摘要:

AbstractThe ADP‐ATP carrier (also referred to as the adenine nucleotide translocator) ofSaccharomyces cerevisiaeis encoded by a nuclear gene, translated in the cytosol, and imported into the mitochondrial inner membrane. In order to study the determinants of mitochondrial import, a series of fusion proteins, consisting of the first 21, 72, and 111 amino acids of the ADP‐ATP carrier, joined to mouse dihydrofolate reductase were generated. Dihydrofolate reductase is a cytosolic protein that does not bind mitochondria. The reticulocyte lysate reaction containing the35S‐methionine‐labeled protein was incubated with mitochondria in a buffer containing 3% BSA. Following incubation for import, the reactions were treated with 1 mM PMSF or 25 μg/ml proteinase K; mitochondria were reisolated and analyzed by gel electrophoresis. The 21 and 72 amino acid hybrid proteins showed a low level of binding to mitochondria: the bound form was entirely protease accessible. The 111 amino acid hybrid protein was imported to a protease‐protected location within mitochondria. It is concluded that the first 72 amino acids of the ADP‐ATP carrier do not suffice to import the protein into mitochondria and that the region between amino acids 72 and 111, a region that contains a transmembrane‐spanning domain, constitutes at least part of the mitochondrial

ISSN:0730-2312    

DOI:10.1002/jcb.240360402

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

年代:1988

数据来源: WILEY

摘要:

AbstractClathrin‐coated vesicles (CVs) were isolated fromSaccharomyces cerevisiaeby using procedures developed by Mueller and Branton [17]. Triskelions were purified from this material by extraction of CVs to release clathrin and by subsequent fractionation on Sepharose CL‐4B. Triskelions were composed of ∼ 180,000 Mrheavy chains and a single light‐chain type of ∼ 38,000 Mrand were able to undergo self‐assembly into polyhedral cages. Trypsin digestion of such reassembled cages showed a peptide pattern very similar to that obtained for mammalian clathrin with two fragments of 125,000 and 110,000 Mr, which represent the major portion of the heavy‐chain arm, and a polypeptide of ∼ 43,000 Mr, which is the presumptive terminal domain.Eight monoclonal antibodies reacting with yeast clathrin heavy chains were produced. All eight bind to the major portion of the heavy‐chain arm, and none bind to the terminal domain fragment. Peptide digestion experiments also indicated that at least three major regions on the arm are recognized by these antibodies. These will be useful in further structural and functional studies of cl

ISSN:0730-2312    

DOI:10.1002/jcb.240360403

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

年代:1988

数据来源: WILEY

摘要:

AbstractTransforming growth factor‐alpha (TGF‐α) is a single chain polypeptide hormone of 50 amino acids that stimulates growth of some human cancer cells via an autocrine mechanism. The domain(s) of TGF‐α that bind and activate its receptor have not been reported. Hydrophilicity plots of TGF‐α indicate three discrete sequences that are theoretically exposed on the hormone's surface and thus potentially able to interact with the TGF‐α receptor. Fragments of TGF‐α encompassing these hydrophilic domains were prepared by using solid‐phase peptide synthesis (SPPS) techniques and purified by use of high performance liquid chromotography (HPLC). Assessment of biological activity of the TGF‐α fragments indicated that none of the fragments significantly inhibited binding of EOF to the receptor, stimulated DNA synthesis of cells, inhibited EGF‐induced DNA synthesis of cells, stimualted growth of cells in soft agar, or induced phosphorylation of the receptor or p35 protein. These results indicate that the receptor binding domain of TGF‐α is not totally encompassed by any of the separate fragments tested and probably is formed by multiple

ISSN:0730-2312    

DOI:10.1002/jcb.240360404

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

年代:1988

数据来源: WILEY

摘要:

AbstractPresented is a comprehensive program designed to isolate human cytokine genes and investigate their relative induction, and to analyze cytokine activities in cell culture, animal tumor models, and human clinical trials. Human cytokine cDNAs have been isolated from a cDNA library made from normal human peripheral blood leukocytes (PBLs) treated with Sendai virus and the relative induction of tumor necrosis factor (TNF), alpha and gamma interferons (IFN‐α, IFN‐γ), and interleukin‐1 beta IL‐1β genes has been analyzed. In the Sendai virus‐induced PBL system, IL‐1β mRNA was shown to be approximately twofold higher than TNF or IFN‐α mRNA whereas IFN‐γ mRNA was 50–100‐fold lower than TNF or IFN‐α mRNA. The cytotoxic activity of TNF was analyzed on several cell lines and IFN‐α and IFN‐γ were shown to potentiate TNF cytotoxicity about 2–200‐fold depending on cell lines. The LD50for recombinant TNF in BALB/c mice was determined to be 6 × 107U/kg and the therapeutic dose of recombinant TNF in sarcoma 180 bearing BALB/c mice was 3 × 105U/kg, indicating a wide therapeutic index. Phase I clinical trials of recombinant TNF given I.V. indicated a tolerated dose of 150,000 U/kg with biphasic half‐life (T‐1/2) of 2 and 31 min following TNF injection. Phase II trials of TNF and trials of TNF combined with IFN‐α are in progress. These studies indicate that cytokines such as TNF and IFN‐α are subject to similar induction systems, potentiate each other's activities, and can be tolerat

ISSN:0730-2312    

DOI:10.1002/jcb.240360405

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

年代:1988

数据来源: WILEY

摘要:

AbstractKaposi's sarcoma (KS) is a relatively low grade neoplasm, classically occurring in the skin of elderly men. A more virulent and invasive form of Kaposi's sarcoma has been described in patients with acquired immune deficiency syndrome (AIDS). The origin and identification of the tumor cells in these lesions is controversial. Here we have studied the behavior of cells derived from KS lesions in an in vitro assay which measures the ability of cells to invade through a reconstituted basement membrane. In agreement with previous work, KS cells obtained under selective culture conditions were invasive showing activity comparable to that of malignant tumor cells. Normal fibroblasts, smooth muscle cells, and endothelial cells did not demonstrate invasive behavior under the same experimental conditions. To characterize further the nature of the KS cells we tested the chemotactic response of cells from the most invasive line to a variety of growth factors and compared their response to those of fibroblasts, smooth muscle, and endothelial cells. These studies suggest that normal cells respond to a unique repertoire of chemotactic factors. The chemotactic response of the KS cells most closely resembled that of smooth muscle cells and was quite distinct from endothelial cells. These results indicate that the KS‐derived cultures contain invasive cells with a smooth muscle cell‐like phenot

ISSN:0730-2312    

DOI:10.1002/jcb.240360406

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

年代:1988

数据来源: WILEY

摘要:

AbstractThe mechanism of therapeutic activity of recombinant murine interferon‐gamma (rMu IFN‐γ) and the IFN inducer polyinosinic‐polycytidylic acid solubilized with poly‐L‐lysine in carboxy methyl cellulose (pICLC) in treating metastatic disease was investigated by comparing effector cell augmentation with therapeutic activity in mice bearing experimental lung metastases (B16‐BL6 melanoma). Effector cell functions in spleen, peripheral blood, and lung (the organ with tumor) were tested after 1 and 3 weeks of rMu IFN‐γ or pICLC administration (intravenous, three times a week). In these studies, natural killer (NK), lymphokine‐activated killer (LAK), cytolytic T lymphocytes (CTL) (against specific and nonspecific targets), and macrophage tumoricidal and tumoristatic activities were measured. rM IFN‐γ and pICLC had therapeutic activity and immunomodulatory activity in most assays of immune function examined. Specific CTL activity of pulmonary parenchymal mononuclear cells (PPMC), but not in splenocytes or peripheral blood lymphocytes (PBL), during week 3 and not during week 1, correlated with the therapeutic activity of rMu IFN‐γ and of pICLC. Macrophage tumoricidal activity in PPMC, but not in alveolar macrophages, also correlated with the therapeutic activity of rMu IFN‐γ, but the opposite was true for the therapeutic activity of pICLC. NK activity of PPMC, but not of splenocytes or PBL, during week 1 correlated with the therapeutic activity of pICLC; in contrast, NK activity at any site did not correlate with the therapeutic activity of rMu IFN‐γ. LAK activity at any site did not correlate with the therape

ISSN:0730-2312    

DOI:10.1002/jcb.240360407

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

年代:1988

数据来源: WILEY

摘要:

AbstractUsing in vivo selection methods, we obtained metastatic sublines of the murine RAW 117 large cell lymphoma that form multiple liver metastases. The highly metastatic subline RAW117‐H10 has a low number of gp70 molecules expressed at the cell surface and low cytostatic sensitivity to activated syngeneic macrophages. This subline was infected with endogenous RNA tumor virus isolated from a high virus‐expressing RAW117‐P subline of low metastatic potential. After superinfection the H10 subline gradually increased its expression of cell surface gp70 and showed enhanced sensitivity to macrophage‐mediated cytostasis, suggesting that gp70 might be involved in host macrophage‐mediated surveillance. Culture of RAW117‐P and H10 cells in media conditioned by activated macrophages indicated that parental cells are severely growth inhibited in a dose dependent fashion while H10 cells showed almost no effect. Examination of differentially expressed genes in the highly metastatic RAW117‐H10 cells by analysis of RNA blots indicated that a mitochondrial gene was expressed at a level that was ∼ 10 times higher in H10 cells than in parental cells. This gene was identified as ND5, which codes for a subunit of NADH dehydrogenase (complex I of the mitochondrial electron transport chain); this complex is the target for an activated macrophage‐released cytostatic factor. Among other possibilities, the results are consistent with the suggestion that highly metastatic RAW 117 cells may escape macrophage surveillance by decreasing the synthesis of specific cell‐surface receptors for cytostatic molecules and increasing the synthesis of specific cellular targets

ISSN:0730-2312    

DOI:10.1002/jcb.240360408

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

年代:1988

数据来源: WILEY

摘要:

AbstractTo determine if the amount of chondroitin sulfate proteoglycan (CSPG) in human colorectal tumor tissue correlates with the tumor's aggressiveness we immunochemically determined the CSPG levels in colorectal carcinomas at different stages. A total of 50 specimens—4 polyps, 15 stage B tumors, 9 stage C tumors, 12 stage D tumors, 7 liver metastases, and 3 lymph node metastases—were examined. Tumor tissues were extracted with 4 M guanidine hydrochloride containing protease inhibitors. The extracts were serially diluted and blotted onto nitrocellulose membranes. Reactivity of a chondroitin sulfate‐specific mouse monoclonal antibody (CS‐56) was determined by biotinylated goat antimouse Ig and avidin‐biotin‐peroxidase complex. After comparing tissues from tumors at different stages (classified by the presence or absence of metastasis), we could not find a positive or negative correlation between the amount of CSPG in primary colorectal carcinoma tissues and the tumor's metastatic potential. However, the metastatic foci in the liver or lymph node contained higher amounts of CSPG than the primary tumors did. Immunohistochemical staining of colon carcinoma tissue with CS‐56 revealed that CSPG is predominantly localized in fibrotic portions in the tumor tissues. Two‐year follow‐up studies indicated that a high level of CSPG in primary tumors was not predict

ISSN:0730-2312    

DOI:10.1002/jcb.240360409

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

年代:1988

数据来源: WILEY

摘要:

AbstractCa2+, through the mediation of calmodulin, stimulates the activity of brain adenylate cyclase. The growing awareness that fluctuating Ca2+, concentrations play a major role in intracellular signalling prompted the present study, which aimed to investigate the implications for neurotransmitter (receptor) regulation of enzymatic activity of this calmodulin regulation. The role of Ca2+/calmodulin in regulating neurotransmitter‐mediated inhibition and stimulation was assessed in a number of rat brain areas. Ca2+/calmodulin stimulated adenylate cyclase activity in EGTA‐washed plasma preparations from each region studied—from 1.3‐fold (in striatum) to 3.4‐fold (in cerebral cortex). The fold‐stimulation produced by Ca2+/calmodulin was decreased in the presence of GTP, forskolin, or Mn2+. In EGTA‐washed membranes, receptor‐mediated inhibition of adenylate cyclase was strictly dependent upon Ca2+/calmodulin stimulation in all regions, except striatum. A requirement for Mg2+in combination with Ca2+/calmodulin to observe neurotransmitter‐mediated inhibition was also observed. In contrast, receptor‐mediated stimulation of activity was much greater in the absence of Ca2+/calmodulin. The findings demonstrate that ambient Ca2+concentrations, in concert with endogenous calmodulin, may play a central role in dictating whether inhibition or stimulation of adenylate cyclase by neurotrans

ISSN:0730-2312    

DOI:10.1002/jcb.240360410

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

年代:1988

数据来源: WILEY

摘要:

AbstractThis paper deals with the detailed mechanisms of signal transduction that lead to exocytosis during regulative secretion induced by specific secretagogues in a eukaryotic cell,Paramecium tetraurelia.There are at least three cellular compartments involved in the process: (I) the plasma membrane, which contains secretagogue receptors and other transmembrane proteins, (II) the cytoplasm, particularly in the region between the cell and secretory vesicle membranes, where molecules may influence interactions of the membranes, and (III) the secretory vesicle itself.The ciliated protozoanParamecium tetraureliais very well suited for the study of signal transduction events associated with exocystosis because this eukaryotic cell contains thousands of docked secretory vesicles (trychocysts) below the cell membrane which can be induced to release synchronously when trioggered with secretagogue. This ensures a high signal‐to‐noise ratio for events associated with this process. Upon release the trichocyst membrane fuses with the cell membrane fuses with the cell membrane and the trichocyst content undergoes a Ca2+‐dependent irreversible expansion. Secretory mutants are available which are blocked at different points in the signal transduction pathway.Aspects of the three components mentioned above that will be discussed here include (a) the properties of the vesicle content, its pH, and its membrane; (b) the role of phosphorylation/dephosphorylation of a cytosolic 63‐kilodalton (kDa)Mrprotein in membrane fusion; and (c) how influx of extracellular Ca2+required for exocytosis may take place via exocytic Ca2+channels which may be associated with specific membrane microdomains (fusion ro

ISSN:0730-2312    

DOI:10.1002/jcb.240360411

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

年代:1988

数据来源: WILEY