Molecular characterisation of formalin-fixed paraffin-embedded (FFPE) breast tumour specimens using a custom 512-gene breast cancer bead array-based platform

Background:

Formalin-fixed, paraffin-embedded (FFPE) tumour tissue represents an immense but mainly untapped resource with respect to molecular profiling. The DASL (cDNA-mediated Annealing, Selection, extension, and Ligation) assay is a recently described, RT–PCR-based, highly multiplexed high-throughput gene expression platform developed by Illumina specifically for fragmented RNA typically obtained from FFPE specimens, which enables expression profiling. In order to extend the utility of the DASL assay for breast cancer, we have custom designed and validated a 512-gene human breast cancer panel.

Methods:

The RNA from FFPE breast tumour specimens were analysed using the DASL assay. Breast cancer subtype was defined from pathology immunohistochemical (IHC) staining. Differentially expressed genes between the IHC-defined subtypes were assessed by prediction analysis of microarrays (PAM) and then used in the analysis of two published data sets with clinical outcome data.

Results:

Gene expression signatures on our custom breast cancer panel were very reproducible between replicates (average Pearson's R²=0.962) and the 152 genes common to both the standard cancer DASL panel (Illumina) and our breast cancer DASL panel were similarly expressed for samples run on both panels (average R²=0.877). Moreover, expression of ESR1, PGR and ERBB2 corresponded well with their respective pathology-defined IHC status. A 30-gene set indicative of IHC-defined breast cancer subtypes was found to segregate samples based on their subtype in our data sets and published data sets. Furthermore, several of these genes were significantly associated with overall survival (OS) and relapse-free survival (RFS) in these previously published data sets, indicating that they are biomarkers of the different breast cancer subtypes and the prognostic outcomes associated with these subtypes.

Conclusion:

We have demonstrated the ability to expression profile degraded RNA transcripts derived from FFPE tissues on the DASL platform. Importantly, we have identified a 30-biomarker gene set that can classify breast cancer into subtypes and have shown that a subset of these markers is prognostic of OS and RFS.

Prostate cancer genes associated with TMPRSS2-ERG gene fusion and prognostic of biochemical recurrence in multiple cohorts

Background:

Recent studies have indicated that prostate cancer patients with the TMPRSS2–ERG gene fusion have a higher risk of recurrence. To identify markers associated with TMPRSS2–ERG fusion and prognostic of biochemical recurrence, we analysed a cohort of 139 men with prostate cancer for 502 molecular markers.

Methods:

RNA from radical prostatectomy tumour specimens was analysed using cDNA-mediated, annealing, selection, extension and ligation (DASL) to determine mRNAs associated with TMPRSS2–ERG T1/E4 fusion and prognostic of biochemical recurrence. Differentially expressed mRNAs in T1/E4-positive tumours were determined using significance analysis of microarrays (false discovery rate (FDR) <5%). Univariate and multivariate Cox regression determined genes, gene signatures and clinical factors prognostic of recurrence (P-value <0.05, log–rank test). Analysis of two prostate microarray studies (GSE1065 and GSE8402) validated the findings.

Results:

In the 139 patients from this study and from a 455-patient Swedish cohort, 15 genes in common were differentially regulated in T1/E4 fusion-positive tumours (FDR <0.05). The most significant mRNAs in both cohorts coded ERG. Nine genes were found prognostic of recurrence in this study and in a 596-patient Minnesota cohort. A molecular recurrence score was significant in prognosticating recurrence (P-value 0.000167) and remained significant in multivariate analysis of a mixed clinical model considering Gleason score and TMPRSS2–ERG fusion status.

Conclusions:

TMPRSS2–ERG T1/E4 fusion-positive tumours had differentially regulated mRNAs observed in multiple studies, the most significant one coded for ERG. Several mRNAs were consistently associated with biochemical recurrence and have potential clinical utility but will require further validation for successful translation.

Wnt Signaling Prognosticates Outcome in Breast Cancer Cohorts

Background: Wnt signaling is highly conserved in Metazoan species. Wnt activation and inactivation have been well studied for their roles in development and tumorigenesis, and has emerged as one the most important core pathways in cancer biology. Wnt activation has long been associated with breast cancer, but has only recently been shown to be specifically upregulated in triple negative (TN) breast cancers.Material and Methods: FFPE specimens were obtained from St. Mary's Hospital, Montreal, QC (Quebec cohort) and Grady Hospital, Atlanta, GA (Georgia cohort). RNA was extracted from FFPE sections or cores using the RNA High Pure Kit (Roche) and quality analyzed as described previously (Abramovitz et al. Biotechniques, 2008). Quebec and Georgia cohort mRNAs were quantified using DASL assays, including a 502-gene panel of cancer related genes and a custom 512-gene panel targeting breast cancer pathologies. After quality control the Quebec cohort composed 97 patients and the Georgia cohort 142. Differential mRNA regulation was assessed by Significance Analysis of Microarrays. Meta-analysis included a cohort from Memorial Sloan-Kettering Cancer Center (MSKCC; GEO Series GSE2603), two cohorts from the UNC Lineberger Cancer Center (UNCCC; GSE6128 and GSE10886) and a study from the Netherlands Cancer Institute (NKI). Survival analysis utilized Kaplan-Meier curves and p-values derived from log-rank tests.Results: In the annotation of differentially expressed genes between TN tumors and other subtypes, a significant number of Wnt transcriptional targets and transducers were overexpressed, whereas Wnt attenuators were downregulated in the TN tumors. Meta-analysis in MSKCC and UNCCC cohorts yielded 9 Wnt-related mRNAs differentially regulated between TN (basal-like in the UNCCC case) and other subtypes. To determine if this 9-gene Wnt signature was a driver of breast cancer pathology, we developed a bioinformatic discriminator to bifurcate patients into high (Wnt+) and low (Wnt-) Wnt-expressing categories and applied this to MSKCC, UNCCC, and NKI published data sets composing 625 tumor profiles. Patients classified as Wnt+ exhibited worse outcome in bone metastasis free survival (BMFS), lung metastasis free survival (LMFS), recurrence free survival (RFS) and overall survival (OS). LMFS (p ≤ 0.001), RFS (p ≤ 0.001), and OS (p ≤ 0.01) were statistically significant, whereas BMFS was not. Furthermore, reapplying this bioinformatic discriminator on ER+ patients yielded similar results with Wnt+ patients experiencing worse metastasis-free survival (MFS) and OS (p ≤ 0.025).Discussion: Characterization of mRNAs in breast tumors from 864 patients across multiple microarray platforms indicated Wnt signaling as upregulated in TN breast cancers. A 9-gene Wnt signature was found to be indicative of outcome with respect to LMFS, RFS, and OS. A separate analysis of luminal patients will be presented which indicates that Wnt signaling, as a key mediator of breast cancer pathogenesis, segregates ER+ patients into good and poor prognoses.

Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 109.

Differential Wnt pathway activation in triple negative breast cancers comparative to HER2 and hormone positive breast cancers identified from formalin-fixed, paraffin-embedded tissues

Abstract #43

Background: Patients afflicted with triple negative (TN) breast cancer (BC) are typically younger and have the worst prognosis of any BC subtype as a result of its aggressive and invasive phenotype. TN BC has been well studied with respect to the associative and prognostic values of its mRNA expression profiles. We have used the Illumina DASL (cDNA mediated, Annealing, Selection, Extension, and Ligation) platform to characterize 502 genes from 96 BC patients sourced from formalin-fixed, paraffin-embedded (FFPE) tissues. RNA extracted from FFPE tissues is highly fragmented and typically unsuited for expression platforms, but recent advances have allowed for accurate expression profiling of RNA from FFPE tissues. This 96 patient cohort included 21 TN BC patients identified by immunohistochemistry (IHC); differential analysis of TN expression was integrated with known pathway mechanisms and identified activation of the Wnt pathway in TN tumors.&#x2028; Material and Methods: The Illumina DASL assay was used to measure mRNA expression levels from BC patients obtained from St. Mary's Hospital, Montreal, Quebec. RNA was extracted from three 5µm tissue sections from FFPE blocks using the RNA High Pure Kit (Roche). Differential mRNA regulation was identified by Significance Analysis of Microarrays (SAM) software using a false discover rate (FDR, q-value &lt; 0.01) or a Bonferroni corrected two-tailed student's t-test (p-value &lt; 0.05). IHC concordance was measured by mRNA expression fold-change for positive versus negative IHC categories.&#x2028; Results: 165 samples from 96 patients were characterized for mRNA expression on 1,488 probes across 502 genes in the DASL assay. Quality control limited the analysis to 150 samples from 91 patients over 500 genes. Comparison of the TN subtype relative to HER2 positive and hormone positive breast carcinomas identified up-regulation [fold-change] of MMP7 [2.9], MMP9 [2.0], MMP1 [1.8], NOTCH1 [1.5], FZD7 [1.5], PPARD [1.3], CCND2 [1.2], MET [1.3], MYC [1.5], and MYCN [2.0] in the TN subtype. Most of these genes are either a component or downstream target of the Wnt signaling pathway. Down-regulated relevant genes included ESR1 [-8.4], PGR [-3.9], ERBB2 [-3.4] as expected, as well as ERRB3, ERBB4, GLI3, TFF1, LAF4/AFF3, and AR.&#x2028; Discussion: Down-regulation of TFF1 suggests inhibition of the ERK/MAPK pathways which have complex effects on cell-cell adhesion. In combination with over-expression of MMPs 1, 7, and 9, these changes may contribute to the invasive nature of TN BCs. GLI3 down-regulation may attenuate Hedgehog signaling potentially contributing to Wnt activation, further leading to cell migration, invasion, and decrease in cell adhesion to cognate integrin-matrix interaction Up-regulation of both the FZD7 receptor as well as the Wnt targets MMP7, MYC, MYCN, PPARD, and CCND2 strongly suggest Wnt pathway activation in the TN subtype.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 43.

Molecular differences in triple negative breast cancer between race/ethnicities

Abstract #2089

Background: A disparity in prognosis of triple negative (TN) breast cancer (BC) has been observed between African American (AA) and Caucasian (CAU) race/ethnicities afflicted with this aggressive and invasive BC subtype. Etiological understanding of these differences involves accounting for several factors associated with phenotype and genotype. Here, we address the latter using the Illumina DASL (cDNA mediated, Annealing, Selection, Extension, and Ligation) assay to quantify mRNA expression of 512 breast cancer related genes in a cohort of 24 CAU and 56 AA TN BC tissues sourced from formalin-fixed, paraffin-embedded (FFPE) blocks.&#x2028; Material and Methods: The DASL assay was used to measure mRNA expression levels from FFPE sourced tissues in both cohorts of self-identified patients. CAU BC patients were obtained from St. Mary's Hospital, Montreal, Quebec and AA BC patients were obtained from Grady Hospital, Atlanta, Georgia. RNA extraction used the RNA High Pure Kit (Roche) and was taken from archival FFPE tissues either 5µm tissue sections or cores. Differential mRNA regulation was identified by Significance Analysis of Microarrays (SAM) software using a false discover rate (FDR) less than 1% and a two fold-change criteria to determine differential regulation.&#x2028; Results: In all, 33 genes were found differentially expressed between AA and CAU TN BC tumor samples, 32 of which were upregulated in the AA cohort, only 1 of which was upregulated in the CAU group. The upregulated gene in CAU TN BC was TFF1. Upregulated genes in the AA cohort (order of statistical significance according to SAM software) were KIF20A, EP300, AURKB, FGF4, C14orf155, USP22, EPOR, ZNF668, SCNN1G, MAPT, FLNB, EP400, LTA, ACOT11, RBP3, CSF3, E2F2, TGFB1, CCNE1, L1CAM, NDP, VWF, RHOB, FEN1, BIN1, KRT17, CDC42EP4, SERPINF1, CHI3L2, NES, BCL2, and RERG.&#x2028; Discussion: TFF1 upregulated in the CAU population, has been indicated as biomarker of favorable prognosis in endocrine therapy in clinical studies which is consistent with race/ethnicity disparities. The remaining genes upregulated in the AA cohort include transcription factors E2F2 and RBP3/E2F1 both with cyclin binding domains which may interact with CCNE1, extracellular and adhesion related genes KRT17, L1CAM and FGF4, genes associated with cell cycle AURKB, EP400, and EP300 (activator of HIF-1A). Several RAS related genes were also found differentially expressed in the AA cohort including RHOB, RERG, BIN1, and EPOR. Moreover, it is worth mentioning that BCL2 which is expressed in the aggressive mammary cancer cell line MCF-7 was also found upregulated in the AA cohort. These initial findings suggest that several differentially regulated genes between AA and CAU race/ethnicities may account for the disparity in outcomes resultant in these populations. These initial data warrant further investigation which is currently ongoing.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 2089.

Effects of fibrates on human organic anion-transporting polypeptide 1B1-, multidrug resistance protein 2- and P-glycoprotein-mediated transport

The effects of different fibric acid derivatives (bezafibrate, clofibrate, clofibric acid, fenofibrate, fenofibric acid and gemfibrozil) on human organic anion transporting-polypeptide 1B1 (OATP2, OATP-C, SLC21A6), multidrug resistance protein 2 (MRP2/ABCC2) and MDR1-type P-glycoprotein (P-gp/ABCB1) were examined in vitro. Cyclosporin A (a known inhibitor of OATP1B1 and P-gp), MK-571 (a known inhibitor of MRP2) and cimetidine (an organic cation) were also tested. Bezafibrate, fenofibrate, fenofibric acid and gemfibrozil showed concentration-dependent inhibition of estradiol 17-beta-D-glucuronide uptake by OATP1B1-stably transfected HEK cells, whereas clofibrate and clofibric acid did not show any significant effects up to 100 microM. Inhibition kinetics of gemfibrozil, which exhibited the most significant inhibition on OATP1B1, was shown to be competitive with a Ki = 12.5 microM. None of the fibrates showed any significant inhibition of MRP2-mediated transport, which was evaluated by measuring the uptake of ethacrynic acid glutathione into MRP2-expressing Sf9 membrane vesicles. Only fenofibrate showed moderate P-gp inhibition as assessed by measuring cellular accumulation of vinblastine in a P-gp overexpressing cell-line. Cyclosporin A significantly inhibited OATP1B1 and P-gp, whereas only moderate inhibition was observed on MRP2. The rank order of inhibitory potency of MK-571 was determined as OATP1B1 (IC50: 0.3 microM) > MRP2 (4 microM) > P-gp (25 microM). Cimetidine did not show any effects on these transporters. In conclusion, neither MRP2- nor P-gp-mediated transport is inhibited significantly by the fibrates tested. Considering the plasma protein binding and IC50 values for OATP1B1, only gemfibrozil appeared to have a potential to cause drug-drug interactions by inhibiting OATP1B1 at clinically relevant concentrations.

Molecular cloning and functional characterization of murine cysteinyl-leukotriene 1 (CysLT(1)) receptors

We sought to clone and characterize the murine cysteinyl-leukotriene D(4) receptor (mCysLT(1)R) to complement our studies with leukotriene-deficient mice. A cDNA, cloned from trachea mRNA by reverse transcriptase-polymerase chain reaction, has two potential initiator ATG codons that would encode for polypeptides of 352 and 339 amino acids, respectively. These two potential forms, predicted to be seven transmembrane-spanning domain proteins, have 87% amino acid identity with the human CysLT(1) receptor (hCysLT(1)R). Membrane fractions of Cos-7 cells transiently expressing the short mCysLT(1)R demonstrated high affinity and specific binding for leukotriene D(4) (LTD(4), K(d) = 0.25 +/- 0.04 nM). In competition binding experiments, LTD(4) was the most potent competitor (K(i) = 0.8 +/- 0.2 nM) followed by LTE(4) and LTC(4) (K(i) = 86.6 +/- 24.5 and 100.1 +/- 17.1 nM, respectively) and LTB(4) (K(i) > 1.5 microM). Binding of LTD(4) was competitively inhibited by the specific CysLT(1) receptor antagonists MK-571 [(+)-3-(((3-(2-(7-chloro-2-quinolinyl)ethenyl)phenyl) ((3-(dimethylamino)-3-oxopropyl)thio)methyl)thio)propanoic acid], pranlukast (Onon), and zafirlukast (Accolate), while the CysLT(1)/CysLT(2) receptor antagonist BAY-u9773 [6(R)-(4'-carboxyphenylthio)-5(S)-hydroxy-7(E),9(E),11(Z),14(Z)-eicosatetrenoic acid] was 1000 times less potent than LTD(4). In transiently transfected HEK293-T cells expressing either the long or short form of mCysLT(1)R, LTD(4) induced an increase of intracellular calcium. In Xenopus laevis melanophores transiently expressing either isoform, LTD(4) induced the dispersion of pigment granules, consistent with the activation by LTD(4) of a G(alphaq) (calcium) pathway. Functional elucidation of mCysLT(1)R properties as described here will enable further experiments to clarify the selective role of LTD(4) in murine models of inflammation and asthma.

Sequestration and phosphorylation of the prostaglandin E2 EP4 receptor: dependence on the C-terminal tail

The prostaglandin E2 (PGE2) EP4 subtype is one of four prostanoid receptors that use PGE2 as the preferred ligand. We have investigated the agonist-mediated regulation of EP4 using a multifaceted approach. Short-term (30 min) agonist challenge of recombinant EP4 expressed in human embryonic kidney 293 cells (EP4-HEK293 cells) with PGE2 (1 microM) resulted in the desensitization of intracellular cyclic AMP (cAMP) accumulation and a reduction in cell surface [3H]PGE2 specific binding sites. These events correlated with sequestration of EP4, as visualized by immunofluorescence confocal microscopy and phosphorylation, as shown by [32P]orthophosphate labeling of the receptor. Stimulation of protein kinase A activity in EP4-HEK293 cells (10 microM forskolin or 1 mM 8-bromo-cAMP) did not induce EP4 desensitization, sequestration, or phosphorylation. In contrast, stimulation of protein kinase C activity (100 nM phorbol 12-myristate 13-acetate) attenuated PGE2-induced adenylyl cyclase activity and increased EP4 phosphorylation, but did not induce sequestration or a reduction in [3H]PGE2 specific binding sites. EP4 receptors containing a third intracellular loop deletion [EP4 (del. 215-263)] or a carboxyl-terminal tail truncation [EP4 (del. 355)] of EP4 were used to demonstrate that the C-terminal tail governs sequestration as well as phosphorylation of the receptor.

Everyone is still on welfare: the role of redistribution in social policy

Most people have an inaccurate assessment of who is "on welfare." Two decades have passed since Social Work published the original version of this article, which applied Titmuss's framework of a three-tiered social welfare system and showed that nearly "everyone is on welfare." Based on new data and a more in-depth analysis, this article re-examines who benefits from and who pays for social, fiscal, and corporate welfare and concludes that all three welfare systems continue to serve and to favor the middle class, wealthy households, and large corporations. Social workers can work to transform the system from one that rewards power and privilege to one that ensures distributive justice for all.

Key Structural Features of Prostaglandin E2 and Prostanoid Analogs Involved in Binding and Activation of the Human EP1 Prostanoid Receptor

The structure-activity relationship (SAR) of prostaglandin (PG) E(2) at the human EP(1) prostanoid receptor (designated hEP(1)) was examined via the binding and activation of this receptor by a series of 55 prostanoids and analogs. Using clonal human embryonic kidney 293 cell lines expressing recombinant hEP(1), affinity (K(i)), potency (EC(50)), and efficacy data were obtained using a radioligand competitive binding assay and an aequorin-based calcium functional assay. All compounds behaved as full agonists (90-100% of the response elicited by PGE(2)) in this assay, and the correlation between the K(i) and EC(50) values was highly significant (R(2) = 0.86). The results from the SAR analysis can be summarized as follows: 1) the existence and configuration of hydroxyl groups at the 11 and 15 positions of PGE(2) and prostanoid analog structures play a critical role in agonist activity; 2) the carboxyl group is also important for activity and modification of the carboxylic acid to various esters results in greatly reduced affinity and potency; 3) the activity of structures with moderate or weak potency can be enhanced by modification of the omega-tail; and 4) modifications to the ketone at the 9-position are better tolerated, with 9-deoxy-9-methylene-PGE(2) being the most potent agonist tested in the functional assay. The impact of other modifications on agonist potency is also discussed. The results from this study have identified, for the first time, the key structural features of PGE(2) and related prostanoids and prostanoid analogs necessary for activation of hEP(1).

Expression of the prostaglandin E(2) (PGE(2)) receptor subtype EP(4) and its regulation by PGE(2) in osteoblastic cell lines and adult rat bone tissue

Prostaglandins E (especially PGE(2)) stimulate bone formation and increase bone mass in several species including man. The mechanism for this effect, the target cells, and the receptors involved are not known. Specific cell-surface receptors for PGE(2) (EP(1-4)) have been cloned and characterized. EP(4) was reported to be the major receptor in embryonic and neonatal bone tissue in mice, especially in preosteoblasts; however, no data are available regarding its expression in adult bone. This study examines the expression of EP(4) in bone tissue of young adult rats, in which PGE(2) is markedly anabolic, and in various osteoblastic cell lines. Using northern blot analysis, we found that osteoblastic cell lines RCT-1, RCT-3, TRAB-11, and RP-1, primary osteoblastic cells harvested from fetal rat calvaria, as well as tibiae and calvariae of 5-week-old rats express 3.8 kb EP(4) messenger RNA (mRNA). Treatment of periosteal cells (RP-1) in vitro with 10(-6) mol/L PGE(2) increased the levels of both EP(4) mRNA and EP(4) protein, peaking at 1-2 h. Similarly, systemic administration of an anabolic dose of PGE(2) (3-6 mg/kg) to young adult rats upregulated the expression of EP(4) in the tibia and calvaria, also peaking at 1-2 h. Using in situ hybridization, we found increased expression of EP(4) in bone marrow cells of the tibial metaphysis in response to systemic PGE(2) treatment. The preosteoblastic nature of these EP(4)-expressing cells was suggested by the fact that dexamethasone-treated bone marrow stromal cells in culture express EP(4) mRNA, which is upregulated by PGE(2). Northern blot analysis failed to detect both basal and PGE(2)-induced EP(2) mRNA in the bone samples or cell lines tested. Taken together, these data implicate EP(4) as the major cyclic AMP-related PGE(2) receptor subtype expressed in bone tissue and osteoblastic cells and indicate that this receptor is upregulated by its ligand, PGE(2).

Characterization of the human cysteinyl leukotriene 2 receptor

The contractile and inflammatory actions of the cysteinyl leukotrienes (CysLTs), LTC(4), LTD(4), and LTE(4), are thought to be mediated through at least two distinct but related CysLT G protein-coupled receptors. The human CysLT(1) receptor has been recently cloned and characterized. We describe here the cloning and characterization of the second cysteinyl leukotriene receptor, CysLT(2), a 346-amino acid protein with 38% amino acid identity to the CysLT(1) receptor. The recombinant human CysLT(2) receptor was expressed in Xenopus oocytes and HEK293T cells and shown to couple to elevation of intracellular calcium when activated by LTC(4), LTD(4), or LTE(4). Analyses of radiolabeled LTD(4) binding to the recombinant CysLT(2) receptor demonstrated high affinity binding and a rank order of potency for competition of LTC(4) = LTD(4) LTE(4). In contrast to the dual CysLT(1)/CysLT(2) antagonist, BAY u9773, the CysLT(1) receptor-selective antagonists MK-571, montelukast (Singulair(TM)), zafirlukast (Accolate(TM)), and pranlukast (Onon(TM)) exhibited low potency in competition for LTD(4) binding and as antagonists of CysLT(2) receptor signaling. CysLT(2) receptor mRNA was detected in lung macrophages and airway smooth muscle, cardiac Purkinje cells, adrenal medulla cells, peripheral blood leukocytes, and brain, and the receptor gene was mapped to chromosome 13q14, a region linked to atopic asthma.

A reporter gene assay for high-throughput screening of G-protein-coupled receptors stably or transiently expressed in HEK293 EBNA cells grown in suspension culture

We describe in detail a robust, sensitive, and versatile functional assay for G-protein-coupled receptors (GPCRs) expressed in human embryonic kidney (HEK) 293-EBNA (Epstein-Barr virus nuclear antigen) (designated 293E) cells. The ability to grow these cells in suspension, in conjunction with the use of the secreted form of the human placental alkaline phosphatase (SEAP) as the reporter enzyme transcriptionally regulated by 5-cyclic AMP (cAMP) response elements (CREs) (Chen et al., Anal. Biochem. 226, 349-354 (1995)), makes this CRE-SEAP assay potentially attractive for high-throughput screening (HTS). A 293E clonal cell line, stably transfected with the CRE-SEAP plasmid, was initially characterized with compounds known to activate intracellular signal transduction pathways similar to those activated by GPCRs. Forskolin and cAMP analogues were potent at inducing SEAP expression but calcium ionophores (A23187 and ionomycin) were without effect. The forskolin response was also potentiated by the protein kinase C activator phorbol myristate acetate as well as the phosphodiesterase inhibitor isobutylmethylxanthine. Previously established cell lines expressing the G(alphas)-coupled DP or the G(alphaq)-coupled-EP(1) prostanoid receptors were stably transfected with the reporter gene construct and clones were selected based on their ability to secrete SEAP upon agonist challenge. Pharmacological characterization of the DP and EP(1) receptors displayed a similar rank order of potency for several known prostanoids and related compounds to that previously reported using classical binding assays or other functional assays. The CRE-SEAP assay was also used to characterize the EP(1) receptor antagonists SC-51322, SC-51089, and AH6809. In summary, we have established a reporter gene assay for GPCRs that couple to both G(alphas) and G(alphaq) and is amenable to HTS of both agonists and antagonists.

Coexpression of full-length gamma-aminobutyric acid(B) (GABA(B)) receptors with truncated receptors and metabotropic glutamate receptor 4 supports the GABA(B) heterodimer as the functional receptor

Direct evidence is lacking to show whether the gamma-aminobutyric acid (GABA)(B) gb1-gb2 heterodimer is the signaling form of the receptor. In this study, we tested whether gb1a or gb2 subunits when coexpressed with truncated receptors or metabotropic glutamate receptor mGluR4 could form functional GABA receptors. Coexpression of the ligand binding N-terminal domain of gb1a or the C-terminal portion of gb1a composing the seven-transmembrane segments and intracellular loops with gb2 could not reconstitute functional receptors. We next examined whether mGluR4, which forms homodimers and is structurally related to GABA(B), could act as a surrogate coreceptor for gb1 or gb2. The coexpression of mGluR4 and gb1a led to the expression of gb1a monomers on cell surface membranes as determined by immunoblot analysis and flow cytometry. However, mGluR4-gb1a heterodimers were not formed, and membrane-expressed gb1a monomers were not functionally coupled to adenylyl cyclase in human embryonic kidney 293 cells or activated inwardly rectifying potassium (Kir) channels in Xenopus oocytes. Similarly, the coexpression of mGluR4 and gb2 led to nonfunctional GABA receptors. GABA-activated distal signaling events resulted only after the coexpression and heterodimerization of gb1 and gb2. Taken together with the truncated receptor studies, the data suggest that a high degree of structural specificity is required to form the functional GABA(B) receptor that is a gb1-gb2 heterodimer.

The utilization of recombinant prostanoid receptors to determine the affinities and selectivities of prostaglandins and related analogs

Stable cell lines that individually express the eight known human prostanoid receptors (EP(1), EP(2), EP(3), EP(4), DP, FP, IP and TP) have been established using human embryonic kidney (HEK) 293(EBNA) cells. These recombinant cell lines have been employed in radioligand binding assays to determine the equilibrium inhibitor constants of known prostanoid receptor ligands at these eight receptors. This has allowed, for the first time, an assessment of the affinity and selectivity of several novel compounds at the individual human prostanoid receptors. This information should facilitate interpretation of pharmacological studies that employ these ligands as tools to study human tissues and cell lines and should, therefore, result in a greater understanding of prostanoid receptor biology.

New class of biphenylene dibenzazocinones as potent ligands for the human EP1 prostanoid receptor

A new class of potent and selective ligands for the human EP1 prostanoid receptor is described. SAR studies reported herein allowed the identification of several potent dibenzazocinones bearing an acylsulfonamide side chain. The binding affinity of these compounds on all eight human prostanoid receptors is reported.

Characterization of the cloned guinea pig leukotriene B4 receptor: comparison to its human orthologue

A cDNA clone coding for the guinea pig leukotriene B4 (BLT) receptor has been isolated from a lung cDNA library. The guinea pig BLT receptor has an open reading frame corresponding to 348 amino acids and shares 73% and 70% identity with human and mouse BLT receptors, respectively. Scatchard analysis of membranes prepared from guinea pig and human BLT receptor-transfected human embryonic kidney (HEK) 293 EBNA (Epstein-Bar Virus Nuclear Antigen) cells showed that both receptors displayed high affinity for leukotriene B4 (Kd value of approximately 0.4 nM) and were expressed at high levels (Bmax values ranging from 9 to 12 pmol/mg protein). The rank order of potency for leukotrienes and related analogs in competition for [3H]leukotriene B4 specific binding at the recombinant guinea pig BLT receptor is leukotriene B4 > 20-OH-leukotriene B4 > 12(R)-HETE ((5Z,8Z,10E,12(R)14Z)-12-hydroxyeicosatetraen -1-oic acid) > 12(S)-HETE ((5Z,8Z,10E,12(S)14Z)-12-Hydroxyeicosatetraen -1-oic acid) > 20-COOH-leukotriene B4 > U75302 (6-(6-(3-hydroxy-1E,5Z-undecadienyl)-2-pyridinyl)-1,5-hexane diol) >> leukotriene C4 = leukotriene D4 = leukotriene E4. For the human receptor the rank order of 12(S)-HETE, 20-COOH-leukotriene B4 and U75302 was reversed. Xenopus melanophore and HEK aequorin-based reporter gene assays were used to demonstrate that the guinea pig and human BLT receptors can couple to both the cAMP inhibitory and intracellular Ca2+ mobilization signaling pathways. However, in the case of the aequorin-expressing HEK cells (designated AEQ17-293) transfected with either the guinea pig or human BLT receptor, expression of Galpha16 was required to achieve a robust Ca2+ driven response. Leukotriene B4 was a potent agonist in functional assays of both the guinea pig and human BLT receptors. U-75302 a leukotriene B4 analogue which possesses both agonistic and antagonistic properties behaved as a full agonist of the guinea pig and human BLT receptors in AEQ17-293 cells and not as an antagonist. The recombinant guinea pig BLT receptor will permit the comparison of the intrinsic potencies of leukotriene B4 receptor antagonists used in guinea pig in vivo models of allergic and inflammatory disorders.

An automated aequorin luminescence-based functional calcium assay for G-protein-coupled receptors

We describe in detail an automated and highly sensitive functional assay for calcium-coupled receptors (those receptors whose activation results in an increase in intracellular calcium levels) utilizing coelenterazine-charged aequorin as a probe for intracellular calcium levels ([Ca(2+)](i)). The assay was originally established to investigate Galpha(q)-coupled prostanoid receptors, which are members of the G-protein-coupled receptor (GPCR) superfamily, signaling through elevation of [Ca(2+)](i), initially focusing on the human EP(1) prostanoid receptor (hEP(1)). The parental human embryonic kidney cell line 293-AEQ17, developed by Button and Brownstein (Cell Calcium 14, 663-671, 1993), constitutively expresses apoaequorin and was used to develop a clonal cell line which stably coexpresses hEP(1). This cell line was used to optimize assay parameters in order to maximize accuracy and throughput in an automated 96-well format with the result that each 96-well plate can be completed in 70 min. Use of this flexible system will greatly simplify the functional analysis of GPCRs and other receptors which when activated result in increases in [Ca(2+)](i).

Receptor for motilin identified in the human gastrointestinal system

Motilin is a 22-amino acid peptide hormone expressed throughout the gastrointestinal (GI) tract of humans and other species. It affects gastric motility by stimulating interdigestive antrum and duodenal contractions. A heterotrimeric guanosine triphosphate-binding protein (G protein)-coupled receptor for motilin was isolated from human stomach, and its amino acid sequence was found to be 52 percent identical to the human receptor for growth hormone secretagogues. The macrolide antibiotic erythromycin also interacted with the cloned motilin receptor, providing a molecular basis for its effects on the human GI tract. The motilin receptor is expressed in enteric neurons of the human duodenum and colon. Development of motilin receptor agonists and antagonists may be useful in the treatment of multiple disorders of GI motility.

Characterization of the human cysteinyl leukotriene CysLT1 receptor

The cysteinyl leukotrienes-leukotriene C4(LTC4), leukotriene D4(LTD4) and leukotriene E4(LTE4)-are important mediators of human bronchial asthma. Pharmacological studies have determined that cysteinyl leukotrienes activate at least two receptors, designated CysLT1 and CysLT2. The CysLT1-selective antagonists, such as montelukast (Singulair), zafirlukast (Accolate) and pranlukast (Onon), are important in the treatment of asthma. Previous biochemical characterization of CysLT1 antagonists and the CysLT1 receptor has been in membrane preparations from tissues enriched for this receptor. Here we report the molecular and pharmacological characterization of the cloned human CysLT1 receptor. We describe the functional activation (calcium mobilization) of this receptor by LTD4 and LTC4, and competition for radiolabelled LTD4 binding to this receptor by the cysteinyl leukotrienes and three structurally distinct classes of CysLT1-receptor antagonists. We detected CysLT1-receptor messenger RNA in spleen, peripheral blood leukocytes and lung. In normal human lung, expression of the CysLT1-receptor mRNA was confined to smooth muscle cells and tissue macrophages. Finally, we mapped the human CysLT1-receptor gene to the X chromosome.

Characterization of a novel serotonin receptor from Caenorhabditis elegans: cloning and expression of two splice variants

Serotonin [5-hydroxytryptamine (5-HT)] modulates feeding activity, egg-laying, and mating behavior in the free-living nematode, Caenorhabditis elegans. We have cloned a novel receptor cDNA from C. elegans (5-HT2Ce) that has high sequence homology with 5-HT2 receptors from other species. When transiently expressed in COS-7 cells, 5-HT2Ce exhibited 5-HT binding activity and activated Ca2+-mediated signaling in a manner analogous to other 5-HT2 receptors. However, 5-HT2Ce displayed unusual pharmacological properties, which resembled both 5-HT2 and 5-HT1-like receptors but did not correlate well with any of the known 5-HT2 subtypes. Two splice variants of 5-HT2Ce that differ by 48 N-terminal amino acids were identified. The two isoforms were found to have virtually identical binding and signaling properties but differed in their levels of mRNA expression, with the longer variant being four times more abundant than the shorter species in all developmental stages tested. Taken together, the results describe two variants of a novel C. elegans 5-HT receptor, which has some of the properties of the 5-HT2 family but whose pharmacological profile does not conform to any known class of receptor.

Nuclear localization of prostaglandin E2 receptors

Prostaglandin E2 receptors (EP) were detected by radioligand binding in nuclear fractions isolated from porcine brain and myometrium. Intracellular localization by immunocytofluorescence revealed perinuclear localization of EPs in porcine cerebral microvascular endothelial cells. Nuclear association of EP1 was also found in fibroblast Swiss 3T3 cells stably overexpressing EP1 and in human embryonic kidney 293 (Epstein-Barr virus-encoded nuclear antigen) cells expressing EP1 fused to green fluorescent protein. High-resolution immunostaining of EP1 revealed their presence in the nuclear envelope of isolated (cultured) endothelial cells and in situ in brain (cortex) endothelial cells and neurons. Stimulation of these nuclear receptors modulate nuclear calcium and gene transcription.

Molecular characterization and expression of cloned human galanin receptors GALR2 and GALR3

Galanin is a 29- or 30-amino acid peptide with wide-ranging effects on hormone release, feeding behavior, smooth muscle contractility, and somatosensory neuronal function. Three distinct galanin receptor (GALR) subtypes, designated GALR1, 2, and 3, have been cloned from the rat. We report here the cloning of the human GALR2 and GALR3 genes, an initial characterization of their pharmacology with respect to radioligand binding and signal transduction pathways, and a profile of their expression in brain and peripheral tissues. Human GALR2 and GALR3 show, respectively, 92 and 89% amino acid sequence identity with their rat homologues. Radioligand binding studies with 125I-galanin show that recombinant human GALR2 binds with high affinity to human galanin (K(D) = 0.3 nM). Human GALR3 binds galanin with less affinity (IC50 of 12 nM for porcine galanin and 75 nM for human galanin). Human GALR2 was shown to couple to phospholipase C and elevation of intracellular calcium levels as assessed by aequorin luminescence in HEK-293 cells and by Xenopus melanophore pigment aggregation and dispersion assays, in contrast to human GALR1 and human GALR3, which signal predominantly through inhibition of adenylate cyclase. GALR2 mRNA shows a wide distribution in the brain (mammillary nuclei, dentate gyrus, cingulate gyrus, and posterior hypothalamic, supraoptic, and arcuate nuclei), and restricted peripheral tissue distribution with highest mRNA levels detected in human small intestine. In comparison, whereas GALR3 mRNA was expressed in many areas of the rat brain, there was abundant expression in the primary olfactory cortex, olfactory tubercle, the islands of Calleja, the hippocampal CA regions of Ammon's horn, and the dentate gyrus. GALR3 mRNA was highly expressed in human testis and was detectable in adrenal gland and pancreas. The genes for human GALR2 and 3 were localized to chromosomes 17q25 and 22q12.2-13.1, respectively.

Medical, cognitive, emotional, and behavioral outcomes in school-age children conceived by in-vitro fertilization

Assessed long-term effects of assisted reproduction technologies of in-vitro fertilization (IVF) and related techniques of embryo transfer (ET) on children's adjustment. 51 school-age Israeli children conceived by IVF/ET were compared with 51 control-matched children conceived spontaneously. The assessment included a comprehensive medical evaluation, a psychological examination, teachers' reports, parents' reports, and children's self-reports. As compared with controls, IVF/ET children did not reveal significant differences in physical and neurological status or on cognitive measures of IQ, visual-motor coordination, visual memory, and verbal comprehension. Nevertheless, the IVF/ET children were scored lower by teachers on measures of socioemotional adjustment in school and on self-report measures of anxiety, aggression, and depression. Among IVF/ET children, the tendency to be at a greater risk for emotional disturbances was exacerbated among boys and among children whose parents were older.

Characterization of the recombinant human prostanoid DP receptor and identification of L-644,698, a novel selective DP agonist

1. A human embryonic kidney cell line [HEK 293(EBNA)] stably expressing the human recombinant prostaglandin D2 (PGD2) receptor (hDP) has been characterized with respect to radioligand binding and signal transduction properties by use of prostanoids and prostanoid analogues. Radioligand binding studies included saturation analyses, the effects of nucleotide analogues, the initial rate of ligand-receptor association and equilibrium competition assays. In addition, adenosine 3':5'-cyclic monophosphate (cyclic AMP) generation in response to ligand challenge was also measured, as this is the predominant hDP signalling pathway. 2. L-644,698 ((4-(3-(3-(3-hydroxyoctyl)-4-oxo-2-thiazolidinyl) propyl) benzoic acid) (racemate)) was identified as a novel ligand having high affinity for hDP with an inhibitor constant (Ki) of 0.9 nM. This Ki value was comparable to the Ki values obtained in this study for ligands that have previously shown high affinity for DP: PGD2 (0.6 nM), ZK 110841 (0.3 nM), BW245C (0.4 nM), and BW A868C (2.3 nM). 3. L-644,698 was found to be a full agonist with an EC50 value of 0.5 nM in generating cyclic AMP following activation of hDP. L-644,698 is, therefore, comparable to those agonists with known efficacy at the DP receptor (EC50): PGD2 (0.5 nM), ZK 110841 (0.2 nM) and BW245C (0.3 nM). 4. L-644,698 displayed a high degree of selectivity for hDP when compared to the family of cloned human prostanoid receptors: EP1 (> 25,400 fold), EP2 (approximately 300 fold), EP3-III (approximately 4100 fold), EP4 (approximately 10000 fold), FP (> 25,400 fold), IP (> 25,400 fold) and TP (> 25,400 fold). L-644,698 is, therefore, one of the most selective DP agonists as yet described. 5. PGJ2 and delta12-PGJ2, two endogenous metabolites of PGD2, were also tested in this system and shown to be effective agonists with Ki and EC50 values in the nanomolar range for both compounds. In particular, PGJ2 was equipotent to known DP specific agonists with a Ki value of 0.9 nM and an EC50 value of 1.2 nM.

Molecular cloning and characterization of the four rat prostaglandin E2 prostanoid receptor subtypes

We have characterized the rat prostanoid EP1, EP2, EP3alpha and EP4 receptor subtypes cloned from spleen, hepatocyte and/or kidney cDNA libraries. Comparison of the deduced amino acid sequences of the rat EP receptors with their respective homologues from mouse and human showed 91% to 98% and 82% to 89% identity, respectively. Radioreceptor binding assays and functional assays were performed on EP receptor expressing human embryonic kidney (HEK) 293 cells. The KD values obtained with prostaglandin E2 for the prostanoid receptor subtypes EP1, EP2, EP3alpha and EP4 were approximately 24, 5, 1 and 1 nM, respectively. The rank order of affinities for various prostanoids at the prostanoid receptor subtypes EP2, EP3alpha and EP4 receptor subtypes was prostaglandin E2 = prostaglandin E1 > iloprost > prostaglandin F2alpha > prostaglandin D2 > U46619. The rank order at the prostanoid EP1 receptor was essentially the same except that iloprost had the highest affinity of the prostanoids tested. Of the selective ligands, butaprost was selective for prostanoid EP2, M&B28767 and sulprostone were selective for EP3alpha and enprostil displayed dual selectivity, interacting with both prostanoid receptor subtypes EP1 and EP3alpha. All four receptors coupled to their predominant signal transduction pathways in HEK 293 cells. Notably, using a novel aequorin luminescence assay to monitor prostanoid EP1 mediated increases in intracellular calcium, both iloprost and sulprostone were identified as partial agonists. Finally, by Northern blot analysis EP3 transcripts were most abundant in liver and kidney whereas prostanoid EP2 receptor mRNA was expressed in spleen, lung and testis and prostanoid EP1 receptor mRNA transcripts were predominantly expressed in the kidney. The rat prostanoid EP1 probes also detected additional and abundant transcripts present in all the tissues examined. These were found to be related to the expression of a novel protein kinase gene and not the prostanoid EP1 gene [Batshake, B., Sundelin, J., 1996. The mouse genes for the EP1 prostanoid receptor and the novel protein kinase overlap. Biochem. Biophys. Res. Commun. 227. 1329-1333].

Molecular cloning and characterization of the human prostanoid DP receptor

A cDNA encoding a functional human prostanoid DP (hDP) receptor has been constructed from a genomic clone and a fragment cloned by 3'-rapid amplification of cDNA ends-polymerase chain reaction. The hDP receptor consists of 359 amino acid residues with a predicted molecular mass of 40,276 and has the putative heptahelical transmembrane domains characteristics of G-protein-coupled receptors. The deduced amino acid sequence of the hDP receptor, when compared with all other members of the prostanoid receptor family, shows the highest degree of identity with the hIP and hEP2 receptors, followed by the hEP4 receptor. Radioreceptor binding studies using membranes prepared from mammalian COS-M6 cells transiently transfected with an expression vector containing the DP receptor cDNA showed that the rank order of affinities for prostaglandins and prostaglandin analogs, in competition for [3H]prostaglandin D2 (PGD2) specific binding sites, was as predicted for the DP receptor, with PGD2 >> PGE2 > PGF2 alpha = iloprost > U46619. The signal transduction pathway of the cloned hDP receptor was studied by transfecting the hDP expression vector in HEK 293(EBNA) cells. Activation of the hDP receptor with PGD2 resulted in an elevation of intracellular cAMP and in mobilization of Ca2+, but did not lead to generation of inositol 1,4,5-trisphosphate. Northern blot analysis of human tissue showed that the hDP receptor was a very discrete tissue distribution and was detectable only in retina and small intestine. In summary, we have cloned and expressed a functional cDNA for the hDP receptor.

Detection of adenylate cyclase-coupled receptors in Xenopus oocytes by coexpression with cystic fibrosis transmembrane conductance regulator

To detect heterologous expression of receptors coupled via G proteins to the stimulation of adenylate cyclase in Xenopus laevis oocytes, the receptor of interest is coexpressed with the cystic fibrosis transmembrane conductance regulator (CFTR)--a cAMP-dependent Cl- channel. The binding of an agonist to the expressed receptor stimulates adenylate cyclase resulting in intracellular cAMP elevation, which in turn activates the CFTR. The CFTR-mediated Cl- current response is then measured using the standard two-electrode voltage-clamp technique. This method has allowed us to detect functional expression in oocytes of the human EP2 and IP prostanoid receptors. This method should prove valuable for expression and identification of putative G protein-coupled receptors signaling through stimulation of adenylate cyclase, for structure/function studies, and for analysis of receptor antagonists and agonists.

Chromosomal localization of the human prostanoid receptor gene family

Prostaglandins (PGD2, PGE2, PGF2 alpha, and PGI2) and thromboxane A2 (TXA2) are biologically active molecules derived from the metabolism of arachidonic acid by cyclooxygenases. They produce a wide variety of physiological and pathophysiological effects mediated through specific G protein-coupled cell surface receptors. In this study, we have mapped the chromosomal positions of the human genes that encode the PGE2 receptor subtypes (PTGER1, PTGER2, and PTGER3), the PGF2 alpha receptor (PTGFR), the PGI2 receptor (PTGIR), and the TXA2 receptor (TBXA2R) using in situ hybridization. The PTGER1, TBXA2R, and PTGIR genes mapped to chromosome 19 at positions 19p13.1, 19p13.3, and 19q13.3, respectively. The PTGFR and PTGER3 genes mapped to chromosome 1 at positions 1p31.1 and 1p31.2, respectively, and PTGER2 gene mapped to chromosome band 5p13.1.

Brain and testis selective expression of the glutathione S-transferase Yb3 subunit is governed by tandem direct repeat octamer motifs in the 5'-flanking region of its gene

To gain insight into mechanisms of cell type-specific transcription of class mu-glutathione S-transferase genes, the gene encoding the Yb3 subunit was cloned. Yb3 subunits are selectively expressed at high levels in rat brain and testis but not in liver or kidney. The Yb3 subunit gene spans over 6 kb and consists of 8 exons and 7 introns and a sequence consisting of tandem direct repeat consensus octamer DNA binding motifs separated by a 6 base pair (bp) spacer was identified in its 5'-flanking region. Gel shift assays with a 40 bp segment of DNA containing the two consensus octamer sequences, revealed the presence of specific binding proteins in nuclear extracts of rat brain, testis and C6 glioma cells. DNA binding activity was greatly reduced in liver, kidney and HTC cells. Reporter vectors carrying segments of the 5'-flanking region of the Yb3 subunit gene fused to a luciferase gene were introduced into C6 glioma cells which express high levels of Yb3 subunits, and into HTC cells which do not. The plasmids consisting of the Yb3 gene promoter up to, but not including, the octamer motifs did not support luciferase transcription in the C6 glioma cells, but larger fragments that included the octamer repeat sequences, effectively directed transcription in the C6 glioma cells. With mutated octameric sequences transcriptional activity was greatly reduced, and none of the same Yb3 constructs directed substantial luciferase transcription in the HTC cells. The results show that octamer motifs in the 5'-flanking region of the Yb3 subunit gene are functional and are the principal cis-acting elements that account for its discrete cell type-selective expression. This gene is one of the few known targets for octamer DNA binding transcription factors in brain.

Cloning and expression of a cDNA for the human prostanoid IP receptor

A cDNA clone coding for a functional human prostanoid IP receptor has been isolated from a lung cDNA library. The human IP receptor consists of 386 amino acid residues with a predicted molecular mass of 40,961, and has the seven putative transmembrane domains characteristic of G-protein-coupled receptors. Challenge of Xenopus oocytes co-expressing the IP receptor and the cystic fibrosis transmembrane conductance regulator (cAMP-activated Cl- channel) with the stable prostacyclin analog iloprost resulted in specific inward Cl- currents, demonstrating that the cDNA encoded a functional IP prostanoid receptor coupled to elevation in cAMP. Radioreceptor binding studies using membranes prepared from mammalian COS cells transfected with the IP receptor cDNA showed that the rank order of potency for prostaglandins and prostaglandin analogs in competition for [3H]iloprost specific binding sites was as predicted for the IP receptor, with iloprost >> carbacyclin >> prostaglandin (PG) E2 > PGF 2 alpha = PGD2 = U46619. Northern blot analysis showed that IP mRNA was most abundantly expressed in kidney, with lesser amounts detected in lung and liver. In summary, we have cloned and expressed a cDNA for the human prostanoid IP receptor that is functionally coupled to a signaling pathway involving stimulation of intracellular cAMP production.

Overexpression of human prostaglandin G/H synthase-1 and -2 by recombinant vaccinia virus: inhibition by nonsteroidal anti-inflammatory drugs and biosynthesis of 15-hydroxyeicosatetraenoic acid

Human prostaglandin G/H synthase (hPGHS)-1 and hPGHS-2, key enzymes in the formation of prostanoids from arachidonic acid, were expressed at high levels in COS-7 cells using a T7 RNA polymerase/vaccinia virus expression system. The open reading frame of hPGHS-2 cloned into vaccinia virus without its natural 5' and 3' untranslated regions directed only low levels of hPGHS-2 enzyme activity in COS-7 cells. High-level hPGHS-2 expression was achieved by appending the 3' untranslated region of hPGHS-1 to the hPGHS-2 open reading frame, with subsequent expression of the hybrid mRNA using vaccinia virus. Enzymatically active recombinant hPGHS-1 and hPGHS-2 were present as glycosylated proteins in the microsomal fraction prepared from infected cells, whereas recombinant hPGHS-1 and hPGHS-2 prepared from the microsomal fraction of cells treated with tunicamycin, an inhibitor of N-linked glycosylation, were enzymatically inactive. The major prostanoid products formed by microsomes from COS-7 cells containing either recombinant hPGHS-1 or hPGHS-2 after incubation with arachidonic acid were prostaglandin D2 and E2, with lower levels of prostaglandin F2 alpha and 6-keto-prostaglandin F1 alpha. A range of potencies were observed for various nonsteroidal anti-inflammatory drugs as inhibitors of prostaglandin E2 synthesis by hPGHS-1 and hPGHS-2. Recombinant hPGHS-1 and hPGHS-2 both produced 15- and 11-hydroxyeicosatetraenoic acid (HETE) from arachidonic acid, with 15-HETE production by hPGHS-2 being stimulated 5-fold by preincubation with aspirin. Chiral phase high performance liquid chromatography analysis showed that aspirin-treated hPGHS-2 produced 15(R)-HETE, with no detectable 15(S)-HETE.

Cloning and expression of three isoforms of the human EP3 prostanoid receptor

Functional cDNA clones coding for three isoforms of the human prostaglandin E receptor EP3 subtype have been isolated from kidney and uterus cDNA libraries. The three isoforms, designated hEP3-I, hEP3-II and hEP3-III, have open reading frames corresponding to 390, 388 and 365 amino acids, respectively. They differ only in the length and amino acid composition of their carboxy-terminal regions, beginning at position 360. The human EP3 receptor has seven predicted transmembrane spanning domains and therefore belongs to the G-protein-coupled receptor family. The rank order of potency for prostaglandins and related analogs in competition for [3H]PGE2 specific binding to membranes prepared from transfected COS cells was comparable for all three isoforms, and as predicted for the EP3 receptor, with PGE2 = PGE1 >> PGF2 alpha = iloprost > PGD2 >> U46619. In addition, the EP3-selective agonist MB28767 was a potent competing ligand with an IC50 value of 0.3 nM, whereas the EP1-selective antagonist AH6909 gave IC50 values of 2-7 microM and the EP2-selective agonist butaprost was inactive. In summary, we have cloned three isoforms of the human EP3 receptor having comparable ligand binding properties.

Cloning and expression of a cDNA for the human prostanoid FP receptor

A cDNA clone coding for a functional human prostanoid FP receptor has been isolated from a uterus cDNA library. The human FP receptor consists of 359 amino acid residues with a predicted molecular mass of 40,060, and has the seven putative transmembrane domains characteristic of G-protein-coupled receptors. Challenge of Xenopus oocytes expressing the FP receptor with 10 nM of either prostaglandin (PG) F2 alpha or the selective FP-receptor agonist fluprostenol resulted in an elevation in intracellular Ca2+. Radioreceptor binding studies using membranes prepared from mammalian COS cells transfected with the FP receptor cDNA showed that the rank order of potency for prostaglandins and prostaglandin analogs in competition for [3H]PGF2 alpha specific binding sites was as predicted for the FP receptor, with PGF2 alpha approximately fluprostenol > PGD2 > PGE2 > U46619 > iloprost. In summary, we have cloned the human prostanoid FP receptor which is functionally coupled to the Ca2+ signalling pathway.

Cloning and expression of a cDNA for the human prostaglandin E receptor EP1 subtype

A functional cDNA clone coding for the human prostaglandin E receptor EP1 subtype has been isolated from a human erythroleukemia cell cDNA library probed by low-stringency hybridization using a polymerase chain reaction fragment of the human thromboxane receptor. The human EP1 receptor is comprised of 402 amino acids with a predicted molecular mass of 41,858 and has the topography common to all G-protein-coupled receptors with seven predicted transmembrane spanning domains. Prostaglandin (PG) E2 challenge of Xenopus oocytes injected with EP1 cDNA resulted in an increase in intracellular Ca2+. In addition, the rank order of potency for prostaglandins in competition for [3H]PGE2 specific binding to membranes prepared from EP1 cDNA transfected COS cells was PGE2 > PGE1 > PGF2 alpha > PGD2. Furthermore, the EP1 receptor-selective antagonists AH 6809 and SC19220 were more potent than the EP2 receptor-selective agonist butaprost in these competition binding assays. In summary, therefore, we have cloned the human EP1 receptor subtype which is functionally coupled to an increase in intracellular Ca2+.

5-lipoxygenase-activating protein stimulates the utilization of arachidonic acid by 5-lipoxygenase

5-Lipoxygenase (5-LO) and its activating protein (FLAP) are both required for cellular leukotriene (LT) synthesis, with 5-LO catalyzing both the synthesis of (5S)-5-hydroperoxy-6,8,11,14-eicosatetraenoic acid (5-HPETE) from arachidonic acid and the subsequent synthesis of LTA4 from 5-HPETE. We have previously expressed both human 5-LO and human FLAP to high levels in Spodoptera frugiperda (Sf9) insect cells, using recombinant baculoviruses. To study the mechanism by which FLAP activates 5-LO, we compared cellular 5-LO activity in Sf9 cells expressing this enzyme to that in Sf9 cells coexpressing FLAP and 5-LO. In this system, FLAP stimulates the utilization of arachidonic acid by 5-LO as a substrate, and increases the efficiency with which 5-LO converts 5-HPETE to LTA4. LT synthesis in cells coexpressing FLAP and 5-LO is inhibited by 3-[1-(p-chlorophenyl)-5-isopropyl-3-tert-butylthio-1H-indol-2-yl]-2,2- dimethyl-propanoic acid (MK-886), an LT biosynthesis inhibitor which specifically binds to FLAP. These studies in Sf9 cells, together with our recent demonstration that FLAP specifically binds arachidonic acid, suggests that FLAP activates 5-LO by acting as an arachidonic acid transfer protein.

5-lipoxygenase-activating protein is an arachidonate binding protein

5-Lipoxygenase-activating protein (FLAP) is an 18-kDa integral membrane protein which is essential for cellular leukotriene (LT) synthesis, and is the target of LT biosynthesis inhibitors. However, the mechanism by which FLAP activates 5-LO has not been determined. We have expressed high levels of human FLAP in Spodoptera frugiperda (Sf9) insect cells infected with recombinant baculovirus, and used this system to demonstrate that FLAP specifically binds [125I]L-739,059, a novel photoaffinity analog of arachidonic acid. This binding is inhibited by both arachidonic acid and MK-886, an LT biosynthesis inhibitor which specifically interacts with FLAP. These studies suggest that FLAP may activate 5-LO by specifically binding arachidonic acid and transferring this substrate to the enzyme.

Amino acid residues of 5-lipoxygenase-activating protein critical for the binding of leukotriene biosynthesis inhibitors

5-Lipoxygenase-activating protein (FLAP) plays an essential role in cellular leukotriene (LT) synthesis and represents the target of three classes of LT biosynthesis inhibitors. We have taken three approaches to localize regions of FLAP involved in the binding of these inhibitors. A comparison of the amino acid sequences of FLAP from eight mammalian species identifies regions of the protein which are highly conserved and consequently may be involved in functional and inhibitor binding properties of the protein. Conversely, amino acids not conserved amongst these species are unlikely to play an essential role in inhibitor binding. Immunoprecipitation of peptide fragments of FLAP cross-linked to photoaffinity analogues of LT biosynthesis inhibitors following site-specific peptide cleavage indicates that the inhibitor attachment site is amino-terminal to 72Trp. Taken together, the cross-species analysis and photoaffinity labelling studies suggest a region within the first hydrophilic loop of FLAP which may be important for inhibitor binding. Site-directed mutagenesis of human FLAP followed by the analysis of FLAP mutants in a radioligand binding assay was used to more accurately define critical amino acid residues within this region. Mutagenesis studies reveal that mutants containing deletions of amino acids in regions of FLAP not conserved between species retain the ability to specifically bind inhibitors. Furthermore, mutants containing deletions in a highly conserved region of the protein (residues 42-61) do not bind inhibitors. These studies have therefore localized specific amino acids of FLAP which are essential for inhibitor binding. The roles that these amino acids play in inhibitor binding and may play in 5-LO activation is under investigation.

Cross-species comparison of 5-lipoxygenase-activating protein

To identify regions of 5-lipoxygenase-activating protein (FLAP) important for the function of the protein and the binding of leukotriene biosynthesis inhibitors, we performed a cross-species analysis of FLAP. FLAP from all 10 mammalian species analyzed (human, monkey, horse, pig, cow, sheep, rabbit, dog, rat, and mouse) were immunologically cross-reactive and specifically bound leukotriene biosynthesis inhibitors with high affinity. Using the polymerase chain reaction, cDNA clones for FLAP from six species (monkey, horse, pig, sheep, rabbit, and mouse) were isolated and sequenced. The deduced amino acid sequences of FLAP show a high degree of identity to each other and to the published sequences for human and rat FLAP. Two regions of the protein are almost totally conserved among all of the species analyzed. This suggests that these regions have functional significance and may be involved in inhibitor binding.

Evaluation of the role of conserved His and Met residues among lipoxygenases by site-directed mutagenesis of recombinant human 5-lipoxygenase

The 5-, 12-, and 15-lipoxygenases contain a highly conserved sequence of the form His-(X)4-His-(X)4-His-(X)17-His-(X)8-His which represents a potential binding site for non heme iron to the protein. The importance of selected amino acids within this His cluster for the activity of human 5-lipoxygenase was investigated by site-directed mutagenesis using bacteria and insect cells expression systems. After single mutation of each of the 5 His residues at positions 363, 368, 373, 391, and 400 by Ser, Cys, or Lys, measurable levels of 5-lipoxygenase activity could be recovered in Escherichia coli only for the Ser363 and Cys363 mutants, with most amino acid substitutions causing a decrease in the levels of expression of the soluble protein. In contrast, 25-80% of soluble 5-lipoxygenase activity was recovered after the replacement of several of the hydrophobic amino acids in this region: Tyr384 by Ser or Phe; Phe394 by Trp and Val375 by Ala. Met436 could be replaced by Leu with little effect on 5-lipoxygenase activity or turnover inactivation half-time. High levels of mutant 5-lipoxygenases containing a Ser residue instead of His at each of the five positions were also expressed in Spodoptera frugiperda (Sf9) cells infected with recombinant baculovirus. The specific activity (58-75% of control) and the reaction time course of the Ser363, Ser391, and Ser400 mutants were comparable with that of native 5-lipoxygenase whereas inactive proteins were obtained for the Ser368 and Ser373 mutants. These results show that His368 and His373 residues are important for 5-lipoxygenase activity and that the other conserved His363, His391, His400, and Met436 residues are not crucial for the catalytic cycle or for the mechanism of self-inactivation of 5-lipoxygenase.

Characterization of the activity of purified recombinant human 5-lipoxygenase in the absence and presence of leukocyte factors

Purified recombinant human 5-lipoxygenase was used to investigate the catalytic properties of the protein in the presence and absence of leukocyte stimulatory factors. Recombinant human 5-lipoxygenase was purified to apparent homogeneity (95-99%) from a high expression baculovirus system by chromatography on ATP-agarose with a yield of 0.6 mg of protein per 100 ml of culture (2 x 10(8) cells) and a specific activity of 3-6 mumol of 5-hydroperoxyeicosatetraenoic acid (5-HPETE) per mg of protein in the presence of ATP, Ca2+, and phosphatidylcholine as the only factors. In the absence of leukocyte factors, the reaction catalyzed by the purified recombinant enzyme showed a half-time of maximal 5-HPETE formation of 0.5-0.7 min and was sensitive to the selective 5-lipoxygenase inhibitors BW755C (IC50 = 13 microM) and L-656,224 (IC50 = 0.8 microM). The reaction products of arachidonic acid oxidation were 5-HPETE and 6-trans- and 12-epi-6-trans-leukotriene B4, the nonenzymatic hydrolysis products of leukotriene A4 (LTA4), indicating that the purified protein expressed both the 5-oxygenase and leukotriene A4 synthase activities (ratio 6:1). The microsomal fraction and the 60-90% ammonium sulfate precipitate fraction from sonicated human leukocytes did not increase product formation by the isolated enzyme when assayed in the presence of ATP, Ca2+, and phosphatidylcholine. These factors were found to stabilize 5-lipoxygenase during preincubation of the enzyme at 37 degrees C with the assay mixture but they failed to stimulate enzymatic activity when added at the end of the preincubation period. The results demonstrate that human 5-lipoxygenase can be isolated in a catalytically active form and that protein factors from leukocytes protect against enzyme inactivation but are not essential for enzyme activity.