Primary structure of the rat beta-2 adrenergic receptor gene

Tumor necrosis factor-α mediates the proliferation of rat C6 glioma cells via β-adrenergic receptors

In the present study, we observed that isoproterenol, a beta-adrenergic receptor (beta-AR) agonist, stimulated rat C6 glioma cell proliferation, while propranolol, a beta-AR blocker, greatly reduced the proliferative effect of TNF-alpha on C6 cells. The gene and protein expressions of both beta1- and beta2-ARs were enhanced in C6 cells after TNF-alpha treatment, and the increase in beta-AR was due to an increased number of binding sites and not due to increase in receptor affinity. We further showed that protein kinase C (PKC) was involved in the TNF-alpha-induced beta-AR expression. Collectively, our results indicate that TNF-alpha-induced proliferation in C6 glioma cells might be via the induction and activation of beta-ARs.

Cloning, pharmacological characterization, and polymorphism screening of the guinea pig beta(2)-adrenoceptor

In asthma, beta(2)-adrenoceptor agonist responsiveness has been associated with Arg16Gly and Gln27Glu polymorphisms of the beta(2)-adrenoceptor. Since the guinea pig is extensively used as an animal model for asthma, we investigated the occurrence of possible polymorphism of the guinea pig beta(2)-adrenoceptor. The guinea pig beta(2)-adrenoceptor coding region was amplified by sequence homology-based cloning. Homology of the translated protein with the human beta(2)-adrenoceptor was 88% with Ala at position 16 and Glu at position 27. Radioligand binding and cAMP- accumulation experiments of Chinese hamster ovary (CHO) cells transfected with the guinea pig beta(2)-adrenoceptor revealed a homogeneous population of functional receptors. Five degenerate single nucleotide polymorphisms were found within the beta(2)-adrenoceptor coding region of outbred Dunkin Hartley guinea pigs, at residues 354, 453, 483, 534 and 642. In conclusion, we have cloned the guinea pig beta(2)-adrenoceptor, which shows to be functional upon expression in a recombinant system and contains five single nucleotide polymorphisms dissimilar to human polymorphisms.

Expression and postnatal changes of adrenergic receptor subtype mRNA in rat submandibular glands

Adrenergic receptors (ARs) are involved in regulating saliva secretion and composition in salivary glands. Nine AR subtypes, including three alpha1-ARs (alpha1a-, alpha1b- and alpha1d-ARs), three alpha2-ARs (alpha2A-, alpha2B- and alpha2C-ARs) and three beta-ARs (beta1,beta2- and beta3-ARs), have been identified through molecular cloning. The five subtype genes, alpha1a-, alpha1b-, alpha2A-, beta1-, and beta2-ARs, were expressed in rat submandibular glands. In contrast, the other four subtype mRNAs, alpha1d-, alpha2B-, alpha2C- and beta3-ARs, were not detected by reverse transcription-polymerase chain reaction (RT-PCR). The steady-state mRNA expression for the five AR subtypes in rat submandibular glands was measured by quantitative competitive RT-PCR using synthetic DNA as internal standard at different stages of postnatal development. The relative rank order of AR subtype mRNA expression was alpha1a>beta2>beta1>alpha2A>alpha1b at all stages except that beta1- and alpha2A-subtypes were reversed at 2 weeks of age. The gene expression of alpha1a-AR subtype relative to total AR was low at 2 weeks of age and increased and reached a maximum at 6 weeks of age, whereas those patterns of alpha2A-, beta1- and beta2-AR subtypes were similar to each other and their gene expressions were high at 2 weeks of age and then decreased. On the other hand, the gene expression of alpha1b-AR subtype did not change over the different stages in relation to that of a housekeeping gene, glyceraldehyde 3-phosphate dehydrogenase, and to total AR. Although rat submandibular glands contain the five AR subtype mRNAs, distinct subtype-specific expression is evident.

Molecular cloning and functional characterization of a vasotocin receptor subtype that is expressed in the shell gland and brain of the domestic chicken

In chickens, oviposition is correlated with increased plasma levels of the neurohypophysial hormone vasotocin, and vasotocin stimulates contraction of uterine strips in vitro. A gene encoding a vasotocin receptor subtype that we have designated the VT1 receptor was cloned from the domestic chicken. The open reading frame encodes a 370-amino acid polypeptide that displays seven segments of hydrophobic amino acids, typical of guanine nucleotide-protein-coupled receptors. Other structural features of the VT1 receptor include two potential N-linked glycosylation sites in the extracellular N-terminal region, a conserved aspartic acid in transmembrane domain 2 that is found in nearly all guanine nucleotide-protein-coupled receptors, and two potential protein kinase C phosphorylation sites in the third intracellular loop and C-terminal tail. Expressed VT1 receptors in COS7 cells bind neurohypophysial hormones with the following rank order of potency: vasotocin congruent with vasopressin > oxytocin congruent with mesotocin > isotocin. In addition, the expressed VT1 receptor mediates vasotocin-induced phosphatidylinositol turnover and Ca(2+) mobilization. In the chicken, expression of VT1 receptor gene transcripts is limited to the shell gland (uterus) and the brain. Thus, the VT1 receptor that we have cloned may mediate contractions of the shell gland during oviposition and activate reproductive behaviors known to be stimulated by vasotocin in lower vertebrates.

Analysis of the AU-rich elements in the 3'-untranslated region of beta 2-adrenergic receptor mRNA by mutagenesis and identification of the homologous AU-rich region from different species

The 35000-Mr beta-adrenergic receptor mRNA binding protein (beta ARB) is induced by beta-adrenergic agonists and binds to G-protein-linked receptor mRNAs that exhibit agonist-induced destabilization. Recently, we identified a 20-nucleotide, AU-rich region in the 3'-untranslated region of the hamster beta 2-adrenergic receptor mRNA consisting of an AUUUUA hexamer flanked by U-rich regions, which constitutes the binding domain for beta ARB. U to G substitution in the hexamer region attenuates the binding of beta ARB, whereas U to G substitution of hexamer and flanking U-rich domains abolishes binding of beta ARB and stabilizes beta 2-adrenergic receptor mRNA levels in transfectant clones challenged with either isoproterenol or cyclic AMP. In the study presented here, we mutated the 20-nucleotide ARE region to establish the minimal AU-rich sequence required for beta ARB binding. U to G substitutions of flanking poly(U) regions and of the hexamer established the nature of the binding properties. Using various mutants, we demonstrated also that binding of beta ARB correlates with the extent of destabilization of beta 2-adrenergic receptor mRNA in response to agonist stimulation. High-affinity binding of hamster, rat, mouse, porcine, and human ARE sequences to beta ARB was revealed by SDS-polyacrylamide gel electrophoresis following UV-catalyzed cross-linking and by gel mobility shift assays. Further, beta ARB was shown to bind more avidly to the 20-nucleotide ARE region than to well-established mRNA destablization sequences of tandem repeats of five pentamers. Thus, for beta 2-adrenergic receptor, mRNA destabilization likely occurs via conserved AU-rich elements present in the 3'-untranslated regions of receptor mRNAs.

Transcriptional and posttranscriptional regulation of beta(2)-adrenergic receptor gene in rat liver during sepsis

Changes in beta(2)-adrenergic receptor (beta(2)-AR) gene expression in the rat liver during different phases of sepsis were studied. Sepsis was induced by cecal ligation and puncture (CLP). Septic rats exhibit two metabolically distinct phases: an initial hyperglycemic (9 h after CLP; early sepsis) followed by a hypoglycemic phase (18 h after CLP; late sepsis). The [(3)H]dihydroalprenolol binding studies show that the density of beta(2)-AR was decreased by 12 and 35% during the early and late phases of sepsis, respectively. Western blot analyses depict that the beta(2)-AR protein level was reduced by 37 and 72% during early and late sepsis, respectively. The reverse transcription polymerase chain reaction and Southern blot analyses reveal that the steady-state level of beta(2)-AR mRNA was decreased by 37% during early phase and 77% during late phase of sepsis. Nuclear run-off assays show that the rate of transcription of beta(2)-AR mRNA was reduced by 36% during early sepsis and 64% during late sepsis. The stability assays indicate that the half-life of beta(2)-AR mRNA was shortened by 21 and 50% during the early and late phases of sepsis, respectively, indicating that the rate of degradation of beta(2)-AR mRNA was progressively enhanced during sepsis. These findings demonstrate that the beta(2)-AR gene was underexpressed in the liver during the progression of sepsis, and, furthermore, the underexpression of the beta(2)-AR gene was the result of a reduction in the rate of transcription coupled with an enhancement in the rate of degradation of beta(2)-AR gene transcripts. Thus our findings that the transcriptional and posttranscriptional regulation of beta(2)-AR gene associated with decreases in beta(2)-AR number and its protein expression may provide a molecular mechanistic explanation for the development of hypoglycemia during the late stage of sepsis.

Identification of a glucocorticoid response element in the rat beta2-adrenergic receptor gene

Regulation of beta2-adrenergic receptor (beta2AR) levels by glucocorticoids is a physiologically important mechanism for altering beta2AR responsiveness. Glucocorticoids increase beta2AR density by increasing the rate of beta2AR gene transcription, but the cis-elements involved have not been well characterized. We now show that one of six potential glucocorticoid response elements (GREs) in the 5'-flanking region of the rat beta2AR gene is necessary for glucocorticoid-dependent stimulation of receptor gene expression. Using a nested set of deletion fragments of the rat beta2AR gene 5'-flanking region fused to a luciferase reporter gene, glucocorticoid-dependent induction of reporter gene expression in HepG2 cells was localized to a region between positions -643 and -152, relative to the transcription initiation site. In electrophoretic mobility shift assays, a double-stranded oligonucleotide incorporating a near-consensus GRE from this region (positions -379 to -365) formed complexes with the human recombinant glucocorticoid receptor, as well as with nuclear protein from dexamethasone-treated HepG2 cells. Mutation of a single base within this GRE sequence greatly diminished interaction of the mutated oligonucleotide with the human recombinant glucocorticoid receptor. The functional activity of the GRE was characterized using a luciferase reporter construct driven by a minimal thymidine kinase promoter. In HepG2 cells transfected with constructs containing the GRE, dexamethasone increased reporter gene expression approximately 3-fold, whereas a dexamethasone effect was not observed with constructs lacking the GRE. Taken together, these findings show that a GRE located at positions -379 to -365 in the 5'-flanking region of the rat beta2AR gene mediates glucocorticoid stimulation of beta2AR gene transcription.

Differential spatiotemporal alterations in adrenoceptor mRNAs and binding sites in cerebral cortex following spreading depression: selective and prolonged up-regulation of alpha1B-adrenoceptors

Noradrenaline, an important transmitter in the CNS, is involved in cerebral plasticity and functional recovery after injury. Experimental brain injury, including KCl application onto the brain surface, induces a slow-moving cortical depolarization/depression wave called cortical spreading depression (CSD). Interestingly, CSD does not produce neuronal damage but can protect cortical neurons against subsequent neurotoxic insults, although the mechanisms involved are unknown. This study examined the status of alpha- and beta-adrenoceptors (ARs) in cerebral cortex following CSD. Anesthetized rats had unilateral CSD induced by a 10-min topical application of KCl to the frontoparietal cortex and were killed at various times thereafter. Levels of alpha1-, alpha2-, beta1-, and beta2-AR mRNA and binding were examined using in situ hybridization histochemistry and radioligand autoradiography. Levels of alpha1b-AR mRNA in the affected neocortex were significantly increased by 20-40% at 1, 2, and 7 days (P </= 0.01) compared with contralateral levels, but were not significantly above control values at 2 and 4 weeks after CSD induction. Cortical alpha1B-AR binding sites were also increased by 45-65% 1 and 2 weeks (P </= 0.01) after CSD in a similar, but delayed, profile to alpha1b-AR mRNA. CSD rapidly increased beta1-AR mRNA by 45% at 1 h (P </= 0.01) and produced a delayed decrease of 25% in alpha2a-AR mRNA at 2 days and 1 week (P </= 0.05), but had no effect on corresponding levels of binding sites. In contrast, CSD had no effect on the remaining AR-subtype mRNAs or binding levels in neocortex under identical conditions. These results reveal a long-term up-regulation of alpha1B-ARs induced by an acute cortical stimulation/depression. Subtype-selective responses of ARs to CSD reflect an important differential regulation of expression of each receptor in vivo and suggest that alpha1B-ARs are particularly likely to be involved in cortical adaptive responses to physical injury at both local and distant locations.

Cloning, genomic organization and chromosomal assignment of the mouse p190-B gene

The p190 family of GTPases consists of at least two different isoforms both containing an N-terminal GTPase and a C-terminal Rho GAP domain. Here we have isolated and characterized genomic and cDNA clones spanning the entire coding region of the mouse p190-B gene. Genomic data were obtained by sequencing plasmid subclones of two overlapping mouse genomic phage clones. Interestingly, a single 3.9 kb exon was found to contain approx. 80% of the coding region of the mouse p190-B protein (amino acid residues 1-1238) including the 5'-untranslated region, the N-terminal GTPase domain and a middle domain of unknown function. Missing from this exon, however, was the C-terminal Rho GAP domain, which was cloned from mouse brain mRNA using reverse transcriptase polymerase chain reaction. Comparison of the mouse with the human p190-B proteins revealed that approx. 97% of the amino acid residues were identical. Northern analysis of total RNA from a variety of mouse tissues detected ubiquitous expression of two p190-B transcripts of 4.0 and 6.8 kb in size. Analysis of two multilocus genetic crosses localized the mouse gene, Gfi2, to a position on chromosome 12, consistent with the mapping of the human gene to a position of conserved synteny on chromosome 14. The high level of sequence homology between the human and the mouse suggests that there is a strong selective pressure to maintain the p190-B protein structure.

Expression of beta3-adrenoceptors in rat detrusor smooth muscle

PURPOSE

To investigate the expression of beta-adrenoceptor (AR) subtypes responsible for detrusor smooth muscle relaxation.

MATERIALS AND METHODS

Isolated rat detrusor smooth muscle was examined by tension measurement and reverse transcription polymerase chain reaction (RT-PCR).

RESULTS

Norepinephrine (NE), epinephrine (EP) and isoproterenol (ISO) were found to relax the detrusor muscle pre-contracted by 6 x 10(-7) M carbachol in the presence of 10(-6) M phentolamine. NE relaxed the detrusor muscle as potently as EP. This potency order (NE=EP) thus indicated the beta-ARs of the rat detrusor muscle to possibly be a beta1 subtype. However, in the presence of 10(-6) M propranolol, beta1- and beta2- but not beta3-AR antagonist, NE showed a more potent relaxation than EP. This observation indicated that the rat detrusor muscle also possesses beta3-AR. RT-PCR revealed all three subtypes of beta-AR mRNA, namely beta1-, beta2- and beta3-AR mRNA, to be expressed in rat detrusor smooth muscle cells.

CONCLUSION

We concluded that beta3-ARs exist in rat detrusor smooth muscle based on both pharmacological and molecular biological studies. Based on these findings, beta-ARs of rat detrusor smooth muscle are considered to be mixed populations consisting of three subtypes which play an important role in relaxing smooth muscle in response to catecholamines.

Distribution of alpha 1a-, alpha 1b- and alpha 1d-adrenergic receptor mRNA in the rat brain and spinal cord

The technique of in situ hybridization with specific ribonucleotide probes was used to determine the distribution patterns of mRNA encoding the alpha 1a-, alpha 1b- and alpha 1d-adrenoceptor (AR) subtypes in rat brain and spinal cord. The expression pattern of alpha 1a-AR mRNA has not been reported previously, and was found to be widespread throughout the rat central nervous system. High levels were found in regions of the olfactory system, several hypothalamic nuclei, and regions of the brainstem and spinal cord, particularly in areas related to motor function. Regions expressing moderate levels of mRNA for this receptor were the septum, bed nucleus of the stria terminalis, cerebral cortex, amygdala, cerebellum and pineal gland. Low expression levels were detected in the hippocampal formation. Most nuclei in the basal ganglia and thalamus expressed extremely low or undetectable levels of alpha 1a-AR mRNA. The expression patterns of the alpha 1b- and alpha 1d-AR mRNAs were similar to those described using oligonucleotide probes in earlier studies. High expression of alpha 1b-AR mRNA was noted in the pineal gland, most thalamic nuclei, lateral nucleus of the amygdala and dorsal and median raphe nuclei. Moderate expression levels were noted throughout the cerebral cortex, and in some olfactory, septal, and brainstem regions. The distribution of alpha 1d-AR mRNA was the most discrete of the three receptors examined. Expression was strong in the olfactory bulb, cerebral cortex, hippocampus, reticular thalamic nucleus, regions of the amygdala, motor nuclei of the brainstem, inferior olivary complex and spinal cord. Comparison of the distributions of the alpha 1a-, alpha 1b- and alpha 1d-AR mRNA suggests unique functional roles for each of these receptors.

DNA elements and protein factors involved in the transcription of the beta 2-adrenergic receptor gene in rat liver. The negative regulatory role of C/EBP alpha

Primer extension and RNase protection analyses of the rat beta 2-adrenergic receptor (beta 2AR) gene identify two transcription start points at -64 and -220 nt, respectively. Transient transfections of putative promoter/pCAT constructs into DDT1 MF-2 cells indicate that fragments -36 to -100 (PI) and -186 to -312 (P2) are sufficient to promote transcription, whereas -911 to -1122 contains a negative regulatory element(s). RNase protection analysis of the 3' untranslated region (3'-UTR) indicates the presence of two transcripts with 3'-UTR of 111 and 604 nt exclusive of the poly(A+) tails. Northern blots of beta 2AR mRNA using full-length and partial cDNA probes indicate that a major 2.2 kb and a minor 1.6 kb species arise from the use of alternative promoters as well as different polyadenylation signals. DNase I footprinting and DNA mobility shift assays (DMSA) using rat liver nuclear extracts identify a number of transcription factors binding to sequence elements within or upstream from P1 and P2, including Spl, CRE, CPl, AP-2, NF-1, NF-kappa B, and C/EBP. Supershift assays using antibodies against C/EBP alpha and C/EBP beta and mutational analyses indicate that the protein binding to the C/EBP consensus recognition site at -925 to -933 is C/EBP alpha. The activity of promoter/CAT constructs containing the C/EBP recognition site is significantly decreased by cotransfection of C/EBP alpha but not C/EBP alpha but not C/EBP beta into either DDT1 MF-2 cells or primary rat hepatocytes. Partial hepatectomy causes a transient decrease in C/EBP alpha, as measured by DMSA, and an increase in beta 2 AR mRNA levels and rate of transcription in the remnant liver. Thus, derepression via C/EBP alpha is likely involved in the up-regulation of beta 2AR in the regenerating rat liver.

Structural and functional analysis of the 5'-flanking region of the rat beta 2-adrenergic receptor gene

We have analyzed 3.4 kb of DNA from the 5'-flanking region of the rat beta 2-adrenergic receptor gene and assessed its promoter activity in A549 cells, a human lung adenocarcinoma cell line. A single transcription start site was identified approx. 223 bp upstream of the ATG start codon. A549 cells were transfected with luciferase reporter plasmids containing segments of the rat beta 2-adrenergic receptor 5'-flanking region. Our results suggest that both positive and negative cis-acting regulatory sequences are present in the 5'-flanking region of the rat beta 2-adrenergic receptor gene.

Sequence of the 5' regulatory domain of the gene encoding the rat beta 2-adrenergic receptor

Restriction mapping and sequence analysis of the gene encoding the rat beta 2 adrenergic receptor (beta 2AR) revealed an error affecting most of the 5'-flanking domain, located between -192 and -2245 bp in the only published sequence of this gene [Buckland et al., Nucleic Acids Res. 18 (1990) 682]. The correct sequence lacks a TATA box, contains 67% G + C residues in the first 500 nucleotides upstream from the start codon, and contains putative glucocorticoid, thyroid hormone and cAMP-response elements.

Regulation of the beta 2-adrenergic receptor and its mRNA in the rat lung by dexamethasone

Glucocorticoids increase beta 2-adrenergic responsiveness and receptor density in the lung, but the underlying mechanisms have not been clearly elucidated. To determine whether changes in beta 2-adrenergic receptor gene expression are involved in vivo, we measured beta 2-adrenergic receptor mRNA levels and beta 2-adrenergic receptor density in lungs from Sprague-Dawley rats treated with a daily injection of dexamethasone (1 mg/kg subcutaneously) for 1, 3, or 7 days. Animals were sacrificed either 2 or 24 h after receiving the last injection. beta 2-Adrenergic receptor mRNA levels were significantly (p < .05) elevated compared to saline-treated controls in the lungs of animals sacrificed 2 h after dexamethasone injection for 1 day (174 +/- 12%), 3 days (236 +/- 18%), and 7 days (220 +/- 11%). Receptor mRNA levels measured 24 h after dexamethasone injection did not differ significantly from the control group. Induction of beta 2-adrenergic receptor mRNA by dexamethasone was transient, since no significant cumulative or sustained increase in receptor mRNA levels was observed during the study period. Treatment with dexamethasone increased beta 2-adrenergic receptor density as expected, but no significant increase in receptor density was detected until 24 h after the third daily injection of dexamethasone, when levels reached 2045 +/- 150 fmol/mg protein compared to 1292 +/- 34 fmol/mg protein in the control group. Receptor density then remained at this elevated level through 7 days of treatment. These results show that dexamethasone up-regulates both the beta 2-adrenergic receptor and its mRNA in vivo in the lung. The induction of beta 2-adrenergic receptor mRNA levels indicates that glucocorticoids may regulate receptor density in the lung through modulation of gene expression. However, the difference between the time course of induction for the beta 2-adrenergic receptor and its mRNA suggests that additional translational or post-translational mechanisms may also be involved.

The evolutionary divergence of neurotransmitter receptors and second-messenger pathways

Members of the superfamily of G-protein-coupled neurotransmitter receptors have a conserved secondary structure, a moderate and reasonably steady rate of sequence change, and usually lack introns within the coding sequence. These properties are advantageous for evolutionary studies. The duplication and divergence of the genes in this gene family led to the formation of distinct neurotransmitter pathways and may have facilitated the evolution of complex nervous systems. I have analyzed this evolutionary divergence by quantitative multiple sequence alignment, bootstrap resampling, and statistical analysis of 49 adrenergic, muscarinic cholinergic, dopamine, and octopamine receptor sequences from 12 animal species. The results indicate that the first event to occur within this gene family was the divergence of the catecholamine receptors from the muscarinic acetylcholine receptors, which occurred prior to the divergence of the arthropod and vertebrate lineages. Subsequently, the ability to activate specific second-messenger pathways diverged independently in both the muscarinic and the catecholamine receptors. This appears to have occurred after the divergence of the arthropod and vertebrate lineages but before the divergence of the avian and mammalian lineages. However, the second-messenger pathways activated by adrenergic and dopamine receptors did not diverge independently. Rather, the ability of the catecholamine receptors to bind to specific ligands, such as epinephrine, norepinephrine, dopamine, or octopamine, was repeatedly modified in evolutionary history, and in some cases was modified after the divergence of the second-messenger pathways.

Association of hepatic beta 2-adrenergic receptor gene transcript destabilization during postnatal development in the Sprague-Dawley rat with a M(r) 85,000 protein that binds selectively to the beta 2-adrenergic receptor mRNA 3'-untranslated region

In the liver, transcript destabilization contributes to the decrease in steady-state levels of beta 2-adrenergic receptor mRNA that occurs during early postnatal development in the rat. From genomic DNA, polymerase chain reaction (PCR) was used to amplify a 718-basepair (bp) fragment of the beta 2-adrenergic receptor gene including the entire 3'-untranslated region. Results from SDS-gel electrophoresis and autoradiography demonstrated a M(r) 85,000 cellular factor present in postnatal day 60, but not fetal day 18 rat liver that was ultraviolet (UV) light-crosslinked to in vitro transcribed beta 2-adrenergic receptor RNA 3'-untranslated region. Unlabeled beta 2-adrenergic receptor RNA 3'-untranslated region, but not mouse beta-actin RNA, competed with labeled beta 2-adrenergic receptor RNA 3'-untranslated region for binding to the M(r) 85,000 protein. Cross-linking of the beta 2-adrenergic receptor RNA 3'-untranslated region to the M(r) 85,000 protein was inhibited by the ribohomopolymer poly(U), with poly(A), poly(C) and poly(G) having little or no effect. Thus, a M(r) 85,000 protein has been identified in adult male rat liver that may interact with U-rich sequences in the 3'-untranslated region of the beta 2-adrenergic receptor mRNA and may account for the decreased stability of hepatic beta 2-adrenergic receptor gene transcripts that occurs during development.

Noradrenergic regulation of cholinergic differentiation

When the sympathetic nerves that innervate rat sweat glands reach their targets, they are induced to switch from using norepinephrine as their neurotransmitter to acetylcholine. Catecholamines (such as norepinephrine) released by nerves growing to the sweat gland induce this phenotypic conversion by stimulating production of a cholinergic differentiation factor [sweat gland factor (SGF)] by gland cells. Here, culture of gland cells with sympathetic, but not sensory, neurons induced SGF production. Blockage of alpha 1- or beta-adrenergic receptors prevented acquisition of the cholinergic phenotype in sympathetic neurons co-cultured with sweat glands, and sweat glands from sympathectomized animals lacked SGF. Thus, reciprocal instructive interactions, mediated in part by small molecule neurotransmitters, direct the development of this synapse.

Sequence of the 3'-noncoding region of the luteinizing hormone receptor gene and identification of two polyadenylation domains that generate the major mRNA forms

We present 6.2 kb of the 3'-noncoding region sequence of the rat luteinizing hormone receptor (LHR) gene and identification of two functional polyadenylation (pA) domains, H1 (nt 2368-2491) and H2 (nt 5579-5768) responsible for 3'-end processing of the 2.6/2.3 kb and the 5.8 kb LHR mRNA, respectively. Two identical copies of pA elements AAUAUA in H1 and of AAUAAA in H2 account for micro-heterogeneous poly(A) addition at each of the two pA regions. Both LH holoreceptor and major splice variant form B (lacking the first 266 bp of exon 11) are identified in H1-terminated (2.6 kb and 2.3 kb) and H2-terminated (5.8 kb) mRNA transcripts. A rodent repetitive DNA LINE R domain 3' of H1 within the major 5.8 kb species and a B2 element downstream of H2 were identified. Alignment of the 3'-noncoding region of LHR with TSH, FSH and beta 2-adrenergic receptors indicate that H1 pA signal is unique to the LHR and may represent an insertion domain.

Human mu opiate receptor. cDNA and genomic clones, pharmacologic characterization and chromosomal assignment

A human mu opiate receptor cDNA has been identified from a cerebral cortical cDNA library using sequences from the rat mu opiate receptor cDNA. The human mu opiate receptor (h mu OR1) shares 95% amino acid identity with the rat sequence. The expressed mu OR1 recognized tested opiate drugs and opioid peptides in a sodium- and GTP-sensitive fashion with affinities virtually identical to those displayed by the rat mu opiate receptor. Effects on cyclic AMP are similar to those noted for the rat mu opiate receptor. An 18 kb genomic clone hybridizing with the h mu OR1 cDNA contains 63 and 489 bp exonic sequences flanked by splice donor/acceptor sequences. Analysis of hybridization to DNA prepared from human rodent hybrid cell lines and chromosomal in situ hybridization studies indicate localization to 6q24-25. An MspI polymorphism, producing a 3.7 kb band, may prove useful in assessing this gene's involvement in neuropsychiatric disorders involving opiatergic systems.

The rhesus macaque beta 1-adrenergic receptor gene: structure of the gene and comparison of the flanking sequences with the rat beta 1-adrenergic receptor gene

We have cloned the gene for the rhesus macaque beta 1-adrenergic receptor. In addition to the protein coding block, we have sequenced its 5' (1424 bp) and 3' (1534 bp) flanking regions and aligned them with comparable sections of the rat beta 1-adrenergic receptor gene. The rhesus macaque gene contains a 1440 bp open reading frame which codes for a deduced protein of 480 amino acids that is 95% and 89% similar to the human and rat beta 1-adrenergic receptors, respectively. The rhesus macaque beta 1-adrenergic receptor contains conserved sites for potential N-linked glycosylation and cAMP-dependent protein kinase phosphorylation identified within the human and rat receptors, but differs in the structure and length of the third cytoplasmic loop. The 400 bases of 5' flanking sequence proximal to the protein coding block are highly conserved (84% similarity) between the rat and rhesus macaque genes. The entire 3' flanking sequence, which extends beyond two potential polyadenylation sites at 1050 and 1337 bp relative to the translation termination codon, is also highly conserved between the two species. Comparison of the flanking sequences of the two species reveals conserved regulatory sequences which may be important for beta 1-adrenergic receptor expression and transcriptional modulation.

mu opiate receptor: cDNA cloning and expression

mu opiate receptors recognize morphine with high affinity. A 2.1-kb rat brain cDNA whose predicted translation product displays 63% identity with recently described delta and kappa opiate receptor sequences was identified through polymerase chain reaction and cDNA homology approaches. This cDNA recognizes a 10.5-kb mRNA that is expressed in thalamic neurons. COS-cell expression confers naloxonazine-, Na(+)-, and GTP-sensitive binding of mu but not delta or kappa opioid ligands. Expressing cells bind morphine, [D-Ala2,N-methyl-Phe4,glyol5]enkephalin (DAMGO), and [D-Ala2,D-Leu5]enkephalin (DADLE) with nanomolar or subnanomolar affinities, defining a mu opiate receptor that avidly recognizes analgesic and euphoric opiate drugs and opioid peptides.

Cellular localization of messenger RNA for beta-1 and beta-2 adrenergic receptors in rat brain: an in situ hybridization study

Selective, 35S-labeled, oligonucleotide probes were designed from sequences of the rat beta-1 and beta-2 adrenoceptor messenger RNAs for use in situ hybridization experiments on sections of unfixed rat brain and spinal cord. After hybridized sections were exposed to film or dipped in autoradiographic emulsion, specific and selective labeling patterns characteristic for each receptor messenger RNA and region of the central nervous system were observed. For example, labeling for beta-1 messenger RNA was found in the anterior olfactory nucleus, cerebral cortex, lateral intermediate septal nucleus, reticular thalamic nucleus, oculomotor complex, vestibular nuclei, deep cerebellar nuclei, trapezoid nucleus, abducens nucleus, ventrolateral pontine and medullary reticular formations, the intermediate gray matter of the spinal cord and in the pineal gland, while beta-2 messenger RNA labeling was strongest in the olfactory bulb, piriform cortex, hippocampal formation, thalamic intralaminar nuclei and cerebellar cortex. In some of these regions the beta-1 labeling seemed mainly confined to the cell nucleus. Whether or not this apparently nuclear labeling is specific, i.e. indicates synthesis of beta-1 receptor, remains to be established. However, all labeling patterns described disappeared when excess unlabeled probes were added to their respective radiolabeled probes or when sense probes were employed. Since the in situ method labels only cell bodies that produce the messenger RNA for these two beta receptor subtypes, a comparison between these maps and those of past autoradiographic studies mapping the location of central beta receptors using drugs as radioligands may produce further insights regarding the pre- and postsynaptic localization of these receptors in the various parts of the central nervous system circuitry.

Distributions of mRNAs for alpha-2 adrenergic receptor subtypes in rat brain: an in situ hybridization study

Selective 35S-labeled oligonucleotide probes were designed to sequences of the rat alpha-2A (RG20), alpha-2B (RNG), and alpha-2C (RG10) adrenoreceptor mRNAs for use in in situ hybridization experiments on sections of unfixed rat brain, spinal cord and kidney. After hybridized sections were exposed to film or dipped in autoradiographic emulsion, specific and selective labeling patterns characteristic for each probe and region of the central nervous system were observed. Alpha-2A mRNA labeling was most pronounced in neurons in layer six of the cerebral cortex, hypothalamic paraventricular nucleus, reticular thalamic nucleus, pontine nuclei, locus coeruleus, vestibular nuclei, trapezoid nuclei, deep cerebellar nuclei, nucleus tractus solitarii, ventrolateral medullary reticular formation, and the intermediolateral cell column of the thoracic spinal cord. In some of these locations, the receptor mRNA, in all probability, is present in noradrenaline and perhaps adrenaline neurons. The alpha-2B probe, which primarily labels the kidney, gave only a very light signal in the thalamus in the central nervous system after extended exposure times. Alpha-2C mRNA labeling was primarily observed in the olfactory bulb, cerebral cortex, islands of Calleja, striatum, hippocampal formation, cerebellar cortex, and dorsal root ganglia. Labeling patterns disappeared when excess unlabeled probes were added to their respective radiolabeled probes, or when sense probes were employed. When a hybrid antisense probe homologous to all three alpha-2 probes was used, labeling patterns also disappeared. The present study therefore justifies the pharmacological subclassification of alpha-2 receptors by providing anatomical evidence for specific and selective cell groups in the rat central nervous system containing mRNA for three alpha-2 receptor subtypes.

Predominant expression of beta 1-adrenergic receptor in the thick ascending limb of rat kidney. Absolute mRNA quantitation by reverse transcription and polymerase chain reaction

Beta 1- and beta 2-adrenergic receptor (beta-ARs) expression in the thick ascending limb of rat kidney was studied at the level of mRNA and receptor coupling to adenylyl cyclase. Absolute quantitation of beta 1- and beta 2-AR mRNAs in microdissected nephron segments was performed with an assay based on reverse transcription and polymerase chain reaction, using in vitro transcribed mutant RNAs as internal standards. In the cortical thick ascending limb (CTAL), the number of mRNA molecules/mm of tubular length was 2,806 +/- 328 (n = 12) for beta 1-AR and 159 +/- 26 for beta 2-AR (P < 0.01). Lower levels were obtained in the medullary thick ascending, beta 1-AR mRNA still being predominant. The pharmacological properties of beta-ARS was also studied in the CTAL. Cyclic AMP accumulation was stimulated by beta-agonist with a rank order of potency of isoproterenol > norepinephrine > epinephrine. This observation, and the higher efficiency of a beta 1 than of a beta 2 antagonist to inhibit isoproterenol-induced cAMP accumulation, establish the typical beta 1-AR sensitivity of the CTAL. No detectable contribution of atypical or beta 3-ARs to adenylyl cyclase stimulation could be found. In conclusion, this study, which shows markedly different levels of beta 1- and beta 2-AR mRNAS in the CTAL, provides a molecular basis for the predominant expression of the beta 1 receptor subtype in this nephron segment.

Rapid inverse changes in alpha 1B- and beta 2-adrenergic receptors and gene transcripts in acutely isolated rat liver cells

In vitro incubation of hepatocytes acutely isolated from adult male rats leads to a rapid conversion of the adrenergic activation of glycogenolysis from an alpha 1-receptor (alpha 1AR) to a beta 2-receptor (beta 2AR) mediated response within 4 h. In order to understand the underlying mechanism, we examined time-dependent changes in alpha 1- and beta 2-adrenergic activation of glycogenolysis and second messenger systems, the cellular density and affinity of alpha 1AR and beta 2AR, and the steady state levels of alpha 1BAR and beta 2AR mRNAs. Incubation of hepatocytes for 4 h resulted in a decrease in phosphorylase activation and inositol 1,4,5 trisphosphate accumulation in response to phenylephrine, a 40% decrease in alpha 1AR density, and a 70% decrease in alpha 1BAR mRNA levels. Incubation of hepatocytes for 4 h also resulted in the emergence of a phosphorylase response to isoproterenol, an increase in isoproterenol-induced but not in glucagon- or forskolin-induced cAMP accumulation, no significant change in beta 2AR density, and a twofold increase in beta 2AR mRNA levels. Exposure of cells to cycloheximide, 2 microM throughout the 4 h incubation, prevented the emergence of the phosphorylase response to isoproterenol and reduced beta 2AR densities, while the decrease in alpha 1AR density was not affected and the decrease in phosphorylase activation by phenylephrine was attenuated. The results indicate that dissociation of rat liver cells triggers a rapidly developing decrease in alpha 1BAR mRNA and increase in beta 2AR mRNA levels and corresponding inverse changes in the synthesis of alpha 1BAR and beta 2AR which account, at least in part, for the rapid conversion from alpha 1- to beta 2-adrenergic glycogenolysis.