Molecular cloning, characterization, and localization of the human homolog to the reported bovine NPY Y3 receptor: lack of NPY binding and activation

Crystal structures of human neuropeptide Y (NPY) and peptide YY (PYY)

Neuropeptide Y (NPY), peptide YY (PYY) and pancreatic polypeptide (PP) form the evolutionarily conserved pancreatic polypeptide family. While the fold is widely utilized in nature, crystal structures remain elusive, particularly for the human forms, with only the structure of a distant avian form of PP reported. Here we utilize a crystallization chaperone (antibody Fab fragment), specifically recognizing the amidated peptide termini, to solve the structures of human NPY and human PYY. Intriguingly, and despite limited sequence identity (~50%), the structure of human PYY closely resembles that of avian PP, highlighting the broad structural conservation of the fold throughout evolution. Specifically, the PYY structure is characterized by a C-terminal amidated α-helix, preceded by a backfolded poly-proline N-terminus, with the termini in close proximity to each other. In contrast, in the structure of human NPY the N-terminal component is disordered, while the helical component of the peptide is observed in a four-helix bundle type arrangement, consistent with a propensity for multimerization suggested by NMR studies.

Correlation between single nucleotide polymorphisms in CXCR4 microRNA binding site and the susceptibility to knee osteoarthritis in Han Chinese population

Background

This study aimed to investigate the relationship between single nucleotide polymorphisms (SNPs) at the microRNA target sequence in CXCR4 and the susceptibility to knee osteoarthritis (KOA).

Methods

A total of 305 patients with KOA and 305 healthy controls were recruited into this study. The genotypes of CXCR4 rs1804029 and rs17848060 loci were analyzed.

Results

The susceptibility to KOA of CXCR4 rs1804029 G allele carriers was 1.33 times (95% CI: 1.09‐1.54, P = .006) that of T allele carriers. The KOA susceptibility in individuals carrying T allele at CXCR4 rs17848060 locus was 1.38 times that of individuals carrying A allele (95% CI: 1.17‐1.57, P < .001). The G allele at CXCR4 rs1804029 locus was the target of hsa‐miR‐146a‐3p, while the A allele at CXCR4 rs17848060 locus could be targeted by hsa‐miR‐20a‐3p. The plasma level of hsa‐miR‐146a‐3p was lower in rs1804029 G allele carriers than T allele carriers (P < .001), whereas plasma level of hsa‐miR‐20a‐3p was higher in rs17848060 T allele carriers than A allele carriers (P < .001).

Conclusion

The SNPs at rs1804029 and rs17848060 loci in CXCR4 were significantly associated with the susceptibility to KOA in Han Chinese population.

Neurological Regulation of the Bone Marrow Niche

The bone marrow (BM) hematopoietic niche is the microenvironment where in the adult hematopoietic stem and progenitor cells (HSPCs) are maintained and regulated. This regulation is tightly controlled through direct cell-cell interactions with mesenchymal stromal stem (MSCs) and reticular cells, adipocytes, osteoblasts and endothelial cells, through binding to extracellular matrix molecules and through signaling by cytokines and hematopoietic growth factors. These interactions provide a healthy environment and secure the maintenance of the HSPC pool, their proliferation, differentiation and migration. Recent studies have shown that innervation of the BM and interactions with the peripheral sympathetic neural system are important for maintenance of the hematopoietic niche, through direct interactions with HSCPs or via interactions with other cells of the HSPC microenvironment. Signaling through adrenergic receptors (ARs), opioid receptors (ORs), endocannabinoid receptors (CRs) on HSPCs and MSCs has been shown to play an important role in HSPC homeostasis and mobilization. In addition, a wide range of neuropeptides and neurotransmitters, such as Neuropeptide Y (NPY), Substance P (SP) and Tachykinins, as well as neurotrophins and neuropoietic growth factors have been shown to be involved in regulation of the hematopoietic niche. Here, a comprehensive overview is given of their role and interactions with important cells in the hematopoietic niche, including HSPCs and MSCs, and their effect on HSPC maintenance, regulation and mobilization.

WHIM Syndrome: from Pathogenesis Towards Personalized Medicine and Cure

WHIM syndrome is a rare combined primary immunodeficiency disease named by acronym for the diagnostic tetrad of warts, hypogammaglobulinemia, infections, and myelokathexis. Myelokathexis is a unique form of non-cyclic severe congenital neutropenia caused by accumulation of mature and degenerating neutrophils in the bone marrow; monocytopenia and lymphopenia, especially B lymphopenia, also commonly occur. WHIM syndrome is usually caused by autosomal dominant mutations in the G protein-coupled chemokine receptor CXCR4 that impair desensitization, resulting in enhanced and prolonged G protein- and β-arrestin-dependent responses. Accordingly, CXCR4 antagonists have shown promise as mechanism-based treatments in phase 1 clinical trials. This review is based on analysis of all 105 published cases of WHIM syndrome and covers current concepts, recent advances, unresolved enigmas and controversies, and promising future research directions.

A Short-Length Peptide YY Analogue with Anorectic Effect in Mice

Peripheral administration of PYY_3-36, a fragment of peptide YY (PYY), has been reported to reduce food intake by activating the neuropeptide Y2 receptor (Y2R). An N-terminally truncated PYY analogue, benzoyl-[Ala²⁶,Ile^28,31]PYY(25-36) (1), showed a relatively potent agonist activity for Y2R but a weak anorectic activity by intraperitoneal administration (2000 nmol/kg) in lean mice because of its markedly poor biological stability in the mouse serum. Notably, two cyclohexylalanine (Cha) substitutions for Tyr residues at positions 27 and 36 (4) improved the stability in the mouse serum concomitant with enhanced anorectic activity. Further optimization at positions 27, 28, 30, and 31 revealed that 21, containing Cha²⁸ and Aib³¹ residues, showed a more potent anorectic activity than PYY_3-36 at a low dose of 300 nmol/kg. The minimum effective dose by intraperitoneal administration of 21 was 30 nmol/kg (ca. 52 μg/kg) in mice, suggesting the biologic potential of short-length PYY_3-36 analogues with a potent anorectic effect.

Inhibition of signaling between human CXCR4 and zebrafish ligands by the small molecule IT1t impairs the formation of triple-negative breast cancer early metastases in a zebrafish xenograft model

Triple-negative breast cancer (TNBC) is a highly aggressive and recurrent type of breast carcinoma that is associated with poor patient prognosis. Because of the limited efficacy of current treatments, new therapeutic strategies need to be developed. The CXCR4-CXCL12 chemokine signaling axis guides cell migration in physiological and pathological processes, including breast cancer metastasis. Although targeted therapies to inhibit the CXCR4-CXCL12 axis are under clinical experimentation, still no effective therapeutic approaches have been established to block CXCR4 in TNBC. To unravel the role of the CXCR4-CXCL12 axis in the formation of TNBC early metastases, we used the zebrafish xenograft model. Importantly, we demonstrate that cross-communication between the zebrafish and human ligands and receptors takes place and human tumor cells expressing CXCR4 initiate early metastatic events by sensing zebrafish cognate ligands at the metastatic site. Taking advantage of the conserved intercommunication between human tumor cells and the zebrafish host, we blocked TNBC early metastatic events by chemical and genetic inhibition of CXCR4 signaling. We used IT1t, a potent CXCR4 antagonist, and show for the first time its promising anti-tumor effects. In conclusion, we confirm the validity of the zebrafish as a xenotransplantation model and propose a pharmacological approach to target CXCR4 in TNBC.

Summary: CXCR4-expressing human tumor cells respond to zebrafish cognate ligands and initiate metastatic events in a zebrafish xenograft model. The CXCR4 antagonist IT1t has promising tumor inhibitory effects.

Ancient Grandeur of the Vertebrate Neuropeptide Y System Shown by the Coelacanth Latimeria chalumnae

The neuropeptide Y (NPY) family receptors and peptides have previously been characterized in several tetrapods, teleost fishes, and in a holocephalan cartilaginous fish. This has shown that the ancestral NPY system in the jawed vertebrates consisted of the peptides NPY and peptide YY (PYY) and seven G-protein-coupled receptors named Y1–Y8 (Y3 does not exist). The different vertebrate lineages have subsequently lost or gained a few receptor genes. For instance, the human genome has lost three of the seven receptors while the zebrafish has lost two and gained two receptor genes. Here we describe the NPY system of a representative of an early diverging lineage among the sarcopterygians, the West Indian Ocean coelacanth Latimeria chalumnae. The coelacanth was found to have retained all seven receptors from the ancestral jawed vertebrate. The receptors display the typical characteristics found in other vertebrates. Interestingly, the coelacanth was found to have the local duplicate of the PYY gene, called pancreatic polypeptide, previously only identified in tetrapods. Thus, this duplication took place very early in the sarcopterygian lineage, before the origin of tetrapods. These findings confirm the ancient complexity of the NPY system and show that mammals have lost more NPY receptors than any other vertebrate lineage. The coelacanth has all three peptides found in tetrapods and has retained the ancestral jawed vertebrate receptor repertoire with neither gains or losses.

Neuropeptide Y-induced feeding is dependent on GABAA receptors in neonatal chicks

In mammals and birds, neuropeptide Y (NPY) and gamma-aminobutyric acid (GABA) are found in brain areas known to be involved in the control of ingestive behavior and act to increase voluntary food intake. In rats, significant evidence suggest a functional and behavioral interaction between NPY and GABA mediated transmission in various brain regions, including the arcuate and paraventricular nuclei of the hypothalamus which can be important in the regulation of feeding behavior. In the present study, the effect of intracerebroventricular (ICV) administration of NPY and GABA receptor antagonists on food intake was examined in neonatal chicks. The ICV injection of NPY strongly stimulated food intake while co-administration of NPY and picrotoxin, a GABA(A) antagonist, (but not CGP54626, a GABA(B) antagonist) weakened food intake induced by NPY. These results suggest that central NPY stimulates food intake in neonatal chicks by interaction with the GABAergic system via GABA(A) receptors.

The biology of CCR5 and CXCR4

PURPOSE OF REVIEW

We discuss the current knowledge concerning the biology of CXCR4 and CCR5 and their roles in HIV-1 infection.

RECENT FINDINGS

Important research findings reported in the last 2 years have advanced our knowledge in the field of HIV coreceptors and pathogenesis. Novel methods have been used to crystallize two new members of the G-protein coupled receptors. It has been demonstrated that expression and stability of the naturally occurring truncated CCR5 protein is critical for resistance to HIV-1. The first stem cell transplantation of donor cells with the CCR5 mutation provided proof of principle. The Food and Drug Administration approved the first CCR5-based entry inhibitor. New CXCL12 isoforms were discovered, one isoform is a potent X4 inhibitor with weak chemotaxis activity.

SUMMARY

The coreceptor discoveries revealed new insights into host and viral factors influencing HIV transmission and disease. The HIV/coreceptor interaction has become a major target for the development of novel antiviral strategies to treat and prevent HIV infection. The first CCR5-based entry inhibitor has been recently approved. New drugs that promote CCR5 and CXCR4 internalization, independent of cellular signaling, might provide clinical benefits with minimum side effects.

Hungry for life: How the arcuate nucleus and neuropeptide Y may play a critical role in mediating the benefits of calorie restriction

Laboratory studies consistently demonstrate extended lifespan in animals on calorie restriction (CR), where total caloric intake is reduced by 10-40% but adequate nutrition is otherwise maintained. CR has been further shown to delay the onset and severity of chronic diseases associated with aging such as cancer, and to extend the functional health span of important faculties like cognition. Less understood are the underlying mechanisms through which CR might act to induce such alterations. One theory postulates that CR's beneficial effects are intimately tied to the neuroendocrine response to low energy availability, of which the arcuate nucleus in the hypothalamus plays a pivotal role. Neuropeptide Y (NPY), a neurotransmitter in the front line of the arcuate response to low energy availability, is the primary hunger signal affected by CR and therefore may be a critical mechanism for lifespan extension.

Neuropeptide Y-family receptors Y6 and Y7 in chicken. Cloning, pharmacological characterization, tissue distribution and conserved synteny with human chromosome region

The peptides of the neuropeptide Y (NPY) family exert their functions, including regulation of appetite and circadian rhythm, by binding to G-protein coupled receptors. Mammals have five subtypes, named Y1, Y2, Y4, Y5 and Y6, and recently Y7 has been discovered in fish and amphibians. In chicken we have previously characterized the first four subtypes and here we describe Y6 and Y7. The genes for Y6 and Y7 are located 1 megabase apart on chromosome 13, which displays conserved synteny with human chromosome 5 that harbours the Y6 gene. The porcine PYY radioligand bound the chicken Y6 receptor with a K(d) of 0.80 +/- 0.36 nm. No functional coupling was demonstrated. The Y6 mRNA is expressed in hypothalamus, gastrointestinal tract and adipose tissue. Porcine PYY bound chicken Y7 with a K(d) of 0.14 +/- 0.01 nm (mean +/- SEM), whereas chicken PYY surprisingly had a much lower affinity, with a Ki of 41 nm, perhaps as a result of its additional amino acid at the N terminus. Truncated peptide fragments had greatly reduced affinity for Y7, in agreement with its closest relative, Y2, in chicken and fish, but in contrast to Y2 in mammals. This suggests that in mammals Y2 has only recently acquired the ability to bind truncated PYY. Chicken Y7 has a much more restricted tissue distribution than other subtypes and was only detected in adrenal gland. Y7 seems to have been lost in mammals. The physiological roles of Y6 and Y7 remain to be identified, but our phylogenetic and chromosomal analyses support the ancient origin of these Y receptor genes by chromosome duplications in an early (pregnathostome) vertebrate ancestor.

Risk for HIV-1 infection associated with a common CXCL12 (SDF1) polymorphism and CXCR4 variation in an African population

CXC chemokine ligand 12 (CXCL12), or stromal cell-derived factor 1 (SDF1), is the only known natural ligand for the HIV-1 coreceptor, CXC chemokine receptor 4 (CXCR4). A single nucleotide polymorphism (SNP) in the CXCL12 gene (SDF1-3'A) has been associated with disease progression to AIDS in some studies, but not others. Mutations in the CXCR4 gene are generally rare and have not been implicated in HIV-1/AIDS pathogenesis. This study analyzed the SDF1-3'A SNP and performed mutation screening for polymorphic markers in the CXCR4 gene to determine the presence or absence of significant associations with susceptibility to HIV-1 infection. The study consisted of 257 HIV-1-seropositive patients and 113 HIV-1-seronegative controls representing a sub-Saharan African population belonging to the Xhosa ethnic group of South Africa. The SDF1-3'A SNP was associated with an increased risk for HIV-1 infection (P = 0.0319) whereas no significant association was observed between the occurrence of the SDF1-3'A SNP and increased or decreased plasma levels of CXCL12. Comprehensive mutation analysis of the CXCR4 gene confirmed a high degree of genetic conservation within the coding region of this ancient population.

Peptide YY administration into the posterior hypothalamic nucleus of the rat evokes cardiovascular changes by non-adrenergic, non-cholinergic mechanisms

1 Microinjection of peptide YY (PYY) (0.23-2.3 nmol) into the posterior hypothalamic nucleus (PHN) of conscious rats evokes a dose-dependent pressor response and a bradycardia. 2 The increase in mean arterial pressure evoked by 2.3 nmol of PYY was not blocked by intravenous pretreatment with: (i) the nicotinic ganglionic receptor antagonist pentolinium (PENT, 10 mg kg(-1)) alone, or in combination with the muscarinic receptor antagonist methylatropine (MeATR, 1 mg kg(-1)); (ii) the alpha(1)-adrenoceptor antagonist prazosin (PRAZ, 0.2 mg kg(-1)); (iii) the V(1)-vasopressin receptor antagonist [d(CH(2))(5)Tyr(Me)]AVP (AVPX, 20 microg kg(-1)); (iv) the combination of AVPX, PENT and MeATR; (v) the combination of PRAZ, AVPX, PENT, MeATR, and the alpha(2)-adrenoceptor antagonist yohimbine (0.3 mg kg(-1)); or (vi) the angiotensin II type 1 receptor antagonist ZD 7155 (1 mg kg(-1)). 3 Adrenal demedullation inhibited the PYY-evoked responses of drug-naive rats, and rats pretreated with the combination of PENT, MeATR and AVPX. 4 Transection of the splanchnic nerve innervating the adrenal medullae attenuated the bradycardia, as did ZD 7155, but not the PYY-evoked pressor response. 5 Systemic pretreatment of rats with the neuropeptide Y(1) receptor antagonist BIBP 3226 (1 mg kg(-1)) blocked the PYY-evoked cardiovascular changes, but not those evoked by microinjection of carbachol (5.5 nmol) into the PHN. 6 These results suggest that the cardiovascular changes evoked from the PHN by PYY requires the presence of the adrenal medullae, which are stimulated by: (i) a hormone to release an NPY-like substance that evokes the pressor response, and (ii) the splanchnic nerve to evoke the release of a substance that results in the bradycardia.

Compensatory changes in [125I]-PYY binding in Y receptor knockout mice suggest the potential existence of further Y receptor(s)

Gene knockout approaches have helped to better understand the functions of the different Y receptors. However, some results obtained from these knockout mice are unexpected and differ from the results of pharmacological intervention experiments. One possible explanation for this is that germ-line gene deletion of a particular Y receptor can influence expression and function of the remaining Y receptors. Here we show that such compensation in mRNA and protein expression does occur in Y receptor single, double and triple knockout models. Radio-ligand binding experiments using [(125)I]-PYY revealed significant up- and down-regulation of remaining Y receptor binding sites in various Y receptor knockout models compared to results from control mice employing Y receptor preferring agonist or antagonists for displacement of the radio-ligand. The most obvious change can be seen in the hippocampus of Y(1) knockout mice, where the level of the remaining Y receptors is strongly down-regulated. In Y(2) knockout mice no such trend can be seen, however, the expression pattern is significantly changed with a strong up-regulation of [(125)I]-PYY specific binding in the dentate gyrus. Interestingly, this pattern was also seen in Y(1)Y(2)Y(4) triple knockout mice. Y(5) receptor mRNA was approximately 20% higher in the hippocampus and dentate gyrus in the triple knockout mice compared to wild-type controls, while Y(6) mRNA expression could not be detected. However, competition binding experiments in Y(1)Y(2)Y(4) triple knockout mice with the Y(5) receptor preferring ligands [Leu(31), Pro(34)] NPY and [A(31), Aib(32)] NPY were able to replace only approximately 50% of [(125)I]-PYY binding in the dentate gyrus suggesting the existence of further yet unidentified Y receptor(s).

Neuropeptide Y, ubiquitous and elusive

This paper reviews aspects of NPY research that were emerging in 1985, shortly after the isolation and characterization of the peptide. NPY had become known for its widespread distribution especially in the central and peripheral nervous systems, but also in the gastro-intestinal and respiratory tracts and in fibers innervating smooth muscle around blood vessels. Consistent with its distribution, it was determined that NPY is a potent vasoconstrictor, affects neuroendocrine systems and is involved in appetite regulation--areas of research still relevant today. Through advances in technology knowledge about NPY's role in these and newly discovered physiological functions has deepened considerably. Successful cloning of a series of NPY receptors has opened up new and complex research vistas. Lately, the creation of mice genetically modified for NPY as well as for several receptor subtypes has brought many puzzling observations--followed by questions yet to be answered.

The Y1 receptor subtype mediates the cardiovascular changes evoked by NPY administered into the posterior hypothalamic nucleus of conscious rat

An earlier study showed that the neuropeptide Y (NPY) receptor antagonist PYX-2 blocks the enhancement of a carbachol (CCh)-evoked pressor response produced by prior NPY administration into the posterior hypothalamic nucleus (PHN). The Y receptor subtype that mediates this response, and an increase in mean arterial pressure (MAP) and heart rate, remained unknown due to the lack of selectivity of PYX-2 for the Y receptor subtypes. Thus, the present study was undertaken to elucidate the Y receptor subtype responsible for mediating the NPY-evoked cardiovascular responses from the PHN by determining the rank order of potency of several NPY-related peptides for increasing MAP, and by correlating the pressor response evoked by these peptides to reported K(i)'s and IC(50)'s for the Y(1), Y(2), Y(4) and Y(5) receptor subtypes. The pharmacological profile (PYY>or=NPY>or=[Leu(31),Pro(34)]NPY>or=NPY(13-36)>or=hPP) and correlations suggest that the Y(1) and/or Y(5) receptor subtypes mediate these cardiovascular changes. Administration of the relatively non-selective Y receptor antagonist PYX-2 or the selective Y(1) receptor antagonist BIBP 3226 into the PHN prior to NPY completely blocked the cardiovascular responses. BIBP 3226 also blocked the cardiovascular changes evoked by [Leu(31),Pro(34)]NPY, NPY(13-36) and human pancreatic polypeptide (hPP). In contrast, neither BIBP 3226 nor PYX-2 inhibited the cardiovascular changes induced by peptide YY (PYY) or CCh microinjection into the PHN. These results show that NPY and PYY act on different receptors to mediate their respective cardiovascular changes from the PHN with NPY stimulating the Y(1) receptor.

Generation of the melatonin endocrine message in mammals: a review of the complex regulation of melatonin synthesis by norepinephrine, peptides, and other pineal transmitters

Melatonin, the major hormone produced by the pineal gland, displays characteristic daily and seasonal patterns of secretion. These robust and predictable rhythms in circulating melatonin are strong synchronizers for the expression of numerous physiological processes in photoperiodic species. In mammals, the nighttime production of melatonin is mainly driven by the circadian clock, situated in the suprachiasmatic nucleus of the hypothalamus, which controls the release of norepinephrine from the dense pineal sympathetic afferents. The pivotal role of norepinephrine in the nocturnal stimulation of melatonin synthesis has been extensively dissected at the cellular and molecular levels. Besides the noradrenergic input, the presence of numerous other transmitters originating from various sources has been reported in the pineal gland. Many of these are neuropeptides and appear to contribute to the regulation of melatonin synthesis by modulating the effects of norepinephrine on pineal biochemistry. The aim of this review is firstly to update our knowledge of the cellular and molecular events underlying the noradrenergic control of melatonin synthesis; and secondly to gather together early and recent data on the effects of the nonadrenergic transmitters on modulation of melatonin synthesis. This information reveals the variety of inputs that can be integrated by the pineal gland; what elements are crucial to deliver the very precise timing information to the organism. This also clarifies the role of these various inputs in the seasonal variation of melatonin synthesis and their subsequent physiological function.

Neuropeptide Y: a new mediator linking sympathetic nerves, blood vessels and immune system?

Neuropeptide Y (NPY(1-36)), a sympathetic cotransmitter and neurohormone, has pleiotropic activities ranging from the control of obesity to anxiolysis and cardiovascular function. Its actions are mediated by multiple Gi/o-coupled receptors (Y1-Y5) and modulated by dipeptidyl peptidase IV (DPPIV/cd26), which inactivates NPY's Y1-agonistic activity but generates the Y2 and Y5-agonist, NPY(3-36). Released by sympathetic activity, NPY is a major mediator of stress, responsible for prolonged vasoconstriction via Y1 receptors. Y1 receptors also mediate NPY's potent vascular growth-promoting activity leading in vivo in rodents to neointima formation. This and the association of a polymorphism of the NPY signal peptide with increased lipidemia and carotid artery thickening in humans strongly suggest NPY's role in atherosclerosis. NPY and DPPIV/cd26 are also coexpressed in the endothelium, where the peptide activates angiogenesis. A similar system exists in immune cells, where NPY and DPPIV/cd26 are coactivated and involved in the modulation of cytokine release and immune cell functions. Thus, NPY, both a messenger and a modulator for all three systems, is poised to play an important regulatory role facilitating interactions among sympathetic, vascular and immune systems in diverse pathophysiological conditions such as hypertension, atherosclerosis and stress-related alterations of immunity.

Neuropeptide Y (NPY) and depression: from animal studies to the human condition

Neuropeptide Y (NPY) is widely distributed throughout the central nervous system (CNS) and is one of the most conserved peptides in evolution, suggesting an important role in the regulation of basic physiological functions. In addition, both pre-clinical and clinical evidence have suggested that NPY, together with its receptors, may have a direct implication in several psychiatric disorders, including depression and related illnesses. NPY-like immunoreactivity and NPY receptors are expressed throughout the brain, with varying concentrations being found throughout the limbic system. Such brain structures have been repeatedly implicated in the modulation of emotional processing, as well as in the pathogenesis of depressive disorders. This review will concentrate on the distribution of NPY, its receptors, and the putative role played by this peptide in depressive illness based on both pre-clinical and clinical evidence.

Receptor subtypes Y1 and Y5 mediate neuropeptide Y induced feeding in the guinea-pig

1. Neuropeptide Y (NPY) is one of the most potent stimulants of food intake. It has been debated which receptor subtype mediates this response. Initially Y(1) was proposed, but later Y(5) was announced as a 'feeding' receptor in rats and mice. Very little is known regarding other mammals. The present study attempts to characterize the role of NPY in feeding behaviour in the distantly related guinea-pig. When infused intracerebroventricularly, NPY dose-dependently increased food intake. 2. PYY, (Leu(31),Pro(34))NPY and NPY(2 - 36) stimulated feeding, whereas NPY(13 - 36) had no effect. These data suggest that either Y(1) or Y(5) receptors or both may mediate NPY induced food intake in guinea-pigs. 3. The Y(1) receptor antagonists, BIBO 3304 and H 409/22 displayed nanomolar affinity for the Y(1) receptor (K(i) values 1.1+/-0.2 nM and 5.6+/-0.9 nM, respectively), but low affinity for the Y(2) or Y(5) receptors. When guinea-pigs were pretreated with BIBO 3304 and H 409/22, the response to NPY was inhibited. 4. The Y(5) antagonist, CGP 71683A had high affinity for the Y(5) receptor (K(i) 1.3+/-0.05 nM) without having any significant activities at the Y(1) and Y(2) receptors. When CGP 71683A was infused into brain ventricles, the feeding response to NPY was attenuated. 5. The present study shows that NPY stimulates feeding in guinea-pigs through Y(1) and Y(5) receptors. As the guinea-pig is very distantly related to the rat and mouse, this suggests that both Y(1) and Y(5) receptors may mediate NPY-induced hyperphagia also in other orders of mammals.

Diverse functions of neuropeptide Y revealed using genetically modified animals

Neuropeptide Y (NPY), a peptide abundantly expressed in the mammalian nervous system, has been extensively studied using traditional pharmacological and behavioral models. Central administration of NPY or synthetic ligands for its receptors has indicated a role of NPY in anxiety-related behaviors, feeding, regulation of blood pressure, circadian rhythm and other functions. Some limitations inherent in pharmacological approaches, such as lack of selectivity of receptor antagonists, can be elegantly circumvented using genetically modified animals. For NPY, mice lacking NPY, the Y1, the Y2 or the Y5 receptors have been generated. In addition, both mice and rats overexpressing NPY in the central nervous system are available. Here, we review the research carried out so far in the NPY-field using genetically modified animals. Together, these models indicate that stress-related behaviors and regulation of voluntary alcohol intake perhaps are among the most important functions of central NPY, and may provide attractive targets for developing novel therapies in depression, anxiety disorders and alcohol dependence.

Survival of B lineage leukemic cells: signals from the bone marrow microenvironment

Stromal cells are an essential component of the bone marrow microenvironment that regulate development of immature hematopoietic progenitor cells. Through production of soluble cytokines, and signaling through adhesion molecule interactions, stromal cells impact survival, proliferation, and differentiation of hematopoietic progenitor cells. Similarities between normal pro-B and pre-B cells and B lineage acute lymphoblastic leukemic (ALL) progenitors have been well characterized which provide a model for investigation of the mechanisms by which ALL cells respond to bone marrow microenvironment signals. In addition to providing survival signals to B lineage ALL during initiation of disease, the bone marrow has long been recognized as a "sanctuary site" for leukemic cells during traditional chemotherapy. In the current review, mechanisms by which stromal cells contribute to leukemic cell survival, and the potential impact on treatment efficacy, are discussed. A growing appreciation of the significance of the bone marrow microenvironment in the progression of ALL, and further investigation of the signaling between leukemic progenitors and stromal cells, may contribute to novel treatment strategies aimed at enhancing sensitivity of ALL cells to currently available chemotherapeutic agents.

Chemokine receptors

Although chemokines were originally defined as host defense proteins it is now clear that their repertoire of functions extend well beyond this role. For example chemokines such as MGSA have growth regulatory properties while members of the CXC chemokine family can be mediators or inhibitors of angiogenesis and may be important targets for oncology. Recent work shows that the chemokine receptor CXCR4 and its cognate ligand SDF play important roles in the development of the immune, circulatory and central nervous systems. In addition, chemokine receptors play an important role in the pathogenesis of the AIDS virus, HIV-1. Taken together these findings expand the biological importance of chemokines from that of simple immune modulators to a much broader biological role than was at first appreciated and these and other properties of the chemokine receptor family are discussed in detail in this review.

Origins of the many NPY-family receptors in mammals

The NPY system has a multitude of effects and is particularly well known for its role in appetite regulation. We have found that the five presently known receptors in mammals arose very early in vertebrate evolution before the appearance of jawed vertebrates 400 million years ago. The genes Y(1), Y(2) and Y(5) arose by local duplications and are still present on the same chromosome in human and pig. Duplications of this chromosome led to the Y(1)-like genes Y(4) and y(6). We find evidence for two occasions where receptor subtypes probably arose before peptide genes were duplicated. These observations pertain to the discussion whether ligands or receptors tend to appear first in evolution. The roles of Y(1) and Y(5) in feeding may differ between species demonstrating the importance of performing functional studies in additional mammals to mouse and rat.

Stromal cell-derived factor-1-CXC chemokine receptor 4 interactions play a central role in CD4+ T cell accumulation in rheumatoid arthritis synovium

Rheumatoid arthritis (RA) is characterized by the accumulation of CD4(+) memory T cells in the inflamed synovium. To address the mechanism, we analyzed chemokine receptor expression and found that the frequency of CXC chemokine receptor (CXCR)4 expressing synovial tissue CD4(+) memory T cells was significantly elevated. CXCR4 expression could be enhanced by IL-15, whereas stromal cell-derived factor (SDF)-1, the ligand of CXCR4, was expressed in the RA synovium and could be increased by CD40 stimulation. SDF-1 stimulated migration of rheumatoid synovial T cells and also inhibited activation-induced apoptosis of T cells. These results indicate that SDF-1-CXCR4 interactions play important roles in CD4(+) memory T cell accumulation in the RA synovium, and emphasize the role of stromal cells in regulating rheumatoid inflammation.

Lack of correlation between chemokine receptor and T(h)1/T(h)2 cytokine expression by individual memory T cells

Chemokine and chemokine receptor interactions may have important roles in leukocyte migration to specific immune reaction sites. Recently, it has been reported that CXC chemokine receptor (CXCR) 3 and CC chemokine receptor (CCR) 5 were preferentially expressed on T(h)1 cells, and CCR3 and CCR4 were preferentially expressed on T(h)2 cells. To investigate chemokine receptor expression by T(h) subsets in vivo, we analyzed cytokine (IL-2, IL-4 and IFN-gamma) and chemokine receptor (CXCR3, CXCR4, CCR3, CCR4 and CCR5) mRNA expression by individual peripheral CD4(+) memory T cells after short-term stimulation, employing a single-cell RT-PCR method. This ex vivo analysis shows that the frequencies of cells expressing chemokine receptor mRNA were not significantly different between T(h)1 and T(h)2 cells in normal peripheral blood. To assess a potential role of in vivo stimulation, we also analyzed unstimulated rheumatoid arthritis synovial CD4(+) memory T cells. CXCR3, CXCR4, CCR3 and CCR5 expression was detected by individual synovial T cells, but the frequencies of chemokine receptor mRNA were not clearly different between T(h)1 and non-T(h)1 cells defined by expression of IFN-gamma or lymphotoxin-alpha mRNA in all RA patients. These data suggest that chemokine receptor expression does not identify individual memory T cells producing T(h)-defining cytokines and therefore chemokine receptor expression cannot be a marker for T(h)1 or T(h)2 cells in vivo.

Impairment of lymphopoiesis and myelopoiesis in mice reconstituted with bone marrow–hematopoietic progenitor cells expressing SDF-1–intrakine

Both SDF-1 and CXCR4 disruption are lethal to mice at the embryonic stage and cause abnormalities in B lymphopoiesis, myelopoiesis, cardiogenesis, vasculogenesis, and cerebellar development. To investigate the role of SDF-1 and CXCR4 in hematopoiesis during the adult stage, mice reconstituted with bone marrow–derived hematopoietic progenitor cells transduced with either the SDF-1 or a genetically modified SDF-1–intrakine gene using a retroviral expression vector were analyzed. Flow cytometric (FCM) analysis showed a dramatic reduction of CXCR4 expression on the cells of intrakine-transduced mice, whereas CCR7 and CCR1 expression was unchanged or marginally decreased on splenocytes. Migration of splenocytes and bone marrow cells to SDF-1 was markedly suppressed in intrakine-transduced mice. FCM analysis of bone marrow cells of intrakine-transduced mice exhibited decreased numbers of pro-B (B220+ CD43+), pre-B (B220+CD43−), and immature B (B220+IgM+) cells and a decreased number of granulocytes/myeloid (Gr1+ CD11b+) cells. Impaired B lymphopoiesis and myelopoiesis in intrakine-transduced mice were confirmed by an in vitro colony-forming assay of bone marrow cells. In contrast, B lymphopoiesis and myelopoiesis were enhanced in SDF-1–transduced mice. Interestingly, T-cell maturation in the thymus was impaired both in intrakine- and SDF-1–transduced mice, suggesting that SDF-1 and CXCR4 play an important role in T lymphopoiesis as well as in B lymphopoiesis and myelopoiesis in adults. These results demonstrate an essential role of CXCR4 and its ligand SDF-1 in adult hematopoiesis, and they indicate the intrakine method as a powerful tool for functional analysis of chemokines/chemokine receptors in vivo and as a potential therapeutic approach for acquired immunodeficiency syndrome.

Impairment of lymphopoiesis and myelopoiesis in mice reconstituted with bone marrow–hematopoietic progenitor cells expressing SDF-1–intrakine

Both SDF-1 and CXCR4 disruption are lethal to mice at the embryonic stage and cause abnormalities in B lymphopoiesis, myelopoiesis, cardiogenesis, vasculogenesis, and cerebellar development. To investigate the role of SDF-1 and CXCR4 in hematopoiesis during the adult stage, mice reconstituted with bone marrow–derived hematopoietic progenitor cells transduced with either the SDF-1 or a genetically modified SDF-1–intrakine gene using a retroviral expression vector were analyzed. Flow cytometric (FCM) analysis showed a dramatic reduction of CXCR4 expression on the cells of intrakine-transduced mice, whereas CCR7 and CCR1 expression was unchanged or marginally decreased on splenocytes. Migration of splenocytes and bone marrow cells to SDF-1 was markedly suppressed in intrakine-transduced mice. FCM analysis of bone marrow cells of intrakine-transduced mice exhibited decreased numbers of pro-B (B220+ CD43+), pre-B (B220+CD43−), and immature B (B220+IgM+) cells and a decreased number of granulocytes/myeloid (Gr1+ CD11b+) cells. Impaired B lymphopoiesis and myelopoiesis in intrakine-transduced mice were confirmed by an in vitro colony-forming assay of bone marrow cells. In contrast, B lymphopoiesis and myelopoiesis were enhanced in SDF-1–transduced mice. Interestingly, T-cell maturation in the thymus was impaired both in intrakine- and SDF-1–transduced mice, suggesting that SDF-1 and CXCR4 play an important role in T lymphopoiesis as well as in B lymphopoiesis and myelopoiesis in adults. These results demonstrate an essential role of CXCR4 and its ligand SDF-1 in adult hematopoiesis, and they indicate the intrakine method as a powerful tool for functional analysis of chemokines/chemokine receptors in vivo and as a potential therapeutic approach for acquired immunodeficiency syndrome.

Evolution of the neuropeptide Y receptor family: gene and chromosome duplications deduced from the cloning and mapping of the five receptor subtype genes in pig

Neuropeptide Y (NPY) receptors mediate a variety of physiological responses including feeding and vasoconstriction. To investigate the evolutionary events that have generated this receptor family, we have sequenced and determined the chromosomal localizations of all five presently known mammalian NPY receptor subtype genes in the domestic pig, Sus scrofa (SSC). The orthologs of the Y(1) and Y(2) subtypes display high amino acid sequence identities between pig, human, and mouse (92%-94%), whereas the Y(4), Y(5), and y(6) subtypes display lower identities (76%-87%). The lower identity of Y(5) is due to high sequence divergence in the large third intracellular loop. The NPY1R, NPY2R, and NPY5R receptor genes were localized to SSC8, the NPY4R to SSC14, and NPY6R to SSC2. Our comparisons strongly suggest that the tight cluster of NPY1R, NPY2R, and NPY5R on human chromosome 4 (HSA4) represents the ancestral configuration, whereas the porcine cluster has been split by two inversions on SSC8. These 3 genes, along with adjacent genes from 14 other gene families, form a cluster on HSA4 with extensive similarities to a cluster on HSA5, where NPY6R and >13 other paralogs reside, as well as another large cluster on HSA10 that includes NPY4R. Thus, these gene families have expanded through large-scale duplications. The sequence comparisons show that the NPY receptor triplet NPY1R-NPY2R-NPY5R existed before these large-scale duplications.

Role of hypothalamic neuropeptide Y in feeding and obesity

The 36-amino-acid peptide, neuropeptide Y (NPY), is the most abundant peptide in the rat brain. When administered into the brain, NPY produces a variety of physiological actions including a pronounced stimulation of feeding in satiated rats. Elevations in hypothalamic NPY have been reported after food deprivation and in genetically obese rodents. NPY is believed to produce its actions through a portfolio of G-protein coupled receptors, Y1, Y2, Y4 and Y5. Studies using peptide analogs, receptor knockout animals and specific receptor antagonists suggest the Y1 and Y5 receptors are important in mediating the effects of NPY on food intake in rats. Development of specific receptor antagonists with improved pharmacokinetic properties will be required to determine the importance of NPY in human obesity and appetite disorders.

Aspects of the molecular structure and dynamics of neuropeptide Y

Human neuropeptide Y (hNPY) and the Q34-->P34 mutant (P34-hNPY) have been characterized by CD spectroscopy. hNPY self-associates in aqueous solution with a dimerization constant in the micromolar range. The self-association correlates with an increase in secondary-structure content which was studied as a function of concentration, temperature and pH. The effects of temperature were measured in water (5-84 degrees C) and in ethanediol/water (2 : 1) (-90 degrees to +90 degrees C). A single-residue mutation, Q34-->P34, affects the pH, thermal and self-association properties of NPY. The CD results are correlated with photochemically induced dynamic nuclear polarization NMR experiments which show that the tyrosines at the interface between two monomer units present limited accessibility to a photoreactive dye. An equilibrium state is described, involving a PP-fold monomer form and a handshake dimer form, that accommodates the physicochemical properties of NPY.

Chemokine receptor (CXCR4) mRNA-expressing leukocytes are increased in human renal allograft rejection

BACKGROUND

Mononuclear cell infiltration is a common feature of cell-mediated renal transplant rejection. Chemokines and their corresponding receptors likely play a central role in directing specific classes of leukocytes to graft sites during rejection. Localization of chemokine receptors may help us understand how specificity in leukocyte trafficking is achieved in renal inflammatory processes. The localization of the chemokine receptor CXCR4 in human kidney and in renal transplant rejection is unknown.

METHODS

We generated a riboprobe specific for the detection of CXCR4 mRNA by in situ hybridization to evaluate cellular sites of synthesis of this receptor in native human kidneys (n=11) and in human allograft nephrectomies with features of severe rejection (n=14).

RESULTS

By in situ hybridization, CXCR4 mRNA expression is undetectable in intrinsic glomerular, tubular, and renovascular cells in native kidneys. When renal interstitial inflammation is present, CXCR4 mRNA expression is localized to a large fraction of infiltrating leukocytes. Large numbers of CXCR4-expressing cells are detected in cell-mediated renal allograft rejection. Double immunolabeling for CD3 antigen identified a large fraction of infiltrating CXCR4 mRNA-expressing cells as T lymphocytes. CXCR4 mRNA-expressing cells were frequently seen in neointimal lesions of vascular rejection in allograft nephrectomies. CXCR4 mRNA expression was identified in infiltrating neointimal T lymphocytes, but not smooth muscle cells by immunolabeling.

CONCLUSIONS

We demonstrate the involvement of CXCR4 mRNA-expressing infiltrating cells in human renal interstitial and vascular allograft rejection. Signaling via the CXCR4 receptor may be one mechanism by which chemokines mediate leukocyte trafficking in renal allograft rejection.

On the relationship of neuropeptide Y Y1 receptor-immunoreactive neuronal structures to the neuropeptide Y-immunoreactive nerve terminal networks. A double immunolabelling analysis in the rat brain

Neuropeptide Y is the most abundant peptide in the mammalian central nervous system and exhibits a variety of potent neurobiological functions. In the present study, double immunolabelling histochemistry was performed, using previously characterized antibodies against neuropeptide Y and the neuropeptide Y Y1 receptor subtype, to clarify the cellular distribution of Y1 receptors in the rat brain in relation to the neuropeptide Y-immunoreactive systems. Based on fluorescence and confocal laser microscopy analysis, morphological evidence is presented that the perikaryal and dendritic Y1 receptor-like immunoreactivity demonstrated in discrete regions of the tel-, diencephalon and of the lower brain stem, shown to be cytoplasmic and membrane associated, in many brain regions is not co-distributed with the neuropeptide Y-immunoreactive terminal network. These findings may partly be explained by the existence of volume transmission in Y1 receptor-mediated neuropeptide Y transmission involving short to long distance diffusion and/or convection of neuropeptide Y from its site of release to the neuronal target cells, containing the high-affinity Y1 receptors. Furthermore, neuropeptide Y and Y1 receptor-like immunoreactivities were in no case co-localized in the same nerve cell, suggesting that, in the rat brain, the Y1 receptor subtype may not be a neuropeptide Y autoreceptor.

Genomic organization and expression of the CXCR4 gene in mouse and man: absence of a splice variant corresponding to mouse CXCR4-B in human tissues

The human CXC chemokine receptor CXCR4 is activated by stromal cell-derived factor 1. The receptor is present in many cell types and regulates a variety of cellular functions, including chemotaxis, adhesion, hematopoiesis, and organogenesis. Human CXCR4 also serves as a cofactor for cell entry by certain strains of HIV-1 and HIV-2. In the mouse, alternative RNA splicing produces two transcripts encoding two CXCR4 isoforms, mCXCR4-A and mCXCR4-B, differing by the presence of two amino acids in the amino terminal portion of the longer protein, mCXCR4-B. Only one CXCR4 transcript, encoding the human counterpart of mCXCR4-A, is known in man. The involvement of the aminoterminal-most portion of CXCR4 in both ligand and HIV envelope protein recognition led us to determine whether a CXCR4 variant corresponding to mCXCR4-B is present in human tissues. To this end, the genomic organization and expression of the human CXCR4 gene was examined. Both the human and the mouse CXCR4 gene consist of two exons separated by an approximately 2.1 kbp intron between codons five and six and carry splice donor sites at the 5' end of their introns. These similarities notwithstanding, single nucleotide primer extension, reverse transcriptase PCR amplification, and sequencing of CXCR4 cDNA clones show that a splice variant of CXCR4 corresponding to mCXCR4-B is absent in man.

Cutting Edge: IL-4 Induces Functional Cell-Surface Expression of CXCR4 on Human T Cells

Here we report that IL-4 specifically enhances cell surface expression of CXCR4 on resting peripheral and cord blood T cells. Whereas polarized Th2 clones express variable levels of CXCR4, expression of this receptor is undetectable on polarized Th1 clones but can be induced on the latter cells as well, following short-term culture in the presence of IL-4. The IL-4-induced CXCR4 is functional since interaction with its ligand, stromal-derived factor (SDF)-1, activates the p42 MAP-kinase ERK-2. In addition, although CXCR4 expression is down-regulated following stimulation of T cells and T cell clones via CD28 or CD3 and CD2 cell surface molecules, respectively, it is re-induced by IL-4. These data indicate an important role for IL-4 in rendering CD4+ T cells susceptible to infection with HIV via CXCR4, as well as in promoting SDF-1-induced migration of these cells.

Localization of neuropeptide Y Y1 receptor mRNA in human tooth pulp

With immunocytochemistry numerous nerve fibres containing neuropeptide Y (NPY) were found in human molar pulp tissue, often around small blood vessels. Reverse transcriptase-polymerase chain reaction, using specific primers, detected mRNA of the human NPY Y1 receptor in the human pulp tissue. Thus, both NPY-containing nerve fibres and NPY Y1 receptor mRNA are present in human tooth pulp, possibly regulating vascular tone and pain perception.

Expression of the rat adrenomedullin receptor or a putative human adrenomedullin receptor does not correlate with adrenomedullin binding or functional response

There has been considerable difficulty in defining distinct adrenomedullin (AM) binding sites and function in vivo. However, a rat adrenomedullin receptor (rAMR) and a putative human adrenomedullin receptor (hAMR) have recently been reported. We attempted to confirm and extend the pharmacological characterization of these cloned receptors. COS-7 cells transfected with rAMR or epitope tagged rAMR display abundant rAMR mRNA expression and cell-surface receptor localization. Specific 125I-AM binding is detected in transfected cells; however, similar levels of binding are also detected in cells transfected with vector DNA alone. This AM binding site fails to mediate any changes in cAMP in response to AM. In contrast, Swiss 3T3 cells, expressing specific endogenous AM receptors, display AM binding and functional cAMP responses. Transfection studies performed with the putative hAMR yield similar results. These data suggest that the proposed rAMR and hAMR do not represent authentic adrenomedullin receptors.

Lymphocyte responses to chemokines

Today, almost three dozen human chemokines have been identified. The main function of these soluble proteins is the recruitment of leukocytes to sites of infection and inflammation. This review emphasizes the new developments in the field of lymphocyte responses to chemokines. Notably, it was shown that lymphocytes require stimulation to become responsive to chemokines, a process that is closely linked to chemokine receptor expression. As an exception, one chemokine, SDF-1, is a highly effective chemoattractant for non-activated T lymphocytes and progenitor B cells. Of particular interest are the chemokines IP10 and Mig which bind to a receptor with selective expression in activated T lymphocytes and, therefore, may be critical mediators of T lymphocyte migration in T cell-dependent immune-responses. All other chemokines with activities in lymphocytes do also induce responses in monocytes and granulocytes. The involvement of chemokine receptors in HIV infection is briefly mentioned, while other interesting areas in chemokine research, such as hematopoiesis and angiogenesis, are not discussed.

Chemokine receptor CXCR4 expression in endothelium

The expression of chemokine receptor and viral coreceptor CXCR4 is reported in cultured endothelial cells and in arterial endothelium. A 1.9 kb transcript was cloned from cultured bovine aortic (BAEC) and human umbilical vein endothelial cells (HUVEC). CXCR4 mRNA was expressed at high levels in BAEC and HUVEC but was not expressed by cultured bovine arterial smooth muscle cells (BASM) or human umbilical vein smooth muscle cells (HUVSM). Western blotting with polyclonal antibodies demonstrated an approximate 46KD protein in endothelial cells only. In situ hybridization and immunocytochemistry (anti-CXCR4 monoclonal antibody 12G5) revealed both transcript and protein expression in cultured endothelial cells, and in the endothelium of normal aorta but not in aortic smooth muscle. The ligand for CXCR4, stromal cell derived factor 1 (SDF-1) stimulated mobilization of intracellular calcium at a moderate level (37% of the peak response to thrombin), confirming the expression of functional receptor at the endothelial surface. The involvement of CXCR4 in chemokine signaling, chemoattraction (through SDF-1), and its potential viral coreceptor activity suggest a multifunctional role in vascular homeostasis and pathophysiology.

Detection and Delineation of CXCR-4 (Fusin) as an Entry and Fusion Cofactor for T Cell-Tropic HIV-1 by Three Different Monoclonal Antibodies

A chemokine receptor, CXCR-4, has been identified as an entry cofactor for T cell line-tropic (T-tropic) HIV-1. To detect expression of CXCR-4 at the single cell level and dissect postbinding events of HIV-1 infection, we generated three mAbs against human CXCR-4. These mAbs inhibited SDF-1-induced intracellular Ca2+ mobilization, and one of the mAbs immunoprecipitated a specific 47-kDa component from CXCR-4+ cells. Flow cytometric analysis showed that most human cell lines examined expressed CXCR-4. A fraction of normal PBMC expressed CXCR-4, but neutrophils were negative. Two-color analysis revealed that the majority of T cells, virtually all B cells, and all monocytes expressed CXCR-4, while it was only weakly present on NK cells. Thus, expression of CXCR-4 is not ubiquitous but cell type specific in hemopoietic cells. The three mAbs were shown to suppress cell fusion mediated by envelope proteins of a T-tropic NL432 virus but not by those of an M-tropic JRCSF virus. Likewise, they suppressed infection of NL432 but not that of an M-tropic NL162 virus. In both cases it was noted that the suppressive activity varied considerably among the mAbs. These data confirmed that CXCR-4 is directly involved in env-mediated entry and fusion of T-tropic HIV-1 and suggest that the epitopes on CXCR-4 recognized by the three mAbs may have different roles in interaction with the envelope proteins of T-tropic HIV-1.

Multiplicity of neuropeptide Y receptors: cloning of a third distinct subtype in the zebrafish

Five different receptor subtypes for neuropeptide Y (NPY) have recently been cloned in mammals. We have discovered three distinct subtypes by PCR in the zebrafish, Danio rerio, and describe here one of these called zYc. The protein sequence identity is 46-51% to mammalian subtypes Y1, Y4 and Y6 and to zebrafish Ya, i.e., the same degree of identity as these subtypes display to one another. The identity to zYb is higher, 75%, indicating that zYb and zYc share a more recent ancestor. The zYc receptor binds NPY and PYY (peptide YY) from mammals as well as zebrafish with high affinities and has a Kd of 16 pM for 125I-pPYY. The pharmacological profile is similar to, but distinct-from, mammalian Y1. zYc inhibits cAMP synthesis. This work suggests that NPY has more receptor subtypes than any other peptide that binds to G protein-coupled receptors. Work is in progress to see if the zebrafish receptors are present in mammals.