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At least 19 recordsLinked to original sources
PubMed2002

Bacterial lipopolysaccharide selectively up-regulates the function of the chemotactic peptide receptor formyl peptide receptor 2 in murine microglial cells.

Receptors for the bacterial chemotactic peptide fMLP are implicated in inflammation and host defense against microbial infection. We investigated the expression and function of fMLPR in microglial cells, which share characteristics of mononuclear phagocytes and play an important role in proinflammatory responses in the CNS. The expression of the genes encoding formyl peptide receptor (FPR)1 and FPR2, the high- and low-affinity fMLPR, was detected in a murine microglial cell line N9, but these cells did not respond to chemotactic agonists known for these receptors. N9 cells incubated with bacterial LPS increased the expression of fMLPR genes and developed a species of specific, but low-affinity, binding sites for fMLP, in association with marked calcium mobilization and chemotaxis responses to fMLP in a concentration range that typically activated the low-affinity receptor FPR2. In addition, LPS-treated N9 cells were chemoattracted by two FPR2-specific agonists, the HIV-1 envelope-derived V3 peptide, and the 42 aa form of the amyloid beta peptide which is a pathogenic agent in Alzheimer's disease. Primary murine microglial cells also expressed FPR1 and FPR2 genes, but similar to N9 cells, exhibited FPR2-mediated activation only after LPS treatment. In contrast to its effect on the function of FPR2, LPS reduced N9 cell binding and biological responses to the chemokine stromal cell-derived factor-1alpha. Thus, LPS selectively modulates the function of chemoattractant receptors in microglia and may promote host response in inflammatory diseases in the CNS.

Animals↗
PubMed2006

Peptides derived from HIV-1, HIV-2, Ebola virus, SARS coronavirus and coronavirus 229E exhibit high affinity binding to the formyl peptide receptor.

Peptides derived from the membrane proximal region of fusion proteins of human immunodeficiency viruses 1 and 2, Coronavirus 229 E, severe acute respiratory syndrome coronavirus and Ebola virus were all potent antagonists of the formyl peptide receptor expressed in Chinese hamster ovary cells. Binding of viral peptides was affected by the naturally occurring polymorphisms at residues 190 and 192, which are located at second extracellular loop-transmembrane helix 5 interface. Substitution of R190 with W190 enhanced the affinity for a severe acute respiratory syndrome coronavirus peptide 6 fold but reduced the affinity for N-formyl-Nle-Leu-Phe by 2.5 fold. A 12 mer peptide derived from coronavirus 229E (ETYIKPWWVWL) was the most potent antagonist of the formyl peptide receptor W190 with a K(i) of 230 nM. Fluorescently labeled ETYIKPWWVWL was effectively internalized by all three variants with EC(50) of approximately 25 nM. An HKU-1 coronavirus peptide, MYVKWPWYVWL, was a potent antagonist but N-formyl-MYVKWPWYVWL was a potent agonist. ETYIKPWWVWL did not stimulate GTPgammaS binding but inhibited the stimulation by formyl-NleLeuPhe. It also blocked beta arrestin translocation and receptor downregulation induced by formyl-Nle-Leu-Phe. This indicates that formyl peptide receptor may be important in viral infections and that variations in its sequence among individuals may affect their likelihood of viral and bacterial infections.

Amino Acid Sequence↗
PubMed1995

Extensive contact between Gi2 and N-formyl peptide receptor of human neutrophils: mapping of binding sites using receptor-mimetic peptides.

The N-formyl peptide receptor (FPR) of human neutrophils is a member of the G protein-coupled receptor (GPCR) superfamily. Sites on agonist-occupied FPR involved in binding the Gi2 protein were investigated by competition with synthetic receptor-mimetic peptides. Twenty-three synthetic FPR-mimetic and control peptides were tested for their ability to disrupt functionally active complexes of FPR and Gi2 in octyl glucoside, assayed by changes in sedimentation rates of FPR in detergent-containing sucrose gradients. GPCRs are thought to contain seven transmembrane segments with three cytoplasmic connecting loops and a cytoplasmic tail. Only certain peptides from regions in or adjoining each of the four predicted cytoplasmic domains of the 350 amino acid FPR, including the first cytoplasmic loop, were able to disrupt the reconstituted FPR-Gi2 complex. The IC50s of the peptides that were able to fully disrupt the FPR-Gi2 complex ranged from 20 microM (C2W 122-134) to 1.4 mM (C3A 230-246), a range similar to peptide inhibition of other G protein-coupled receptor-G protein interactions. Detergent concentrations above and below the critical micelle concentration had no effect on the activity of even the most hydrophobic peptide, C3B, and there was no apparent correlation of activity with hydrophobic moment, hydrophilic index, or net charge of the peptides. Control peptides from irrelevant proteins with similar physical properties and FPR extracellular domains did not dissociate the reconstituted FPR-Gi2 complex up to 5 mM, the highest concentration tested.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1994

Domains of the human neutrophil N-formyl peptide receptor involved in G protein coupling. Mapping with receptor-derived peptides.

Chemotactic signaling by the human neutrophil N-formyl peptide receptor requires its association with heterotrimeric G protein. Synthetic peptides and a fusion protein derived from the intracellular regions of the receptor were used to identify sites which interact with G protein. A peptide derived from the second intracellular loop (C12R), and peptides (F15R and S22L) and a fusion protein derived from the receptor's carboxyl terminus inhibited binding of anti-Gi alpha antibody (R16,17) to Gi alpha in a competitive enzyme-linked immunoassay, and antagonized pertussis-toxin catalyzed ADP-ribosylation of Gi alpha. C12R also inhibited G protein-dependent, high affinity ligand binding to the receptor and physical coupling of receptor to G protein. In contrast, a peptide consisting of the entire third loop of the N-formyl peptide receptor was totally inactive in these assays. Collectively, these data suggest that the second intracellular loop and the carboxyl-terminal tail are important for effective N-formyl peptide receptor/G protein coupling, but that the third intracellular loop is less important in coupling, unlike previous findings with other G protein-coupled receptor systems. The chemoattractant receptor family may rely on different structural determinants to interact with GTP-binding proteins.

Amino Acid Sequence↗
PubMed2006

Pharmacological characterization of novel alpha-Calcitonin Gene-Related Peptide (CGRP) receptor peptide antagonists that are selective for human CGRP receptors.

Human alpha-calcitonin gene-related peptide (CGRP) is a 37-residue neuropeptide that produces a variety of cardiovascular and other effects via activation of specific CGRP receptors that produce cAMP. Functional CGRP receptors are a heterodimeric complex composed of the heptahelical calcitonin receptor-like receptor and the single transmembrane receptor activity-modifying protein 1. Based on the known structures of the antagonist CGRP((8-37)) and the human CGRP receptor, we designed novel CGRP receptor peptide antagonists with modifications to promote high affinity and selectivity for human CGRP receptors. Antagonist affinity (K(B)) at CGRP receptors was determined using the mouse thoracic aorta and human SK-N-MC cells. In aorta, CGRP((8-37)), [N-alpha-benzoyl]human alpha-CGRP((8-37)) [bzl-CGRP((8-37))], and [N-alpha-benzoyl-His(10)-benzyl]human alpha-CGRP((8-37)) [bzl-bn-CGRP((8-37))] caused rightward shifts in the concentration-response relaxation curve for CGRP with K(B) values of 1000, 88, and 50 nM, respectively. In human SK-N-MC cells, CGRP((8-37)), bzl-CGRP((8-37)), and bzl-bn-CGRP((8-37)) caused rightward shifts in the concentration-response curve for CGRP-stimulated cAMP production with K(B) values of 797, 15, and 0.63 nM, respectively. Thus, CGRP((8-37)) had the same affinity for human and mouse CGRP receptors, whereas bzl-CGRP((8-37)) and bzl-bn-CGRP((8-37)) displayed 6- and 80-fold higher affinities, respectively, for human CGRP receptors. In addition, the selectivity of the antagonists for human CGRP receptors was highly correlated with the antagonist hydrophobicity index. These relatively high-affinity, species-selective peptide antagonists provide novel tools to differentiate structural and functional features that are unique to the human CGRP receptor. Thus, these analogs may be useful compounds for development of drugs to treat migraine headache and other cardiovascular diseases.

Animals↗
PubMed2005

The synthetic peptide Trp-Lys-Tyr-Met-Val-D-Met inhibits human monocyte-derived dendritic cell maturation via formyl peptide receptor and formyl peptide receptor-like 2.

Trp-Lys-Tyr-Met-Val-D-Met (WKYMVm) has been reported to stimulate monocytes, neutrophils, and dendritic cells (DCs). However, although WKYMVm has been reported to function as a DC chemoattractant, its role on DC maturation has not been examined. In this study, we investigated the effects of WKYMVm on human DC maturation. The costimulation of DCs with WKYMVm and LPS dramatically inhibited LPS-induced IL-12 production, CD86 and HLA-DR surface expression, and DC-mediated T cell proliferation. However, DC phagocytic activity was increased by WKYMVm stimulation. These findings demonstrate that WKYMVm inhibits DC maturation by LPS. In terms of the mechanism underlying DC maturation inhibition by WKYMVm, we found that LPS-induced DC maturation was negatively regulated by WKYMVm-stimulated ERK activity. Moreover, the costimulation of DCs with WKYMVm and LPS dramatically inhibited the LPS-induced accumulations of IL-12 mRNA, thus suggesting that WKYMVm inhibits LPS-induced IL-12 production at the transcriptional level. We also found that DCs express two WKYMVm receptors, formyl peptide receptor (FPR) and FPR-like 2 (FPRL2). In addition, formyl-Met-Leu-Phe (a FPR ligand), Trp-Lys-Tyr-Met-Val-Met, Hp(2-20) peptide, and F2L (three FPRL2 ligands) inhibited LPS-induced IL-12 production in DCs. Taken together, our findings indicate that the activations of FPR and FPRL2 inhibit LPS-induced DC maturation, and suggest that these two receptors should be regarded as important potential therapeutic targets for the modulation of DC maturation.

Amino Acid Sequence↗
PubMed1995

The C-type natriuretic peptide receptor is the predominant natriuretic peptide receptor mRNA expressed in rat hypothalamus.

The natriuretic peptide receptors (NPR) are membrane-bound guanylate cyclases with extracellular binding domains specific for particular members of the natriuretic peptide family. NPR-A binds atrial natriuretic peptide (ANP) with high affinity, whereas the NPR-B appears to be specific for C-type natriuretic peptide (CNP). Previous data indicating extensive overlap between localization of ANP and CNP in hypothalamic neuroendocrine circuits suggest the importance of determining whether specificity of natriuretic peptide action may be conferred via receptor type present on target cells. To address this issue, we used in situ hybridization histochemistry to localize NPR-A and NPR-B mRNA in the hypothalamus. NPR-A mRNA was not found in substantial abundance in any hypothalamic nucleus; however, detectable NPR-A signal was observed in other brain regions, including the subfornical organ and medial habenula. In contrast, NPR-B mRNA was expressed throughout the hypothalamus, including neurons of the magnocellular and parvocellular paraventricular, the arcuate, and the supraoptic nuclei. Expression was also seen in other nuclei essential to neuroendocrine control, including the median preoptic, anteroventral periventricular, tuberomammilary, ventromedial and suprachiasmatic nuclei. NPR-B mRNA was also observed in the neural lobe of the pituitary gland, suggesting expression by pituicytes. The results suggest that NPR-B is the primary natriuretic peptide receptor in hypothalamus, and by inference indicate that CNP is the primary active natriuretic peptide in neuroendocrine regulation.

Animals↗
PubMed2003

Differential activation of formyl peptide receptor signaling by peptide ligands.

Formyl peptide receptor (FPR) and formyl peptide receptor like 1 (FPRL1) play important roles in inflammation and immunity. Stimulation of FPR and FPRL1 initiates a cascade of signaling events, leading to activation of various phagocyte responses, including chemotaxis, superoxide generation, and exocytosis. Trp-Lys-Tyr-Met-Val-d-Met-NH2 (WKYMVm) is a synthetic peptide that binds to and activates FPR and FPRL1. To develop agonists that selectively activate phagocyte functions and therefore protect host from unwanted tissue damage, we generated various WKYMVm analogs and examined their effects on cellular responses in FPR- or FPRL1-expressing RBL-2H3 cells. Analogs with substitution at the third position such as WKGMVm, WKRMVm, as well as analogs with substitution at the sixth d-Met, selectively altered calcium mobilization in cells expressing FPRL1 but not in cells expressing FPR. Whereas binding of WKYMVm to FPR activates a broad spectrum of cellular signaling events, including phospholipase C-mediated intracellular calcium concentration ([Ca2+]i) mobilization and activation of extracellular signal-regulated kinase (ERK) and Akt, WKGMVm and WKRMVm could only activate ERK and Akt but did not induce [Ca2+]i mobilization. With respect to phagocyte functions, WKYMVm could induce both chemotaxis and exocytosis, but the two analogs WKGMVm and WKRMVm could only induce chemotaxis but not exocytosis. This study demonstrates that a major phagocyte chemoattractant receptor FPR may be activated differentially by distinct peptide ligands. Our results suggest that WKGMVm and WKRMVm may be useful model for further development of pharmacological agents that selectively activate FPR-mediated functions.

Cell Line↗
PubMed2005

Peptide receptor radionuclide therapy for non-radioiodine-avid differentiated thyroid carcinoma.

UNLABELLED: In patients with progressive metastatic (or recurrent) differentiated thyroid carcinoma (DTC) who do not respond to radioiodine therapy or do not show uptake on radioiodine scintigraphy, treatment options are few. Because these tumors may express somatostatin receptors, peptide receptor radionuclide therapy might be effective. We evaluated the therapeutic efficacy of the radiolabeled somatostatin analog (177)Lu-1,4,7,10-tetraazacyclododecane-N,N',N'',N'''-tetraacetic acid(0) (DOTA), Tyr(3)-octreotate ((177)Lu-DOTATATE) in patients with DTC. The uptake of radioactivity in tumors was also studied in relation to treatment outcome. METHODS: Five patients with DTC (3 with Hurthle cell thyroid carcinoma [HCTC], 1 with papillary thyroid carcinoma [PTC], and 1 with follicular thyroid carcinoma [FTC]) were treated with 22.4-30.1 GBq of (177)Lu-DOTATATE. Response to therapy was evaluated with CT. Uptake on (177)Lu-DOTATATE scintigraphy (24 h after treatment), expressed as percentage of injected dose, was compared with uptake on pretherapy (111)In-octreotide scintigraphy (24 h after injection). RESULTS: After the last treatment with (177)Lu-DOTATATE, 1 patient with HCTC had stable disease as a maximum response, 1 patient with HCTC had minor remission (tumor shrinkage between 25% and 50%), and 1 patient with HCTC had partial remission (shrinkage > or =50%). The responses in PTC and FTC were stable disease and progressive disease, respectively. A decrease in serum thyroglobulin level was found in patients with HCTC. Patients with minor and partial remissions had the highest (177)Lu-DOTATATE-to-(111)In-diethylenetriamine pentaacetic acid(0)-octreotide ((111)In-octreotide) uptake ratios (3.2 and 2.4, respectively) whereas the other patients had uptake ratios smaller than 1.5. CONCLUSION: (177)Lu-DOTATATE therapy can be effective in patients with progressive DTC who have no therapeutic options and sufficient uptake of (111)In-octreotide in tumor lesions as shown on (111)In-octreotide scintigraphy. This finding is especially important in patients with HCTC, because they cannot benefit from radioiodine therapy because of non-iodine-avid lesions at diagnosis.

Aged↗
PubMed1998

Peptide receptors on astrocytes.

In recent years, it has become apparent that astrocytes (at least in vitro) harbor functional receptors to almost all possible neurotransmitters (with the potential noticeable exception of acetylcholine nicotinic receptors). Peptides are no exception, since receptors to all neuropeptides known to be produced in the CNS have been found on cultured astrocytes, and the presence of many of these has been confirmed on astrocytes in vivo. A variety of methodologies have been used to detect peptide receptors on astrocytes, as summarized in the current review. Special emphasis is also put on the possible roles that peptides may play in the regulation of astrocyte functions. These include proliferation, morphology, release of eicosanoids and arachidonic acid, induction of calcium transients and calcium waves, and control of internal pH, glucose uptake, glycogen metabolism, and gap junctional conductance. Recent data concerning the effects of natriuretic peptides on astrocytes are reviewed, and why these peptides may constitute priviledged tools to test the effects of peptides on astrocyte-neuron interactions is also discussed.

Animals↗
PubMed2004

Down-regulation of C-type natriuretic peptide receptor by vasonatrin peptide in cardiac myocytes and fibroblasts.

AIM: To investigate the regulatory effects of vasonatrin peptide (VNP) on the expression of C-type natriuretic peptide receptor (NPR-C) in cultured neonatal rat cardiac myocytes and fibroblasts. METHODS: Quantitative RT-PCR was undertaken to evaluate the levels of NPR-C mRNA and radioimmunoassay was used to determine the formation of intracellular cGMP. RESULTS: Twenty-four hours hypoxic exposure increased the level of NPR-C mRNA in cardiomyocytes, while did not alter the expression of NPR-C in cardiac fibroblasts. VNP (10(-8)-10(-6) mol/L) reduced the levels of NPR-C mRNA in cardiac myocytes induced by hypoxia in a concentration-dependent manner, and with high concentration (10(-6) mol/L) also decreased the expression of NPR-C in cardiac fibroblasts and air-control cardiac myocytes. The inhibitory effects of VNP on the expression of NPR-C was mimicked by 8-bromo-cGMP 10(-6) mol/L (a membrane permeable analog of cGMP). VNP (10(-8)-10(-6) mol/L) increased the formation of intracellular guanosine-3',5'-cyclic monophosphate (cGMP) in both cardiac myocytes and fibroblasts. HS-142-1, the particulate guanylyl cyclase-coupled receptor antagonist, partially abrogated the above effects of VNP. CONCLUSION: Hypoxic exposure for 24 h up-regulated the expression of NPR-C in cultured neonatal rat cardiac myocytes. VNP decreased the expression of NPR-C in cardiac myocytes and fibroblasts under both air-control and hypoxic condition, which was at least partially mediated by guanylate cyclase linked natriuretic peptide receptors through increasing the intracellular cGMP.

Animals↗
PubMed2005

ATP-independent activation of natriuretic peptide receptors.

Natriuretic peptide receptor A (NPR-A) is an essential cardiovascular regulator that is stimulated by atrial natriuretic peptide and B-type natriuretic peptide, whereas natriuretic peptide receptor B (NPR-B) stimulates long bone growth in a C-type natriuretic peptide-dependent manner. Many reports indicate that ATP is essential for NPR-A and NPR-B activation. Current models suggest that natriuretic peptide binding to receptor extracellular domains causes ATP binding to intracellular kinase homology domains, which derepresses adjacent catalytic domains. Here, we report 100-fold activations of natriuretic peptide receptors in the absence of ATP. The addition of a nonhydrolyzable ATP analog had no effect at early time periods (measured in seconds) but increased cGMP production about 2-fold after longer incubations (measured in minutes), consistent with a stabilization, not activation, mechanism. These data indicate that ATP does not activate natriuretic peptide receptors as has been repeatedly reported. Instead, ATP increases activity primarily by maintaining proper receptor phosphorylation status but also serves a previously unappreciated enzyme stabilizing function.

Adenosine Triphosphate↗
PubMed2000

The synthetic peptide Trp-Lys-Tyr-Met-Val-D-Met is a potent chemotactic agonist for mouse formyl peptide receptor.

Formyl peptides are potent neutrophil chemoattractants. In humans and rabbits, the formyl peptide receptor (FPR) binds N-formyl-Met-Leu-Phe (fMLF) with high affinity (K(d) approximately 1 nM). The mouse FPR (mFPR) is a low-affinity receptor for fMLF (K(d) approximately 100 nM); therefore, other agonists for this receptor may exist. Using mFPR-transfected rat basophilic leukemia cells, we found that a recently identified synthetic peptide Trp-Lys-Tyr-Met-Val-D-Met (WKYMVm) is a potent agonist for mFPR. WKYMVm induced calcium mobilization with an EC(50) of 1.2-1.5 nM. Optimal chemotaxis was achieved with 1 nM of WKYMVm, but it required 100 nM of fMLF. WKYMVm stimulated rapid and potent phosphorylation of the mitogen-activated protein kinases extracellular signal-related kinases 1 and 2 when used at 50 nM. Pertussis toxin only partially blocked calcium mobilization and production of inositol 1,4,5-trisphosphate in the stimulated mFPR cells, suggesting the possibility that this receptor couples to Galpha proteins other than Gi and Go. Competitive binding and desensitization data suggest that both peptides interact with the same receptor but may use nonoverlapping binding sites because WKYMVm was unable to effectively displace [(3)H]fMLF bound to mFPR. These results provide evidence for the presence of an alternative potent agonist for mFPR, and suggest a potential usage of WKYMVm for probing the ligand-receptor interactions with the murine formyl peptide receptor homologs.

Animals↗
PubMed1995

Fibronectin peptide DRVPHSRNSIT and fibronectin receptor peptide DLYYLMDL arrest gastrulation of Rana pipiens.

Gastrulation is characterized by dramatic cell migration which is thought to require the interaction of cell adhesion molecules with extracellular molecules. We have tested two novel peptides, a fibronectin peptide and a fibronectin receptor peptide, for their effects on gastrulation of the leopard frog Rana pipiens. The fibronectin peptide DRVPHSRNSIT corresponds to residues 1373-1383 of the cell-binding domain of fibronectin; the receptor peptide DLYYLMDL corresponds to residues 124-131 of beta 1 subunit of a variety of integrins including alpha 5 beta 1. Either of these peptides significantly inhibited gastrulation after being microinjected into mid-blastulae. These results indicate that these sequences may correspond to the ligand/receptor interaction sites of fibronectin and its receptor(s).

Amino Acid Sequence↗
PubMed2006

Superoxide production in human neutrophils is enhanced by treatment with transmembrane peptides derived from human formyl peptide receptor.

Formyl peptide receptor (FPR) mediates a number of important host defense functions. Although studies have been performed on the ligand binding site of FPR, FPR dynamic behavior such as receptor dimerization on the cell surface remains unknown. Recently, peptides derived from the transmembrane (TM) domains of GPCRs were shown to disrupt dimer formation by receptors and to result in specific regulation of receptor function. To reveal the function of FPR TM domains, hFPRTM peptides derived from FPR were synthesized, and their biological activities were evaluated with human neutrophils. Synthetic peptides did not exhibit agonistic or antagonistic activity toward superoxide anion production. However, Neutrophils treated with hFPRTM4 produced 4-fold superoxide anion compared with untreated cells when stimulated with FPR agonist fMLP. Short peptide fragments derived from the fourth TM region of FPR did not enhance superoxide anion production, which suggests that hFPRTM4 did not behave as a ligand. CD and fluorescence spectra suggested that hFPRTM peptides were inserted into the membrane. The addition of hFPRTM4 increased the intracellular calcium concentration, which meant the peptide activated some membrane protein on the cell surface. The present study suggests that the fourth TM domain of FPR has a function related to a priming effect.

Amino Acid Sequence↗
PubMed1998

Phosphorylation of the kinase homology domain is essential for activation of the A-type natriuretic peptide receptor.

Natriuretic peptide receptor A (NPR-A) is the biological receptor for atrial natriuretic peptide (ANP). Activation of the NPR-A guanylyl cyclase requires ANP binding to the extracellular domain and ATP binding to a putative site within its cytoplasmic region. The allosteric interaction of ATP with the intracellular kinase homology domain (KHD) is hypothesized to derepress the carboxyl-terminal guanylyl cyclase catalytic domain, resulting in the synthesis of the second messenger, cyclic GMP. Here, we show that phosphorylation of the KHD is essential for receptor activation. Using a combination of phosphopeptide mapping techniques, we have identified six residues within the ATP-binding domain (S497, T500, S502, S506, S510, and T513) which are phosphorylated when NPR-A is expressed in HEK 293 cells. Mutation of any one of these Ser or Thr residues to Ala caused reductions in the receptor phosphorylation state, the number and pattern of phosphopeptides observed in tryptic maps, and ANP-dependent guanylyl cyclase activity. The reductions were not explained by decreases in NPR-A protein levels, as indicated by immunoblot analysis and determinations of cyclase activity in the presence of detergent. Conversion of Ser-497 to Ala resulted in the most dramatic decrease in cyclase activity (approximately 20% of wild-type activity), but conversion to an acidic residue (Glu), which mimics the charge of the phosphoserine moiety, had no effect. Simultaneous mutation of five of the phosphorylation sites to Ala resulted in a dephosphorylated receptor which was unresponsive to hormone and had potent dominant negative inhibitory activity. We conclude that phosphorylation of the KHD is absolutely required for hormone-dependent activation of NPR-A.

Adenosine Triphosphate↗
PubMed2004

Down-regulation does not mediate natriuretic peptide-dependent desensitization of natriuretic peptide receptor (NPR)-A or NPR-B: guanylyl cyclase-linked natriuretic peptide receptors do not internalize.

Natriuretic peptide receptor A (NPR-A/GC-A) and B (NPR-B/GC-B) are members of the transmembrane guanylyl cyclase family that mediate the effects of natriuretic peptides via the second messenger, cGMP. Despite numerous reports of these receptors being down-regulated in response to various pathological conditions, no studies have actually measured desensitization and receptor internalization in the same cell line. Furthermore, the ligand-dependent trafficking properties of NPR-A remain controversial, whereas nothing is known about the trafficking of NPR-B. In this report, we tested whether down-regulation explains the ligand-dependent desensitization of NPR-A and NPR-B and characterized their trafficking properties using a combination of hormone-binding and antibody-based assays. Quantitative partition analysis indicated that (125)I-atrial natriuretic peptide (ANP) was rapidly released into the medium after 293T cells stably expressing NPR-A were warmed from 4 degrees to 37 degrees C. High-performance liquid chromatography fractionation of medium supplemented with the protease inhibitor phosphoramidon indicated that the (125)I-ANP was mostly intact. In contrast, (125)I-ANP purified from medium bathing cells expressing NPR-C, a receptor known to internalize natriuretic peptides, was degraded. Cleavable biotinylation and noncleavable biotinylation assays indicated that neither NPR-A nor NPR-B was internalized or degraded in response to natriuretic peptide binding. In contrast, agonist-dependent internalization of a G protein-coupled receptor was clearly apparent in the same cell line. Finally, we show that NPR-A and NPR-B are desensitized in cells in which they are not internalized. We suggest that mechanisms other than receptor down-regulation account for the desensitization of NPR-A and NPR-B that occurs in response to various physiological and pathological stimuli.

Atrial Natriuretic Factor↗
PubMed1997

Cloning of a novel member of the G protein-coupled receptor family related to peptide receptors.

We have used PCR with degenerate oligonucleotide primers to clone novel members of the G protein-coupled receptor (GPCR) superfamily. We report here a novel gene, CEPR, which encodes a candidate receptor that is most similar to the peptide receptor family. The coding region of the human CEPR gene predicts a seven transmembrane domain (TM) receptor of 375 amino acids. CEPR has 28-30 percent amino acid identity to angiotensin II and interleukin 8 receptors, and slightly lower percent identity to many other GPCRs. Northern blot analysis reveals a 3.3 kb CEPR transcript in different regions of human brain and in various peripheral tissues. The ubiquitous tissue distribution of CEPR, its expression in early development, and its conservation in evolution indicate a potentially important biological function for this receptor and its putative peptide ligand.

Amino Acid Sequence↗