Prisoners as Patients: The Opioid Epidemic, Medication-Assisted Treatment, and the Eighth Amendment

This article argues that correctional institutions violate the Eighth Amendment when they refuse to establish MAT programs and prevent doctors from exercising medical judgment to properly treat incarcerated people with OUD.

A haplotype of the human CXCR1 gene protective against rapid disease progression in HIV-1+ patients

Chemokines and their receptors are key factors in the onset and progression of AIDS. Among them, accumulating evidence strongly indicates the involvement of IL-8 and its receptors, CXCR1 and CXCR2, in AIDS-related conditions. Through extensive investigation of genetic variations of the human CXCR1-CXCR2 locus, we identified a haplotype of the CXCR1 gene (CXCR1-Ha) carrying two nonsynonymous single nucleotide polymorphisms, CXCR1_300 (Met to Arg) in the N terminus extracellular domain and CXCR1_142 (Arg to Cys) in the C terminus intracellular domain. Transfection experiments with CXCR1 cDNAs corresponding to the CXCR1-Ha and the alternative CXCR1-HA haplotype showed reduced expression of CD4 and CXCR4 in CXCR1-Ha cells in human osteosarcoma cells as well as in Jurkat and CEM human T lymphocytes. Furthermore, the efficiency of X4-tropic HIV-1(NL4-3) infection was significantly lower in CXCR1-Ha cells than in CXCR1-HA cells. The results were further confirmed by a series of experiments using six HIV-1 clinical isolates from AIDS patients. A genetic association study was performed by using an HIV-1(+) patient cohort consisting of two subpopulations of AIDS with extreme phenotypes of rapid and slow progression of the disease. The frequency of the CXCR1-Ha allele is markedly less frequent in patients with rapid disease onset than those with slow progression (P = 0.0003). These results provide strong evidence of a protective role of the CXCR1-Ha allele on disease progression in AIDS, probably acting through modulation of CD4 and CXCR4 expression.

Nitric oxide synthase 1 as a potential modifier gene of decline in lung function in patients with cystic fibrosis

BACKGROUND

The severity of lung disease varies widely in patients with cystic fibrosis (CF) who have the same type of mutations of the cystic fibrosis transmembrane regulator (CFTR) gene, suggesting involvement of "modifier" genes. The nitric oxide synthase 1 (NOS1) gene is a candidate for this role because exhaled nitric oxide (NO) is reduced in patients with CF and NOS1 activity contributes to transepithelial ionic transport, immune defence, and non-specific inflammation of the airways.

METHODS

Dinucleotide GT repeat polymorphism was studied in the 5' untranslated region of the NOS1 gene, immediately upstream from the transcription initiation site, in 59 patients with CF and 59 healthy controls.

RESULTS

Nineteen alleles of the NOS1 gene were identified according to the number of GT repeats (from 18 to 36) in the 5 untranslated region. Exhaled NO levels were significantly correlated with the number of GT repeats. Patients with CF who had the NOS1 genotype associated with high NO production had a slower decline in lung function during the 5 year follow up period. There was no confounding effect of age, chronic bacterial colonisation of the airway, or CFTR genotype.

CONCLUSIONS

These data suggest a possible link between the NOS1 gene locus and the rate of decline in lung function in patients with CF.

Quantification of static and dynamic supraglottic activity

For estimating supraglottic compression in disordered voice production, categorical rating scales of true vocal fold coverage by supraglottic structures are the current standard. Quantification of change in the position of supraglottic structures compared to no supraglottic activity would be a better method for distinguishing between and within voice-disordered groups. This study developed a method for quantifying static supraglottic activity and extent of false vocal fold (FVF) motion during dynamic supraglottic activity. Twelve control participants and 12 individuals with voice disorders (6 with complaints of vocal fatigue and 6 with vocal fold nodules) were enrolled in the study. These individuals participated in a transnasal fiberoptic laryngeal examination in which various speech tasks were recorded. Single-frame images were selected to represent the positions of minimum and maximum supraglottic compression for each speech task. Two individuals rated these single-frame images using a categorical rating scale. Two other individuals measured the anterior-to-posterior (A-P) distance, vocal fold length, and vocal fold area. A-P and FVF compression were derived from these three measures. Reliability was demonstrated between judges for the ratings and between and within judges for the measures. Significant differences in normalized static supraglottic compression measures corresponded to the rating scale categories. Significant differences in normalized dynamic supraglottic compression measures corresponded to the differences in category ratings between minimum and maximum compression. Using the normalized measures, the voice-disordered groups demonstrated significantly greater static A-P compression (t test, p < .03) than did the control participants. These results suggest that static supraglottic activity may be diagnostic of voice disorder. Normalized dynamic FVF compression ratios were not significantly different between groups. This supports a previous hypothesis that dynamic supraglottic activity serves as an articulatory function at the level of the larynx and is part of the linguistic/phonemic system, rather than evidence of disordered laryngeal function.

Pharmacological Properties of Peptides Derived from Stromal Cell-Derived Factor 1: Study on Human Polymorphonuclear Cells

Small compounds capable of blocking the stromal cell-derived factor 1 (SDF-1) receptor CXCR4 may be potentially useful as anti-inflammatory, antiallergic, immunomodulatory, and anti-human immunodeficiency virus (HIV) agents. SDF-1-derived peptides have proven to target CXCR4 efficiently despite a 100-fold lower affinity (or more) than SDF-1. Here we studied the binding and antiviral properties of a series of substituted SDF-1-derived N-terminal peptides and tested their functional effects on human polymorphonuclear cells, because these cells are very reactive to chemokines and chemoattractants. All peptides bound to CXCR4 and inhibited HIV entry in a functional assay on CD4(+) HeLa cells. A 10-residue substituted dimer, derived from the 5-14 sequence of SDF-1, displayed the highest affinity for CXCR4 (K(i) value of 290 nM, a reduction of only 15-fold compared with SDF-1) and was also the best competitor for HIV entry (IC(50) value of 130 nM). Whereas most peptides displayed CXCR4-independent functional effects on human polymorphonuclear cells, including the modulation of calcium fluxes and the activation of superoxide anion production at high concentration (10 microM), the peptide dimer was devoid of these nonspecific effects at antiviral concentrations. Overall, this study shows that appropriate modifications of SDF-1-derived N-terminal peptides may ameliorate their binding and viral blocking properties without generating significant unspecific side effects.

CXCR4 is down-regulated in cells infected with the CD4-independent X4 human immunodeficiency virus type 1 isolate m7NDK

Macrophages and T cells infected in vitro with CD4-dependent human immunodeficiency virus type 1 (HIV-1) isolates have reduced levels of CD4 protein, a phenomenon involved in retroviral interference. We have previously characterized the first CD4-independent HIV-1 X4 isolate m7NDK, which directly interacts with CXCR4 through its mutated gp120. We thus investigate CXCR4 expression in cells infected with this m7NDK CXCR4-dependent HIV-1 mutant. We present evidence of the down-regulation of CXCR4 membrane expression in CD4-positive or -negative cells chronically infected with the HIV-1 m7NDK, a phenomenon which is not observed in the CD4-dependent HIV-1 NDK parental strain. This down-regulation of CXCR4 was demonstrated by fluorescence-activated cell sorter analysis and was confirmed by the absence of CXCR4 functionality in m7NDK-infected cells, independently of the presence of CD4 protein. Furthermore, a drastic reduction of the intracellular level of CXCR4 protein was also observed. Reduced levels of CXCR4 mRNA transcripts were found in m7NDK-infected HeLa and CEM cells, reduced levels that could not be attributed to a reduced stability of CXCR4 mRNA. Down-regulation of CXCR4 on m7NDK-infected cells may thus be explained by transcriptional regulation.

Annexin 1 binds to U937 monocytic cells and inhibits their adhesion to microvascular endothelium: involvement of the alpha 4 beta 1 integrin

Annexin 1 (ANX1), a calcium-binding protein, participates in the regulation of early inflammatory responses. Whereas some of its effects depend on intracellular interactions, a growing number of observations indicate that ANX1 may also act via autocrine/paracrine functions following externalization to the outer side of the plasma membrane. We studied the effects of ANX1 on leukocyte adhesion to endothelial cells using as a model system the monocytic cell line U937 and human bone marrow microvascular endothelial cells. Exogenous rANX1, as well as endogenous ANX1 externalized by U937 differentiated in vitro, inhibited monocyte firm adhesion to vascular endothelium. Both binding of ANX1 to U937 cells and ANX1-mediated inhibition of cell adhesion involved the short N-terminal domain of the ANX1 molecule. Under experimental conditions in which ANX1 inhibited U937 adhesion to human bone marrow microvascular endothelial cells, this protein specifically colocalized with the alpha 4 integrin, and a direct interaction between ANX1 and the alpha 4 integrin could be documented by immunoprecipitation experiments. Moreover, ANX1 competed with the endothelial integrin counterreceptor, VCAM-1, for binding to alpha 4 integrin. These results indicate that ANX1 plays an important physiological role in modulating monocyte firm adhesion to the endothelium.

Activation of the beta(2)-adrenergic receptor-Galpha(s) complex leads to rapid depalmitoylation and inhibition of repalmitoylation of both the receptor and Galpha(s)

Palmitoylation is unique among lipid modifications in that it is reversible. In recent years, dynamic palmitoylation of G protein alpha subunits and of their cognate receptors has attracted considerable attention. However, very little is known concerning the acylation/deacylation cycle of the proteins in relation to their activity status. In particular, the relative contribution of the activation and desensitization of the signaling unit to the regulation of the receptors and G proteins palmitoylation state is unknown. To address this issue, we took advantage of the fact that a fusion protein composed of the stimulatory alpha subunit of trimeric G protein (Galpha(s)) covalently attached to the beta(2)-adrenergic receptor (beta(2)AR) as a carboxyl-terminal extension (beta(2)AR-Galpha(s)) can be stimulated by agonists but does not undergo rapid inactivation, desensitization, or internalization. When expressed in Sf9 cells, both the receptor and the Galpha(s) moieties of the fusion protein were found to be palmitoylated via thioester linkage. Stimulation with the beta-adrenergic agonist isoproterenol led to a rapid depalmitoylation of both the beta(2)AR and Galpha(s) and inhibited repalmitoylation. The extent of depalmitoylation induced by a series of agonists was correlated (0.99) with their intrinsic efficacy to stimulate the adenylyl cyclase activity. However, forskolin-stimulated cAMP production did not affect the palmitoylation state of beta(2)AR-Galpha(s), indicating that the agonist-promoted depalmitoylation is linked to conformational changes and not to second messenger generation. Given that, upon activation, the fusion protein mimics the activated receptor-G protein complex but cannot undergo desensitization, the data demonstrate that early steps in the activation process lead to the depalmitoylation of both receptor and G protein and that repalmitoylation requires later events that cannot be accommodated by the activated fusion protein.

Beta(2)-adrenergic receptor down-regulation. Evidence for a pathway that does not require endocytosis

Sustained activation of most G protein-coupled receptors causes a time-dependent reduction of receptor density in intact cells. This phenomenon, known as down-regulation, is believed to depend on a ligand-promoted change of receptor sorting from the default endosome-plasma membrane recycling pathway to the endosome-lysosome degradation pathway. This model is based on previous studies of epidermal growth factor (EGF) receptor degradation and implies that receptors need to be endocytosed to be down-regulated. In stable clones of L cells expressing beta(2)-adrenergic receptors (beta(2)ARs), sustained agonist treatment caused a time-dependant decrease in both beta(2)AR binding sites and immuno-detectable receptor. Blocking beta(2)AR endocytosis with chemical treatments or by expressing a dominant negative mutant of dynamin could not prevent this phenomenon. Specific blockers of the two main intracellular degradation pathways, lysosomal and proteasome-associated, were ineffective in preventing beta(2)AR down-regulation. Further evidence for an endocytosis-independent pathway of beta(2)AR down-regulation was provided by studies in A431 cells, a cell line expressing both endogenous beta(2)AR and EGF receptors. In these cells, inhibition of endocytosis and inactivation of the lysosomal degradation pathway did not block beta(2)AR down-regulation, whereas EGF degradation was inhibited. These data indicate that, contrary to what is currently postulated, receptor endocytosis is not a necessary prerequisite for beta(2)AR down-regulation and that the inactivation of beta(2)ARs, leading to a reduction in binding sites, may occur at the plasma membrane.

Beta 2-adrenergic receptor endocytic pathway is controlled by a saturable mechanism distinct from that of transferrin receptor

Agonist-dependent internalization is an important phase of beta 2-adrenergic receptor (beta 2AR) regulation. Recent reports have indicated that early steps of beta 2AR endocytosis may involve mechanisms different from those which regulate the internalization of constitutively recycling receptors, such as transferrin receptor (TfR). In the present study, we addressed this issue by comparing, in the same cells, the endocytic pathway of beta 2AR with that of the TfR. Upon incubation at 15 degrees C, activated beta 2ARs accumulated in peripheral endosomes of HEK-293 cells while they were targeted to perinuclear organelles at 37 degrees C. The temperature block was not specific to beta 2ARs, since both peripheral and perinuclear beta 2AR-containing endosomes comigrated on sucrose gradients with those containing transferrin receptors and were loaded with horseradish peroxidase-coupled transferrin. Endocytosis of beta 2ARs was saturable in HEK-293 cells and did not increase upon overexpression of beta-arrestin 1. TfR endocytosis was unaffected by the simultaneous internalization of overexpressed beta 2AR, indicating that the limiting components which regulate endocytosis of these two receptors are different. In conclusion, ligand activated beta 2AR and constitutively recycling receptors, such as TfR, enter the endocytic pathway via distinct saturable mechanisms but converge in the same endosomal compartments. Our results also indicate that a still unidentified component(s) controls beta 2AR endocytosis.

Reactive oxygen and nitrogen intermediates increase transforming growth factor-beta1 release from human epithelial alveolar cells through two different mechanisms

Transforming growth factor (TGF)-beta1 is a growth factor involved in the mechanisms of lung repair and fibrosis that follow inflammatory processes. We sought to examine the link between the generation of reactive oxygen intermediates (ROI) or reactive nitrogen intermediates (RNI) by inflammatory cells and the expression of TGF-beta1 by alveolar epithelial cells. Exposure of the A549 lung epithelial cell line to either an ROI generating system (xanthine and xanthine oxidase) or an RNI donor (S-nitroso-N-acetyl-penicillamine [SNAP]) promoted a time- and dose-dependent increase in TGF-beta1 release, as measured by a specific enzyme-linked immunosorbent assay. At the peak, the levels of TGF-beta1 were twice the control values. The induction of TGF-beta1 release by ROI was blunted by catalase and unaffected by superoxide dismutase, indicating the involvement of hydrogen peroxide. The response was also blunted by 5, 6-dichloro-1-beta-D-ribofuranosyl benzimidazole (DRB), a specific RNA polymerase II inhibitor, and accompanied by a corresponding increase in TGF-beta1 messenger RNA, as measured by quantitative/competitive reverse transcription polymerase chain reaction, suggesting the involvement of transcriptional mechanisms and possibly other downstream mechanisms. In contrast, RNI-induced TGF-beta1 release was unaffected by DRB and blunted by the protein synthesis inhibitor cycloheximide, suggesting the involvement of translational and post-translational mechanisms. This response required cyclic guanosine monophosphate (cGMP)- mediated processes because (1) immunoreactive cGMP accumulated in the culture medium of SNAP-treated cells; (2) SNAP-induced TGF-beta1 release was blunted by KT 5823, an inhibitor of cGMP-dependent protein kinase; and (3) similar increase in TGF-beta1 release was obtained by cell exposure to membrane-permeable dibutyryl-cGMP or to atrial natriuretic factor, a known agonist of particulate guanylate cyclase. These data suggest that in vitro exposure of human alveolar epithelial cells to ROI and RNI enhances TGF-beta1 release through different mechanisms. In vivo, this control may constitute a molecular link between inflammatory and fibrotic processes.

Role of transforming growth factor beta type II receptor in hepatic fibrosis: studies of human chronic hepatitis C and experimental fibrosis in rats

Transforming growth factor beta (TGF-beta) is an antiproliferative and profibrogenic cytokine that signals through a receptor consisting of type I and type II (TbetaRII) components. We have examined changes in the expression of TbetaRII during liver injury, correlating this with the antiproliferative and profibrogenic effects of TGF-beta1. The experimental material consisted of biopsy samples of liver from patients with chronic hepatitis C and rats in which liver injury was induced by ligation of the common bile duct. Stellate cells were isolated from normal or injured rat liver and studied as fresh isolates. In the biopsy samples from patients, mRNAs for TGF-beta1 and TbetaRII were measured using competitive reverse polymerase chain reaction (PCR). TGF-beta1 mRNA was significantly increased in chronic hepatitis C relative to healthy controls (P =.03), while TbetaRII mRNA was significantly decreased (P =.001). In the rat model, 5 days after bile duct ligation during increased TGF-beta expression, mRNA for TbetaRII in stellate cells was 40% of that in stellate cells from control livers. This coincided with increased expression of collagen I mRNA and proliferation of stellate cells. The reciprocal relationship between expression of TGF-beta and the type II receptor suggest ligand-mediated receptor down-regulation. The decreased level of TbetaRII appears to be permissive for proliferation while supporting ongoing fibrogenesis. We conclude that modulation of this receptor may be critical to the progression of wound repair in liver.

Beta-adrenergic receptor-dependent and -independent stimulation of adenylate cyclase is impaired during severe sepsis in humans

OBJECTIVES

a) To investigate the functional consequences of sepsis on the beta-adrenergic signal transduction in human circulating lymphocytes; b) to appreciate sepsis-associated catecholamine and cytokine release.

DESIGN

Experimental, comparative study.

SETTING

Research laboratory in a university hospital.

SUBJECTS

Healthy controls (n = 10); critically ill patients who were not septic (n = 7); septic patients with severe sepsis or septic shock (n = 11).

MEASUREMENTS AND MAIN RESULTS

Experiments were carried out using freshly isolated peripheral blood mononuclear cells (PBMC). We measured beta-adrenergic receptor (betaAR) number and affinity, and intracellular cAMP content at baseline and after the pharmacological stimulation of each component of the beta-adrenergic complex: betaAR with isoproterenol, Gs-protein with sodium fluoride (NaF), adenylate cyclase with forskolin. Catecholamine (adrenaline, noradrenaline) and cytokine (TNFalpha, IL-1alpha, IL-1beta, IL-6) serum levels were measured. In both septic and non-septic patients we observed a similar 40 % down-regulation of betaARs compared to controls, and a reduced basal and isoproterenol-stimulated cAMP accumulation (p < 0.05). The cAMP production elicited by NaF or forskolin was lower in septic patients than in the controls (p < 0.01). Forskolin-stimulated cAMP accumulation was significantly lower in septic patients than it was in non-septic ones (p < 0.001). Catecholamine serum concentrations were increased in the two patient groups without any significant difference. Elevated cytokine serum levels were detected in 45% of the septic patients (versus 14% of non-septic patients p < 0.05).

CONCLUSIONS

Patients presenting with severe sepsis or septic shock have extended postreceptor defects of the beta-adrenergic signal transduction. This finding suggests a heterologous desensitization of adenylate cyclase stimulation.

Expression and recovery of functional G-protein-coupled receptors using baculovirus expression systems

Baculovirus expression systems have been used for more than ten years as the tool of choice to over-express G-protein-coupled receptors. Although this expression system has also been used to study the signaling mechanisms of the receptors at the cellular level, it was found to be a most useful method to produce large quantities of receptors for biochemical and biophysical studies. Methods that allow easy and selective recovery of properly folded and mature receptors in viral particles open new perspectives for such applications.

Background for and development of a brief Adult Behavioral Classification Project Inventory

An abridgement of the Adult Behavioral Classification Project Inventory (AdBCP) was accomplished. The creation and development of the full-scale Inventory is described in Phase I. In Phase II, the participant pool was divided into half, and each half of the data set was subjected to both exploratory and confirmatory factor analyses with a factor control of 11 of the strongest factors in the original data set. Items identifying these factors had to have at least magnitude of .35 factor structure weights, leaving a 42-item instrument, the Brief AdBCP Inventory. Predicting from the first half to the second half by confirmatory factor analysis resulted in a fair confirmation of the factor structure. A rough norm table is offered based on the factor scores of the first half of the participants' records.

Desensitization of the beta-adrenergic response in human brown adipocytes

Activation of adenylyl cyclase by beta-adrenergic receptors (betaARs) plays a major role in adipose tissue homeostasis. The increase in cAMP promotes lipolysis in white adipose tissue, activates both thermogenesis and lipolysis in brown adipose tissue (BAT), and induces BAT hypertrophy. Previous studies indicated that among the three betaAR subtypes present in adipose tissue, beta3AR could be a potential target for antiobesity treatments in humans. We studied immortalized human brown adipocytes (PAZ6 adipocytes) as a model of beta-adrenergic response in human BAT. PAZ6 adipocytes and freshly isolated mature human brown adipocytes display the same proportions of betaAR subtypes, with beta3AR being the most abundant (approximately 80% of the total). However, beta3AR was poorly coupled to the adenylyl cyclase pathway in PAZ6 cells, contributing to only 10% of the isoproterenol-induced accumulation of cAMP, whereas 20% and 70% of the signal depended on beta1- and beta2-subtypes, respectively. Upon isoproterenol stimulation, beta1- and beta2AR down-regulated with a half-life of about 3 h and the beta3AR with a half-life of 30-40 h. Long term stimulation with both saturating (micromolar) and nonsaturating (nanomolar) concentrations of beta-adrenergic agonists caused a complete desensitization of the beta-adrenergic response at the adenylyl cyclase level and loss of stimulated protein kinase A activity and CREB phosphorylation. These results suggest that cAMP-dependent processes will be desensitized upon permanent treatment with beta3AR agonists. Further studies should establish whether the beta3AR is coupled to other signaling pathways in human brown adipocytes and whether these may contribute to BAT hypertrophy and/or thermogenesis.

Recovery of homogeneous and functional beta 2-adrenergic receptors from extracellular baculovirus particles

Expression in baculovirus-infected insect cells allows sufficient production of G-protein coupled receptor for structural studies. An important drawback of this expression system comes from the presence of unprocessed and biologically inactive receptors that have to be eliminated during receptor purification steps. We show that viral particles released from Sf9 cells infected with a recombinant baculovirus coding for the human beta 2-adrenergic receptor (beta 2AR) cDNA contain glycosylated and biologically active beta 2AR. In addition, post-translational modifications known to modulate receptor activity were found to occur in these particles.

Novel isoforms of Mel1c melatonin receptors modulating intracellular cyclic guanosine 3',5'-monophosphate levels

Two cDNAs encoding novel isoforms of Xenopus laevis melatonin receptors were cloned using PCR primers specific for the X. laevis-melanophore Mel1c melatonin receptor described in a recent publication. The novel isoforms were highly homologous to the described frog Mel1c cDNA, although the C-terminal tail of both was shorter by 65 amino acid residues. Nucleotide sequences of these novel isoforms, called Mel1c(alpha) and Mel1c(beta), differed from each other by only 35 nucleotides and six amino acid residues. Studies on several animals of various Xenopus species indicate that Mel1c(alpha) and Mel1c(beta) receptors may correspond to allelic variants of the same locus. Studies on cells transfected with both receptor cDNAs showed the expression of high-affinity 2-[125I]iodomelatonin binding sites. Agonist stimulation of Mel1c(alpha) receptor was associated with the inhibition of cAMP accumulation stimulated by forskolin (IC50 approximately 10(-10) M) in HeLa, Ltk-, and human embryonic kidney 293 (HEK 293) cells. Mel1c(beta) receptor modulated cAMP in HeLa and HEK 293 cells but not in Ltk- cells. Both receptors inhibited, in a dose-dependent manner, cGMP accumulation in all three cell lines incubated with a phosphodiesterase inhibitor. This effect was localized upstream of soluble guanylyl cyclase and was blocked by pertussis toxin treatment. However, IC50 values (approximately 10(-10) M for Mel1c(beta) and 10(-9) to 10(-7) M for Mel1c(alpha)) and maximal inhibition levels showed that Mel1c(alpha) receptors are much less efficiently coupled to the cGMP pathway. Coupling differences may be explained by the fact that five of the six amino acid substitutions between Mel1c(alpha) and Mel1c(beta) receptors are located within cytoplasmic regions potentially involved in signal transduction. The existence of coupling differences is in agreement with the observation that expression of both receptors is evolutionally conserved in native tissue. In conclusion, two novel, potentially allelic, isoforms of Xenopus Mel1c melatonin receptors display identical ligand-binding characteristics, but different potencies in modulating cAMP and cGMP levels through G(i)/G(o)-dependent pathways. Furthermore, to our knowledge, this study provides the first data on the modulation of intracellular cGMP levels by cloned melatonin receptors.

Human beta2-adrenergic receptor/GS alpha fusion protein, expressed in 2 ras-dependent murine carcinoma cell lines, prevents tumor growth in syngeneic mice

We report a strategy of tumor growth inhibition based on the expression of a foreign protein with both potential anti-proliferative and immunogenic properties. To validate our approach, we used 2 ras-mutated murine carcinoma cell lines (carB and C57/PDV) transfected with the gene encoding a fusion protein containing the human beta2-adrenergic receptor and the alpha subunit of the Gs protein (beta2Gs). We previously showed that the sustained activation of the beta2Gs fusion protein expressed in carB cells (carB beta2Gs cells) induced a cAMP-dependent inhibition of cell growth in vitro. Here, we observed inhibition of tumor growth after s.c. inoculation of 2 carB beta2Gs clones (10C2 and 20F4) in syngeneic ICFW mice. We thus selected 3 C57/PDV beta2Gs clones (2D3, 5F3 and 1G1) in which activation of the fusion protein was not efficiently coupled to the cAMP-PKA signaling pathway. Contrasting with carB beta2Gs clones, activation of the fusion protein in these C57/PDV beta2Gs clones did not have any anti-proliferative effect in vitro. Therefore, they were good candidates to assess the immunogenic property of the fusion protein. Accordingly, none of the C57/PDV beta2Gs clones formed tumors in immunocompetent syngeneic C57BL/6 mice, while they were still tumorigenic in nude mice. Most interestingly, all of the beta2Gs clones that did not form tumors, from both cell lines, provided protection against respective wild-type tumor development. Our results show that expression of the beta2Gs fusion protein in cancer cells elicits inhibition of cell proliferation and/or immune rejection of both beta2Gs-modified and wild-type tumor cells.

Activation of a beta 2-adrenergic receptor/Gs alpha fusion protein elicits a desensitization-resistant cAMP signal capable of inhibiting proliferation of two cancer cell lines

We showed in a previous study that the expression, in Gs-deficient S49 cyc- cells, of a fusion gene encoding the beta 2-adrenergic Receptor (beta 2AR) and the alpha subunit of the Gs protein (Gs alpha) restored beta 2AR-dependent activation of adenylyl cyclase. We report here the extensive characterization of short- and long-term regulation of the beta 2AR/Gs alpha fusion protein activity and its pharmacological effect after expression in two cancer cell lines. In contrast with native beta 2ARs and Gs, the receptor and the alpha s subunit moieties of the beta 2AR/Gs alpha fusion protein did not undergo functional uncoupling. After a sustained incubation with isoproterenol or forskolin, the accumulation of cAMP could still be observed in S49 beta Gs cells, expressing the fusion gene, which showed, in addition, an up-regulation of their beta 2AR binding sites, while in S49 wt cells, the same treatments completely abolished the rise of cAMP and markedly reduced the number of receptors. cAMP-activation of protein kinase A (PKA) is known to modulate proliferation of most cells. We studied the effect of long term beta 2AR/Gs alpha activation on the growth rate of S49 lymphoma cells and carcinoma carB cells, a highly proliferative cancer cell line expressing oncogenic ras protein. The beta 2AR agonist salmeterol blocked the proliferation of both S49 and carB beta 2Gs cells, while this treatment did not change the growth of wild-type cells. In carB beta 2Gs cells, this effect may be reinforced by a significant basal activity of the fusion protein and by agonist-promoted MAP kinase inhibition. In conclusion, the stimulatory overload provided by the beta 2AR/Gs alpha fusion protein led to the inhibition of cAMP-sensitive cancer cell proliferation in vitro.

New molecular and structural determinants involved in beta 2-adrenergic receptor desensitization and sequestration. Delineation using chimeric beta 3/beta 2-adrenergic receptors

As the beta 3-adrenergic receptor (beta3AR) is resistant to short term agonist-promoted desensitization and sequestration, chimeric beta3/beta2 receptors were generated to identify the molecular determinants responsible for these regulatory processes in the beta2AR. By exchanging single or multiple intracellular domains of the beta3AR for the corresponding regions of the beta2AR, we show that specific domains can be identified as additive determinants for desensitization, while sequestration is more dependent on global structural conformation. The carboxyl-terminal tail, the third and the second intracellular loops of the beta2AR provided additive contributions to the desensitization observed upon short term agonist stimulation. The second intracellular loop plays a role which is as important as that of third cytoplasmic loop and carboxyl-terminal tail which had previously been identified as the major determinants of agonist-promoted desensitization. Additive contributions of the cytoplasmic domains of the beta2AR were also observed for agonist-promoted sequestration. The substitution of the first and second intracellular loops and the carboxyl tail were associated with a beta2-like sequestration phenotype. However, in contrast to what is observed for desensitization the co-substitution of the third cytoplasmic loop with any of the other domains completely suppressed sequestration. These results suggest that sequestration depends not only on appropriate interactions of multiple molecular determinants within the cytoplasmic region of the beta2AR but also on conformational determinants that may influence their orientation.

Functional effects of long-term activation on human beta 2- and beta 3-adrenoceptor signalling

The functional effects of long-term activation of beta-adrenoceptors were investigated by measuring adenylyl cyclase activity, cyclic AMP accumulation and cyclic AMP-dependent protein kinase activity in CHW and L cells expressing either human beta 2- or beta 3-adrenoceptors. Pre-incubation of CHW and L cells expressing beta 2-adrenoceptors with 10 microM isoprenaline for 24 h produced a marked reduction in the total receptor number and dramatically reduced the capacity of the receptor to stimulate adenylyl cyclase maximally. In contrast, the ability of beta 3-adrenoceptors number was observed in L but not in CHW cells. Maximal levels of intracellular cyclic AMP concentrations were reached during the first hour of receptor activation with isoprenaline in all four cell lines. In the absence of phosphodiesterase inhibitors, cyclic AMP decreased to basal levels within 24 h of continuous stimulation. This phenomenon occurred more rapidly in cells expressing the beta 2- than the beta 3-adrenoceptors. These results confirm that, at the level of adenylyl cyclase stimulation and cyclic AMP accumulation, the beta 3-adrenoceptor is more resistant than the beta 2-adrenoceptor to long-term desensitization. However, when cyclic AMP-dependent protein kinase activity was considered, a 24 h stimulation of beta 2- and when cyclic AMP-dependent protein kinase activity was considered, a 24 h stimulation of beta 2- and beta 3-adrenoceptor expressing cells led to the desensitization of the kinase in L but not in CHW cells. In conclusion, long-term desensitization may have distinct functional effects on cell signalling depending on the receptor subtype and the cell type considered. These findings might have practical implications for future strategies involving long-term therapies with receptor agonists.

Quantitative analysis of transforming growth factor beta 1 messenger RNA in the liver of patients with chronic hepatitis C: absence of correlation between high levels and severity of disease

Transforming growth factor beta 1 (TGF beta 1) is a cytokine involved in liver fibrogenesis. Previous semiquantitative studies of patients with chronic viral hepatitis showed that liver TGF beta 1 messenger RNA (mRNA) was increased, compared with normal controls and with patients with chronic hepatitis C virus (HCV) infection who responded favorably to interferon alfa (IFN alpha) treatment. To evaluate its potential prognostic significance, we measured liver TGF beta 1 mRNA, using a new competitive reverse gene amplification assay, in a total of 35 patients with chronic HCV. This technique was reproducible and sensitive; we could measure as few as 5,000 molecules of TGF beta 1 mRNA per microgram of total liver RNA. In patients with chronic HCV, the mean level of TGF beta 1 mRNA was 200-fold higher than in controls. However, no correlation could be found between TGF beta 1 mRNA and either the biological (serum amino-terminal peptide of type III procollagen) and histological (Knodell scores) indices of liver fibrosis or a favorable response to IFN alpha therapy. In 9 patients, second liver specimens were obtained after treatment; in most cases, TGF beta 1 mRNA levels and hepatic histological findings varied in parallel. These data are consistent with the hypothesis that TGF beta 1 plays a role in stimulating liver fibrogenesis during chronic HCV, despite the lack of prognostic value of TGF beta 1 mRNA levels measured before treatment.(ABSTRACT TRUNCATED AT 250 WORDS)

Species difference in the G protein selectivity of the human and bovine A1-adenosine receptor

The purified bovine brain A1-adenosine receptor has previously been shown to discriminate among closely related G protein alpha-subunits. To obtain analogous information for the human receptor, the cDNA coding for the human A1-adenosine receptor was inserted into a plasmid placing the synthesis of the receptor protein under the control of the MalE promoter. Following induction by maltose, active receptor accumulated in Escherichia coli membranes. Binding of the antagonist 8-[3H]cyclopentyl-1,3-dipropylxanthine to E. coli membranes (KD approximately 2 nM, Bmax approximately 0.2-0.4 pmol/mg) showed the appropriate pharmacological profile. Incubation of E. coli membranes with purified Go,i-reconstituted guanine nucleotide-sensitive high affinity binding of the agonist (-)[125I] N6-3-(iodo-4-hydroxyphenylisopropyl)adenosine to the receptor (KD approximately 1 nM). In the presence of purified beta gamma-subunit, the recombinant receptor interacted equally well with the recombinant G protein alpha-subunits Gi alpha-1, Gi alpha-2, Gi alpha-3; G(o) alpha displayed a lower affinity for the receptor while Gs alpha was inactive. Parallel experiments were carried out in bovine and human brain membranes pretreated with N-ethylmaleimide to inactivate the endogenous G(o)/Gi proteins; Gi alpha-3 was most potent in reconstituting 125I-HPIA binding to bovine membranes, while Gi alpha-1, Gi alpha-2, and G(o) alpha displayed similar affinities. However, in human membranes, Gi alpha-1, Gi alpha-2, and Gi alpha-3, were equipotent and high concentrations of G(o) alpha were required to promote 125I-HPIA binding. These observations show (i) that functional human A1-adenosine receptors were synthesized in E. coli; (ii) that the pattern of G protein coupling is identical for the recombinant human A1-receptor and its counterpart in the native membrane; (iii) and that species differences between bovine and human receptor exist not only in their pharmacological profile but also in their G protein specificity suggesting that species homologues of receptors may use different signaling mechanisms.

Cellular signaling by an agonist-activated receptor/Gs alpha fusion protein

The consequences of agonist-dependent activation of guanine nucleotide-binding protein (G protein)-coupled receptors vary from cell to cell, depending on a complex network of regulations between components of the signaling cascade. Specific interactions between receptors, G proteins, and effectors are difficult to analyze in intact cells. Engineering of receptor-transducer fusion proteins might be an effective strategy to target cellular effectors more efficiently and specifically. As a model, we evaluated the ability of a fusion protein of beta 2-adrenergic receptor bound to the alpha subunit of adenylyl cyclase-stimulatory G protein (Gs alpha) to restore the defective activation of adenylyl cyclase in S49 cyc- cells that lack endogenous Gs alpha. The coupling between the two partners of the fusion protein was functional, and the agonist-dependent activation of the effector was more potent and more productive in transfected than in wild-type S49 cells. The covalent link between receptor and Gs alpha could thus convey an advantage over freely interacting components. Such receptor-G alpha fusion proteins may help to elucidate the complex interactions between members of signaling pathways and may also constitute a useful tool for studying the effects of single effector activation.

Cell-specific down-regulation of the beta 3-adrenergic receptor

Previous studies have shown that beta 3-adrenergic receptors, in contrast to the beta 1 and beta 2 subtypes, do not undergo desensitization following short term activation (minutes) with agonists. Longer activation (hours) has been shown to induce desensitization of the beta 3-adrenergic receptor in some, but not all, cases, suggesting that cell- or species-specific mechanisms may be involved. We investigated the contribution of the cell type to the pattern of beta 3-adrenergic receptor long term desensitization by studying, in parallel, two cell lines (Chinese hamster fibroblasts and murine Ltk- cells) expressing the human beta 3-adrenergic receptor. Sustained agonist-promoted down-regulation of the beta 3-adrenergic receptor could be induced in Ltk- cells, whereas only a transient and weak reduction of receptor number was observed in Chinese hamster fibroblasts. The half-life of the beta 3-adrenergic receptor was not affected by the agonist activation in either cell line, indicating that in contrast to the beta 2-adrenergic receptor, degradation of preexisting receptor protein does not contribute to down-regulation. Sustained reduction of receptor RNA levels, monitored by reverse transcriptase polymerase chain reaction, was exclusively shown in Ltk- cells and probably accounted for most of the observed down-regulation. Differences in the ability of the receptor to stimulate adenylyl cyclase activity in the two cell lines may be responsible for the distinct patterns of beta 3-adrenergic receptor down-regulation.

Lupoid sclerosis with antiphospholipid and antimyelin antibodies

Lupoid sclerosis is a rare syndrome associating clinical symptoms of multiple sclerosis (MS), positive false tests for syphilis and positive tests for antinuclear and anticardiolipin antibodies. In a patient with lupoid sclerosis, antimyelin antibodies were detected by indirect immunofluorescence on human sciatic nerve sections. These antibodies were not found in the serum of control patients with MS nor in sera of patients with antiphospholipid autoantibodies and focal ischemic neurologic disease. The presence of such antimyelin antibodies may contribute to the underlying physiopathological mechanism of this syndrome.

The human beta 3-adrenergic receptor is resistant to short term agonist-promoted desensitization

The human beta 3-adrenergic receptor (beta 3AR) lacks most of the structural determinants that, in the beta 2AR, contribute to agonist-induced receptor desensitization. To evaluate the effect of these structural differences on the beta 3AR desensitization profile, the human beta 2- and beta 3AR were stably expressed in Chinese hamster fibroblasts (CHW) and murine Ltk- cells (L cells). Incubation of CHW-beta 2 or L-beta 2 cells with 10 microM isoproterenol for 30 min induced a decrease in the maximal agonist-stimulated adenylyl cyclase activity and a cAMP-dependent reduction in the potency of isoproterenol to stimulate the receptor. In addition, this pretreatment impaired the formation of the high affinity heterotrimeric agonist-receptor-guanine nucleotide-binding protein complex and induced the sequestration of approximately 30% of the beta 2AR away from the cell surface. In contrast, similar treatment of CHW-beta 3 and L-beta 3 cells did not affect the maximal receptor-stimulated adenylyl cyclase activity, nor did it induce any significant sequestration of the beta 3AR. In fact, only a modest cAMP-independent decrease in the potency of isoproterenol to stimulate the receptor could be observed after isoproterenol treatment. The rapid desensitization pattern of a chimeric beta 3AR, in which the third cytoplasmic loop and the carboxyl-terminal tail were exchanged with those of the beta 2AR (which include potential phosphorylation sites and other possible molecular determinants of desensitization), was found to be intermediate between those of the two original receptor subtypes. These results demonstrate that (i) the beta 3AR is less prone than the beta 2AR to undergo rapid agonist-promoted desensitization and, (ii) in addition to the phosphorylation sites located in the third cytoplasmic loop and the carboxyl-terminal tail of the beta 2AR, other molecular determinants contribute to short term desensitization.

Functional expression of the human serotonin 5-HT1A receptor in Escherichia coli. Ligand binding properties and interaction with recombinant G protein alpha-subunits

Signaling through serotonin 5-HT1A receptors involves multiple pathways. We have investigated the functional coupling of the human 5-HT1A receptor to different G proteins using an in vitro reconstitution system based on the expression of recombinant receptor (r5-HT1A) and G alpha-subunits (rG alpha) in Escherichia coli. The r5-HT1A receptor was expressed by insertion in a vector allowing its active expression in E. coli inner membranes. Binding of the selective agonist [3H] +/- 8-hydroxy-(2-N-dipropylamine)tetralin ([3H]8-OH-DPAT) to intact bacteria or E. coli membranes was saturable with a KD of approximately 8 nM and an average of 120 sites/bacterium. Binding properties of several serotoninergic ligands to r5-HT1A receptors were comparable with those measured in mammalian cells. Incubation of rG alpha.beta gamma with E. coli membranes resulted in high affinity agonist [3H]8-OH-DPAT binding (KD = 0.7 nM) and titration with a panel of rG alpha subtypes showed the order of potency: rGi alpha-3 greater than rGi alpha-2 greater than rGi alpha-1 much greater than rGo alpha, while rGs alpha appeared incapable of interacting with 5-HT1A receptors. Moreover, agonist-mediated enhancement of [35S]guanosine 5'-O-(3-thiotriphosphate) binding to rGi alpha confirmed the achievement of the functional interaction between receptor and G proteins. Our findings are in agreement with the in vivo ability of 5-HT1A receptors to activate Gi alpha related to adenylyl cyclase inhibition or K+ channel activation, but do not support previously reported adenylyl cyclase stimulation through interaction with Gs alpha.

The human beta 3-adrenergic receptor: relationship with atypical receptors

Atypical beta-adrenergic receptors (beta AR), different from beta 1 and beta 2ARs, have been suggested to modulate energy expenditure. We have characterized a gene coding for a third human beta AR, beta 3AR, whose sequence is 402 amino acids long and is 50.7% and 45.5% homologous to that of the human beta 1 and beta 2AR, respectively. The KD of [125I]-iodocyanopindolol for beta 3AR is 10-fold higher than for beta 1 or beta 2AR. The receptor has an apparent molecular weight of 65,000. Agonists for the beta 3AR induce cyclic AMP accumulation. Among 11 beta antagonists tested, only ICI118551 and CGP20712A, previously classified as, respectively, beta 1 and beta 2 selective, inhibit this effect. The beta 1 and beta 2 antagonists pindolol, oxprenolol, and CGP12177 are agonists of the beta 3AR. The potency order of beta agonists at beta 3 sites correlates with that for stimulation of lipolysis in rat fat tissues. Moreover, because beta 3AR mRNA was detected in rodent adipose tissues, liver, and muscle, we propose that the beta 3AR participates to the control by catecholamines of energy expenditure.

Expression of two human beta-adrenergic receptors in Escherichia coli: functional interaction with two forms of the stimulatory G protein

When expressed in Escherichia coli, the human beta 1- and beta 2-adrenergic receptors retain their ligand binding specificity. Their functional integrity was investigated by analyzing receptor-guanine nucleotide-binding regulatory (G) protein coupling by using two splice variants of the alpha subunit of the stimulatory G protein Gs synthesized in E. coli (rGs alpha-S and rGs alpha-L) and the beta gamma subunits of G protein purified from bovine brain. In competition binding experiments with (-)-[125I]iodocyanopindolol and (-)-isoproterenol, rGs alpha-S.beta gamma and rGs alpha-L.beta gamma reconstituted guanine nucleotide-sensitive high-affinity agonist binding with comparable affinities, whereas rGs alpha PT, a mutant of rGs alpha-L with an altered carboxyl terminus, and a recombinant subtype of the alpha subunit of the inhibitory G protein, rGi alpha-1, were approximately 20- and approximately 200-fold less potent, respectively. A comparison of the beta 1- and beta 2-adrenergic receptor expressed in E. coli with the beta 2-receptor in S49 murine lymphoma cyc- cell membranes revealed a similar affinity of rGs alpha-S and rGs alpha-L for the recombinant and native receptors. After stable incorporation of rGs alpha-S.beta gamma into E. coli membranes, receptor-G protein coupling was also verified by determining the isoproterenol-mediated acceleration of the rate for guanine 5'-[gamma-[35S]thio]triphosphate binding. These results show that (i) receptor-G protein coupling can be reconstituted in E. coli using recombinant components and that (ii) such an approach may be more generally used to evaluate coupling preferences between defined molecular species of receptors and G-protein subunits.

Expression of three human beta-adrenergic-receptor subtypes in transfected Chinese hamster ovary cells

The genes coding for three pharmacologically distinct subtypes of human beta-adrenergic receptors (beta 1 AR, beta 2 AR and beta 3 AR) were transfected for expression in Chinese hamster ovary (CHO) cells. Stable cell lines expressing each receptor were analyzed by ligand binding, adenylate cyclase activation and photoaffinity labeling, and compared to beta AR subtypes observed in previously described tissues, primary cultures and transfected cell lines. Each of the three receptor subtypes displayed saturable [125I]iodocyanopindolol-binding activity. They showed the characteristic rank order of potencies for five agonists, determined by measuring the accumulation of intracellular cAMP. These recombinant cell lines express a homogeneous population of receptors and display the known pharmacological properties of beta 1 AR and beta 2 AR, in human tissues. It is therefore likely that the pattern of ligand binding and adenylate cyclase activation, mediated by the new beta 3 AR in CHO cells, also reflects the yet-undetermined pharmacological profile in humans.

Mapping of a functional autoimmune epitope on the beta 1-adrenergic receptor in patients with idiopathic dilated cardiomyopathy

The presence and properties of serum autoantibodies against beta-adrenergic receptors in patients with idiopathic dilated cardiomyopathy were studied using synthetic peptides derived from the predicted sequences of the human beta-adrenergic receptors. Peptides corresponding to the sequences of the second extracellular loop of the human beta 1- and beta 2-adrenergic receptors were used as antigens in an enzyme immunoassay to screen sera from patients with dilated cardiomyopathy (n = 42), ischemic heart disease (n = 17), or healthy blood donors (n = 34). The sera of thirteen dilated cardiomyopathy patients, none of the ischemic heart disease patients, and four of the healthy controls monospecifically recognized the beta 1-peptide. Only affinity-purified antibodies of these patients had a inhibitory effect on radioligand binding to the beta 1 receptor of C6 rat glioma cells. They recognized the receptor protein by immunoblot and bound in situ to human myocardial tissue. We conclude that a subgroup of patients with idiopathic dilated cardiomyopathy have in their sera autoantibodies specifically directed against the second extracellular loop of the beta 1-adrenergic receptor. These antibodies could serve as a marker of an autoimmune response with physiological and/or pathological implications.

Selective binding of ligands to beta 1, beta 2 or chimeric beta 1/beta 2-adrenergic receptors involves multiple subsites

The molecular basis of ligand binding selectivity to beta-adrenergic receptor subtypes was investigated by designing chimeric beta 1/beta 2-adrenergic receptors. These molecules consisted of a set of reciprocal constructions, obtained by the exchange between the wild-type receptor genes of one to three unmodified transmembrane regions, together with their extracellular flanking regions. Eight different chimeras were expressed in Escherichia coli and studied with selective beta-adrenergic ligands. The evaluation of the relative effect of each chimeric exchange on ligand binding affinity was based on the analysis of delta G values, calculated from the equilibrium binding constants, as a function of the number of substituted beta 2-adrenergic receptor transmembrane domains. The data showed that the contribution of each exchanged region to subtype selectivity varies with each ligand; moreover, while several regions are critical for the pharmacological selectivity of all ligands, others are involved in the selectivity of only some compounds. The selectivity displayed by beta-adrenergic compounds towards beta 1 or beta 2 receptor subtypes thus results from a particular combination of interactions between each ligand and each of the subsites, variably distributed over the seven transmembrane regions of the receptor; these subsites are presumably defined by the individual structural properties of the ligands.

Localization and characterization of three different beta-adrenergic receptors expressed in Escherichia coli

After fusion with the N-proximal portion of the outer membrane protein LamB, three beta-adrenergic receptors, the human beta 1- and beta 2- and turkey beta 1-adrenergic receptor, were expressed in Escherichia coli with retention of their own specific pharmacological properties. Molecular characterization and localization of the three receptors in bacteria and comparison of the behaviour of each hybrid protein are reported. The bacteria were lysed and fractionated on a sucrose gradient. Saturable [125I]iodocyanopindolol binding activity was found associated mainly with the inner membrane fraction, suggesting that the receptor is correctly folded in this membrane. Binding activity was also found in the outer membrane fraction but varied according to the receptor type. Photoaffinity labeling experiments revealed that the receptors exhibit binding activity only after proteolytic removal of the LamB moiety from the fusion protein. The three hybrid proteins, detected in immunoblots by anti-peptide antibodies, were found mainly in the outer membrane fraction. Each of them exhibited different susceptibility to intrinsic bacterial proteolytic enzymes; sites of proteolytic cleavage were localized by the use of anti-peptide antibodies. The functional expression in E. coli of three beta-adrenergic receptors with similar structure but different amino acid sequences suggests that this expression system may be a general feature among similar receptors of the family of G-protein-coupled receptors. The level of expressed binding activity of a given receptor will be within the control of proteolytic degradation processes, depending on the primary sequence of the receptor. Constructions of new hybrid proteins, in combination with expression in protease mutants of E. coli, should help in controlling such processes.

Molecular characterization of the human beta 3-adrenergic receptor

Since the classification of beta-adrenergic receptors (beta-ARs) into beta 1 and beta 2 subtypes, additional beta-ARs have been implicated in the control of various metabolic processes by catecholamines. A human gene has been isolated that encodes a third beta-AR, here referred to as the "beta 3-adrenergic receptor." Exposure of eukaryotic cells transfected with this gene to adrenaline or noradrenaline promotes the accumulation of adenosine 3',5'-monophosphate; only 2 of 11 classical beta-AR blockers efficiently inhibited this effect, whereas two others behaved as beta 3-AR agonists. The potency order of beta-AR agonists for the beta 3-AR correlates with their rank order for stimulating various metabolic processes in tissues where atypical adrenergic sites are thought to exist. In particular, novel beta-AR agonists having high thermogenic, antiobesity, and antidiabetic activities in animal models are among the most potent stimulators of the beta 3-AR.