摘要:

AbstractPhosphotyrosine (P‐Tyr) antibodies have been used to identify the phosphorylated forms of growth factor receptors and oncogene‐coded tyrosine kinases. Western blot analysis of a gastric carcinoma cell line with P‐Tyr antibodies revealed a tyrosine‐phosphorylated protein of Mr145,000 (P145). In addition, in vitro phosphorylation with (γ‐32P)ATP of P‐Tyr immunoprecipitates of the same cells resulted in labelling of this protein on tyrosine. P145 appears to be a transmembrane glycoprotein, with features suggestive of a growth factor receptor. However, the in vivo or in vitro addition of known growth factors did not affect P145 tyrosine phosphorylation. We now report that P145 is rapidly dephosphorylated in vivo when cells are exposed to low pH, a condition known to dissociate ligands from their receptors. The addition of serum‐free medium, conditioned by the gastric carcinoma cells, fully restores the tyrosine phosphorylation lost with acid treatment. These data suggest that the activity responsible for P145 phosphorylation on tyrosine, whether intrinsic to P145 itself or due to an associated kinase, is stimulated by a factor secreted by the tumor ce

ISSN:0730-2312    

DOI:10.1002/jcb.240380402

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1988

数据来源: WILEY

摘要:

AbstractWe have previously identified by chemical cross‐linking a cell surface protein in Swiss 3T3 cells of apparent Mr 75,000–85,000, which may represent a major component of the receptor for peptides of the bombesin family in these cells [1]. Because bombesin‐like peptides may interact with other cell surface molecules, it was important to establish the correlation between receptor binding and functions of this complex and further characterize the Mr 75,000–85,000 cross‐linked protein. Detailed time courses carried out at different temperatures demonstrated that the Mr 75,000–85,000 affinity‐labelled band was the earliest cross‐linked complex detected in Swiss 3T3 cells incubated with125I‐labelled gastrin‐releasing peptide (125I‐GRP). Furthermore, the ability of various nonradioactive bombesin agonists and antagonists to block the formation of the Mr 75,000–85,000 cross‐linked complex correlated extremely well (r = 0.994) with the relative capacity of these peptides to inhibit125I‐GRP specific binding. Pretreatment with unlabelled GRP for up to 6 h caused only a slight decrease in both specific125I‐GRP binding and the affinity labelling of the Mr 75,000–85,000 protein. We also show that the cross‐linked complex is a glycoprotein. First, solubilized affinity labelled Mr 75,000–85,000 complex applied to wheat germ lectin‐sepharose columns was cluted by addition of 0.3 M N‐acetyl‐D‐glucosamine. Second, treatment with endo‐β‐N‐actylglucosaminidase F reduced the apparent molecular weight of the affinity‐labelled band from 75,000–85,000 to 43,000, indi

ISSN:0730-2312    

DOI:10.1002/jcb.240380403

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1988

数据来源: WILEY

摘要:

AbstractHuman α or β interferons inhibit the proliferation of Daudi Burkitt lymphoma cells and induce the differentiation of these cells towards a mature plasma cell phenotype. Similar responses are seen when Daudi cells are treated with the phorbol ester, TPA. Both interferons and TPA down‐regulate expression of the c‐myc oncogene in these cells. Although TPA can mimic the effect of interferon on cell differentiation, it does not induce 2′5′ oligoadenylate synthetase or the interferon‐sensitive mRNAs, 6–16 or 9–27. Thus chronic stimulation of protein kinase C by TPA cannot mimic all of the effects of interferon treatment on gene expression. Inhibition of ADP‐ribosyl transferase activity by 3‐methoxybenzamide impairs interferon‐ or TPA‐induced differentiation of Daudi cells. This agent induces a higher level of c‐myc mRNA in the cells and stimulates the incorporation of [3H]thymidine into DNA; although these effects are partially counteracted by interferon or TPA treatment, the elevated expression of the c‐myc gene may be sufficient to prevent terminal differentiation and allow cel

ISSN:0730-2312    

DOI:10.1002/jcb.240380404

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1988

数据来源: WILEY

摘要:

AbstractWe assayed fragments of the 5′ flanking sequence of the human 2–5A synthetase gene for their ability to respond to interferon‐α (IFN) and platelet‐derived growth factor (PDGF). Transient transfection assays identified a 40‐base pair fragment, which, regardless of orientation, could confer IFN‐inducibility on the thymidine kinase promoter. This same fragment was active in monkey and mouse cells and in the latter was responsive to PDGF. The effect of PDGF could be inhibited by anti‐interferon antibodies. Gel retardation assays, using the 40‐base pair probe, detected the presence of IFN‐modulated DNA‐binding factors in nuclear extracts from monkey cells. In mouse cells both IFN and PDGF induced the binding of nuclear factors to a synthetic 2–5A synthetase response sequence. Thus, both IFN and growth factors directly or indirectly modulate the binding of nuclear factors to the same region of th

ISSN:0730-2312    

DOI:10.1002/jcb.240380405

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1988

数据来源: WILEY

摘要:

AbstractCHO cell lines that constitutively produce the murine interferon‐α (IFN‐α) subspecies α4 and α6 were constructed. The producer cell lines were protected against viral (vesicular stomatitis virus) infection by the IFN species secreted, but were resistant to the growth inhibitory activity of the IFN species. As compared with α4, the α6 protein displayed a high antiproliferative activity when added to normal CHO cells, which correlates completely with the high antiviral activity of a6 on these cells. Three messenger ribonucleic acid (mRNA) species, which are normally induced in CHO cells by IFN treatment (1–8, 2–5A synthetase, and ISG 15) were constitutively present in CHO producer cell lines. The level of another mRNA (ISG 54), however, was very low in the producer cells as compared with its expression in short‐term IFN‐treated cells. These data indicate that 1–8, 2–5A synthetase and ISG 15 are not involved in the antigrowth activity of IFN in this system, but rather suggest a function of I

ISSN:0730-2312    

DOI:10.1002/jcb.240380406

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1988

数据来源: WILEY

摘要:

AbstractCarboxypeptidase E (CPE) is a Carboxypeptidase B‐like enzyme that is thought to be involved in the processing of peptide hormones and neurotransmitters. Soluble and membrane‐associated forms of CPE have been observed in purified secretory granules from various hormone‐producing tissues. In this report, the influence of membrane association on CPE activity has been examined. A substantial amount of the membrane‐associated CPE activity is solubilized upon extraction of bovine pituitary membranes with either 100 mM sodium acetate buffer (pH 5.6) containing 0.5% Triton X‐100 and 1 M NaCl, or by extraction with high pH buffers (pH>8). These treatments also lead to a two‐ to threefold increase in CPE activity. CPE extracted from membranes with either NaCl/Triton X‐100 or high pH buffers hydrolyzes the dansyl‐Phe‐Ala‐Arg substrate with a lower Km than the membrane‐associated CPE. The Vmaxof CPE present in extracts and membrane fractions after the NaCl/Triton X‐100 treatment is twofold higher than in untreated membranes. Treatment of membranes with high pH buffers does not affect the Vmaxof CPE in the soluble and particulate fractions. Pretreatment of membranes with bromoacetyl‐D‐arginine, an active site‐directed irreversible inhibitor of CPE, blocks the activation by NaCl/Triton X‐100 treatment. Thus the increase in CPE activity upon extraction from membranes is probably not because of the conversion of an inactive form to an active one, but is the result of changes in the conformation of the enzyme tha

ISSN:0730-2312    

DOI:10.1002/jcb.240380407

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1988

数据来源: WILEY

摘要:

AbstractSerine proteases in mast cell granules, such as chymase, atypical chymase, and tryptase, which are major proteins in the granules, may play important roles in the process of immunoglobulin E (IgE)‐mediated degranulation and in pathobiological alterations in tissues. Indeed, inhibitors of chymase, substrate analogs, and antichymase F(ab′)2, but not inhibitors of tryptase, markedly inhibited histamine release induced by IgE‐receptor bridging but not that induced by Ca ionophore. In contrast, inhibitors of metalloprotease inhibited histamine release induced not only by IgE‐receptor bridging but also by Ca ionophore. These results suggest that chymase and metalloprotease are involved at different steps in the process of degranulation. The extents of inhibition of histamine release were closely correlated with the amounts of the inhibitors of chymase accumulated in the granules. After degranulation, the released proteases may in part contribute to pathobiological alterations in allergic disorders through generations of C3a anaphylatoxin and thrombin by human and rat tryptase, respectively, and those of angiotensin n and a chemotactic factor of neutrophils by human and rat chymase, respectively. Moreover, chymase and atypical chymase from rat were shown to destroy type IV collagen, and human tryptase was found to hydrolyze various plasma proteins, such as fibrinogen and high‐molecular‐weight kininogen. The biological activities of tryptase and chymase from rat may be regulated by their dissociation from and association with trypstatin, an endogenous inhibitor of thes

ISSN:0730-2312    

DOI:10.1002/jcb.240380408

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1988

数据来源: WILEY

摘要:

AbstractWe assessed the efficacy and safety of peripheral intravenous recombinant human tissue‐type plasminogen activator (rt‐PA) in 47 patients with angiographically documented pulmonary embolism (PE). We administered 50 mg/2 h and, if necessary, an additional 40 mg/4 h. By 6 hours, 94% of the patients had angiographic evidence of clot lysis that was slight in 5, moderate in 12, and marked in 27 patients. Among the 34 patients with pulmonary hypertension prior to treatment, average pulmonary artery pressure decreased from 43/17 (27) to 31/13 (19) mm Hg (P<0.0001). The average lung scan perfusion defect decreased from 37% before therapy to 16% (P<0.01) after therapy among the 19 patients who had pre‐ and post‐treatment lung scans. Of 7 patients with pre‐ and post‐treatment imaging and Doppler echocardiograms, hypokinetic right ventricular wall movement (mild in 1, moderate in 2, and severe in 4) normalized in 5 and improved to mild hypokinesis in 2. Right ventricular diameter decreased from 3.9 ± 1.0 to 2.0 ± 0.5 cm (P<0.005). Fibrinogen decreased 33% from baseline at 2 h and 42% from baseline at 6 h. However, patients with the greatest degree of angiographic clot lysis at 2 h had a preponderance of fibrinogenolysis over fibrinolysis, demonstrated by a lower ratio of cross‐linked fibrin degradation products to fibrin(ogen) degradation products (0.14 ± 0.09 vs. 0.54 ± 0.82) (P<0.04). Among selected patients, peripheral intravenous rt‐PA is associated with rapid lysis of PE, improved pulmonary perfusion, and improved right v

ISSN:0730-2312    

DOI:10.1002/jcb.240380409

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1988

数据来源: WILEY

ISSN:0730-2312    

DOI:10.1002/jcb.240380401

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1988

数据来源: WILEY