| 12542366 |
Isolation and structure of the cytotoxic cycloheptapeptide phakellistatin 13 |
10.1021/np020223y. |
J Nat Prod |
Isolation and structure of the cytotoxic cycloheptapeptide phakellistatin 13
Abstract
- A new cyclic heptapeptide phakellistatin 13 (1) had been isolated from the sponge Phakellia fusca Thiele, collected at Yongxing Island of China. Its structure was elucidated as cyclo-(Pro1-Trp-Leu-Thr-Pro2-Gly-Phe) on the basis of MS, UV, IR, and high-field NMR (600 MHz) analysis. The compound was significantly cytotoxic against the human hepatoma BEL-7404 cell line with an ED(50) < 10(-2) microg/mL.
|
| 12556535 |
Type 1 insulin-like growth factor receptor (IGF-IR) signaling inhibits apoptosis signal-regulating kinase 1 (ASK1) |
10.1074/jbc.M211398200. |
J Biol Chem |
Type 1 insulin-like growth factor receptor (IGF-IR) signaling inhibits apoptosis signal-regulating kinase 1 (ASK1)
Abstract
- The type 1 insulin-like growth factor receptor (IGF-IR) is a receptor-tyrosine kinase that plays a critical role in signaling cell survival and proliferation. IGF-IR binding to its ligand, insulin-like growth factor (IGF-I) activates phosphoinositide 3-kinase (PI3K), promotes cell proliferation by activating the mitogen-activated protein kinase (MAPK) cascade, and blocks apoptosis by inducing the phosphorylation and inhibition of proapoptotic proteins such as BAD. Apoptosis signal-regulating kinase 1 (ASK1) is a MAP kinase kinase kinase (MAPKKK) that is required for c-Jun N-terminal kinase (JNK) and p38 activation in response to Fas and tumor necrosis factor (TNF) receptor stimulation, and for oxidative stress- and TNFalpha-induced apoptosis. The results presented here indicate that ASK1 forms a complex with the IGF-IR and becomes phosphorylated on tyrosine residue(s) in a manner dependent on IGF-IR activity. IGF-IR signaling inhibited ASK1 irrespective of TNFalpha-induced ASK1 activation and resulted in decreased ASK1-dependent JNK1 stimulation. Signaling through IGF-IR rescued cells from ASK1-induced apoptotic cell death in a manner independent of PI3K activity. These results indicate that IGF-IR signaling suppresses the ASK-1-mediated stimulation of JNK/p38 and the induction of programmed cell death. The simultaneous activation of MAP kinases and the inhibition of the stress-activated arm of the cascade by IGF-IR may constitute a potent proliferative signaling system and is possibly a mechanism by which IGF-I can stimulate growth and inhibit cell death in a wide variety of cell types and biological settings.
|
| 12565734 |
Synthesis and organotropism of 3H-dihydro derivatives of the cyanobacterial peptide hepatotoxin nodularin |
10.1016/s0041-0101(02)00245-3. |
Toxicon |
Synthesis and organotropism of 3H-dihydro derivatives of the cyanobacterial peptide hepatotoxin nodularin
Abstract
- Tritium-labelled dihydro derivatives of the cyanobacterial peptide hepatotoxin nodularin were prepared by reduction with sodium boro[3H]hydride. The optimised reaction gave two dihydronodularin stereoisomers which were purified by high-performance liquid chromatography with a mobile phase of methanol-0.7% sodium sulfate (6:4) and a C(18) stationary phase. The specific activities of the stereoisomers were 1780-1807 dis min(-1) ng(-1). The radiolabelled dihydronodularins were tested for stability and used for toxicokinetic studies in mice. Liver was the main site of toxin accumulation.
|
| 12571157 |
A novel loss of function mutation in exon 10 of the FSH receptor gene causing hypergonadotrophic hypogonadism: clinical and molecular characteristics |
10.1093/humrep/deg046. |
Hum Reprod |
A novel loss of function mutation in exon 10 of the FSH receptor gene causing hypergonadotrophic hypogonadism: clinical and molecular characteristics
Abstract
- Background:
Inactivating mutations of the FSH receptor (FSHR) are a rare cause of hypergonadotrophic hypogonadism in women. Only one patient with primary amenorrhoea due to an FSHR gene mutation has been reported outside of Finland, where the prevalence of Ala189Val mutations is particularly high.
Methods and results:
Here, we describe the clinical, molecular genetic and functional characteristics associated with a novel inactivating mutation in exon 10 of the FSHR gene identified in a patient who presented with primary amenorrhoea at 17 years of age. The C to G transversion found at nucleotide 1043 causes a Pro348Arg substitution in the extracellular region of the FSHR and results in a mutant FSHR that is completely inactive in functional studies and that does not bind FSH. The proband exhibits apparent homozygosity for this recessive mutation. Her father is heterozygous for the mutation while analysis of exon 10 of the FSHR gene from her mother revealed only wild-type sequence. Chromosome painting was used to exclude deletions or rearrangements of 2p, and microsatellite markers did not show paternal uniparental isodisomy for this region. These findings suggest that the proband is hemizygous, with an inherited or de-novo microdeletion, or alternatively a de-novo gene conversion, of the accompanying FSHR allele.
Conclusions:
This case confirms the importance of the FSHR in female pubertal development and reproduction, and supports a relationship between phenotype and function for FSHR mutations.
|
| 12574251 |
Clonal diversity among streptogramin A-resistant Staphylococcus aureus isolates collected in French hospitals |
10.1128/JCM.41.2.586-591.2003. |
J Clin Microbiol |
Clonal diversity among streptogramin A-resistant Staphylococcus aureus isolates collected in French hospitals
Abstract
- We analyzed 62 clinical isolates of streptogramin A-resistant (SGA(r)) Staphylococcus aureus collected between 1981 and 2001 in 14 hospitals located in seven French cities. These isolates, including five with decreased susceptibility to glycopeptides, were distributed into 45 antibiotypes and 38 SmaI genotypes. Each of these genotypes included between 1 and 11 isolates, the SmaI patterns of which differed by no more than three bands. Although numerous clones were identified, we observed the spread of monoclonal isolates either within the same hospital or within hospitals in distinct cities and at large time intervals. Hybridization with probes directed against 10 SGA(r) genes (vatA, vatB, vatC, vatD, vatE, vgaA, vgaB, vgaAv, vgbA, and vgbB) revealed six patterns: vgaAv (21 isolates), vatA-vgbA (24 isolates), vgaAv-vatB-vgaB (14 isolates), vgaAv-vatA-vgbA (1 isolate), vgaAv-vatA-vgbA-vatB-vgaB (1 isolate), and vgaA (1 isolate). We detected at least one SGA(r) determinant in all of the tested isolates. vgaAv, which is part of the recently characterized transposon Tn5406, was found in 59.7% of the tested isolates. Of the 16 streptogramin B-susceptible isolates, 14 carried vgaAv alone and were susceptible to the mixtures of streptogramins, whereas the 2 isolates carrying vgaAv-vatB-vgaB were resistant to these mixtures. vatA-vgbA was found on plasmids of the same apparent size in 26 (42%) of the tested clinical isolates from 18 unrelated SmaI genotypes. The possible dissemination of some of the multiple clones characterized in the present study with an expected increased selective pressure of streptogramins following the recent licensing of Synercid (quinupristin-dalfopristin) must be carefully monitored.
|
| 12590964 |
A novel antimicrobial peptide from the sea hare Dolabella auricularia |
10.1016/s0145-305x(02)00105-2. |
Dev Comp Immunol |
A novel antimicrobial peptide from the sea hare Dolabella auricularia
Abstract
- The sea hare Dolabella auricularia is a marine shell-less gastropod. Four cytotoxic glycoproteins named dolabellanin A, C, E and P were found in the animal previously. An antimicrobial factor was newly isolated from the sea hare's body-wall including skin and mucus. This factor is a novel peptide which consists of 33 amino acid residues, and is called dolabellanin B2. Dolabellanin B2 was cytotoxically effective against some pathogenic microorganisms at a concentration of 2.5-100 microg/ml.
|
| 12591264 |
Structure, chemistry, and biological activity of pseudophomins A and B, new cyclic lipodepsipeptides isolated from the biocontrol bacterium Pseudomonas fluorescens |
10.1016/s0031-9422(02)00617-9. |
Phytochemistry |
Structure, chemistry, and biological activity of pseudophomins A and B, new cyclic lipodepsipeptides isolated from the biocontrol bacterium Pseudomonas fluorescens
Abstract
- Pseudophomins A and B are cyclic lipodepsipeptides isolated from Pseudomonas fluorescens strain BRG100, a bacterium with potential application for biocontrol of plant pathogens and weeds. Their chemical structures were established by a combination of spectroscopic data, X-ray crystallography, and selective chemical degradation. This unique chemical degradation allowed the unambiguous determination of the absolute configuration of the amino acid residue Leu-1, due to gamma-lactam formation followed by selective cleavage of the adjacent N(8)-C(7) bond. To the best of our knowledge this is the first application of gamma-lactam formation to the determination of absolute configuration of an adjacent amino acid. Pseudophomin B showed higher antifungal activity against the phytopathogens Phoma lingam/Leptosphaeria maculans and Sclerotinia sclerotiorum than pseudophomin A, and is likely to be the main component responsible for the antifungal activity of EtOAc extracts of strain BRG100. By contrast, pseudophomin A showed stronger inhibition of green foxtail (Setaria viridis) root germination than pseudophomin B.
|
| 12612081 |
Regulation of insulin receptor signaling by the protein tyrosine phosphatase TCPTP |
10.1128/MCB.23.6.2096-2108.2003. |
Mol Cell Biol |
Regulation of insulin receptor signaling by the protein tyrosine phosphatase TCPTP
Abstract
- The human protein tyrosine phosphatase TCPTP exists as two forms: an endoplasmic reticulum-targeted 48-kDa form (TC48) and a nuclear 45-kDa form (TC45). Although targeted to the nucleus, TC45 can exit in response to specific stimuli to dephosphorylate cytoplasmic substrates. In this study, we investigated the downregulation of insulin receptor (IR) signaling by TCPTP. In response to insulin stimulation, the TC48-D182A and TC45-D182A "substrate-trapping" mutants formed stable complexes with the endogenous tyrosine-phosphorylated IR beta-subunit in 293 cells. Moreover, in response to insulin stimulation, the TC45-D182A mutant accumulated in the cytoplasm of cells overexpressing the IR and in part colocalized with the IR beta-subunit at the cell periphery. These results indicate that the IR may serve as a cellular substrate for both TC48 and TC45. In immortalized TCPTP(-/-) murine embryo fibroblasts, insulin-induced IR beta-subunit tyrosine phosphorylation and protein kinase PKB/Akt activation were enhanced relative to the values in TCPTP(+/+) cells. Importantly, the expression of TC45 or TC48 to physiological levels suppressed the enhanced insulin-induced signaling in TCPTP(-/-) cells. These results indicate that the differentially localized variants of TCPTP may dephosphorylate the IR and downregulate insulin-induced signaling in vivo.
|
| 12620231 |
The human Sir2 ortholog, SIRT2, is an NAD+-dependent tubulin deacetylase. |
10.1016/s1097-2765(03)00038-8 |
Mol. |
The human Sir2 ortholog, SIRT2, is an NAD+-dependent tubulin deacetylase.
Abstract
- The silent information regulator 2 protein (Sir2p) of Saccharomyces cerevisiae is an NAD-dependent histone deacetylase that plays a critical role in transcriptional silencing. Here, we report that a human ortholog of Sir2p, sirtuin type 2 (SIRT2), is a predominantly cytoplasmic protein that colocalizes with microtubules. SIRT2 deacetylates lysine-40 of alpha-tubulin both in vitro and in vivo. Knockdown of SIRT2 via siRNA
Results in tubulin hyperacetylation. SIRT2 colocalizes and interacts in vivo with HDAC6, another tubulin deacetylase. Enzymatic analysis of recombinant SIRT2 in comparison to a yeast homolog of Sir2 protein (Hst2p) shows a striking preference of SIRT2 for acetylated tubulin peptide as a substrate relative to acetylated histone H3 peptide. These observations establish SIRT2 as a bona fide tubulin deacetylase.
|
| 12620237 |
EGF activates its receptor by removing interactions that autoinhibit ectodomain dimerization |
10.1016/s1097-2765(03)00047-9. |
Mol Cell |
EGF activates its receptor by removing interactions that autoinhibit ectodomain dimerization
Abstract
- Epidermal growth factor (EGF) receptor is the prototype of the ErbB (HER) family receptor tyrosine kinases (RTKs), which regulate cell growth and differentiation and are implicated in many human cancers. EGF activates its receptor by inducing dimerization of the 621 amino acid EGF receptor extracellular region. We describe the 2.8 A resolution crystal structure of this entire extracellular region (sEGFR) in an unactivated state. The structure reveals an autoinhibited configuration, where the dimerization interface recently identified in activated sEGFR structures is completely occluded by intramolecular interactions. To activate the receptor, EGF binding must promote a large domain rearrangement that exposes this dimerization interface. This contrasts starkly with other RTK activation mechanisms and suggests new approaches for designing ErbB receptor antagonists.
|
| 12620847 |
Identification and characterization of two novel clostridial bacteriocins, circularin A and closticin 574 |
10.1128/AEM.69.3.1589-1597.2003. |
Appl Environ Microbiol |
Identification and characterization of two novel clostridial bacteriocins, circularin A and closticin 574
Abstract
- Two novel antibacterial peptides of clostridial species were purified, N-terminally sequenced, and characterized. Moreover, their structural genes were identified. Closticin 574 is an 82-amino-acid bacteriocin produced by Clostridium tyrobutyricum ADRIAT 932. The supernatant of the producing strain showed a high level of activity against the indicator strain C. tyrobutyricum. The protein is synthesized as a preproprotein that is possibly secreted via the general secretion pathway, after which it is hydrolyzed at an Asp-Pro site. Circularin A is produced by Clostridium beijerinckii ATCC 25752 as a prepeptide of 72 amino acids. Cleavage of the prepeptide between the third leucine and fourth valine residues followed by a head-to-tail ligation between the N and C termini creates a circular antimicrobial peptide of 69 amino acids. The unusually small circularin A leader peptide of three amino acids is cleaved off in this process. The supernatant of C. beijerinckii ATCC 25752 showed a broad antibacterial activity range.
|
| 12639558 |
Antineoplastic agents 390. Isolation and structure of phakellistatin 12 from a Chuuk archipelago marine sponge |
10.1016/s0960-894x(02)01054-5. |
Bioorg Med Chem Lett |
Antineoplastic agents 390. Isolation and structure of phakellistatin 12 from a Chuuk archipelago marine sponge
Abstract
- A new cancer cell growth inhibitory (P388 lymphocytic leukemia ED(50) 2.8 microg/mL) cyclodecapeptide designated phakellistatin 12 (2) has been isolated as a trace (1.7 x 10(-6)% yield) constituent of the Western Pacific Ocean (Federated States of Micronesia-Chuuk) sponge Phakellia sp. Employing principally a combination of high resolution FAB with high field (500 MHz) 1H, 13C and 2-D NMR and chiral GC analyses the structure (all S chirality) cyclo-Ile-Phe-Thr-Leu-Pro-Pro-Tyr-Ile-Pro-Pro was assigned.
|
| 12639942 |
Somatostatin inhibits tumor angiogenesis and growth via somatostatin receptor-3-mediated regulation of endothelial nitric oxide synthase and mitogen-activated protein kinase activities |
10.1210/en.2002-220949. |
Endocrinology |
Somatostatin inhibits tumor angiogenesis and growth via somatostatin receptor-3-mediated regulation of endothelial nitric oxide synthase and mitogen-activated protein kinase activities
Abstract
- Somatostatin was reported to inhibit Kaposi's sarcoma (KS) cell (KS-Imm) xenografts through an antiangiogenic activity. Here, we show that somatostatin blocks growth of established KS-Imm tumors with the same efficacy as adriamycin, a clinically effective cytotoxic drug. Whereas KS-Imm cells do not express somatostatin receptors (SSTRs), endothelial cells express several SSTRs, in particular SSTR3. We investigated the molecular mechanisms and receptor specificity of somatostatin inhibition of angiogenesis. Somatostatin significantly inhibited angiogenesis in vivo in the matrigel sponge assay; this inhibition was mimicked by the SSTR3 agonist L-796778 and reversed by the SSTR3 antagonist BN81658, demonstrating involvement of SSTR3. In vitro experiments showed that somatostatin directly affected different endothelial cell line proliferation through a block of growth-factor-stimulated MAPK and endothelial nitric oxide (NO) synthase (eNOS) activities. BN81658 reversed somatostatin inhibition of cell proliferation, NO production, and MAPK activity, indicating that SSTR3 activation is required for the effects of somatostatin in vitro. Finally in vivo angiogenesis assays demonstrated that eNOS inhibition was a prerequisite for the antiangiogenic effects of somatostatin, because high concentrations of sodium nitroprusside, an NO donor, abolished the somatostatin effects. In conclusion, we demonstrate that somatostatin is a powerful antitumor agent in vivo that inhibits tumor angiogenesis through SSTR3-mediated inhibition of both eNOS and MAPK activities.
|
| 12639956 |
Crystal structures of allosamidin derivatives in complex with human macrophage chitinase. |
10.1074/jbc.m300362200 |
J. Biol. Chem. |
Crystal structures of allosamidin derivatives in complex with human macrophage chitinase.
Abstract
- The pseudotrisaccharide allosamidin is a potent family 18 chitinase inhibitor with demonstrated biological activity against insects, fungi, and the Plasmodium falciparum life cycle. The synthesis and biological properties of several derivatives have been reported. The structural interactions of allosamidin with several family 18 chitinases have been determined by x-ray crystallography previously. Here, a high resolution structure of chitotriosidase, the human macrophage chitinase, in complex with allosamidin is presented. In addition, complexes of the allosamidin derivatives demethylallosamidin, methylallosamidin, and glucoallosamidin B are described, together with their inhibitory properties. Similar to other chitinases, inhibition of the human chitinase by allosamidin derivatives lacking a methyl group is 10-fold stronger, and smaller effects are observed for the methyl and C3 epimer derivatives. The structures explain the effects on inhibition in terms of altered hydrogen bonding and hydrophobic interactions, together with displaced water molecules. The data reported here represent a first step toward structure-based design of specific allosamidin derivatives.
|
| 12644678 |
Isolation and properties of floral defensins from ornamental tobacco and petunia |
10.1104/pp.102.016626. |
Plant Physiol |
Isolation and properties of floral defensins from ornamental tobacco and petunia
Abstract
- The flowers of the solanaceous plants ornamental tobacco (Nicotiana alata) and petunia (Petunia hybrida) produce high levels of defensins during the early stages of development. In contrast to the well-described seed defensins, these floral defensins are produced as precursors with C-terminal prodomains of 27 to 33 amino acids in addition to a typical secretion signal peptide and central defensin domain of 47 or 49 amino acids. Defensins isolated from N. alata and petunia flowers lack the C-terminal domain, suggesting that it is removed during or after transit through the secretory pathway. Immunogold electron microscopy has been used to demonstrate that the N. alata defensin is deposited in the vacuole. In addition to the eight canonical cysteine residues that define the plant defensin family, the two petunia defensins have an extra pair of cysteines that form a fifth disulfide bond and hence define a new subclass of this family of proteins. Expression of the N. alata defensin NaD1 is predominantly flower specific and is most active during the early stages of flower development. NaD1 transcripts accumulate in the outermost cell layers of petals, sepals, anthers, and styles, consistent with a role in protection of the reproductive organs against potential pathogens. The floral defensins inhibit the growth of Botrytis cinerea and Fusarium oxysporum in vitro, providing further support for a role in protection of floral tissues against pathogen invasion.
|
