[Cell transformation by Src kinase: role of cell adhesion system as a signal transducer].
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Cadherins↗
Biomedical subjects
M Hamaguchi
Publications and source records attributed to M Hamaguchi.
Evidence of a novel redox-linked activation mechanism for the Src kinase which is independent of tyrosine 527-mediated regulation.
The kinase activity of p60c-src has been shown to be basically regulated through phosphorylation and dephosphorylation of Y527. We found that catalytic activity of the immunoprecipitated c-Src kinase from NIH3T3 cells was elevated several folds by exposure to 0.5-50 microM of sulfhydryl-reactive Hg2+. Vmax of the kinase was increased whereas Km was decreased. N-acetylcysteine neutralized this Hg2+ effect, suggesting a critical role of the Hg2+-mediated sulfhydryl modification of the kinase in the mechanism. Addition of protein tyrosine phosphatase inhibitor Na3VO4 into the reaction mixture did not inhibit the Hg2+-mediated activation. Further study revealed that Hg2+ was capable of activating the v-Src kinase lacking Y527 and the c-Src kinase from mutant cells defective of the Y527-phosphorylating Csk kinase. Cyanogen bromide cleavage maps of radiolabeled Src proteins showed that Hg2+ selectively promoted the autophosphorylation at Y416 and that the previously in vivo radiolabeled phosphorous on Y527 was not deleted during the promotion of Y416 autophosphorylation by Hg2+. Phosphoamino acid analysis demonstrated selective promotion of phosphorylation at tyrosine but not at serine/threonine. Not like bivalent Hg2+, monovalent p-chloromercuribenzenesulfonic acid was incapable of activating c-Src kinase. These results suggest a novel Y416 phosphorylation-linked activation pathway for Src kinases which is initially triggered independent of Y527-mediated or serine/threonine phosphorylation-linked regulation, possibly through sulfhydryl-based protein structural modification for functional alteration.
3T3 Cells↗
Calcium modulates plasmin cleavage of the fibrinogen D fragment gamma chain N-terminus: mapping of monoclonal antibody J88B to a plasmin sensitive domain of the gamma chain.
Plasmin sensitive sites are found on the A alpha, B beta and gamma chains of fibrinogen at regions joining the two C-terminal D fragments with the central E fragment. We have developed a monoclonal antibody (MoAb) reactive with this plasmin sensitive region on the human fibrinogen gamma chain and mapped its epitope. MoAb J88B reacts with gamma chains of both native as well as with reduced and denatured fibrinogen and fibrin, the CNBr fragment of the fibrinogen central domain, plasmin cleaved fragments D, gamma-gamma dimers, but not with plasmic fragments E. These data indicate that J88B maps to the plasmin sensitive domain localized to gamma 63-78. MoAb J88B failed to react with synthetic peptide gamma 70-78, which suggests that the epitope includes the newly exposed N-terminal residues gamma 63-70 of the early plasmic fragment D1A. As calcium has a marked influence on plasmin cleavage of C-terminal sites on the gamma chain, the effects of calcium on modulating plasmin cleavage of D1A to D1 were assessed in the absence or presence of J88B. The results indicated that calcium delays and J88B (+/- calcium) protects the gamma chain from plasmin cleavage at the N-terminus of D1A, suggesting that this enzymatically labile site is calcium-sensitive. Thus, MoAb J88B should prove useful in studies examining the structure of plasmin cleaved fibrinogen and fibrin.
Antibodies, Monoclonal↗
Tyrosine phosphorylation is crucial for growth signaling by tissue inhibitors of metalloproteinases (TIMP-1 and TIMP-2).
[3H]Thymidine (TdR) incorporation by human osteosarcoma cell line MG-63 was significantly stimulated at as early as 3 h after the addition of either TIMP-1 or TIMP-2 alone. Maximum stimulation was attained at a concentration of either 20 ng/ml (0.71 nM) TIMP-1 or 1.0 ng/ml (46 pM) TIMP-2. Tyrosine kinase inhibitors such as genistein, erbstatin, and herbimycin A almost completely inhibited the [3H]TdR incorporation stimulated by either of the TIMPs. However, essentially no effect was observed with H-89, H-7, bisindolylmaleimide and K-252a. These inhibition studies suggest a crucial role for tyrosine kinase in the signal transduction of TIMPs. Phosphotyrosine-containing proteins were significantly elevated by the treatment with both TIMPs. We also found that either TIMP stimulated an increase in mitogen-activated protein (MAP) kinase activity, suggesting that MAP kinase plays a role in TIMP-dependent growth signaling.
Benzoquinones↗
Evaluation of the FHIT gene in colorectal cancers.
A variety of studies suggests that tumor suppressor loci on chromosome 3p are important in various forms of human neoplasia. Recently, a chromosome 3p14.2 gene called FHIT was discovered and proposed as a candidate tumor suppressor gene in colorectal and other cancers. We evaluated the FHIT gene in a panel of colorectal cancer cell lines and xenografts, which allowed a comprehensive mutational analysis. A transcript containing the complete coding sequence was found to be expressed at robust levels in 29 of 31 cancers tested. The complete sequence of the coding region of the gene was determined and found to be normal in all 29 of these cases. These studies suggest either that FHIT is inactivated by an unusual mechanism or that it plays a role in relatively few colorectal tumors.
Acid Anhydride Hydrolases↗
Molecular basis of a hereditary type I protein S deficiency caused by a substitution of Cys for Arg474.
The molecular basis for a hereditary type I protein S (PS) deficiency was investigated. DNA sequence analysis in the proband showed a novel missense mutation substituting Cys (TGT) for Arg474 (CGT) that is a highly conserved amino acid residue among the related proteins. This missense mutation cosegregated with the type I PS deficiency in this family. Transient expression studies showed that the secretion of the recombinant Cys-mutant PS was markedly decreased compared with that of the recombinant wild-type PS, reproducing the observed phenotype of type I deficiency. Stable expression and pulse-chase experiments demonstrated an intracellular degradation and an impaired secretion of the recombinant Cys-mutant PS. Furthermore, the substitution of Arg474 by Ala or Glu, but not by Lys, markedly reduced the secretion of the recombinant PS mutants in transient expression studies, suggesting that a positively charged basic amino acid might be needed at residue 474 and might play a key role in the protein structure and conformation of the sex hormone binding globulin-homology domain of the PS molecule. We postulate that the loss of the highly conserved Arg474 might be responsible for the type I PS deficiency inherited in this family.
Androgen-Binding Protein↗
Protein C Nagoya, an elongated mutant of protein C, is retained within the endoplasmic reticulum and is associated with GRP78 and GRP94.
Protein C Nagoya, an elongated variant of the human protein C, is retained and degraded within the cells in which it is produced (Yamamoto et al, J Clin Invest 90:2439, 1992). To determine the subcellular localization of the protein C Nagoya, the recombinant protein C bearing this mutation was expressed in Chinese hamster ovary (CHO) cells. The mutant protein C was not secreted from the cells and remained susceptible to endo-beta-N-acetylglucosaminidase H (endo H). Immunoelectron microscopy indicated that protein C Nagoya was retained in the endoplasmic reticulum (ER), whereas wild-type protein C was observed in both the ER and the Golgi apparatus. Metabolic radiolabeling with [35S] methionine in combination with chemical cross-linking showed that the protein C Nagoya existed in the ER as a complex with 78-kD glucose-regulated protein (GRP78) and 94-kD glucose-regulated protein (GRP94). Because both GRP78 and GRP94 associate to a far lesser degree with wild-type protein C than with protein C Nagoya, our data suggest that both stress proteins function as molecular chaperones and work in concert with the folding and assembly of protein C. These findings extend our understanding the molecular pathogenesis of protein C deficiency.
Animals↗
Mercuric chloride mediates a protein sulfhydryl modification-based pathway of signal transduction for activating Src kinase which is independent of the phosphorylation/dephosphorylation of a carboxyl terminal tyrosine.
Little is known about the regulatory mechanism of c-Src kinase in cells except the suggested regulation through phosphorylation and dephosphorylation of its carboxyl terminal tyrosine residue (Y527). We here demonstrated that exposure of NIH3T3 cells to mercuric chloride (HgCl2) induces both aggregation and activation of Src kinase protein through a redox-linked mechanism. The aggregation of Src proteins was suggested to be induced by the sulfhydryl groups-to-Hg2+ reaction-mediated polymerization of cell membrane proteins to which the Src proteins associate noncovalently. The possibility was ruled out that the aggregation occurred secondarily to the promotion of protein tyrosine phosphorylation. Further study revealed that the Src kinase was activated by HgCl2 at least in part independent of the known Csk kinase-linked or Y527-phosphorylation/dephosphorylation-mediated control. Correspondingly, CNBr cleavage mapping of phosphopeptides for autophosphorylated c-Src protein demonstrated selective promotion of phosphorylation at Y416 in HgCl2-treated cells without obvious change in the phosphorylation level at Y527. These results suggest a unique protein sulfhydryl modification-based pathway of signal transduction for activating Src kinase in NIH3T3 cells.
3T3 Cells↗
Analysis for heterozygosity of protein S mRNA: application to genetic screening and family studies in hereditary protein S deficiency.
We genetically screened patients with hereditary protein S deficiency for heterozygosity of protein S mRNA using PCR-RFLP for Pro626 polymorphism. All patients who showed hemizygous state of protein S mRNA, characterized by markedly decreased levels of one allele, had a phenotype of type I protein S deficiency. A putative mutation, such as a nonsense or splice site mutation, in the silent alleles may have affected the mutated mRNA metabolism and reduced the mutated mRNA accumulation, and consequently resulted in type I protein S deficiency in these patients. We also applied this mRNA-based analysis to family studies in hereditary protein S deficiency. In a family with type I protein S deficiency, all affected individuals showed a loss of one allele at the mRNA level and the silent allele cosegregated with the disease phenotype. Detection of hemizygous expression of protein S mRNA provided direct evidence for type I protein S deficiency without further precise genetic analysis. Our findings indicate that this mRNA-based analysis can be a useful strategy for genetic screening and family studies in hereditary protein S deficiency.
Codon↗
Serum thrombopoietin level after allogeneic bone marrow transplantation: possible correlations with platelet recovery, acute graft-versus-host disease and hepatic veno-occlusive disease. Nagoya Bone Marrow Transplantation Group.
Thrombopoietin (TPO) is a growth and differentiation factor for megakaryocytes and platelets. An ELISA was developed for measuring TPO concentrations in human sera. The mean +/- S.D. of TPO level obtained in 29 control subjects was 0.87 +/- 0.35 fmol/ml. We measured the TPO level in 36 patients after allogeneic bone marrow transplantation (BMT) and determined the relationship between blood levels of TPO and changes in the circulating platelet mass. In general, a reciprocal relationship was observed between TPO and platelet count (r = -0.609, P < 0.0001; n = 165). With the decrease in the platelet mass after myeloablative therapy, the TPO level increased proportionally and peaked during the platelet nadir. The peak concentration of TPO ranged from 20-50 fmol/ml. The TPO level decreased with the normalization of the platelet mass. In contrast, the TPO level decreased during acute graft-versus-host disease (GVHD) in several patients. Furthermore, the TPO level was significantly lower in the patients with hepatic veno-occlusive disease (VOD) than in the patients after BMT without GVHD and VOD in the samples of less than 50000/microliters platelets (P < 0.005). These findings suggest that in the patients given allogeneic BMT, TPO has an important role in the physiologic regulation of platelet production and that liver damage due to acute GVHD and VOD may decrease the TPO level.
Acute Disease↗
Tyrosine phosphorylation of 100-130 kDa proteins in lung cancer correlates with poor prognosis.
To search for the signalling pathways in lung cancer relevant to its aggressive behaviour, we studied tyrosine phosphorylated proteins in lung cancer cell lines and surgical specimens. We found that the profiles of protein phosphorylation were closely matched among these cell lines and cancer tissues of different histological origins, and 100-130 kDa proteins were the major components of phosphorylated proteins. In surgical specimens, approximately half of the cases showed tyrosine phosphorylation of these proteins in a tumour-specific manner, and phosphorylation of these proteins showed good correlation with the survival length of patients after operation. By immunoprecipitation with specific antibodies, we found that p125FAK, p120 and beta-catenin were the major components of tyrosine-phosphorylated proteins in the surgical specimens. These results suggest that tyrosine phosphorylation of these proteins may play a role in tumour relapse and is available as a clinical marker.
Aged↗
Structural organization and promoter activity of the human ryudocan gene.
To better understand the regulation of ryudocan (syndecan-4) expression, we have determined the structural organization of the human ryudocan gene. The human ryudocan gene extends approximately 24 kilobases and is divided into five exons, which appear to be conserved in syndecan family members. Exon I encodes the signal peptide; exons II-IV, the extracellular domain; and exon V, the transmembrane and cytoplasmic domains, which are highly homologous among syndecan family members. Primer extension analysis showed that human ryudocan gene had a single transcription initiation site, located 3 bases upstream from the described cDNA [Kojima et al. (1993) BBRC 190, 814-822]. The 5'-flanking sequences of human ryudocan gene contain a TATA-like sequence as well as a variety of other potential binding sites for transcription factors, including Sp1, Ap-2, NF-kB, E-alpha H box, H4TF-2, and LBP-1, and were capable of functioning as a promoter. The determination of the human ryudocan gene structure will allow elucidation of constitutive, cell-specific, tissue-specific, and developmentally regulated expression.
Animals↗
Systemic anaphylaxis after eating storage-mite-contaminated food.
We describe 2 cases in whom systemic anaphylaxis developed shortly after they had eaten food contaminated by a storage mite, Tyrophagus putrescentiae. We were able to demonstrate that these cases were sensitive to the storage mites but not to food allergens, leading us to conclude that the cases' anaphylactic episodes were the result of ingestion of the storage mites. This is the first report of the ingestion of storage mites causing systemic anaphylaxis in sensitive persons.
Adolescent↗
Observation of velopharyngeal closure patterns following isolated stimulation of levator veli palatini and pharyngeal constrictor muscles.
This study, using mongrel dogs, showed the individual movements caused by the levator veli palatini muscle (LVP) and pharyngeal constrictor (PC) contraction, induced by electrical stimulation to each peripheral motor nerve. Each bilateral peripheral motor nerve of the LVP and PC muscles was isolated and stimulated electrically to induce the individual contraction of bilateral LVP and PC muscles. The movements were visualized by use of a fiberscope. Vertical movement of the middle soft palate was observed mainly at LVP contraction. Circular closure in the posterior region of the velopharynx was induced by contraction of the PC muscle. The posterior and lateral wall movements clearly occurred following PC contraction.
Animals↗
[Comparative study of bone marrow transplantation from unrelated donors and identical sibling donors in a single institute].
This retrospective study analyzes the result of bone marrow transplantation in 28 patients with unrelated donors compared with 75 patients transplanted from identical HLA sibling donors at a single institute during the same time period. One unrelated donor patient with severe aplastic anemia died without evidence of engraftment. The incidence of grade III-IV acute graft-versus-host disease (GVHD) in unrelated donor patients (19%) was higher than sibling donors (0%) and the probability of survival more than 30 years was lower compared with sibling donors. However, the probability of survival without grade III-IV acute GVHD was similar in the two groups, 62% (n = 21) vs. 65% (n = 75), and there was no significant difference in relapse-free survival, good prognostic factors; 76% (n = 11) vs. 66% (n = 37), higher risk factors; 30% (n = 11) vs. 31% (n = 21). Death due to viral infection were significantly higher among unrelated donor patients. We conclude that bone marrow transplantation for patients younger than 30 years old from unrelated donors should be considered equally to sibling donors with great care to engraftment for severe aplastic anemia, grade III-IV acute GVHD and viral infection.
Adolescent↗
Ganglioside GM1 binds to the Trk protein and regulates receptor function.
Several lines of evidence have suggested that ganglioside GM1 stimulates neuronal sprouting and enhances the action of nerve growth factor (NGF), but its precise mechanism is yet to be elucidated. We report here that GM1 directly and tightly associates with Trk, the high-affinity tyrosine kinase-type receptor for NGF, and strongly enhances neurite outgrowth and neurofilament expression in rat PC12 cells elicited by a low dose of NGF that alone is insufficient to induce neuronal differentiation. The potentiation of NGF activity by GM1 appears to involve tyrosine-autophosphorylation of Trk, which contains intrinsic tyrosine kinase activity that has been localized to the cytoplasmic domain. In the presence of GM1 in culture medium, there is a > 3-fold increase in NGF-induced autophosphorylation of Trk as compared with NGF alone. We also found that GM1 could directly enhance NGF-activated autophosphorylation of immunoprecipitated Trk in vitro. Monosialoganglioside GM1, but not polysialogangliosides, is tightly associated with immunoprecipitated Trk. Furthermore, such tight association of GM1 with Trk appears to be specific, since a similar association was not observed with other growth factor receptors, such as low-affinity NGF receptor (p75NGR) and epidermal growth factor receptor (EGFR). Thus, these results strongly suggest that GM1 functions as a specific endogenous activator of NGF receptor function, and these enhanced effects appear to be due, at least in part, to tight association of GM1 with Trk.
Animals↗
Dissociated control by glycyrrhizin of proliferation and IL-2 production of murine thymocytes.
The action of glycyrrhizin (GL) modulating the proliferation and IL-2 production of murine thymocytes in response to anti-CD3 and concanavalin A was studied. Different from the previously reported GL effect of accelerating both IL-2 production and proliferation of mature T lymphocytes, GL displayed a dissociated action on immature thymocytes promoting IL-2 production/IL-2 receptor expression but inhibiting cell growth. Hydrocortisone-resistant mature thymocytes behaved like peripheral T lymphocytes, demonstrating the dependency of the GL action on cell maturation stage. GL-mediated growth inhibition of thymocytes was not due the cytotoxic action of GL that induces cell death or DNA fragmentation. In parallel to these dissociated actions, GL promoted the tyrosine phosphorylation of p56 but suppressed the phosphorylation of p40 induced by anti-CD3. Moreover, GL and anti-CD3 showed a combination effect suppressing the transcription of c-fos, which was promoted by anti-CD3 alone or GL alone. It is suggested that whereas mature and immature T cells share a common signal pathway for IL-2 production augmented by the action of GL, they have signaling steps for DNA synthesis which are under different mechanisms receiving the modulation effects of GL in opposite directions.
Animals↗
Direct evidence of involvement of glycosylphosphatidylinositol-anchored proteins in the heavy metal-mediated signal delivery into T lymphocytes.
The biological significance of the action of glycosylphosphatidylinositol (GPI)-anchored proteins in cell physiology and pathology when stimulated with their natural agonists is not known. Here we provide evidence that GPI-anchored proteins play a crucial role in the recently defined heavy metal (HgCl2)-triggered signal delivery to T lymphocytes. Thiol-reactive HgCl2, a multi-potent crosslinker of cell membrane proteins, induced heavy aggregation of Thy-1, a representative GPI-anchored protein, on murine thymocytes, and delivered a signal to induce heavy tyrosine phosphorylation of cellular proteins. This rather unusual signal delivery by HgCl2 is diminished by the pre-treatment of cells with phosphatidylinositol-specific phospholipase C, which partially cleaved GPI-anchored proteins from the cell surface. Direct evidence for the involvement of GPI or GPI-anchored proteins in the HgCl2-mediated signaling is provided by the loss of signaling in a mutant thymoma cell line defective in the phosphatidylinositol glycan-class A gene (PIG-A), and its restoration in a transfectant with PIG-A.
Animals↗