Efficient production of membrane-integrated and detergent-soluble G protein-coupled receptors in Escherichia coli

G protein-coupled receptors (GPCRs) are notoriously difficult to express, particularly in microbial systems. Using GPCR fusions with the green fluorescent protein (GFP), we conducted studies to identify bacterial host effector genes that result in a general and significant enhancement in the amount of membrane-integrated human GPCRs that can be produced in Escherichia coli. We show that coexpression of the membrane-bound AAA+ protease FtsH greatly enhances the expression yield of four different class I GPCRs, irrespective of the presence of GFP. Using this new expression system, we produced 0.5 and 2 mg/L of detergent-solubilized and purified full-length central cannabinoid receptor (CB1) and bradykinin receptor 2 (BR2) in shake flask cultures, respectively, two proteins that had previously eluded expression in microbial systems.

Relaxin-3 stimulates the hypothalamic-pituitary-gonadal axis

The hypothalamus plays a key role in the regulation of both energy homeostasis and reproduction. Evidence suggests that relaxin-3, a recently discovered member of the insulin superfamily, is an orexigenic hypothalamic neuropeptide. Relaxin-3 is thought to act in the brain via the RXFP3 receptor, although the RXFP1 receptor may also play a role. Relaxin-3, RXFP3, and RXFP1 are present in the hypothalamic paraventricular nucleus, an area with a well-characterized role in the regulation of energy balance that also modulates reproductive function by providing inputs to hypothalamic gonadotropin-releasing hormone (GnRH) neurons. Other members of the relaxin family are known to play a role in the regulation of reproduction. However, the effects of relaxin-3 on reproductive function are unknown. We studied the role of relaxin-3 in the regulation of the hypothalamo-pituitary-gonadal (HPG) axis. Intracerebroventricular (5 nmol) and intraparaventricular (540-1,620 pmol) administration of human relaxin-3 (H3) in adult male Wistar rats significantly increased plasma luteinizing hormone (LH) 30 min postinjection. This effect was blocked by pretreatment with a peripheral GnRH antagonist. Central administration of human relaxin-2 showed no significant effect on plasma LH. H3 dose-dependently stimulated the release of GnRH from hypothalamic explants and GT(1)-7 cells, which express RXFP1 and RXFP3, but did not influence LH or follicle-stimulating hormone release from pituitary fragments in vitro. We have demonstrated a novel role for relaxin-3 in the stimulation of the HPG axis, putatively via hypothalamic GnRH neurons. Relaxin-3 may act as a central signal linking nutritional status and reproductive function.

Roles of short-chain fatty acids receptors, GPR41 and GPR43 on colonic functions

Short chain fatty acids (SCFAs) are the major anions in the large intestine. They are produced by a bacterial fermentation of dietary fiber. SCFAs are known to have a variety of physiological and pathphysiological effects on intestine. However, the mechanisms by which intraluminal SCFAs are sensed are not known. In 2003, two orphan G protein coupled receptors (GPRs), GPR41 and GPR43, have been cloned and demonstrated to be receptors for SCFAs. Thus, we had attempted to make antibodies raised against GPR43 and GPR41 to elucidate the roles of SCFAs on colonic functions. We have also evaluated the effects of SCFAs on colonic motility to define the physiological roles on luminal SCFAs. In rat and human colon, GPR43 protein was detected by Western blot analysis in extracts of whole wall and separated mucosa, but not in muscle plus submucosa extract. By immunohistochemistry, GPR43 immunoreactivity was localized with enteroendocrine cells expressing peptide YY, whereas 5-HT immunoreactive enteroendocrine cells were not immunoreactive for GPR43. GPR41 immunoreactivity was also found in human colon. In functional studies, propionate and butyrate concentration-dependently (10 microM - 10 mM) induced phasic and tonic contractions in rat colonic circular muscle. The propionate-induced phasic contraction was attenuated by atropine, tetrodotoxin and the 5-HT(4) receptor antagonists SB204070. However, acetate did not induce phasic or tonic contractions. Propionate-induced responses were not observed in mucosal free preparations. The present results suggest that the SCFA-induced physiological effects on colonic functions might be attributable to the activation of SCFA receptors on epithelial cells in the colon.

[Transcriptional expression of GPR43 gene in adipose tissue and primary cultured adipocytes of pig]

GPR43 (G protein-coupled receptor 43) is a recently discovered short-chain free fatty acid receptor which plays important role in adipogenesis. Here we explored the transcriptional expression rule of GPR43 in porcine adipose tissue and primary cultured adipocytes. Partial cDNA of GPR43 was successfully cloned from swine by RT-PCR and the expression profile of GPR43 mRNA was studied from different types, different growing stages, and different sites of porcine adipose tissue as well as porcine primary cultured adipocytes. The results showed that porcine GPR43 shared high homology with human (89%), mouse (84%) and rat (83%). The expression level of GPR43 mRNA was significantly higher in adipose tissue of obese pigs than that of lean pigs, and also the expression level gradually increased with age. Further, the abundance of GPR43 mRNA level was higher in subcutaneous fat than in visceral fat. In addition, during the adipocytes differentiation, the expression of GPR43 mRNA increased in a time-dependent manner. These data indicated that GPR43 gene expression was relate to the site of adipose tissue, economic type, and age of pig as well as differentiating state of adipocytes, implying that GPR43 can be a potential factor to regulate adipogenesis.

PCR cloning of neural gene products

Of the many proteins that are known to be involved in neuronal signaling, one family of gene products, collectively referred to as the G protein-coupled receptors (GPCRs), has received considerable attention. Within the transmembrane domains of GPCRs are clusters of amino acids that tend to be conserved among receptors that bind related ligands. Polymerase chain reaction (PCR)-based approaches to cloning novel GPCRs typically begin with the identification of these well-conserved amino acid motifs, which are then back-translated into degenerate oligonucleotide primers. These pools of degenerate oligonucleotides are the most important variables in PCR cloning of GPCRs. Although GPCRs are used as the focus of this unit, the strategies and techniques described are applicable to the cloning of a wide variety of neuronal gene products. In the first procedure in this unit, either total or poly(A)(+) purified RNA is reverse transcribed into first-strand cDNA. In subsequent steps the cDNA product serves as the template for synthesis and amplification of target receptor sequences by PCR primed with degenerate oligodeoxynucleotides. The product is ready to be cloned and screened as described. Guidelines for database searching are provided to help identify the cloned gene from the known sequence. Typically, only a portion of the receptor coding region is cloned by the above approach. Rapid amplification of cDNA ends (RACE) or anchored PCR is described in this unit and is used to obtain a full-length cDNA amenable for expression studies.

Regulation of G protein-coupled receptor signalling: focus on the cardiovascular system and regulator of G protein signalling proteins

G protein-coupled receptors (GPCRs) are involved in many biological processes. Therefore, GPCR function is tightly controlled both at receptor level and at the level of signalling components. Well-known mechanisms by which GPCR function can be regulated comprise desensitization/resensitization processes and GPCR up- and downregulation. GPCR function can also be regulated by several proteins that directly interact with the receptor and thereby modulate receptor activity. An additional mechanism by which receptor signalling is regulated involves an emerging class of proteins, the so-called regulators of G protein signalling (RGS). In this review we will describe some of these control mechanisms in more detail with some specific examples in the cardiovascular system. In addition, we will provide an overview on RGS proteins and the involvement of RGS proteins in cardiovascular function.

A day in the life of a G protein-coupled receptor: the contribution to function of G protein-coupled receptor dimerization

G protein-coupled receptors are one of the most actively studied families of proteins. However, despite the ubiquity of protein dimerization and oligomerization as a structural and functional motif in biology, until the last decade they were generally considered as monomeric, non-interacting polypeptides. For the metabotropic glutamate-like group of G protein-coupled receptors, it is now firmly established that they exist and function as dimers or, potentially, even within higher-order structures. Despite some evidence continuing to support the view that rhodopsin-like G protein-coupled receptors are predominantly monomers, many recent studies are consistent with the dimerization/oligomerization of such receptors. Key roles suggested for dimerization of G protein-coupled receptors include control of protein maturation and cell surface delivery and providing the correct framework for interactions with both hetero-trimeric G proteins and arrestins to allow signal generation and its termination. As G protein-coupled receptors are the most targeted group of proteins for the development of therapeutic small molecule medicines, recent indications that hetero-dimerization between co-expressed G protein-coupled receptors may be a common process offers the potential for the development of more selective and tissue restricted medicines. However, many of the key experiments have, so far, been limited to model cell systems. Priorities for the future include the generation of tools and reagents able to identify unequivocally potential G protein-coupled receptor hetero-dimers in native tissues and detailed analyses of the influence of hetero-dimerization on receptor function and pharmacology.

[Expressions of urotensin II and its receptor in pulmonary arteries in rats with chronic thromboembolic pulmonary hypertension]

OBJECTIVE

To investigate the expressions of Urotensin II (UII) protein and mRNA and its receptor (UT) mRNA of medium and small pulmonary arteries of rats with chronic thromboembolic pulmonary hypertension.

METHODS

The Wistar rats were injected thrombi through the jugular vein 2 times in 2 weeks and tranexamic acid was injected peritoneally once daily during the experiment to prevent thrombolysis. The mean pulmonary artery pressure (mPAP) was measured using right cardiac atheterzation. The expressions of UII protein in pulmonary arteries were studied by immunohischemistry with a polycolonal antibody. The expressions of UII mRNA and UT mRNA were detected by in situ hybridization using UII and UT oligonuclear probes. The changes of structures in pulmonary vessle were observed, including relative medial thickness of pulmonary artery (PAMT) and vessle wall area/total vessle area (WA/TA).

RESULTS

The mPAP of the 4 weeks to the 12 weeks groups were (19.9 +/- 6.2) mm Hg (1 mm Hg = 0.133 kPa), (23.8 +/- 4.1) mm Hg and (27.4 +/- 5.4) mm Hg, higher than that of the control group (F = 13.75, P < 0.01, respectively). The PAMT of the 4 weeks to the 12 weeks groups were (42.6 +/- 11.16)%, (47.82 +/- 10.02)% and (53.79 +/- 10.41)%, and WA/TA of the 4 weeks to the 12 weeks groups were (22.75 +/- 6.79)%, (25.32 +/- 4.90)% and (27.05 +/- 7.71)%, both changed significantly as compared to the control group (F = 5.52 and 6.61, P < 0.01, respectively; P < 0.05 in 4 weeks group; P < 0.01 in 8 weeks and 12 weeks groups, respectively). The expressions of UIIprotein, UII mRNA and UT mRNA in the 4 weeks to the 12 weeks groups were obviously higher than the control group (F = 30.39, 30.78 and 14.49, P < 0.01, respectively), and their expressions were more marked in the small pulmonary arteries than in medium pulmonary arteries. The expressions of UIIprotein, UII mRNA and UT mRNA were positively correlated with mPAP and PAMT. The pulmonary vascular remodeling was time-dependently aggravated after embolism (r: 0.822, 0.866 and 0.846; 0.675, 0.712 and 0.756, P < 0.01, respectively).

CONCLUSIONS

The expressions of UII protein, UII mRNA and UT mRNA of pulmonary arteries in the animal models were higher than those in the control group. These dynamic changes of UII mRNA, UIIprotein and UT mRNA may contribute to the development of pulmonary hypertension and vascular remodeling after pulmonary thromboembolism.

EMR1, the human homolog of F4/80, is an eosinophil-specific receptor

The EGF-TM7 F4/80 is a defining marker of murine macrophage populations. Applying flow cytometric analysis using the newly generated mAb A10, and quantitative real-time PCR, we here report the surprising observation that the human ortholog of F4/80, EGF-like module containing mucin-like hormone receptor (EMR)1, is absent on mononuclear phagocytic cells including monocytes, macrophages, and myeloid dendritic cells. Unexpectedly, we found that EMR1 expression is restricted to eosinophilic granulocytes, where expression is overlapping with the eotaxin receptor CCR3 and the immunoglobulin-like lectin Siglec-8. Absence on other leukocytes, including basophils, implies that EMR1 is a highly specific marker for eosinophils in humans.

The ghrelin system in acinar cells: localization, expression, and regulation in the exocrine pancreas

OBJECTIVES

Ghrelin and its receptor are expressed abundantly in the stomach and pituitary. Recently, a ghrelin system, consisting of both ligand and receptor, has also been found to exist in the endocrine cells of pancreatic islets. This ghrelin system may play a role in regulating insulin secretion and glucose homeostasis. The aim of the present study was to investigate whether a functional ghrelin system also exists in the exocrine pancreas.

METHODS

Precise localization and expression of ghrelin and its receptor in rat pancreatic acinar cells were examined by immunocytochemistry and Western blot, whereas messenger RNA levels were examined by semiquantitative reverse transcription-polymerase chain reaction. The roles of physiological and pathophysiological conditions, such as gastric acid inhibition, starvation, and acute pancreatitis, in regulation of ghrelin and its receptor were also examined.

RESULTS

Both ghrelin and its receptor were detected, at both protein and messenger RNA levels, in the acinar cells of the exocrine pancreas. Ghrelin receptor expression was up-regulated by gastric acid inhibition and down-regulated by acute pancreatitis, whereas levels remained unchanged after food deprivation. In contrast, ghrelin expression did not exhibit significant changes in any condition.

CONCLUSIONS

Our data indicate that a ghrelin system exists in the acinar cells of the exocrine pancreas. This system is subject to regulation by physiological and pathophysiological stimuli and may thus regulate exocrine functions by paracrine and/or autocrine mechanisms.

Ghrelin affects the release of luteolytic and luteotropic factors in human luteal cells

CONTEXT

Ghrelin, well-known modulator of food intake and energy balance, is a rather ubiquitous peptide involved in several endocrine and nonendocrine actions. A possible as-yet-unknown role for ghrelin in modulating luteal function has been suggested because both ghrelin and its receptor (GRLN-R) have been immunohistochemically detected in human corpus luteum.

OBJECTIVE

We first investigated GRLN-R mRNA expression in midluteal phase human luteal cells. Ghrelin effect on basal and human chorionic gonadotropin (hCG)-stimulated progesterone (P) release was then analyzed. Finally, we investigated whether ghrelin could affect luteal release of vascular endothelial growth factor (VEGF), prostaglandin (PG) E(2), both luteotropic factors, and PGF(2alpha), luteolytic modulator. Ghrelin effect on both basal and hypoxia-stimulated VEGF luteal expression was analyzed.

METHODS

Human luteal cells were incubated for 24 h with ghrelin (10(-13) to 10(-7) m) or hCG (100 ng/ml) or CoCl(2) (10 microm), chemical hypoxia, or with hCG or CoCl(2) in combination with ghrelin. Both GRLN-R mRNA and VEGF mRNA were evaluated by real-time RT-PCR. PGs and P release was assayed by RIA, whereas VEGF release by ELISA.

RESULTS

GRLN-R mRNA expression was demonstrated in human luteal cells. Both basal and hCG-stimulated P release was significantly decreased by ghrelin, which was able to reduce PGE(2) and increase PGF(2alpha) luteal release. Both basal and hypoxia-stimulated VEGF release was significantly decreased by ghrelin, which did not affect VEGF mRNA luteal expression.

CONCLUSIONS

The present in vitro study provides the first evidence of a direct inhibitory influence of ghrelin on human luteal function.

Food-induced expression of orexin receptors in rat duodenal mucosa regulates the bicarbonate secretory response to orexin-A

Presence of appetite-regulating peptides orexin-A and orexin-B in mucosal endocrine cells suggests a role in physiological control of the intestine. Our aim was to characterize orexin-induced stimulation of duodenal bicarbonate secretion and modulation of secretory responses and mucosal orexin receptors by overnight food deprivation. Lewis x Dark Agouti rats were anesthetized and proximal duodenum cannulated in situ. Mucosal bicarbonate secretion (pH stat) and mean arterial blood pressure were continuously recorded. Orexin-A was administered intra-arterially close to the duodenum, intraluminally, or into the brain ventricles. Total RNA was extracted from mucosal specimens, reverse transcribed to cDNA and expression of orexin receptors 1 and 2 (OX1 and OX2) measured by quantitative real-time PCR. OX1 protein was measured by Western blot. Intra-arterial orexin-A (60-600 nmol.h(-1).kg(-1)) increased (P < 0.01) the duodenal secretion in fed but not in fasted animals. The OX1 receptor antagonist SB-334867, which was also found to have a partial agonist action, abolished the orexin-induced secretory response but did not affect secretion induced by the muscarinic agonist bethanechol. Atropine, in contrast, inhibited bethanechol but not orexin-induced secretion. Orexin-A infused into the brain ventricles (2-20 nmol.kg(-1).h(-1)) or added to luminal perfusate (1.0-100 nM) did not affect secretion, indicating that orexin-A acts peripherally and at basolateral receptors. Overnight fasting decreased mucosal OX1 and OX2 mRNA expression (P < 0.01) as well as OX1 protein expression (P < 0.05). We conclude that stimulation of secretion by orexin-A may involve both receptor types and is independent of cholinergic pathways. Intestinal OX receptors and secretory responses are markedly related to food intake.

Conditional overexpression of Stat3alpha in differentiating myeloid cells results in neutrophil expansion and induces a distinct, antiapoptotic and pro-oncogenic gene expression pattern

Normal neutrophil development requires G-CSF signaling, which includes activation of Stat3. Studies of G-CSF-mediated Stat3 signaling in cell culture and transgenic mice have yielded conflicting data regarding the role of Stat3 in myelopoiesis. The specific functions of Stat3 remain unclear, in part, because two isoforms, Stat3alpha and Stat3beta, are expressed in myeloid cells. To understand the contribution of each Stat3 isoform to myelopoiesis, we conditionally overexpressed Stat3alpha or Stat3beta in the murine myeloid cell line 32Dcl3 (32D) and examined the consequences of overexpression on cell survival and differentiation. 32D cells induced to overexpress Stat3alpha, but not Stat3beta, generated a markedly higher number of neutrophils in response to G-CSF. This effect was a result of decreased apoptosis but not of increased proliferation. Comparison of gene expression profiles of G-CSF-stimulated, Stat3alpha-overexpressing 32D cells with those of cells with normal Stat3alpha expression revealed novel Stat3 gene targets, which may contribute to neutrophil expansion and improved survival, most notably Slc28a2, a purine nucleoside transporter, which is critical for maintenance of intracellular nucleotide levels and prevention of apoptosis, and Gpr65, an acid-sensing, G protein-coupled receptor with pro-oncogenic and antiapoptotic functions.

Regulation of GH secretagogue receptor gene expression in the rat nodose ganglion

It has been shown that the ghrelin receptor, GH secretagogue receptor (GHS-R), is synthesized in neurons of the nodose ganglion and then transmitted to axon terminals, where it binds to ghrelin. The orexigenic signal of ghrelin secreted from the stomach is transmitted to the brain via the vagal afferent nerve. To explore the regulation of GHS-R synthesis in the nodose ganglion, we examined whether or not GHS-R type a mRNA expression shows circadian rhythm, and is affected by starvation, vagotomy, or i.v. administration of gastrointestinal peptides. Nodose ganglion GHS-R mRNA levels showed a diurnal rhythm, being high during periods of light and low during darkness. Although starvation tended to increase the level of GHS-R mRNA, a more significant increase was observed upon re-feeding. Vagotomy decreased the level of GHS-R mRNA significantly in comparison with animals that underwent a sham procedure. Cholecystokinin and gastrin increased the level of GHS-R mRNA after 2 h, but after 4 h, the level decreased. These results suggest that GHS-R synthesis in the nodose ganglion is regulated centrally and peripherally by neuronal and humoral information, and that these dynamic changes of GHS-R mRNA expression may be involved in the regulation of feeding by ghrelin.

Expression of trace amine-associated receptors in the Grueneberg ganglion

The Grueneberg ganglion (GG) in the vestibule of the anterior nasal cavity is considered as an olfactory subcompartment based on expression of the olfactory marker protein (OMP) and axonal projection to the olfactory bulb. Searching for olfactory receptors present in the GG, it has been observed recently that V2r83, a member of the V2R class of olfactory receptors, is expressed in numerous cells in the GG of mice. However, no other olfactory receptors have been found to be present in a considerable number of GG neurons so far. Here, we report that GG neurons express trace amine-associated receptors (TAARs) that have most recently been described as a novel class of olfactory receptors. It was observed that several TAAR subtypes are expressed by defined subpopulations of GG neurons distinct from the V2r83-positive cells. Analyzing the time course of TAAR expression during pre- and postnatal development revealed that TAARs are expressed by a substantial portion of GG neurons in late embryonic and neonatal stages, whereas in juveniles and adults, the number of TAAR-positive cells in the GG was significantly decreased.

Cell-free production of G protein-coupled receptors for functional and structural studies

G-protein coupled receptors (GPCRs) are key elements in signal transduction pathways of eukaryotic cells and they play central roles in many human diseases. So far, most structural and functional approaches have been limited by the immense difficulties in the production of sufficient amounts of protein samples in conventional expression systems based on living cells. We report the high level production of six different GPCRs in an individual cell-free expression system based on Escherichia coli extracts. The open nature of cell-free systems allows the addition of detergents in order to provide an artificial hydrophobic environment for the reaction. This strategy defines a completely new technique for the production of membrane proteins that can directly associate with detergent micelles upon translation. We demonstrate the efficient overproduction of the human melatonin 1B receptor, the human endothelin B receptor, the human and porcine vasopressin type 2 receptors, the human neuropeptide Y4 receptor and the rat corticotropin releasing factor receptor by cell-free expression. In all cases, the long chain polyoxyethylene detergent Brij78 was found to be highly effective for solubilization and milligram amounts of soluble protein could be generated in less than 24 h. Single particle analysis indicated a homogenous distribution of predominantly protein dimers of the cell-free expressed GPCR samples, with dimensions similar to the related rhodopsin. Ligand interaction studies with the endothelin B receptor and a derivative of its peptide ligand ET-1 gave further evidence of a functional folding of the cell-free produced protein.

Placental expression of EG-VEGF and its receptors PKR1 (prokineticin receptor-1) and PKR2 throughout mouse gestation

Compelling evidence indicates that vascular endothelial growth factor (VEGF) is an important mediator of placental angiogenesis and appears to be disregulated in pre-eclampsia (PE). Recently, we characterised the expression of EG-VEGF (endocrine gland-derived vascular endothelial growth factor), also known as prokineticin 1 (PK1) in human placenta during the first trimester of pregnancy and showed that this factor is likely to play an important role in human placentation. However, because it is impossible to prospectively study placentation in humans, it has been impossible to further characterise EG-VEGF expression throughout complete gestation and especially at critical gestational ages for PE development. In the present study, we used mouse placenta to further characterise EG-VEGF expression throughout gestation. We investigated the pattern of expression of EG-VEGF and its receptors, PKR1 and PKR2 at the mRNA and protein levels. Our results show that EG-VEGF and VEGF exhibit different patterns of expression and different localisations in the mouse placenta. EG-VEGF was mainly localised in the labyrinth whereas VEGF was mainly present in glycogen and giant cells. EG-VEGF mRNA and protein levels were highest before 10.5days post coitus (dpc) whereas those of VEGF showed stable expression throughout gestation. PKR1 protein was localised to the labyrinth layer and showed the same pattern of expression as EG-VEGF whereas PKR2 expression was maintained over 10.5dpc with both trophoblastic and endothelial cell localisations. Altogether these findings suggest that EG-VEGF may have a direct effect on both endothelial and trophoblastic cells and is likely to play an important role in mouse placentation.

Upregulation of endothelial adhesion molecules by lysophosphatidylcholine. Involvement of G protein-coupled receptor GPR4

Lysophosphatidylcholine induces expression of adhesion molecules; however, the underlying molecular mechanisms of this are not well elucidated. In this study, the intracellular signaling by which lysophosphatidylcholine upregulates vascular cell adhesion molecule-1 and P-selectin was delineated using YPEN-1 and HEK293T cells. The results showed that lysophosphatidylcholine dose-dependently induced expression of vascular cell adhesion molecule-1 and P-selectin, accompanied by the activation of transcription factor nuclear factor kappaB. However, the nuclear factor kappaB inhibitor caffeic acid phenethyl ester (CAPE) and the antioxidant N-acetylcysteine only partially blocked lysophosphatidylcholine-induced adhesion molecules. Subsequently, we found that the lysophosphatidylcholine receptor G protein-coupled receptor 4 (GPK4) was expressed in YPEN-1 cells and triggered the cAMP/protein kinase A/cAMP response element-binding protein pathway, resulting in upregulation of adhesion molecules. Further evidence showed that overexpression of human GPK4 enhanced lysophosphatidylcholine-induced expression of adhesion molecules in YPEN-1 cells, and enabled HEK293T cells to express adhesion molecules in response to lysophosphatidylcholine. In conclusion, the current study suggested two pathways by which lysophosphatidylcholine regulates the expression of adhesion molecules, the lysophosphatidylcholine/nuclear factor-kappaB/adhesion molecule and lysophosphatidylcholine/GPK4/cAMP/protein kinase A/cAMP response element-binding protein/adhesion molecule pathways, emphasizing the importance of the lysophosphatidylcholine receptor in regulating endothelial cell function.

Histamine H1 and H2 receptors but not H4 receptors are upregulated during bone marrow regeneration

The role of histamine receptors in radiation-induced bone marrow (BM) regeneration was investigated with aspects of functional genomics. H1R and H2R mRNA expression increased during regeneration in both histidine decarboxylase knockout (HDC-/-) and wild type (HDC+/+) mice, though to a lesser extent in HDC-/- mice. H4R mRNA expression was downregulated in both groups. Mainly CD34+ cells were responsible for the elevation of intracellular histamine and HDC content in HDC+/+ BM cell populations. The differential changes in the expression of its receptors, and also its elevated levels in hematopoietic progenitors support the regulatory role of histamine in BM regeneration, that could be further explored by future gene expression studies.

GPR30: a novel indicator of poor survival for endometrial carcinoma

OBJECTIVE

This study was undertaken to evaluate the relationship between GPR30, classical steroidal receptor expression, and clinical outcome in patients with endometrial carcinoma.

STUDY DESIGN

Immunohistochemistry was used to investigate the expression of GPR30, estrogen, progesterone, epidermal growth factor receptors and Ki-67 in 47 consecutive consenting patients with endometrial carcinoma diagnosed between 1997 and 2001. Results were correlated with clinical and pathologic predictors of adverse outcome and survival.

RESULTS

GPR30 correlated positively with epidermal growth factor receptor (P = .005), but negatively with progesterone (P = .05) receptor expression. GPR30 overexpression occurred more frequently in tumors with deep myometrial invasion, high-grade, biologically aggressive histologic subtypes, and advanced stage. In patients with GPR30 overexpression, survival was significantly poorer (65.2% vs 100%, P = .005).

CONCLUSION

GPR30 represents an alternative estrogen-responsive receptor that is overexpressed in tumors where estrogen and progesterone receptors are downregulated, and in high-risk endometrial cancer patients with lower survival rates.

Expression of mRNA encoding G protein-coupled receptors involved in congestive heart failure--a quantitative RT-PCR study and the question of normalisation

Congestive heart failure (CHF) induces changes in the neurohumoral system and gene expression in viable myocardium. Several of these genes encode G protein-coupled receptors (GPCRs) involved in mechanisms which compensate for impaired myocardial function. We used real-time quantitative RT-PCR (Q-RT-PCR) to investigate the expression of mRNA encoding 15 different GPCRs possibly involved in CHF, and the effect of normalisation to GAPDH mRNA (GAPDH) or 18S rRNA (18S). CHF was induced in rats by coronary artery ligation, with sham-operated controls (Sham). After 6 weeks, mRNA expression in viable left ventricular myocardium was determined using both 18S and GAPDH as the normalisation standard. An apparent 30% reduction in GAPDH mRNA levels vs. 18S in CHF compared to Sham, although not significant in itself, influenced the interpretation of regulation of other genes.Thus, levels of mRNA encoding receptors for angiotensin II (AT(1)), endothelin (ET(A), ET(B)) and the muscarinic acetylcholine (mACh) receptor M(1) increased significantly in CHF only when normalised to GAPDH. Levels of mRNA encoding the mACh receptors M(3) and M(4) and the serotonin receptors 5-HT(2A) and 5-HT(4) increased, whereas alpha(1D)-adrenoceptor mRNA decreased in CHF irrespective of the normalisation standard. No significant change was detected for M2 and M5 mACh receptors or alpha(1A)-, alpha(1B)-, beta(1)- or beta(2)-adrenoceptors. Q-RT-PCR is a sensitive and powerful method to monitor changes in GPCR mRNA expression in CHF. However, the normalisation standard used is important for the interpretation of mRNA regulation.

[Changes of Smoothened expression during retinofugal pathway development in mouse embryos]

OBJECTIVE

To examine the change of Smoothened (Smo) expression in the retinofugal pathway and in the growth cones during the period of embryonic day 13 (E13) to E15.

METHODS

Smo expression in the chiasm and growth cones was observed by fluorescent immunostaining and retinal explant culture.

RESULTS

On E13 and E14, Smo was expressed moderately in the retina and optic disc, and in the corner of the retina, Smo expression was especially dense. On E13, Smo expression was detected in the optic nerves and ventral diencephalon, but only in the superficial region of the optic tract on E14. Smo was also detected in the stem and filopodia of the growth cones in the retinal explant culture during this period.

CONCLUSION

Smo expression changes in different developmental phases, suggesting that Smo might play a role in signal optic axon growth during the development of the retinofugal pathway.

Hypersusceptibility to Invasive Pneumococcal Infection in Experimental Sickle Cell Disease Involves Platelet‐Activating Factor Receptor

Children with sickle cell disease have a 600-fold increased incidence of invasive pneumococcal disease. Platelet-activating factor receptor (PAFr) mediates pneumococcal invasion, and up-regulation of PAFr on chronically activated endothelia could contribute to increased bacterial invasion. Mice transplanted with sickle cell bone marrow developed more extensive infection, and 57% died, compared with 16% of wild-type mice. Histopathological analysis revealed that sickle cell mice expressed significantly more PAFr on endothelia and epithelia. Pharmacological blockade or genetic deletion of PAFr protected sickle cell mice from mortality. We conclude that PAFr plays an important role in hypersusceptibility to pneumococcal infection in sickle cell disease.