Inhibitory effect of 2-(piperidinoethoxyphenyl)-3-(4-hydroxyphenyl)-2H-benzo(b)pyran (K-1) on human primary endometrial hyperplasial cells mediated via combined suppression of Wnt/β-catenin signaling and PI3K/Akt survival pathway

Endometrial hyperplasia is a precursor to the most common gynecologic cancer diagnosed in women. Apart from estrogenic induction, aberrant activation of the Wnt/β-catenin signal is well known to correlate with endometrial hyperplasia and its carcinoma. The benzopyran compound 2-(piperidinoethoxyphenyl)-3-(4-hydroxyphenyl)-2H-benzo (b) pyran(K-1), a potent antiestrogenic agent, has been shown to have apoptosis-inducing activity in rat uterine hyperplasia. The current study was undertaken to explore the effect of the benzopyran compound K-1 on growth and Wnt signaling in human endometrial hyperplasial cells. Primary culture of atypical endometrial hyperplasial cells was characterized by the epithelial cell marker cytokeratin-7. Results revealed that compound K-1 reduced the viability of primary endometrial hyperplasial cells and expression of ERα, PR, PCNA, Wnt7a, FZD6, pGsk3β and β-catenin without affecting the growth of the primary culture of normal endometrial cells. The β-catenin target genes CyclinD1 and c-myc were also found to be reduced, whereas the expression of axin2 and Wnt/β-catenin signaling inhibitor Dkk-1 was found to be upregulated, which caused the reduced interaction of Wnt7a and FZD6. Nuclear accumulation of β-catenin was found to be decreased by compound K-1. K-1 also suppressed the pPI3K/pAkt survival pathway and induced the cleavage of caspases and PARP, thus subsequently causing the apoptosis of endometrial hyperplasial cells. In conclusion, compound K-1 suppressed the growth of human primary endometrial hyperplasial cells through discontinued Wnt/β-catenin signaling and induced apoptosis via inhibiting the PI3K/Akt survival pathway.

Understanding nuclear receptor form and function using structural biology

Nuclear receptors (NRs) are a major transcription factor family whose members selectively bind small-molecule lipophilic ligands and transduce those signals into specific changes in gene programs. For over two decades, structural biology efforts were focused exclusively on the individual ligand-binding domains (LBDs) or DNA-binding domains of NRs. These analyses revealed the basis for both ligand and DNA binding and also revealed receptor conformations representing both the activated and repressed states. Additionally, crystallographic studies explained how NR LBD surfaces recognize discrete portions of transcriptional coregulators. The many structural snapshots of LBDs have also guided the development of synthetic ligands with therapeutic potential. Yet, the exclusive structural focus on isolated NR domains has made it difficult to conceptualize how all the NR polypeptide segments are coordinated physically and functionally in the context of receptor quaternary architectures. Newly emerged crystal structures of the peroxisome proliferator-activated receptor-γ-retinoid X receptor α (PPARγ-RXRα) heterodimer and hepatocyte nuclear factor (HNF)-4α homodimer have recently revealed the higher order organizations of these receptor complexes on DNA, as well as the complexity and uniqueness of their domain-domain interfaces. These emerging structural advances promise to better explain how signals in one domain can be allosterically transmitted to distal receptor domains, also providing much better frameworks for guiding future drug discovery efforts.

Abstract 3430: How important is the “post TMZ-treatment recovery” of GBM neoplastic cells

Glioblastoma multiforme (GBM) is the most prevalent central nervous system malignancy portending dismal prognosis. The median overall survival (OS) is 14.6 months with currently available standard care of surgery, radiotherapy and Temozolomide (TMZ) chemotherapy. TMZ, which is the best chemotherapeutic drug till date for this malignancy, gives a median OS advantage of only 2.5 months over surgery and radiotherapy alone. It is not clear how the benefit of TMZ is severely limited in a large majority of patients. To understand this we investigated genome wide sequence alterations of GBM neoplastic cells in response to TMZ. We present here two cases of GBM, A49910 and M45481, where the first one (A49910) showed response and the second one (M45481) showed no response to standard treatment in clinic. We isolated their primary tumor cells at the time of surgery and cultured them in vitro as neurospheres. When we exposed these two patient-derived neurospheres to clinically relevant dose of TMZ in vitro differential responses were observed among the two neurospheres which mirrored the clinical outcomes of the two patients respectively. Initially, at the end of 5 days of TMZ treatment, both A49910 and M45481 neurospheres showed 50% and 65% reduction in viable cell numbers respectively but after a 23 days of gap (“post TMZ-treatment recovery” from the 5 days long drug treatment), at 28th day of the treatment cycle, the total number of viable cells was 5% in TMZ-treated A49910 with a stark contrast of 60% in the TMZ-treated M45481 as compared to their respective DMSO-treated controls. Their growth curves, as measured by MTT assays, showed the exact reflection of this pattern, i.e., after 5 days of treatment both TMZ-treated A49910 and TMZ-treated M45481 showed equally retarded growth compared to their DMSO-treated controls, and at 28th day, only the TMZ-treated A49910 but not the TMZ-treated M45481 cells showed growth retardation. Moreover, almost every single cell of TMZ-treated A49910 appeared bigger and stained intensely with SA-βgal confirming drug induced senescence at 28th day whereas this phenotype was completely absent in TMZ-treated M45481, where no apparent sign of senescence was observed. However, apoptosis was two-fold higher in M45481 than in A49910 after 5 days of TMZ treatment. Whether this “drug induced cellular senescence (DICS)” phenotype is more beneficial to the patients claims further investigation with a larger cohort of GBM patients. For the proof of principle we sequenced the whole exome and also analyzed the genome wide single nucleotide polymorphisms (SNPs, intronic and exonic) in these two patient-derived neurospheres before and after TMZ treatment in vitro and detected a list of unique sequence alterations in both the cases, in response to TMZ.

Citation Format: Neeta Sarkar Roy, Nidhan Biswas, Vikas Chandra, Tapojyoti Das, Ankita Chatterjee, Rabindra Narayan Bhattacharya, Laxminarayan Tripathy, Sunandan Basu, Arindam Maitra, Pryiadarshi Basu, Analabha Basu, Surajit Dhara. How important is the “post TMZ-treatment recovery” of GBM neoplastic cells. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 3430. doi:10.1158/1538-7445.AM2013-3430

Abstract 5587: An objective clustering of GBM patients to identify clinically relevant subgroup with Hedgehog pathway activity

A targeted therapy with lesser or no toxicity is an immediate need for glioblastoma multiforme (GBM). A group of Hedgehog (Hh) pathway inhibitor drugs is one among the most promising targeted therapies in a wide number of malignancies including medulloblastoma, a lethal childhood central nervous system (CNS) malignancy, about a third of which is presented with high Hh pathway activity. However, in case of GBM a great degree of ambiguity is reported in terms of this pathway activity. GBM is known to be highly heterogeneous at molecular level. It is indeed not clear whether any specific subgroup of GBM shows considerable Hh pathway activity so that could be targeted with appropriate Hh pathway inhibitory drugs. We estimated here the mRNA expression levels of 7 Hh pathway component genes — the ligand Sonic Hedgehog (SHH), trans-membrane receptors Patched (PTCH1) and Smoothened (SMO), Hh transcription factors Gli-1 (GLI1), Gli-2 (GLI2) and Gli-3 (GLI3), and also the Gli-1 target gene Snail (SNAI1), relative to the levels of β-actin expression, by quantitative reverse transcriptase polymerase chain reaction (qRT-PCR) method, in a cohort of GBM patients from the Eastern part of India. We have so far estimated the relative expression levels of these genes in 10 GBM, 8 low grade astrocytoma, 2 meningioma, 2 schwannoma, 1 medulloblastoma biopsy samples and 2 normal cerebellar tissue samples. CNS tumors with astrocytic origin were confirmed by Glial fibrillary acidic protein (GFAP) mRNA expression. We selected only the GBM cases for further analysis in the present study. We calculated the squared Pearson correlation coefficient between expression levels (2–ΔCt) of all the 7 genes and found the best correlations between three of them — SHH, GLI1 and SNAI1 respectively. High correlation of the expression of SHH with that of GLI1 (r2 = 0.9964) is suggestive of ligand-driven mechanism of this pathway activity in this disease. Although both PTCH1 and SNAI1 are bona fide targets of the Hh transcription factor GLI1, interestingly, we observed that the expression of GLI1 had a low correlation with that of PTCH1 (r2 = 0.0472) but was highly correlated with SNAI1 expression (r2 = 0.9986). Moreover, by using k-means clustering analysis three subgroups of patients were identified based on their expression patterns of all 7 Hh pathway component genes that were included in the present study. We have found detectable levels of SMO mRNA in all GBM patients included in the study so far, suggesting a potential benefit of the targeted therapy with smoothened antagonist drugs in this disease.

Citation Format: Tapojyoti Das, Uttara Chatterjee, Samarendra Nath Ghosh, Sumit Deb, Suniti Kumar Saha, Puneet Gulati, Sarang Rote, Vikas Chandra, Ankur Mukherjee, Surajit Dhara. An objective clustering of GBM patients to identify clinically relevant subgroup with Hedgehog pathway activity. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 5587. doi:10.1158/1538-7445.AM2013-5587

Multidomain integration in the structure of the HNF-4α nuclear receptor complex

The hepatocyte nuclear factor 4 alpha (HNF4α, NR2A1) is a member of the nuclear receptor (NR) family of transcription factors that use conserved DNA binding domains (DBDs) and ligand binding domains (LBDs)^1,2. HNF4α is the most abundant DNA-binding protein in the liver, where some 40% of the actively transcribed genes have a HNF4α response element ^1,3,4. These regulated genes are largely involved in the hepatic gluconeogenic program and lipid metabolism^3,5,6. In the pancreas too, HNF4α is a master regulator controlling an estimated 11% of islet genes⁷. HNF4α protein mutations are linked to Maturity Onset of Diabetes in Young 1 (MODY1) and hyperinsulinemic hypoglycemia (HH)^8–11. Prior structural analyses of NRs, while productive with individual domains, have lagged in revealing the connectivity patterns of NR domains. Here, we describe the 2.9 Å crystal structure of the multi-domain HNF4α homodimer bound to its DNA response element and coactivator-derived peptides. A convergence zone connects multiple receptor domains in an asymmetric fashion joining distinct elements from each monomer. An arginine target of PRMT1 methylation protrudes directly into this convergence zone and sustains its integrity. A serine target of protein kinase C is also responsible for maintaining domain-domain interactions. These post-translational modifications manifest into changes in DNA binding by communicating through the tightly connected surfaces of the quaternary fold. We find that some MODY1 mutations, positioned on the LBD and hinge regions of the receptor, compromise DNA binding at a distance by communicating through the inter-junctional surfaces of the complex. The overall domain representation of the HNF4α homodimer is different from that of the PPARγ-RXRα heterodimer, even when both NR complexes are assembled on the same DNA element. Our findings suggest that unique quaternary folds and inter-domain connections in NRs could be exploited by small-molecule allosteric modulators that impact distal functions in these polypeptides.

Development and characterization of novel cell lines from Etroplus suratensis and their applications in virology, toxicology and gene expression

Four novel cell lines from tissues of eye, gill, kidney and brain of Etroplus suratensis were developed and characterized. The cell lines of eye, gill, kidney and brain were sub-cultured for 245, 185, 170 and 90 passages, respectively, since 2008. These cell lines showed predominantly epithelial-like cells. Effects of temperature and foetal bovine serum concentration on the growth of these cell lines were examined and optimum growth was found at the temperature of 28° C with 20% foetal bovine serum. All the four cell lines were successfully cryopreserved and revived at different passage levels. Cell-cycle analysis of these cell lines was carried out by fluorescence-activated cell sorting. Polymerase chain reaction (PCR) products obtained from the cells and tissues of E. suratensis with primers specific to the conserved region of 16S ribosomal RNA and cytochrome oxidase I genes of E. suratensis revealed the origin of cell lines from E. suratensis. Antibodies raised against the tissues and cells of eye, kidney and gill were highly cross reacted to their specific tissue and cells of E. suratensis. Chromosomal analysis revealed that E. suratensis cells have a normal diploid karyotype with 2n = 48. The cells of these cell lines were successfully transfected with pEGFP vector DNA. The eye (IEE), gill (IEG) and kidney (IEK) cell lines were found to be susceptible to nodavirus but resistant to infectious pancreatic necrosis virus (IPNV). The cells of gill, kidney and eye were applied to test the cytotoxicity of tannery effluents.

2,3-Diaryl-2H-1-benzopyran derivatives interfere with classical and non-classical estrogen receptor signaling pathways, inhibit Akt activation and induce apoptosis in human endometrial cancer cells

OBJECTIVES

The present study was undertaken to explore the mechanism of anti-proliferative action of benzopyran compound D1 (2-[piperidinoethoxyphenyl]-3-phenyl-2H-benzopyran) and its hydroxy-(D2) and methoxy-(D3) derivatives in Ishikawa and human primary endometrial adenocarcinoma cells.

METHODS

Transcriptional activation assays were performed using luciferase reporter system and cell viability was determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT). The stage of cell cycle was determined by flow-cytometry and real time analysis of cyclinE1 and cdc2 genes. The apoptotic effects were measured by AnnexinV/PI staining and TUNEL. The expression of PCNA, cyclinD1, pAkt, XIAP, cleaved caspase-9, -3, PARP, Bax and Bcl2 were determined by immunoblotting. The caspase-3 activity and mitochondrial membrane potential were measured by colorimetric assay.

RESULTS

All three compounds inhibited E(2)-induced ERE- and AP-1-mediated transactivation and proliferation in endometrial adenocarcinoma cells dose-dependently. Compound D1 caused the arrest of cells in the G(2) phase while D2 and D3 caused arrest in G(1) phase of the cell cycle. All compounds interfered with Akt activation, decreased XIAP expression leading to an increased cleavage of caspase-9, -3, PARP, increased Bax/Bcl2 ratio and caspase-3 activity.

CONCLUSION

Findings suggest that benzopyran derivatives inhibit cellular proliferation via modulating ER-dependent classical and non-classical signaling mechanisms, interfere with Akt activation and induce apoptosis via intrinsic pathway in endometrial adenocarcinoma cells.

Establishment and characterization of a fin cell line from Indian walking catfish, Clarias batrachus (L.)

A new cell line, Indian Catfish Fin, derived from the fin tissue of Indian walking catfish, Clarias batrachus, was established and characterized. The cell line grew well in Leibovitz's L-15 medium supplemented with 15% foetal bovine serum (FBS) and has been subcultured more than 110 times since its initiation in 2007. The cells were able to grow at a range of temperature from 28 to 37 °C with optimal growth at 28 °C. The cell line predominantly consists of fibroblast-like cells. The growth rate of fin cells increased as the FBS concentration increased from 2% to 20% at 28 °C with optimum growth at a concentration of 15% or 20% and poor growth at a concentration of 5%. The cells were found to be susceptible to fish nodavirus and IPNV-ab and infection was confirmed by cytopathic effect and reverse transcriptase-polymerase chain reaction. PCR amplification of mitochondrial 12S rRNA using primers specific to C. batrachus confirmed the catfish origin of the cell line. The cell line was characterized further by immunocytochemistry, transfection efficiency with pEGFP-N1 and cell cycle analysis by fluorescent-activated cell sorting.

Corecognition of DNA and a methylated histone tail by the MSL3 chromodomain

MSL3 resides in the MSL (male-specific-lethal) complex that upregulates transcription by spreading the H4K16 acetyl-mark. We discovered a DNA-dependent interaction of MSL3 chromodomain with the histone H4K20 monomethyl-mark. Structure of a ternary complex shows DNA minor groove accommodates the histone H4 tail, and monomethyllysine inserts in a four-residue aromatic cage in MSL3. Histone H4K16 acetyl-mark antagonizes MSL3 binding, suggesting MSL function is regulated by a combination of post-translational modifications.

Structural overview of the nuclear receptor superfamily: insights into physiology and therapeutics

As ligand-regulated transcription factors, the nuclear hormone receptors are nearly ideal drug targets, with internal pockets that bind to hydrophobic, drug-like molecules and well-characterized ligand-induced conformational changes that recruit transcriptional coregulators to promoter elements. Yet, due to the multitude of genes under the control of a single receptor, the major challenge has been the identification of ligands with gene-selective actions, impacting disease outcomes through a narrow subset of target genes and not across their entire gene-regulatory repertoire. Here, we summarize the concepts and work to date underlying the development of steroidal and nonsteroidal receptor ligands, including the use of crystal structures, high-throughput screens, and rational design approaches for finding useful therapeutic molecules. Difficulties in finding selective receptor modulators require a more complete understanding of receptor interdomain communications, posttranslational modifications, and receptor-protein interactions that could be exploited for target gene selectivity.

Tamarindus indica L. and Moringa oleifera M. extract administration ameliorates fluoride toxicity in rabbits

Aqueous extracts of T. indica fruit pulp (100 mg/kg body weight) and M. oleifera seeds (50 mg/kg body wight) orally once daily for 90 days lowered plasma fluoride concentrations in rabbits receiving fluorinated drinking water (200 mg NaF/ Liter water). Cortical indices and metaphysial width in animals receiving extracts also revealed beneficial effects of plant extracts. Changes in plasma biochemistry suggested less hepatic and renal damages in animals receiving plant extracts along with fluorinated water in comparison to that receiving fluorinated water alone. Preliminary results revealed these plant extracts have some potential to mitigate fluoride toxicity.

Development and characterization of cell lines derived from rohu, Labeo rohita (Hamilton), and catla, Catla catla (Hamilton)

Two new cell lines, designated RE and CB, were derived from the eye of rohu, Labeo rohita, and the brain of catla, Catla catla, respectively. The cell lines were maintained in Leibovitz's L-15 supplemented with 20% foetal bovine serum. The RE cell line was sub-cultured for more than 70 passages and the CB cell line for more than 35 passages. The RE cells are rounded and consist predominantly of epithelial cells. The CB cell line consists of predominantly fibroblastic-like cells. Both cell lines are able to grow at temperatures between 25 and 32 degrees C with an optimum of 28 degrees C. The growth rate of the cells increased as the foetal bovine serum concentration increased from 2% to 20% at 28 degrees C, with optimum growth at concentrations of 15% or 20% foetal bovine serum. The cells were successfully cryopreserved and revived at different passage levels. The cell lines were not susceptible to four marine fish viruses. Extracellular products from Aeromonas sp. were toxic to the cell lines. When the cells were transfected with plasmid eukaryotic green fluorescent protein (pEGFP [Clontech, Carlsbad, CA, USA]) vector DNA, a significant fluorescent signal was observed suggesting that these cell lines could be a useful tool for transgenic and genetic manipulation studies. Polymerase chain reaction amplification of mitochondrial 12S rRNA from rohu and catla confirmed that the cell lines originated from these fish species. The cell lines were further characterized by immunocytochemistry using confocal laser scanning microscopy.

Effect of Ru-Mn redox interactions on the hole carrier density in pulsed electron deposited La(1-x)Pb(x)Mn(0.8)Ru(0.2)O(3) (0.2≤x≤0.4) thin films

Pulsed electron deposited thin films of Ru substituted La(1-x)Pb(x)Mn(0.8)Ru(0.2)O(3) (0.2≤x≤0.4) show an increase in the magneto-resistance ratio by ∼5-15% at the respective metal to insulator transition (T(MIT)) temperature when compared to the parent La(0.6)Pb(0.4)MnO(3) thin film. A systematic decrease in T(MIT) is observed from ∼310 to ∼260 K when the hole (Pb) concentration varies from 40 to 20% with constant 20% Ru substitution at the Mn site. The x-ray rocking curve and high-resolution transmission electron microscopy (HRTEM) images of the thin films suggest that Ru occupies the Mn site and shows epitaxial growth of the films on the LaAlO(3) (LAO) substrate. Transport and magneto-resistive properties show that Ru substitution maintains a considerable hole carrier density (due to Mn(4+):t(2g)(3)e(g)(0)/Ru(5+):t(2g)(3)e(g)(0)) even for La(0.8)Pb(0.2)Mn(0.8)Ru(0.2)O(3) (8282) composition, which influences the double exchange interactions.

273 EXPRESSION PATTERN OF CONNEXIN 43 (Cx43) AND POLY-(A) POLYMERASE (PAP) GENES IN BUFFALO (BUBALUS BUBALIS) EMBRYOS PRODUCED IN VITRO

Polyadenylation of pre-mRNA is carried out by poly-(A) polymerase (PAP), and study of the transcription pattern of this gene is said to indicate the developmental competence of the embryos. Connexin 43 (Cx43) is one of the important gap junction proteins that controls growth, cellular differentiation, and embryonic development. The objective of the present investigation was to study the expression pattern of PAP and Cx43 genes in buffalo (Bubalus bubalis) embryos produced in vitro. Embryos were produced from the slaughterhouse ovaries using standard IVMFC protocol (Rajhans et al. 2006 J. Reprod. Fertil. Dev. 18, 253–254). Briefly, oocytes were aspirated from follicles (2–8 mm in diameter) and matured in vitro in TCM-199 supplemented with 10% FCS and epidermal growth factor (20 ng mL-1) for 24 h. Presumptive zygotes after 18 h of fertilization were cultured in mSOF containing insulin-like growth factor-1 (100 ng mL-1) and β-mercaptoethanol (100 �M) for 9 days or until blastocyst formation, whichever was earlier. Pools of immature (n = 200), in vitro-matured (n = 200), oocytes and embryos (2–4 cell, n = 83; 8–16 cell, n = 80; morula, n = 77), and blastocysts (n = 40) were collected for mRNA isolation. Immature and in vitro-matured oocytes were treated with 1X trypsin-EDTA solution to remove the attached cumulus and then washed with TCM-199 before mRNA isolation to avoid any contamination of these cells during RNA isolation. mRNA from each pool was isolated using a commercially available direct mRNA isolation kit (Oligotex Direct mRNA kit; Qiagen, Valencia, CA, USA). cDNA was prepared using specific reverse primer and M-MLV RT in 20 �L reaction volume following manufacturer's instructions. Polymerase chain reaction was done for 35 cycles with annealing temperatures of 60�C and 58�C for 252 bp of PAP and 425 bp of Cx43, respectively. Amplicons were subjected to restriction endonuclease digestion for further confirmation of expressed genes. RT-PCR amplicon of PAP was digested with HaeIII to obtain characteristic band patterns at 119 bp and 133 bp, and Cx43 RT-PCR amplicon was digested with EcoR1 to obtain characteristic band patterns at 137 bp and 288 bp. While PAP expression could be detected in all stages of developing embryos starting from immature oocytes to blastocyst stage, Cx43 mRNA was detected in immature oocytes to morula stage but not in blastocyst-stage embryos. It could be concluded that the expression patterns of PAP and Cx43 genes in buffalo embryos produced in vitro are similar to those of cattle embryos.

Crystal structure of the complex of the secretory phospholipase A2 from Daboia russelli pulchella with an endogenic indole derivative, 2-carbamoylmethyl-5-propyl-octahydro-indol-7-yl-acetic acid at 1.8 A resolution

Phospholipase A2 (PLA2) enzymes from snake venoms are approximately 14 kDa secretory proteins and catalyze the release of arachidonic acid which is the precursor of proinflammatory mediators such as prostaglandins, leukotrienes, thromboxanes and platelet-activating factors. The structure of the PLA2 enzyme purified from the venom of Daboia russelli pulchella was determined using molecular replacement method and refined to an R value of 18.3% for all the reflections to 1.8 A resolution. The structure contains two crystallographically independent molecules A and B which form an asymmetric homodimer. The Ca2+ ion was not detected in the present structure, however, a characteristic non-protein high quality electron density was observed at the substrate-binding site of molecule A which allowed a clear interpretation of a natural ligand identified as a derivative of indole, 2-carbamoylmethyl-5-propyl-octahydro-indol-7-yl)-acetic acid. The corresponding substrate-binding site in molecule B was empty. The ligand present in molecule A is involved in extensive interactions with the protein atoms including important catalytic residues such as Asp-49 and His-48. The results also show that the indole derivatives act as potent inhibitors of secretory group II PLA2 enzymes that can be further modified to be used as potential therapeutic agents.

Renal artery stenosis and a functioning hilar paraganglioma: a rare cause of renovascular hypertension--a case report

Surgically correctable causes of hypertension are uncommon. Simultaneous occurrence of 2 such causes in the same individual is extremely rare. The authors describe a 25-year-old woman with congenital erythrocytosis, renal artery stenosis, and a paraganglioma. The possible mechanisms of renal artery stenosis in the presence of a catecholamine-secreting tumor are discussed.

Enzymatic activity and inhibition of the neurotoxic complex vipoxin from the venom of Vipera ammodytes meridionalis

Vipoxin from the venom of Vipera ammodytes meridionalis is an unique neurotoxic complex between a toxic phospholipase A2 and a highly homologous non-toxic protein inhibitor. It is an example of evolution of a catalytic and toxic function into inhibitory and non-toxic one. The activity of the V. ammodytes meridionalis toxin is 1.7 times higher than that of the closely related (92% sequence identity) neurotoxic complex RV4/RV7 from the venom of Vipera russelli formosensis The enhanced enzymatic activity of vipoxin is attributed to limited structural changes, in particular to the substitutions G54R and Q78K in the PLA2 subunit of the complex and to the T54R substitution in the inhibitor. Oleyloxyethylphosphocholine, aristolochic acid and vitamin E suppressed the enzymatic activity of vipoxin and its isolated PLA2 subunit. These compounds influence inflammatory processes in which PLA2 is implicated. The peptide Lys-Ala-Ile-Tyr-Ser, which is an integral part of the PLA2 components of the two neurotoxic complexes from V. ammodytes meridionalis and V. russelli formosensis (sequence 70-74) activated vipoxin increasing its PLA2 activity by 23%. This is in contrast to the inhibitory effect of the respective pentapeptides with 70-74 sequences on other group II PLA2s. Surprisingly, the same peptide inhibited 46% of the V. russelli formosensis PLA2 activity. The limited changes in the structure of the two highly homologous neurotoxins lead to considerable differences in their interaction with native peptides.

Crystal structure of a complex formed between a snake venom phospholipase A(2) and a potent peptide inhibitor Phe-Leu-Ser-Tyr-Lys at 1.8 A resolution

Phospholipase A(2) is an important enzyme involved in the production of prostaglandins and their related compounds causing inflammatory disorders. Among the several peptides tested, the peptide Phe-Leu-Ser-Tyr-Lys (FLSYK) showed the highest inhibition. The dissociation constant (K(d)) for this peptide was calculated to be 3.57 +/- 0.05 x 10(-9) m. In order to further improve the degree of inhibition of phospholipase A(2), a complex between Russells viper snake venom phospholipase A(2) and a peptide inhibitor FLSYK was crystallized, and its structure was determined by crystallographic methods and refined to an R-factor of 0.205 at 1.8 A resolution. The structure contains two crystallographically independent molecules of phospholipase A(2) (molecules A and B) and a peptide molecule specifically bound to molecule A only. The two molecules formed an asymmetric dimer. The dimerization caused a modification in the binding site of molecule A. The overall conformations of molecules A and B were found to be generally similar except three regions i.e. the Trp-31-containing loop (residues 25-34), the beta-wing consisting of two antiparallel beta-strands (residues 74-85) and the C-terminal region (residues 119-133). Out of the above three, the most striking difference pertains to the conformation of Trp-31 in the two molecules. The orientation of Trp-31 in molecule A was suitable for the binding of FLSYK, while it disallowed the binding of peptide to molecule B. The structure of the complex clearly shows that the peptide is so placed in the binding site of molecule A that the side chain of its lysine residue interacted extensively with the enzyme and formed several hydrogen bonds in addition to a strong electrostatic interaction with critical Asp-49. The C-terminal carboxylic group of the peptide interacted with the catalytic residue His-48.

Design of specific peptide inhibitors of phospholipase A2: structure of a complex formed between Russell's viper phospholipase A2 and a designed peptide Leu-Ala-Ile-Tyr-Ser (LAIYS)

Phospholipase A(2) (EC 3.1.1.4) is a key enzyme of the cascade mechanism involved in the production of proinflammatory compounds known as eicosanoids. The binding of phospholipase A(2) to membrane surfaces and the hydrolysis of phospholipids are thought to involve the formation of a hydrophobic channel into which a single substrate molecule diffuses before cleavage. In order to regulate the production of proinflammatory compounds, a specific peptide inhibitor of PLA(2), Leu-Ala-Ile-Tyr-Ser, has been designed. Phospholipase A(2) from Daboia russelli pulchella (DPLA(2)) and peptide Leu-Ala-Ile-Tyr-Ser (LAIYS) have been co-crystallized. The structure of the complex has been determined and refined to 2.0 A resolution. The structure contains two crystallographically independent molecules of DPLA(2), with one molecule of peptide specifically bound to one of them. The overall conformations of the two molecules are essentially similar except in three regions; namely, the calcium-binding loop including Trp31 (residues 25-34), the beta-wing consisting of two antiparallel beta-strands (residues 74-85) and the C-terminal region (residues 119-133). Of these, the most striking difference pertains to the orientation of Trp31 in the two molecules. The conformation of Trp31 in molecule A was suitable to allow the binding of peptide LAIYS, while that in molecule B prevented the entry of the ligand into the hydrophobic channel. The structure of the complex clearly showed that the OH group of Tyr of the inhibitor formed hydrogen bonds with both His48 N(delta1) and Asp49 O(delta1), while O(gamma)H of Ser was involved in a hydrogen bond with Trp31. Other peptide backbone atoms interact with protein through water molecules, while Leu, Ala and Ile form strong hydrophobic interactions with the residues of the hydrophobic channel.