in which pathogens are continually selected for variation of their own molecular signatures.

The neonatal Fc receptor (FcRn) transports maternal IgG across epithelial barriers (1,2), thereby providing the fetus or newborn with humoral immunity before its immune system is fully functional. In newborn [...]

The neonatal Fc receptor for IgG (FcRn) is a distant member of the MHC class I protein family. It binds IgG and albumin in a pH-dependent manner and protects these from catabolism by diverting them from a degradative fate in lysosomes. In addition, FcRn-mediated IgG transport across epithelial barriers is responsible for the transmission of IgG from mother to infant and can also enhance IgG-mediated antigen uptake across mucosal epithelia. We now show a previously undescribed role for FcRn in mediating the presentation of antigens by dendritic cells when antigens are present as a complex with antibody by uniquely directing multimeric immune complexes, but not monomeric IgG, to lysosomes. IgG | immune complexes | dendritic cells

Understanding the genetic origin of cancer at the molecular level has facilitated the development of novel targeted therapies. Aberrant activation of the ErbB family of receptors is implicated in many [...]

Toll-like receptors (TLRs) are a family of transmembrane proteins that recognize conserved molecular motifs on microorganisms. Ligand binding to TLRs initiates signaling cascades that activate NF-[kappa]B, MAPK, and interferon response factors. These culminate in cellular responses including activation of antimicrobial killing mechanisms, production of cytokines and chemokines, maturation of antigen presenting cells, and the recruitment of the adaptive immune response. Intestinal epithelial cells represent a unique population of cells that exist in direct contact with a biomass of bacteria. Initiation of TLR signaling is tightly regulated because prolonged and excessive activation of TLRs can lead to uncontrolled inflammation detrimental to the host. Varied mechanisms appear to contribute to control of TLR activation in the intestinal epithelium. These include the collective effects of several negative regulators that include IRAK-M, TOLLIP, SIGIRR, A20, Nod2, and PPAR[gamma]. However, it remains to be determined whether they comprise the entire spectrum of negative control mechanisms and how they are bypassed to trigger activation during challenge by pathogens. Toll-like receptors; innate immunity; inflammation; ligand inhibition doi:10.1152/ajpgi.00531.2006

Sudden cardiac death due to abnormal heart rhythm kills 400,000-460,000 Americans each year. To identify genes that regulate heart rhythm, we are developing a screen that uses mouse embryonic stem cells (mESCs) with gene disruptions that can be differentiated into cardiac cells for phenotyping. Here, we show that the heterozygous disruption of the Akap10 (D-AKAP2) gene that disrupts the final 51 aa increases the contractile response of cultured cardiac cells to cholinergic signals. In both heterozygous and homozygous mutant mice derived from these mESCs, the same Akap10 disruption increases the cardiac response to cholinergic signals, suggesting a dominant interfering effect of the Akap10 mutant allele. The mutant mice have cardiac arrhythmias and die prematurely. We also found that a common variant of AKAP10 in humans (646V, 40% of alleles) was associated with increased basal heart rate and decreased heart rate variability (markers of low cholinergic/vagus nerve sensitivity). These markers predict an increased risk of sudden cardiac death. Although the molecular mechanism remains unknown, our findings in mutant mESCs, mice, and a common human AKAP10 SNP all suggest a role for AKAP10 in heart rhythm control. Our stem cell-based screen may provide a means of identifying other genes that control heart rhythm. G protein | receptor | signaling

Parathyroid hormone (PTH), the major systemic calcium-regulating hormone, has been linked to uremic vascular changes. Considering the possible deleterious action of PTH on vascular structures, it seemed logical to evaluate the impact of PTH on the receptor of advanced glycation end products (RAGE) and interleukin 6 (IL-6) mRNA and protein expression, taking into account that such parameters might be involved in the pathogenesis of vascular calcification, atherosclerosis, and/or arteriolosclerosis. Human umbilical vein cord endothelial cells (HUVEC) were stimulated for 24 h with [10.sup.-12]-[10.sup.-10] mol/l PTH. The mRNA expression of RAGE and IL-6 was established by reverse transcriptase/PCR techniques. RAGE protein levels were determined by Western blot and IL-6 secretion was measured by ELISA. The pathways by which PTH may have an effect on HUVEC functions were evaluated. PTH ([10.sup.-11]-[10.sup.-10] mol/l) significantly increased RAGE mRNA and protein expression. PTH also significantly increased IL-6 mRNA expression without changes at protein levels. The addition of protein kinase (PKC or PKA) inhibitors or nitric oxide (NO) synthase inhibitors significantly reduced the RAGE and IL-6 mRNA expression and the RAGE protein expression. PTH stimulates the mRNA expressions of RAGE and IL-6 and the protein expression of RAGE. These stimulatory effects are probably through PKC and PKA pathways and are also NO dependent. Such data may explain the possible impact of PTH on the atherosclerotic and arteriosclerotic progression. endothelial cells; IL-6; receptor of advanced glycation end products

Endothelin-1 (ET-1) is increased in rats on a high-salt (HS) diet and participates in salt-dependent hypertension. Afferent arterioles (AA) are important for long-term blood pressure control, and therefore we hypothesized that a HS diet would alter their responsiveness to ET-1. Sprague-Dawley rats were fed either a normal-salt (NS; 0.66% NaCl) or HS (8%) diet for 1 wk. Diameters of AA were determined in response to increasing concentrations of big ET-1, ET-1, sarafotoxin 6c (S6c), or norepinephrine (NE), using the blood-perfused juxtamedullary nephron technique. ET-1 responses were also determined during blockade of endothelin type A (E[T.sub.A]) or type B (E[T.sub.B]) receptors with 10 nM ABT-627 or 30 nM A-192621, respectively. Expression of E[T.sub.A] and E[T.sub.B] receptors was determined in renal microvessels. Responses of AA to big ET-1, ET-1, and S6c were significantly attenuated during a HS diet (e.g., response to [10.sup.-10] M ET-1 in NS vs. HS rats: -52.5 [+ or -] 10.2 vs. +5.6 [+ or -] 11.3% of control diameter; P < 0.05), with no change in the responses to NE. E[T.sub.B], but not E[T.sub.A] receptor blockade abolished the different response to ET-1 between the NS and HS groups. E[T.sub.B] receptor expression in renal microvessels was increased in response to HS (17.7 [+ or -] 2.4 vs. 6.6 [+ or -] 3.0% of [beta]-actin, P = 0.02), whereas E[T.sub.A] receptor expression was unchanged. These results suggest that the reduced vasoconstrictor response of AA to endothelin peptides during a HS diet is mediated by increased vasodilatory function of endothelial E[T.sub.B] receptors. By preserving renal blood flow, this may be an important mechanism to restore sodium balance during a HS diet. endothelin-1; sodium; renal circulation; hypertension

We recently demonstrated that treatment with the 5-H[T.sub.1A/7] receptor agonist [(R)-(+)-8-hydroxy-2-di-n-propylamino]tetralin (8-OH-DPAT) increases bladder capacity in chloralose-anesthetized female cats with chronic spinal cord injury. In the current study, we investigated the effects of 8-OH-DPAT on bladder capacity and external urethral sphincter (EUS) activity in urethane-anesthetized female rats (initial body mass 175-200 g) with chronic spinal cord injury (transsection at T10). Cystometric study took place 8-12 wk posttranssection. Intravesical pressure was monitored in urethane-anesthetized rats with a transvesical catheter, and EUS activity was assessed electromyographically. Spinal cord injury disrupts phasic activity of the EUS, resulting in decreased voiding efficiency and increased residual volume. 8-OH-DPAT induced a dose-dependent decrease in bladder capacity (the opposite of its effect in chronic spinal cord-injured cats) with an increase in micturition volume and decrease in residual volume resulting from improvement in voiding efficiency. The unexpected improvement in voiding efficiency can be explained by the 8-OH-DPAT-induced emergence of phasic EUS relaxation. Phasic EUS relaxation was also altered by 8-OH-DPAT in spinally intact rats, whereas the 5-H[T.sub.1A] receptor antagonist N-tert-butyl-3-[4-(2-methoxyphenyl)-piperazin-1-yl]-2-phenylpropanamide (WAY-100635), on its own, was without effect. It remains to be determined when phasic relaxation is restored after spinal cord injury, and indeed whether it is ever truly lost or is only temporarily separated from excitatory input. bladder; micturition; neurogenic voiding; detrusor; urethra

Upper urinary tract obstruction results in tubulointerstitial fibrosis and a progressive decline in renal function. Although several inflammatory mediators have been implicated in the pathophysiology of renal obstruction, the contribution of TNF-[alpha] to obstruction-induced fibrosis and renal dysfunction has not been thoroughly evaluated. To study this, male Sprague-Dawley rats were subjected to left unilateral ureteral obstruction vs. sham operation. Rats received either vehicle or a pegylated form of soluble TNF receptor type 1 (PEG-sTNFR1) every 84 h. The kidneys were harvested 1, 3, or 7 days postoperatively, and tissue samples were analyzed for TNF-[alpha] expression (ELISA), macrophage infiltration (ED-1 staining), transforming growth factor-[[beta].sub.1] expression (ELISA, RT-PCR), collagen I and IV activity (Western Blot, immunohistochemistry), [alpha]-smooth muscle actin accumulation (immunohistochemistry, Western blot analysis), and angiotensinogen expression (Western blot). In a separate arm, the glomerular filtration rate (inulin clearance) of rats subjected to unilateral ureteral obstruction in the presence of either vehicle or PEG-sTNFR1 was determined. Renal obstruction induced increased tissue TNF-a and transforming growth factor-[[beta].sub.1] levels, collagen I and IV activity, interstitial volume, [alpha]-smooth muscle actin accumulation, angiotensinogen expression, and renal dysfunction, whereas treatment with PEG-sTNFRI significantly reduced each of these markers of renal fibrosis. These results demonstrate that TNF-[alpha] mediates obstruction-induced renal fibrosis and identify TNF-a neutralization as a potential therapeutic option for the amelioration of obstruction-induced renal injury. kidney; glomerular filtration rate; cytokine; smooth muscle actin; transforming growth factor

Plants have the potential to produce a wide array of secondary metabolites that have utility as drugs to treat human diseases. To tap this potential, functional human nuclear receptors have [...]

Human progesterone receptors (PR) exist as two functionally distinct isoforms, PR-A and PR-B. The proteins are identical except for an additional 164 residues located at the N terminus of PR-B. To determine the mechanisms responsible for isoform-specific functional differences, we present here a thermodynamic dissection of PR-A-promoter interactions and compare the results to our previous work on PR-B. This analysis has generated a number of results inconsistent with the traditional, biochemically based model of receptor function. Specifically, statistical models invoking preformed PR-A dimers as the active binding species demonstrate that intrinsic binding energetics are over an order of magnitude greater than is apparent. High-affinity binding is opposed, however, by a large energetic penalty. The consequences of this penalty are 2-fold: Successive monomer binding to a palindromic response element is thermodynamically favored over preformed dimer binding, and DNA-induced dimerization of the monomers is largely abolished. Furthermore, PR-A binding to multiple PREs is only weakly cooperative, as judged by a 5-fold increase in overall stability. Comparison of these results to our work on PR-B demonstrates that whereas both isoforms appear to have similar DNA binding affinities, PR-B in fact has a greatly increased intrinsic binding affinity and cooperative binding ability relative to PR-A. These differences thus suggest that residues unique to PR-B allosterically regulate the energetics of cooperative promoter assembly. From a functional perspective, the differences in microscopic affinities predict receptor--promoter occupancies that accurately correlate with the transcriptional activation profiles seen for each isoform. nuclear receptor | protein-DNA interactions | quantitative footprint titrations | statistical mechanics

Notch receptors control differentiation and contribute to pathologic states such as cancer by interacting directly with a transcription factor called CSL (for CBF-1/Suppressor of Hairless/Lag-1) to induce expression of target genes. A number of Notch-regulated targets, including genes of the hairy/enhancer-of-split family in organisms ranging from Drosophila to humans, are characterized by paired CSL-binding sites in a characteristic head-to-head arrangement. Using a combination of structural and molecular approaches, we establish here that cooperative formation of dimeric Notch transcription complexes on promoters with paired sites is required to activate transcription. Our findings identify a mechanistic step that can account for the exquisite sensitivity of Notch target genes to variation in signal strength and developmental context, enable new strategies for sensitive and reliable identification of Notch target genes, and lay the groundwork for the development of Notch pathway inhibitors that are active on target genes containing paired sites. Mastermind | Notch signaling | signal transduction | dimerization | gene expression

Hemozoin (HZ) is an insoluble crystal formed in the food vacuole of malaria parasites. HZ has been reported to induce inflammation by directly engaging Toll-like receptor (TLR) 9, an endosomal receptor. 'Synthetic' HZ ( [beta]-hematin), typically generated from partially purified extracts of bovine hemin, is structurally identical to natural HZ. When HPLC-purified hemin was used to synthesize the crystal, [beta]-hematin had no inflammatory activity. In contrast, natural HZ from Plasmodium falciparum cultures was a potent TLR9 inducer. Natural HZ bound recombinant TLR9 ectodomain, but not TLR2. Both TLR9 stimulation and TLR9 binding of HZ were abolished by nuclease treatment. PCR analysis demonstrated that natural HZ is coated with malarial but not human DNA. Purified malarial DNA activated TLR9 but only when DNA was targeted directly to the endosome with a transfection reagent. Stimulatory quantities of natural HZ contain fever | immunomodulator | parasitic diseases

Lysophosphatidic acid (LPA) is a potent bioactive phospholipid that stimulates a variety of cellular responses by acting on cognate G protein-coupled receptors (GPCRs). There is increasing evidence that LPA signaling reprograms gene expression, but the GPCR-induced pathways connecting LPA receptor stimulation to downstream transcription factors are not well characterized. Here, we identify the adapter proteins Bcl10 and Malt1 as essential mediators of LPA-induced NF-[kappa]B activation. Both proteins were previously known to activate NF-[kappa]B in response to antigen receptor ligation on lymphocytes, but their functions in nonimmune cells are still largely undefined. By using murine embryonic fibroblasts from Bcl10- or Malt1-deficient mice as a genetic model, we report that Bal10 and Malt1 are critically required for the degradation of I[kappa]B-[alpha] and the subsequent NF-[kappa]B induction in response to LPA stimulation. Bcl10 and Malt1 cooperate with PKCs selectively for LPA-induced NF-[kappa]B activation but are dispensable for the activation of the Jnk, p38, Erk MAP kinase, and Akt signaling pathways. In a biological readout, we demonstrate that LPA-induced IL-6 production is abolished in the absence of Bcl10. Thus, our results identify a NF-[kappa]B-inducing signaling pathway downstream of GPCRs and reveal previously unrecognized functions for Bcl10/ Malt1 signaling in nonimmune cells. G protein-coupled receptor | signal transduction

Y receptors couple to G proteins and either mobilize intracellular [Ca.sup.2+] or alter cAMP levels to modulate the activity of [Ca.sup.2+]- and cAMPsensitive ion channels. We hypothesize that increased ion transport into the lumen of MDCK cysts can osmotically drive fluid movement and increase cyst size. Furthermore, activation of the adenylate cyclase/cAMP pathway may trigger cell proliferation via an extracellular signal-related kinase cascade. To test this hypothesis, several P2Y receptor inhibitors were used on the MDCK in vitro model of renal cyst formation. The nonspecific P2 receptor inhibitors reactive blue 2 and suramin reduced cyst growth significantly, as did PPADS and, to a lesser extent, the [P2Y.sub.1]-specific antagonist MRS2179. Cyst growth was reduced by ~50% when ATP was removed from the culture medium with apyrase, although stable analogs of ATP failed to increase cyst size. The nonselective P2X receptor inhibitor Coomassie brilliant blue G was ineffective at reducing cyst growth, suggesting no involvement of P2X receptors. Finally, the presence of selective inhibitors of ERK activation (either PD98059 or U0126) greatly reduced cyst growth, whereas in untreated cysts ERK activity was observed to increase with time. We conclude that stimulation of endogenous P2Y receptors by extracellular ATP increases growth of MDCK cysts via cAMP-dependent activation of the ERK pathway. P2Y receptor antagonists may have therapeutic potential in reducing cyst size and slowing disease progression; although further studies in vitro and in vivo are needed to investigate the specificity and role of these P2Y receptors in renal cystic diseases. ATP; polycystic kidney disease; Madin-Darby canine kidney; extracellular signal related kinase; renal cyst growth; ADPKD

The innate immune system includes microbial pattern recognition receptors that detect bacteria and viral products at the cell surface, in vesicles, and within the cytoplasm. Transmembrane signaling occurs through Toll-like receptors (TLRs). Cytoplasmic receptors are generally members of the nucleotide-binding domain (NOD)-leucine-rich repeat (LRR) family (CATERPILLER family). They influence the effects of other family members and of TLRs. Most NOD-LRR members enhance signal transduction, but Monarch-1 counterbalances TLR activity. NOD-LRR family members also act within the adaptive immune system. The class II transactivator regulates major histocompatibility complex class II expression. In the intestine, it is developmentally regulated, and its expression depends on weaning and, independently, on age. CATERPILLER; nucleotide-binding domain; leucin-rich repeat; Toll-like receptor; class II transactivator; leucin-rich repeat- and pyrin domain-containing protein 3

Dopaminergic systems in the brain adapt in response to various stimuli from the internal and external world, but the mechanisms underlying this process are incompletely understood. Here, we review recent evidence that certain types of transcription factor of the nuclear receptor family, specifically Nur77 and retinoid X receptors, have important roles in adaptation and homeostatic regulation of dopaminergic systems. These findings call for a reassessment of our fundamental understanding of the molecular and cellular basis of dopamine-mediated transmission. Given that diseases such as Parkinson's disease and schizophrenia are thought to involve adaptation of dopamine signalling, these findings might provide new insight into these pathologies and offer new avenues for drug development.

TRP channels play an important role as multifunctional cellular sensors. They are involved in so many fundamental cell functions that the investigation of their role in human pathophysiology and disease [...]

The TGF-[deta] signaling pathway has a complex role in regulating mammary carcinogenesis. Here we demonstrate that the type III TGF-β receptor (TβRIII, or betaglycan), a ubiquitously expressed TGF-β coreceptor, regulated [...]

The renin-angiotensin system is well known to be involved in the pathophysiological changes in renal function after obstruction of the ureter. Previously, we demonstrated that bilateral ureteral obstruction (BUO) is associated with dramatic changes in the expression of both renal sodium transporters and aquaporin water channels (AQPs). We now examined the effects of the [AT.sub.1]-receptor antagonist candesartan on the dysregulation of AQPs and key renal sodium transporters in rats subjected to 24-h BUO and followed 2 days after release of BUO (BUO-2R). Consistent with previous observations, BUO-2R resulted in a significantly decreased expression of AQP1, -2, and -3 compared with control rats. Concomitantly, the rats developed polyuria and reduced urine osmolality. Moreover, expression of the type 2 Na-phosphate cotransporter (NaPi-2) and type 1 bumetanide-sensitive Na-K-2Cl cotransporter (NKCC2) was markedly reduced, consistent with postobstructive natriuresis. Candesartan treatment from the onset of obstruction attenuated the reduction in GFR (3.1 [+ or -] 0.4 vs. 1.7 [+ or -] 0.3 ml x [min.sup.-1] x [kg.sup.-1]) and partially prevented the reduction in the expression of AQP2 (66 [+ or -] 21 vs. 13 [+ or -] 2%, n = 7; P < 0.05), NaPi-2 (84 [+ or -] 6 vs. 57 [+ or -] 10%, n = 7; P < 0.05), and NKCC2 (89 [+ or -] 12 vs. 46% [+ or -] 11, n = 7; P < 0.05). Consistent with this, candesartan treatment attenuated the increase in urine output (58 [+ or -] 4 vs. 97 [+ or -] 5 [micro]l x [min.sup.-1] x [kg.sup.-1], n = 7; P < 0.01) and the reduction in sodium reabsorption (433 [+ or -] 62 vs. 233 [+ or -] 45 [micro]mol x [min.sup.-1] x [kg.sup.-1], n = 7; P < 0.05) normally found in rats subjected to BUO. Moreover, candesartan treatment attenuated induction of cyclooxygenase 2 (COX-2) expression in the inner medulla, suggesting that COX-2 induction in response to obstruction is regulated by ANG II. In conclusion, candesartan prevents dysregulation of AQP2, sodium transporters, and development of polyuria seen in BUO. This strongly supports the view that candesartan protects kidney function in response to urinary tract obstruction. aquaporins; angiotensin; [AT.sub.1]-receptor blockade

Insulin and insulin-like growth factor I (IGF-I) are known to affect cardiovascular disease. We have investigated ligand binding and the dose-response relationship for insulin and IGF-I on vascular smooth muscle cells (VSMCs) at the receptor level. VSMCs from rat thoracic aorta were serum starved, stimulated with IGF-I or insulin, lysed, immunoprecipitated, and analyzed by Western blot. D-[U-[sup.14]C]Glucose accumulation and [6-[sup.3]H]thymidine incorporation into DNA were also measured. Specific binding of both insulin and IGF-I was demonstrated, being higher for IGF-I. Both IGF-I receptor (IGF-IR) and insulin receptor (IR) [beta]-subunits were detected and coprecipitated after immunoprecipitation (IP) against either of the two. No coprecipitation was found after reduction of disulphide bonds with dithiotreitol before IP. After stimulation with [10.sup.-10]-[10.sup.-9] M IGF-I, IP of the IGF-IR, or IR [beta]-subunit and immunoblot with anti-phosphotyrosine antibody, we found two distinct bands indicating phosphorylation of both the IGF-IR and the IR [beta]-subunit. Stimulation with [10.sup.-10]-[10.sup.-9] M insulin and IP against the IGF-IR did not show phosphorylation of either [beta]-subunit, whereas after IP of the IR we found phosphorylation of the IR [beta]-subunit. [[sup.14]C]Glucose accumulation and [[sup.3]H]thymidine incorporation were elevated in cells stimulated with IGF-I at [10.sup.-10]- [10.sup.-7] M, reaching maximum by 10-9 M. Insulin stimulation showed measurable effects only at supraphysiological concentrations, [10.sup.-8]-[10.sup.-7] M. In conclusion, coprecipitation of both the IGF-IR and the IR [beta]-subunit indicates the presence of hybrid insulin/IGF-I receptors in VSMC. At a physiological concentration, insulin activates the IR but does not affect either glucose metabolism or DNA synthesis, whereas IGF-I both activates the receptor and elicits biological effect. insulin-like growth factor I; ligand binding; receptor phosphorylation; immunopreciptation; dexoyribonucleic acid synthesis; glucose metabolism

Kisspeptin is a 54-amino acid peptide, encoded by the anti-metastasis gene KiSS-1, that activates G protein-coupled receptor 54 (GPR54). The kisspeptin-GPR54 system is critical to normal reproductive development. KISS-1 gene expression is increased in the human placenta in normal and molar pregnancies. Circulating kisspeptin is dramatically increased in normal pregnancy, but levels in GTN have not previously been reported. The present study was designed to determine whether plasma kisspeptin levels are altered in patients with malignant GTN. Thirty-nine blood samples were taken from 11 patients with malignant GTN at presentation during and after chemotherapy. Blood was also sampled from nonpregnant and pregnant volunteers. Plasma kisspeptin IR and hCG concentrations were measured. Plasma kisspeptin IR concentration in nonpregnant (n = 16) females was metastin; human chorionic gonadotropin; G protein-coupled receptor 54

The role of interaction between SER-1, a 5-HT(sub 2)-like receptor and MPZ-1, a multi-PDZ domain containing protein, in the vulva of Caenorhabditis elegans in easing egg-laying, is studied.

The role of Frizzled7 receptor in controlling canonical Wnt signaling during the formation of neural crest in Xenopus embryo is studied.

By using rational design, antibody fragments (Fabs) that mimic thrombopoietin (TPO) were created. A peptide with cMpl receptor-binding capability was grafted into different complementarity-determining regions of a fully human Fab scaffold. Functional presentation of the peptide was optimized by using phage display and cell-based panning. Select antibodies and fragments containing two grafted peptides were assayed for their ability to stimulate the cMpl receptor in vitro. Several candidates demonstrated agonist activity in an in vitro cMpl receptor signaling reporter assay, including Fab59, which was estimated to be equipotent to TPO. Fab59 additionally was able to effectively stimulate platelet production in normal mice. These rationally designed mimetic Fabs may provide a therapeutic intervention for thrombocytopenia while avoiding the potential generation of neutralizing antibodies to endogenous TPO. Furthermore, this study demonstrates a method by which short-lived linear peptides with binding activity may be converted to more stable and potent agonists capable of activating cell surface receptors. cMp| receptor

Axial skeleton development and the role of Tgfbr2 receptor in this is examined.

Experiments carried out in conscious guinea pigs suggest that citric acid-0evoked coughing is partly mediated by transient receptor potential vanilloid type 1 (TRPV1) receptor-dependent activation of tachykinin-containing, capsaicin-sensitive C fibers. In vitro electrophysiological analyses indicate, however, that acid also activates capsaicin-sensitive and -insensitive vagal afferent nerves by a TRPV1-independent mechanism, and studies in anesthetized guinea pigs show that coughing evoked by acid is mediated by activation of capsaicin-insensitive vagal afferent nerves. In the present study, we have characterized the mechanisms of citric acid-evoked coughing in anesthetized guinea pigs. Drugs were administered directly to the Krebs buffer perfusing the extrathoracic trachea. Citric acid was applied topically to the tracheal mucosa, directly into the tracheal perfusate in increasing concentrations and at 1-min intervals. Citric acid dose dependently evoked coughing in anesthetized guinea pigs. This was mimicked by hydrochloric acid but not by sodium citrate. The coughing evoked by acid was nearly or completely abolished by TTX or by cutting the recurrent laryngeal nerves. Perfusing the trachea with a low [Cl.sup.-] buffer potentiated the acid-induced cough reflex. In contrast, prior capsaicin desensitization, 10 [micro]M capsazepine, [Ca.sup.2+]-free perfusate, 0.1 [micro]M iberiotoxin, 1 [micro]M atropine, 10 [micro]M isoproterenol, 10 [micro]M albuterol, 3 [micro]M indomethacin, 0.1 [micro]M HOE-140, a combination of [neurokinin.sub.1] (N[K.sub.1]; CP-99994), N[K.sub.2] (SR-48968), and N[K.sub.3] (SB-223412) receptor antagonists (0.1 p[micro]M each), a combination of histamine [H.sub.1] (3 [micro]M pyrilamine) and cysL[T.sub.1] (1 [micro]M ICI-198615) receptor antagonists, superior laryngeal nerve transection, or epithelium removal did not inhibit citric acid-evoked coughing. These and other data indicate that citric acid-evoked coughing in anesthetized guinea pigs is mediated by direct activation of capsaicin-insensitive vagal afferent nerves, perhaps through sequential activation of acid-sensing ion channels and chloride channels. TRPV1; capsaicin; rapidly adapting receptor doi:10.1152/ajpregu.00862.2005

Using a study on mice, the influence of signaling activity of retinoic acid receptors on initial lung development is examined.

Neonicotinoids are emerging as a major class of insecticides with promising insecticidal activity having a specific affinity towards the nicotinic acetylcholine receptors (nAChR). A quantitative structure-activity relationship (QSAR) study was performed on some azidopyridinyl neonicotinoids for their selective insecticidal activity over mammalian toxicity. The result showed that increased surface area of the molecules may help to increase the binding affinity of the compounds towards the Drosophila receptor and the presence of the azido group on the other hand may be detrimental towards the affinity. Compounds having low polarity, increased probability of nucleophilic attack at the particular position (N-1), and a higher positive charge at the C-12 position can reduce the binding affinity of these compounds towards the mammalian receptor. Key words: QSAR, neonicotinoids, Drosophila nicotinic receptor, mammalian [α.sub.4][β.sub.2] receptor, AM1. Les neonicotinoides emergent comme une classe majeure de composes possedant une activite insecticide interessante et une activite specifique pour les recepteurs de l'acetylcholine nicotinique (<>). Une etude de relation structure-activite quantitative (RSAQ) a ete realisee sur quelques neonicotinoides de l'azidopyridinyle pour evaluer leur activite insecticide selective sur la toxicite mammifere. Le resultat montre que la superficie accrue de la surface des molecules pourrait eventuellement leur permettre d'augmenter les affinites de fixation des composes sur le recepteur Drosophila alors que, par ailleurs, la presence du groupe azido pourrait nuisible a cette affinite. Les composes de faible polarite augmentent la probabilite d'une attaque nucleophile a la position particuliere (N-1) et d'une charge plus positive en position C-12 et peuvent reduire l'affinite de fixation de ces composes vis-a-vis des recepteurs mammiferes. Mots cles : RSTQ, neonicotinoides, recepteur nicotinique Drosophila, recepteur mammifere [α.sub.4][β.sub.2], AM1. [Traduit par la Redaction], Introduction The neonicotinoids (1) are one of the major classes of insecticides, having very promising potency (2). They are nicotinic agonists that interact with nicotinic acetylcholine receptors (nAChR) in a [...]

The natural killer (NK) receptor gene complex (NKC) encodes a large number of C-type lectin-like receptors, which are expressed on NK and other immune-related cells. These receptors play an important role in regulating NK-cell cytolytic activity, protecting cells against virus infection and tumorigenesis. To understand the evolutionary history of the NKC, we characterized the C-type lectin-like NKC genes and their organization from four major orders of placental mammals, primates (human), rodents (mouse and rat), carnivores (dog), and artiodactyls (cattle) and then conducted phylogenetic analysis of these genes. The results indicate that the NKC of placental mammals is highly heterogeneous in terms of the gene content and rates of birth and death of different gene lineages, but the NKC is also remarkably conserved in its gene organization and persistence of orthologous gene lineages. Among the 28 identified NKC gene lineages, 4, KLRA1, KLRB1, CLEC2D, and CLEC4A/B/C, have expanded rapidly in rodents only. The high birth and death rate of these 4 gene families might be due to functional differentiation driven by positive selection. Identification of putative NKC sequences in opossum and chicken genomes implies that the expansion of the NKC gene families might have occurred before the radiation of placental mammals but after the divergence of birds from mammals. contraction-expansion | evolution | genomic organization

The mechanisms of pathogen recognition by the innate immune system are reviewed, focusing on host Pattern-Recogniton Receptors (PRRs) and their signaling pathways. There is considerable expansion in the knowledge of host innate immune responses against pathogen infection and these involve sophisticated mechanisms for detecting various pathogens using limited number of PRRs and induction of adaptive responses.

A study was conducted to determine structural aspects of Melanocortin-3 receptor responsible for ligand binding and receptor signaling. The results provide important information about the molecular determinants of human melanocortin-3 receptor ligand-receptor (hMC3R) responsible for ligand binding and receptor signaling.

Extracellular signals are transmitted to cells through two classes of cell-surface receptors: signaling receptors that directly transduce signals and signaling co-receptors that bind ligand but that, traditionally, have not been thought to signal directly. Signaling co-receptors modulate the ligand binding and signaling of their respective signaling receptors. In recent years, roles for co-receptors have expanded to include essential functions in morphogen gradient formation, localizing signaling, signaling independently, regulating cell adhesion and orchestrating the signaling of several pathways. The importance of signaling co-receptors is demonstrated by their ubiquitous expression, their conservation during evolution, their prominent role in signaling cascades, their indispensable role during development and their frequent mutation or altered expression in human disease.

Vascular smooth muscle cell (VSMC) phenotypic modulation is a key factor in vascular pathology. We have investigated the role of Notch receptor signaling in controlling human vascular smooth muscle cell (hVSMC) differentiation in vitro and established a role for cyclic strain-induced changes in Notch signaling in promoting this phenotypic response. The expression of [actin]-actin, calponin, myosin, and smoothelin was examined by performing immunocytochemistry, Western blot analysis, and quantitative real-time PCR in hVSMCs cultured under static conditions after forced overexpression of constitutively active Notch 1 and 3 receptors, inhibition of endogenous Cp-binding factor 1 (CBF-1)/recombination signal sequence-binding protein-J[kappa] (RBP-J[kappa]) signaling, and exposure to cyclic strain using a Flexercell Tension Plus unit. Overexpression of constitutively active Notch intracellular (IC) receptors (Notch 1 IC and Notch 3 IC) resulted in a significant downregulation of [alpha]-actin, calponin, myosin, and smoothelin expression, an effect that was significantly attenuated after inhibition of Notch-mediated, CBF1/RBP-J[kappa]-dependent signaling by coexpression of RPMS-1 (Epstein-Barr virus-encoded gene product) and selective knockdown of basic helix-loop-helix factors [hairy enhancer of split (HES) gene and Hes-related transcription (Hrt) factors Hrt-1, Hrt-2, and Hrt-3] using targeted small interfering RNA. Cells cultured under conditions of defined equibiaxial cyclic strain (10% strain, 60 cycles/min, 24 h) exhibited a significant reduction in Notch 1 IC and Notch 3 IC expression concomitant with a significant increase in VSMC differentiation marker expression. Moreover, this cyclic strain-induced increase was further enhanced after inhibition of CBF-1/RBP-J[kappa]-dependent signaling with RPMS-1. These findings suggest that Notch promotes changes in hVSMC phenotype via activation of CBF-1/ RBP-J[kappa]-dependent pathways in vitro and contributes to the phenotypic response of VSMCs to cyclic strain-induced changes in VSMC differentiation. basic helix-loop-helix; cyclic strain; myosin; smoothelin

Receptor tyrosine kinases (RTKs) regulate cellular processes ranging from cell growth and proliferation to survival and differentiation. After binding of their cognate ligands, these receptors undergo autophosphorylation on multiple tyrosine [...], Closely related signals often lead to very different cellular outcomes. We found that the differentiation of human mesenchymal stem cells into boneforming cells is stimulated by epidermal growth factor (EGF) but not platelet-derived growth factor (PDGF). We used mass spectrometry-based proteomics to comprehensively compare proteins that were tyrosine phosphorylated in response to EGF and PDGF and their associated partners. More than 90% of these signaling proteins were used by both ligands, whereas the phosphatidylinositol 3-kinase (P13K) pathway was exclusively activated by PDGF, implicating it as a possible control point. Indeed, chemical inhibition of P13K in PDGF-stimulated cells removed the differential effect of the two growth factors, bestowing full differentiation effect onto PDGF. Thus, quantitative proteomics can directly compare entire signaling networks and discover critical differences capable of changing cell fate.

Byline: Lutz Hamann (1), Abuzeid Gomma (2), Nicolas W. J. Schroder (1), Cordula Stamme (3), Christiane Glaeser (4), Susanne Schulz (4), Michael Gross (5), Stefan D. Anker (2,5), Kim Fox (2), Ralf R. Schumann (1) Keywords: Atherosclerosis; Coronary artery disease; Gene polymorphism; Genetics; Innate immunity; Restenosis Abstract: Restenosis is a major problem for patients undergoing percutaneous transluminal coronary angioplasty (PTCA). Inflammatory processes and genetic factors have been suggested to be involved in the pathogenesis of both atherosclerosis and restenosis. The recently discovered family of Toll-like receptors (TLRs) consists of molecules that initiate signaling after host-pathogen interactions. Recently it has been shown that the TLRs are involved in the development and progression of atherosclerosis by interfering with lipid metabolisms and by mediating inflammation. TLR-2 is a key innate immunity receptor for sensing both endogenous inflammatory mediators and ligands of several microbial pathogens postulated to be involved in atherosclerosis. A frequent single nucleotide polymorphism (SNP) for the TLR-2 gene, resulting in a non-functional receptor, has been described. By genotyping two independent groups of patients receiving PTCA, followed by stent implantation in one group, we found a significantly enhanced frequency of the TLR-2 Arg753Gln SNP in patients with restenosis as compared to those without restenosis (PTCA: 7.21 versus 2.45%, P=0.014 PTCA/stent: 6.86 versus 1.53%, P=0.013). In contrast, a common TLR-4 SNP was similarly distributed among the patient groups investigated. We furthermore compared the frequency of both SNPs in the patients with an age-matched group of individuals without atherosclerosis and found a trend towards a lower frequency of the TLR-4 SNP in the atherosclerotic group (PTCA: 5.58 PTCA/stent: 3.85 versus 7.14%). We conclude that in restenosis a functional TLR-2 is protective and potentially involved in a reaction pattern preventing restenosis. Screening for the TLR-2 Arg753Gln SNP may be of importance for stratifying a patient's risk and for preventive and therapeutic measures. Author Affiliation: (1) Institute for Microbiology and Hygiene, Charite University Medical Center, Humboldt University, Dorotheenstrasse 96, 10117, Berlin, Germany (2) Cardiology Department, National Heart and Lung Institute and Royal Brompton Hospital, London, UK (3) Department of Anesthesiology, University of Lubeck and Research Center Borstel, Lubeck, Germany (4) Institute of Human Genetics and Medical Biology, University of Halle, Halle, Germany (5) Department of Cardiology, Charite University Medical Center, Berlin, Germany Article History: Registration Date: 31/01/2005 Received Date: 24/09/2004 Accepted Date: 07/01/2005 Online Date: 04/05/2005 Article note: L. Hamann and A. Gomma contributed equally to this work

The kinsein-3, KIF16B, transports early endosomes to the plus end of microtubules in a process regulated by the small GTPase Rab5 and its effector, the phosphatidylinositol-3-OH kinase hVPS34. The results reveal that KIF16B, by regulating the plus end motility of early endosomes, modulates the intracellular localization of early endosomes and the balance between receptor recycling and degradation.

Ischemic brain damage represents a major source of morbidity and mortality in westernized society and poses a significant financial burden on the health care system. To date, few effective therapies [...]

A series of internal deletion mutants of the vitamin D receptor (VDR) hinge is generated and found that deletion of a few as five amino acids from the C-terminus of the hinge significantly reduces transcriptional activation in vivo. The ability to delete more of the RxR hinge may be related to the additional plasticity required by its role as the common hetereodimer partner for nuclear receptors on differing DNA elements.

A N,N-(dimethylamino)pyridine monomer is incorporated into the backbone of a m-phenyleneethynyleen oligomer such that the pyridine nitrogen is located on the interior surface of the binding cavity in the folded structure of the oligomer. By comparison of k(sub u) for the 13-mer with the second-order rate constant for a 3-mer that is too short to fold and thus unable to bind methyl iodide the effective morality is calculated to be 230 M.

The underlying intermolecular interactions of the receptors anion complexes along with the insight into the structures, intrinsic binding affinities that supports the experimental characterization via computations of NMR and UV-visible spectra is studied. DFT calculations lend further support affinity and high selectivity of the fluoride ion for receptors.

The way in which the perception of G protein-coupled receptor (GPCR) oligomerization has progressed and changed over the years, and the potential significance of Oligomerization to the mechanism of G protein-mediated signaling is presented. It is concluded that the organization of GPCR's into complex containing multiple equivalents of both receptor and G protein provides a platform for various cooperative effects and may allow for a form of fine control in GPCR-mediated signaling.

Liver X receptors (LXRs) are nuclear receptors. They not only regulate macrophage cholesterol metabolism, but also impact antimicrobial responses.

Liver X receptors (LXRs) belong to the nuclear receptor superfamily. They function as master regulators of cholesterol metabolism.

A specific agonist of the endothelin-B receptor subtype (ET(sub B)), a few photosensitive analogues is developed to investigate the binding domain of the receptor. Using the photoaffinity-labeling technique, a key segment of the ET(sub B) receptor participating in the interaction with the ET-1 of IRL-1620 ligands is identified.

The use of cyclic peptides in the selection of single-chain (ScFv) antibodies specific for the HIV-1 coreceptor CCR5, a representative G-protein-coupled receptor (GPCR) is described. Results illustrate that surface-antigen mimetics of a GPCR are effective tools for selecting active, site-specific ScFv antibodies that hold promise as immunological reagents and therapeutics.