| 11302484 |
A family of depsi-peptide fungal metabolites, as selective and competitive human tachykinin receptor (NK2) antagonists: fermentation, isolation, physico-chemical properties, and biological activity |
10.7164/antibiotics.54.125. |
J Antibiot (Tokyo) |
A family of depsi-peptide fungal metabolites, as selective and competitive human tachykinin receptor (NK2) antagonists: fermentation, isolation, physico-chemical properties, and biological activity
Abstract
- Four tachykinin (NK2) receptor inhibitors, SCH 378161 (1), SCH 217048 (2), SCH 378199 (3), and SCH 378167 (4) were isolated from the fermentation broth of a taxonomically unidentified fungus. These compounds were separated from the fermentation broth by ethyl acetate extraction. Purification and separation of the individual compounds were achieved by NK2 assay-guided fractionation using gel filtration, reverse phase chromatography and HPLC. They were identified to be a family of depsipeptides by spectroscopic and degradation studies. Compounds 1 and 3 contain proline and differ as an amide and acid whereas 2 and 4 contain pipecolic acid and differ in being an amide and acid. All of these compounds contain an identical hydroxy acid. They are selective NK2 inhibitors with Ki values ranging from 27-982 nM and demonstrate no activity at 10 microM in the NK1 and NK3 assays. In addition, compounds 1 and 2 inhibited NKA-induced increases in the concentration of intracellular Ca2+, [Ca2+]i, in a CHO cell expressing the human NK2 receptor; this inhibition was competitive in nature with pA2 values of 7.2 and 7.5, respectively. These data demonstrate that these natural products are selective and competitive receptor antagonists of the human NK2 receptor.
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| 11302492 |
Cyclo(D-Pro-L-Val), a specific beta-glucosidase inhibitor produced by Aspergillus sp. F70609 |
10.7164/antibiotics.54.179. |
J Antibiot (Tokyo) |
Cyclo(D-Pro-L-Val), a specific beta-glucosidase inhibitor produced by Aspergillus sp. F70609
Abstract
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| 11302494 |
Phoenistatin, a new gene expression-enhancing substance produced by Acremonium fusigerum |
10.7164/antibiotics.54.187. |
J Antibiot (Tokyo) |
Phoenistatin, a new gene expression-enhancing substance produced by Acremonium fusigerum
Abstract
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| 11331609 |
Sharp, an inducible cofactor that integrates nuclear receptor repression and activation. |
10.1101/gad.871201 |
Genes Dev. |
Sharp, an inducible cofactor that integrates nuclear receptor repression and activation.
Abstract
- A yeast two-hybrid screen using the conserved carboxyl terminus of the nuclear receptor corepressor SMRT as a bait led to the isolation of a novel human gene termed SHARP (SMRT/HDAC1 Associated Repressor Protein). SHARP is a potent transcriptional repressor whose repression domain (RD) interacts directly with SMRT and at least five members of the NuRD complex including HDAC1 and HDAC2. In addition, SHARP binds to the steroid receptor RNA coactivator SRA via an intrinsic RNA binding domain and suppresses SRA-potentiated steroid receptor transcription activity. Accordingly, SHARP has the capacity to modulate both liganded and nonliganded nuclear receptors. Surprisingly, the expression of SHARP is itself steroid inducible, suggesting a simple feedback mechanism for attenuation of the hormonal response.
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| 11344221 |
Somatostatin receptor subtypes 2 and 5 differentially affect proliferation in vitro of the human medullary thyroid carcinoma cell line tt |
10.1210/jcem.86.5.7489. |
J Clin Endocrinol Metab |
Somatostatin receptor subtypes 2 and 5 differentially affect proliferation in vitro of the human medullary thyroid carcinoma cell line tt
Abstract
- Somatostatin and its receptors (SSTR1 to SSTR5) are expressed in normal human parafollicular C cells and medullary thyroid carcinoma (MTC), but the role of SSTR subtypes in cell growth regulation is still not clear. The present study demonstrates that the human MTC cell line TT stably expresses all the SSTR subtypes and responds to SSTR2 and SSTR5 activation by subtype-selective agonists with two different patterns in terms of [(3)H]thymidine ([(3)H]thy) incorporation and cell number. The SSTR2 preferential agonists (BIM-23120, BIM-23197, BIM-23190, and BIM-23014; 10(-9)-10(-6) M), significantly suppressed [(3)H]thy incorporation (58-13%) and reduced cell proliferation (50-28%), whereas the SSTR5-selective agonist, BIM-23206 (10(-9)-10(-6) M), significantly increased [(3)H]thy incorporation in TT cells (80-175%), but failed to influence cell proliferation. SSTR2 antagonist (BIM-23627) counteracted the action of SSTR2 preferential agonists on TT cells. Furthermore, increasing concentrations of SSTR5-selective agonists, BIM-23206, dose-dependently prevented the suppression of TT cell [(3)H]thy incorporation and proliferation produced by SSTR2 preferential agonist, BIM-23120, showing an antagonism between these compounds. The following conclusions were reached: 1) the human MTC cell line TT expresses all SSTR subtypes; 2) SSTR2 activation inhibits DNA synthesis and cell proliferation, whereas SSTR5 activation increases DNA synthesis; and 3) SSTR2 preferential agonist (BIM-23120) can antagonise SSTR5-selective agonist (BIM-23206) action and vice versa. These findings suggest a tissue-specific function and a tissue-specific interaction between the two receptors.
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| 11344322 |
Solution structure and backbone dynamics of an omega-conotoxin precursor |
10.1110/ps.30701. |
Protein Sci |
Solution structure and backbone dynamics of an omega-conotoxin precursor
Abstract
- Nuclear magnetic resonance spectroscopy was used to characterize the solution structure and backbone dynamics of a putative precursor form of omega-conotoxin MVIIA, a 25-amino-acid residue peptide antagonist of voltage-gated Ca(2+) channels. The mature peptide is found in the venom of a fish-hunting marine snail Conus magus and contains an amidated carboxyl terminus that is generated by oxidative cleavage of a Gly residue. The form examined in this study is identical to the mature peptide except for the presence of the unmodified carboxy-terminal Gly. This form, referred to as omega-MVIIA-Gly, has previously been shown to refold and form its disulfides more efficiently than the mature form, suggesting that the presence of the terminal Gly may favor folding in vivo. The nuclear magnetic resonance (NMR) structure determination indicated that the fold of omega-MVIIA-Gly is very similar to that previously determined for the mature form, but revealed that the terminal Gly residue participates in a network of hydrogen bonds involving both backbone and side chain atoms, very likely accounting for the enhanced stability and folding efficiency. (15)N relaxation experiments indicated that the backbone is well ordered on the nanosecond time scale but that residues 9-15 undergo a conformational exchange processes with a time constant of approximately 35 microseconds. Other studies have implicated this segment in the binding of the peptide to its physiological target, and the observed motions may play a role in allowing the peptide to enter the binding site
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| 11352590 |
Rescuing a destabilized protein fold through backbone cyclization |
10.1006/jmbi.2001.4631. |
J Mol Biol |
Rescuing a destabilized protein fold through backbone cyclization
Abstract
- We describe the physicochemical characterization of various circular and linear forms of the approximately 60 residue N-terminal Src homology 3 (SH3) domain from the murine c-Crk adapter protein. Structural, dynamic, thermodynamic, kinetic and biochemical studies reveal that backbone circularization does not prevent the adoption of the natural folded structure in any of the circular proteins. Both the folding and unfolding rate of the protein increased slightly upon circularization. Circularization did not lead to a significant thermodynamic stabilization of the full-length protein, suggesting that destabilizing enthalpic effects (e.g. strain) negate the expected favorable entropic contribution to overall stability. In contrast, we find circularization results in a dramatic stabilization of a truncated version of the SH3 domain lacking a key glutamate residue. The ability to rescue the destabilized mutant indicates that circularization may be a useful tool in protein engineering programs geared towards generating minimized proteins.
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| 11374898 |
Cloning, mapping, and characterization of the human sorbin and SH3 domain containing 1 (SORBS1) gene: a protein associated with c-Abl during insulin signaling in the hepatoma cell line Hep3B |
10.1006/geno.2001.6541. |
Genomics |
Cloning, mapping, and characterization of the human sorbin and SH3 domain containing 1 (SORBS1) gene: a protein associated with c-Abl during insulin signaling in the hepatoma cell line Hep3B
Abstract
- SH3P12/CAP/ponsin, a gene product with a sorbin homology domain and three consecutive SH3 domains in the carboxy-terminus, has been isolated from murine adipocytes and identified as an important adaptor during insulin signaling. Here we describe the cloning, mapping, and expression of the human homologue, termed SORBS1 (sorbin and SH3 domain containing 1). Multiple transcripts of this gene with different mRNA isoforms were observed among different tissues. Here we report 13 alternatively spliced exons, which were ascertained from the full-length cDNA cloned in adipose, liver, and skeletal muscle tissues. Among the major isoforms, the shortest, 2223-bp, open reading frame (ORF) encodes a protein with a predicted molecular weight of 81.5 kDa, while the longest, 3879-bp, ORF encodes a protein of about 142.2 kDa. This gene was mapped to human chromosome 10q23.3-q24.1, which is a candidate region for insulin resistance found in Pima Indians. In human hepatoma Hep3B cells, SORBS1 was partly dissociated from the insulin receptor complex and bound to c-Abl protein upon insulin stimulation. This interaction with c-Abl was through the third SH3 domain and a possible conformational change of SORBS1 induced by insulin. Our data suggest that c-Abl oncoprotein via SORBS1 might play a role in the insulin signaling pathway.
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| 11374942 |
Pseudodestruxins A and B: new cyclic depsipeptides from the coprophilous fungus Nigrosabulum globosum |
10.1021/np000547r. |
J Nat Prod |
Pseudodestruxins A and B: new cyclic depsipeptides from the coprophilous fungus Nigrosabulum globosum
Abstract
- Pseudodestruxins A (1) and B (2), two new cyclic peptides, have been isolated from cultures of the coprophilous fungus Nigrosabulum globosum. The structure of pseudodestruxin A (1) was elucidated using 2D NMR techniques and confirmed by single-crystal X-ray diffraction analysis. The structure of 2 was assigned by comparing its NMR and FABMS data with those of compound 1. The known compounds ascochlorin and 5-chlorocollectorin B were also isolated from N. globosum. Although 1 and 2 display antibacterial effects, ascochlorin was found to be responsible for the antifungal activity of the crude extract.
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| 11375057 |
Biological and genetic characterization of a human immunodeficiency virus strain resistant to CXCR4 antagonist T134 |
10.1089/088922201300119716. |
AIDS Res Hum Retroviruses |
Biological and genetic characterization of a human immunodeficiency virus strain resistant to CXCR4 antagonist T134
Abstract
- The chemokine receptors CXCR4 and CCR5 are considered to be potential targets for the inhibition of HIV-1 replication. We have reported that T134 and T140 inhibited X4 HIV-1 infection specifically because they acted as CXCR4 antagonists. In the present study, we have generated a T134-resistant virus (trHIV-1(NL4-3)) in a cell culture with gradually increasing concentrations of the compound. The EC(50) of T134 against trHIV-1(NL4-3) recovered after 145 passages was 15 times greater than that against wild-type HIV-1(NL4-3). This adapted virus was resistant to other CXCR4 antagonists, T140, AMD3100, and ALX40-4C, and SDF-1; from 10 to 145 times greater than that against wild-type HIV-1(NL4-3). On the other hand, T134, T140, and ALX40-4C were still active against AMD3100-resistant viruses (arHIV-1(018A)). The trHIV-1(NL4-3) contained the following mutations in the V3 loop of gp120: N269K, Q278T, R279K, A284V, F285L, V286Y, I288T, K290E, N293D, M294I, and Q296K; an insertion of T at 290; and Delta274-275 (SI). In addition, many other mutations were recognized in the V1, V2, and V4 domains. Thus, resistance to T134 may be the consequence of amino acid substitutions in the envelope glycoprotein of X4 HIV-1. The trHIV-1(NL4-3) could not utilize CCR5 as an HIV infection coreceptor, although many amino acid substitutions were recognized. The trHIV-1(NL4-3) acquired resistance to vMIP II, which could inhibit both X4 and R5 HIV-1 infection. However, neither the ligands of CCR5, RANTES, and MIP-1alpha, nor a CCR5 low molecular antagonist, TAK-779, were able to influence the infection of trHIV-1(NL4-3). Those results indicated that alternation of coreceptor usage of trHIV-1(NL4-3) was not induced.
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| 11377489 |
Cyclosporine A metabolite AM19 as a potential biomarker in urine for CSA nephropathy |
10.1016/s0041-1345(01)01929-7. |
Transplant Proc |
Cyclosporine A metabolite AM19 as a potential biomarker in urine for CSA nephropathy
Abstract
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| 11382241 |
Cyclolinopeptides F-I, cyclic peptides from linseed |
10.1016/s0031-9422(00)00442-8. |
Phytochemistry |
Cyclolinopeptides F-I, cyclic peptides from linseed
Abstract
- Four cyclic peptides, cyclolinopeptides F-I, were isolated from seeds of Linum usitatissimum. Their structures were elucidated by extensive 2D NMR spectroscopic methods and by chemical degradation. Further, their immunosuppressive activity is examined.
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| 11389621 |
Total structure determination of apratoxin A, a potent novel cytotoxin from the marine cyanobacterium Lyngbya majuscula |
10.1021/ja010453j. |
J Am Chem Soc |
Total structure determination of apratoxin A, a potent novel cytotoxin from the marine cyanobacterium Lyngbya majuscula
Abstract
- Apratoxin A (1), a potent cytotoxin with a novel skeleton, has been isolated from the marine cyanobacterium Lyngbya majuscula Harvey ex Gomont. This cyclodepsipeptide of mixed peptide-polyketide biogenesis bears a thiazoline ring flanked by polyketide portions, one of which possesses an unusual methylation pattern. Its gross structure has been elucidated by spectral analysis, including various 2D NMR techniques. The absolute configurations of the amino acid-derived units were determined by chiral HPLC analysis of hydrolysis products. The relative stereochemistry of the new dihydroxylated fatty acid unit, 3,7-dihydroxy-2,5,8,8-tetramethylnonanoic acid, was elucidated by successful application of the J-based configuration analysis originally developed for acyclic organic compounds using carbon-proton spin-coupling constants ((2,3)J(C,H)) and proton-proton spin-coupling constants ((3)J(H,H)); its absolute stereochemistry was established by Mosher analysis. The conformation of 1 in solution was mimicked by molecular modeling, employing a combination of distance geometry and restrained molecular dynamics. Apratoxin A (1) possesses IC(50) values for in vitro cytotoxicity against human tumor cell lines ranging from 0.36 to 0.52 nM; however, it was only marginally active in vivo against a colon tumor and ineffective against a mammary tumor.
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| 11403208 |
Species dependence for binding of small molecule agonist and antagonists to the C5a receptor on polymorphonuclear leukocytes |
10.1023/a:1011036414353. |
Inflammation |
Species dependence for binding of small molecule agonist and antagonists to the C5a receptor on polymorphonuclear leukocytes
Abstract
- This study investigated the receptor binding affinities of a C5a agonist and cyclic antagonists for polymorphonuclear leukocytes (PMNs) isolated from human, sheep, pig, dog, rabbit, guinea pig, rat and mouse. The affinities of the two small molecule antagonists, F-[OPdChaWR] and AcF-[OPdChaWR], and the agonist, YSFKPMPLaR, revealed large differences in C5a receptor (C5aR) affinities between species. The antagonists bound to human, rat and dog PMNs with similar high affinities, but with lower affinities to PMNs from all other species. The C5a agonist also bound with varying affinities between species, but showed a different affinity profile to the antagonists. In contrast, recombinant human C5a had similar affinity for PMNs of all species investigated. The low correlation between the affinities of the antagonists and the agonist between species either suggests that different receptor residues are important for distinguishing between agonist/antagonist binding, or that the agonist and antagonist peptides bind to two distinct sites within the C5aR.
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| 11408484 |
A novel mouse beta-defensin, mBD-6, predominantly expressed in skeletal muscle |
10.1074/jbc.M104149200. |
J Biol Chem |
A novel mouse beta-defensin, mBD-6, predominantly expressed in skeletal muscle
Abstract
- Defensins comprise a family of cationic antimicrobial peptides that is characterized by the conserved 6 cysteine residues. They are expressed in the epithelial cells of various organs and are identified as key elements in the host defense system at the mucosal surface. We isolated a novel mouse beta-defensin gene from the bacterial artificial chromosome DNA containing the mouse beta-defensin-3 gene. The full-length cDNA was cloned from skeletal muscle cDNA and called mouse beta-defensin-6 (mBD-6). The predicted peptide conserved the 6-cysteine motif and had 59% amino acid sequence identity with mouse beta-defensin-3 and 59% identity with mouse beta-defensin-4. We demonstrated the expression of mBD-6 in skeletal muscle in addition to the esophagus, tongue, and trachea. In animal models of endotoxemia, mBD-6 expression was also induced in the lung. mBD-6 showed potent antimicrobial activity against Escherichia coli and would play an important role in host defense in the esophagus, airways, and skeletal muscle. mBD-6 is the first reported beta-defensin predominantly expressed in skeletal muscle. This unique tissue specificity suggests some novel physiological roles of this peptide family.
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