| 9062191 |
A family of proteins that inhibit signalling through tyrosine kinase receptors |
10.1038/386181a0. |
Nature |
A family of proteins that inhibit signalling through tyrosine kinase receptors
Abstract
- Phosphotyrosine phosphatases are critical negative or positive regulators in the intracellular signalling pathways that result in growth-factor-specific cell responses such as mitosis, differentiation, migration, survival, transformation or death. The SH2-domain-containing phosphotyrosine phosphatase SHP-2 is a positive signal transducer for several receptor tyrosine kinases (RTKs) and cytokine receptors. To investigate its mechanism of action we purified a tyrosine-phosphorylated glycoprotein which in different cell types associates tightly with SHP-2 and appears to serve as its substrate. Peptide sequencing in conjunction with complementary DNA cloning revealed a new gene family of at least fifteen members designated signal-regulatory proteins (SIRPs). They consist of two subtypes distinguished by the presence or absence of a cytoplasmic SHP-2-binding domain. The transmembrane polypeptide SIRP alpha1 is a substrate of activated RTKs and in its tyrosine-phosphorylated form binds SHP-2 through SH2 interactions and acts as its substrate. It also binds SHP-1 and Grb2 in vitro and has negative regulatory effects on cellular responses induced by growth factors, oncogenes or insulin. Our findings indicate that proteins belonging to the SIRP family generally regulate signals defining different physiological and pathological processes.
|
| 9090868 |
Metabolic cleavage of frangufoline in rodents: in vitro and in vivo study |
10.1021/np9606613. |
J Nat Prod |
Metabolic cleavage of frangufoline in rodents: in vitro and in vivo study
Abstract
- Frangufoline, a sedative 14-membered frangulanine-type cyclopeptide alkaloid, was found to be rapidly converted, via enzymatic process, in vitro and in vivo in rodents to M1 ((S)-(N,N-dimethylphenylalanyl)-(2S,3S)-3-(p-formylphenoxy) leucyl-(S)-leucine); which is a substituted linear tripeptide. The reaction did not require low molecular weight cofactors, and mammalian serum failed to catalyze the reaction. Structure-reactivity study of cyclopeptide alkaloid analogs suggested that the enamide bond is the site being cleaved, and the reaction was inhibited by organophosphorus esters such as BPNP and by eserine at higher concentrations but not by eserine at lower concentrations or by EDTA and PCMB. On the basis of these results, a possible mechanism for metabolic conversion of frangufoline to M1 was proposed, in which oxidation of the vinyl group and enzyme-catalyzed hydrolysis of the adjacent amide bond, possibly by B-esterase-like enzyme, proceed in a concerted manner.
|
| 9095176 |
Neurotrophic actions of nonimmunosuppressive analogues of immunosuppressive drugs FK506, rapamycin and cyclosporin A |
10.1038/nm0497-421. |
Nat Med |
Neurotrophic actions of nonimmunosuppressive analogues of immunosuppressive drugs FK506, rapamycin and cyclosporin A
Abstract
- We show that the nonimmunosuppressive analogues of the immunosuppressive drugs FK506, rapamycin and cyclosporin A promote neurite outgrowth both in PC12 cells and sensory neuronal cultures of dorsal root ganglia with potencies resembling their immunosuppressive homologues. Neurotrophic potencies of the immunophilin ligands resemble their potencies in binding to and inhibiting the rotamase activity of FKBP-12 of cyclophilin. Since nonimmunosuppressive immunophilin ligands, which are devoid of calcineurin inhibitory activity, are equally neurotrophic, inhibition of calcineurin activity is not the mediator of the neurotrophic effects. The immunophilin ligands are neurotrophic in intact animals. FK506 and L-685,818 (the C18-hydroxy, C21-ethyl derivative of FK506) treatment of rats with crushed sciatic nerves enhances both functional and morphologic recovery. The striking potency of these agents, their bioavailability and the dissociation of neurotrophic from immunosuppressant actions argue for their therapeutic relevance in the treatment of neurodegenerative diseases.
|
| 9096086 |
Yttrium-90 and indium-111 labelling, receptor binding and biodistribution of DOTA0,d-Phe1,Tyr3octreotide, a promising somatostatin analogue for radionuclide therapy |
10.1007/BF00881807. |
Eur J Nucl Med |
Yttrium-90 and indium-111 labelling, receptor binding and biodistribution of DOTA0,d-Phe1,Tyr3octreotide, a promising somatostatin analogue for radionuclide therapy
Abstract
- In vitro octreotide receptor binding of 111In-DOTA0,d-Phe1, Tyr3octreotide (111In-DOTATOC) and the in vivo metabolism of 90Y- or 111In-labelled DOTATOC were investigated in rats in comparison with 111In-DTPA0octreotide 111In-DTPAOC). 111In-DOTATOC was found to have an affinity similar to octreotide itself for the octreotide receptor in rat cerebral cortex microsomes. Twenty-four hours after injection of 90Y- or 111In-labelled DOTATOC, uptake of radioactivity in the octreotide receptor-expressing tissues pancreas, pituitary, adrenals and tumour was a factor of 2-6 that after injection of 111In-DTPAOC. Uptake of labelled DOTATOC in pituitary, pancreas, adrenals and tumour was almost completely blocked by pretreatment with 0.5 mg unlabelled octreotide, indicating specific binding to the octreotide receptors. These findings strongly indicate that 90Y-DOTATOC is a promising radiopharmaceutical for radiotherapy and that 111In-DOTATOC is of potential value for diagnosis of patients with octreotide receptor-positive lesions, such as most neuroendocrine tumours.
|
| 9100567 |
A mutation in the follicle-stimulating hormone receptor occurs frequently in human ovarian sex cord tumors. |
10.1210/jcem.82.4.3870 |
J. Clin. Endocrinol. Metab. |
A mutation in the follicle-stimulating hormone receptor occurs frequently in human ovarian sex cord tumors.
Abstract
- A subset of ovarian tumors, referred to as sex cord-stromal tumors, produce endocrine manifestations due to the secretion of estrogens or androgens. Because gonadotropins induce the growth, differentiation, and function of the steroid-producing cells of the ovary, we hypothesized that mutations in the FSH receptor (FSH-R) might occur in this group of tumors. Ovarian sex cord tumors (n = 13), small cell carcinomas of the ovary (n = 3), and control DNA specimens (n = 116) were screened for mutations in the transmembrane domains of the FSH-R. A heterozygous T-->C mutation was found at nucleotide 1777 that converts codon 591 from phenylalanine to serine (F591S). This sixth transmembrane domain mutation was found in 9 of 13 (69%) sex cord tumors and 2 of 3 ovarian small cell carcinomas, but it was not present in control specimens, including 5 normal ovaries, 5 nonsex cord ovarian tumors, 16 thyroid tumors, or 90 specimens of peripheral blood leukocyte DNA, suggesting that this nucleotide change is not a polymorphism. The functional effects of identified mutations were assessed by expression of the wild-type or the F591S mutant FSH-R in COS-7 cells. The F591S mutation eliminated FSH-stimulated cAMP production, and a similar effect was observed when this mutation was introduced into the homologous location of the LH receptor. The high prevalence of the F591S mutation in the FSH-R suggests that it plays a role in the development of ovarian sex cord tumors.
|
| 9103388 |
Expression of a truncated epidermal growth factor receptor-like protein (TEGFR) in ovarian cancer. |
10.1006/gyno.1996.4526 |
Gynecol. Oncol. |
Expression of a truncated epidermal growth factor receptor-like protein (TEGFR) in ovarian cancer.
Abstract
- The epidermal growth factor receptor (EGFR) system has been implicated in the etiology of numerous cancers, including that of ovarian cancer. Elevated levels of EGFR are associated with poor patient prognosis. Moreover, a significant number of ovarian cancers express both the receptor and one of its ligands, suggesting an autocrine mechanism for autonomous tumor growth. Because of the implicated role of the EGFR system in neoplasia, a greater understanding of the factors involved in this system is necessary. We have recently characterized a truncated EGFR-like protein (TEGFR) in human placenta, and we now extend this investigation to ovarian cancer. We report that TEGFR is expressed in ovarian cancer and its level correlates to that of EGFR. Moreover, the level of TEGFR is reduced in metastatic compared to primary tumors. These
Results suggest that TEGFR may play a role in the EGFR system.
|
| 9106068 |
Rapid, sensitive high-performance liquid chromatographic method for the determination of cyclosporin A and its metabolites M1, M17 and M21 |
10.1016/s0378-4347(96)00364-7. |
J Chromatogr B Biomed Sci Appl |
Rapid, sensitive high-performance liquid chromatographic method for the determination of cyclosporin A and its metabolites M1, M17 and M21
Abstract
- Cyclosporin A (CyA) and its metabolites seem to have nephro-, hepato- and neurotoxic side effects. Immunosuppressive therapy is a narrow path between the risk of rejection by underimmunosuppression and toxic organ damage by overdosage. Thus CyA dosage must be calculated to avoid the risks of organ rejection through underdosage and toxic organ damage through overdosage or accumulation of metabolites. In routine monitoring of CyA therapy, it can be important to measure not only the parent drug but also the metabolites. We describe a rapid and isocratic high-performance liquid chromatographic method for measurement of CyA and its metabolites M1, M17 and M21 in whole blood. CyA was detected by ultraviolet absorption at 212 nm with a CN analytical column maintained at 50 degrees C and recycling of hexane-isopropanol as mobile phase for improved long-term column stability and efficiency. The minimum detectable concentration of CyA and the three metabolites was 10 ng/ml blood. Our modified HPLC method for the determination of CyA and its metabolites is a simple (isocratic), rapid (the retention times were 7.1 min for CYD, internal standard, 8.9 min for CyA, 11.0 min for M21, 12.9 min for M17 and 16.3 min for M1) and economical method suitable for measuring the concentration of the major metabolite, M17, and for routine monitoring of CyA-treated patients.
|
| 9108242 |
Purification, characterisation and cDNA cloning of an antimicrobial peptide from Macadamia integrifolia |
10.1111/j.1432-1033.1997.00743.x. |
Eur J Biochem |
Purification, characterisation and cDNA cloning of an antimicrobial peptide from Macadamia integrifolia
Abstract
- An antimicrobial peptide with no significant amino acid sequence similarity to previously described peptides has been isolated from the nut kernels of Macadcamia integrifolia. The peptide, termed MiAMP1, is highly basic with an estimated pI of 10.1, a mass of 8.1 kDa and contains 76 amino acids including 6 cysteine residues. A cDNA clone containing the entire coding region corresponding to the peptide was obtained. The deduced amino acid sequence of the cDNA indicated a 26-amino-acid signal peptide at the N-terminus of the preprotein. Purified MiAMP1 inhibited the growth of a variety of fungal, oomycete and gram-positive bacterial phytopathogens in vitro. Some pathogens exhibited close to 100% inhibition in less than 1 microM peptide (5 microg/ml). Antimicrobial activity was diminished against most, but not all, microbes in the presence of calcium and potassium chloride salts (1 mM and 50 mM, respectively). MiAMP1 was active against bakers yeast, was inactive against Escherichia coli and was non-toxic to plant and mammalian cells. Analysis of genomic DNA indicated that MiAMP1 was encoded on a single copy gene containing no introns. The MiAMP1 gene may prove useful in genetic manipulations to increase disease resistance in transgenic plants.
|
| 9108392 |
Purification and molecular cloning of SH2- and SH3-containing inositol polyphosphate-5-phosphatase, which is involved in the signaling pathway of granulocyte-macrophage colony-stimulating factor, erythropoietin, and Bcr-Abl |
None |
Blood |
Purification and molecular cloning of SH2- and SH3-containing inositol polyphosphate-5-phosphatase, which is involved in the signaling pathway of granulocyte-macrophage colony-stimulating factor, erythropoietin, and Bcr-Abl
Abstract
- Grb2/Ash and Shc are the adapter proteins that link tyrosine-kinase receptors to Ras and make tyrosine-kinase functionally associated with receptors and Ras in fibroblasts and hematopoietic cells. Grb2/Ash and Shc have the SH3, SH2, or phosphotyrosine binding domains. These domains bind to proteins containing proline-rich regions or tyrosine-phosphorylated proteins and contribute to the association of Grb2/Ash and Shc with other signaling molecules. However, there could remain unidentified signaling molecules that physically and functionally interact with these adapter proteins and have biologically important roles in the signaling pathways. By using the GST fusion protein including the full length of Grb2/Ash, we have found that c-Cbl and an unidentified 135-kD protein (pp135) are associated with Grb2/Ash. We have also found that they become tyrosine-phosphorylated by treatment of a human leukemia cell line, UT-7, with granulocyte-macrophage colony-stimulating factor (GM-CSF). We have purified the pp135 by using GST-Grb2/Ash affinity column and have isolated the full-length complementary DNA (cDNA) encoding the pp135 using a cDNA probe, which was obtained by the degenerate polymerase chain reaction based on a peptide sequence of the purified pp135. The cloned cDNA has 3,958 nucleotides that contain a single long open reading frame of 3,567 nucleotides, encoding a 1,189 amino acid protein with a predicted molecular weight of approximately 133 kD. The deduced amino acid sequence reveals that pp135 is a protein that has one SH2, one SH3, and one proline-rich domain. The pp135, which contains two motifs conserved among the inositol polyphosphate-5-phosphatase proteins, was shown to have the inositol polyphosphate-5-phosphatase activity. The pp135 was revealed to associate constitutively with Grb2/Ash and inducibly with Shc using UT-7 cells stimulated with GM-CSF. In the cell lines derived from human chronic myelogenous leukemia, pp135 was constitutively tyrosine-phosphorylated and associated with Shc and Bcr-Abl. These facts suggest that pp135 is a signaling molecule that has a unique enzymatic activity and should play an important role in the signaling pathway triggered by GM-CSF and in the transformation of hematopoietic cells caused by Bcr-Abl.
|
| 9113340 |
Thionation of segetalins A and B, cyclic peptides with estrogen-like activity from seeds of Vaccaria segetalis |
10.1016/s0968-0896(97)00001-1. |
Bioorg Med Chem |
Thionation of segetalins A and B, cyclic peptides with estrogen-like activity from seeds of Vaccaria segetalis
Abstract
- Thionation of estrogen-like active cyclic peptides, segetalins A (1) and B (2), with Lawesson's reagent provided each two thiosegetalins; thiosegetalin A1 Gly-1-psi(CS-NH)-Val-2; Trp-5-psi (CS-NH)-Ala-6segetalin A, thiosegetalin A2 Gly-1-psi(CS-NH)-Val-2; Ala-6-psi(CS-NH)-Gly-1segetalin A, thiosegetalin B1 Gly-1-psi (CS-NH)-Val-2; Ala-3-psi(CS-NH)-Trp-4segetalin B, and thiosegetalin B2 Gly-1-psi(CS-NH)-Val-2; Trp-4-psi(CS-NH)-Ala-1segetalin B. Thiosegetalin A2 only showed estrogen-like activity against ovariectomized rats. On the basis of their conformations analysed by NMR experiments, the backbone conformation was considered to play an important role in estrogen-like activity for segetalins."
|
| 9115446 |
Solution structure of the sodium channel antagonist conotoxin GS: a new molecular caliper for probing sodium channel geometry |
10.1016/s0969-2126(97)00212-8. |
Structure |
Solution structure of the sodium channel antagonist conotoxin GS: a new molecular caliper for probing sodium channel geometry
Abstract
- The venoms of Conus snails contain small, disulfide-rich inhibitors of voltage-dependent sodium channels. Conotoxin GS is a 34-residue polypeptide isolated from Conus geographus that interacts with the extracellular entrance of skeletal muscle sodium channels to prevent sodium ion conduction. Although conotoxin GS binds competitively with mu conotoxin GIIIA to the sodium channel surface, the two toxin types have little sequence identity with one another, and conotoxin GS has a four-loop structural framework rather than the characteristic three-loop mu-conotoxin framework. The structural study of conotoxin GS will form the basis for establishing a structure-activity relationship and understanding its interaction with the pore region of sodium channels.
The three-dimensional structure of conotoxin GS was determined using two-dimensional NMR spectroscopy. The protein exhibits a compact fold incorporating a beta hairpin and several turns. An unusual feature of conotoxin GS is the exceptionally high proportion (100%) of cis-imide bond geometry for the three proline or hydroxyproline residues. The structure of conotoxin GS bears little resemblance to the three-loop mu conotoxins, consistent with the low sequence identity between the two toxin types and their different structural framework. However, the tertiary structure and cystine-knot motif formed by the three disulfide bonds is similar to that present in several other polypeptide ion channel inhibitors.
This is the first three-dimensional structure of a 'four-loop' sodium channel inhibitor, and it represents a valuable new structural probe for the pore region of voltage-dependent sodium channels. The distribution of amino acid sidechains in the structure creates several polar and charged patches, and comparison with the mu conotoxins provides a basis for determining the binding surface of the conotoxin GS polypeptide.
|
| 9127193 |
Fusaricidins B, C and D, new depsipeptide antibiotics produced by Bacillus polymyxa KT-8: isolation, structure elucidation and biological activity |
None |
J Antibiot (Tokyo) |
Fusaricidins B, C and D, new depsipeptide antibiotics produced by Bacillus polymyxa KT-8: isolation, structure elucidation and biological activity
Abstract
- Fusaricidins B, C and D, new depsipeptide antibiotics, have been isolated as minor components from the culture broth of Bacillus polymyxa KT-8 which was obtained from the rhizosphere of garlic suffering from the basal rot caused by Fusarium oxysporum. The structure of fusaricidin B has been elucidated mainly by various NMR experiments coupled with amino acid analysis in relation to fusaricidin A, the main component of the complex, whose structure was reported previously. The fraction consisting of fusaricidins C and D was unsuccessfully separated, giving roughly a 4:1 mixture of the two, respectively. The structures of fusaricidins C and D have been determined within the mixture by detailed analyses of the 2D NMR spectra. Fusaricidins B, C and D are active against fungi and Gram-positive bacteria almost as well as fusaricidin A.
|
| 9140047 |
Metanephric osteopontin regulates nephrogenesis in vitro |
10.1152/ajprenal.1997.272.4.F469. |
Am J Physiol |
Metanephric osteopontin regulates nephrogenesis in vitro
Abstract
- Renal expression of osteopontin is enhanced in the setting of acute ischemic injury. Because of the parallels that exist between recovery from renal ischemia and renal development, we characterized the role that osteopontin plays during metanephrogenesis in the rat. Osteopontin mRNA is present in kidneys obtained from rat embryos as early as embryonic day 13 (E13). Immunohistochemical staining of metanephroi obtained from E16 rat embryos and metanephroi obtained from E13 embryos and cultured for 3 days in vitro demonstrated that osteopontin is expressed both in the developing nephron and in the ureteric bud. Addition of anti-osteopontin antibodies to metanephric organ cultures results in failure of the metanephric blastema to undergo normal tubulogenesis. Addition of the arginine-glycine-aspartic acid-containing peptide, cyclo-RGDfV, or the anti-alpha(v)beta3-integrin antibody, LM609, to cultures has a similar effect. These findings establish that osteopontin is produced within the rat metanephros during development in vivo and suggest that the binding of osteopontin to the alpha(v)beta3-integrin is required for tubulogenesis to occur in vitro. Blastemal cells within metanephroi cultured in the presence of OP199 manifest increased apoptosis compared with controls. It is possible that osteopontin plays an important anti-apoptotic role during the process of metanephric blastema condensation that is a prerequisite for the formation of nephrons in vivo.
|
| 9148935 |
Focal adhesion kinase overexpression enhances ras-dependent integrin signaling to ERK2/mitogen-activated protein kinase through interactions with and activation of c-Src |
10.1074/jbc.272.20.13189. |
J Biol Chem |
Focal adhesion kinase overexpression enhances ras-dependent integrin signaling to ERK2/mitogen-activated protein kinase through interactions with and activation of c-Src
Abstract
- Cell adhesion to extracellular matrix proteins such as fibronectin (FN) triggers a number of intracellular signaling events including the increased tyrosine phosphorylation of the cytoplasmic focal adhesion protein-tyrosine kinase (PTK) and also the stimulation of the mitogen-activated protein kinase ERK2. Focal adhesion kinase (FAK) associates with integrin receptors, and FN-stimulated phosphorylation of FAK at Tyr-397 and Tyr-925 promotes the binding of Src family PTKs and Grb2, respectively. To investigate the mechanisms by which FAK, c-Src, and Grb2 function in FN-stimulated signaling events to ERK2, we expressed wild type and mutant forms of FAK in human 293 epithelial cells by transient transfection. FAK overexpression enhanced FN-stimulated activation of ERK2 approximately 4-fold. This was blocked by co-expression of the dominant negative Asn-17 mutant Ras, indicating that FN stimulation of ERK2 was Ras-dependent. FN-stimulated c-Src PTK activity was enhanced by wild type FAK expression, whereas FN-stimulated activation of ERK2 was blocked by expression of the c-Src binding site Phe-397 mutant of FAK. Expression of the Grb2 binding site Phe-925 mutant of FAK enhanced activation of ERK2, whereas a kinase-inactive Arg-454 mutant FAK did not. Expression of wild type and Phe-925 FAK, but not Phe-397 FAK, enhanced p130(Cas) association with FAK, Shc tyrosine phosphorylation, and Grb2 binding to Shc after FN stimulation. FN-induced Grb2-Shc association is another pathway leading to activation of ERK2 via Ras. The inhibitory effects of Tyr-397 FAK expression show that FAK-mediated association and activation of c-Src is essential for maximal signaling to ERK2. Moreover, multiple signaling pathways are activated upon the formation of an FAK.c-Src complex, and several of these can lead to Ras-dependent ERK2 mitogen-activated protein kinase activation.
|
| 9157189 |
Cyclic peptides from higher plants. 34. Segetalins G and H, structures and estrogen-like activity of cyclic pentapeptides from Vaccaria segetalis |
10.1021/np960617n. |
J Nat Prod |
Cyclic peptides from higher plants. 34. Segetalins G and H, structures and estrogen-like activity of cyclic pentapeptides from Vaccaria segetalis
Abstract
- Segetalins G and H (1-2) possessing estrogen-like activity are cyclic pentapeptides from the seeds of Vaccaria segetalis. Their structures, cyclo(-Gly-Ala-Lys-Tyr-Val) (1) and cyclo(-Gly-Phe-Ser-Tyr-Arg-) (2), were determined by interpretation of spectral data.
|
