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Available from: James S Malter, Sep 01, 2015
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    ABSTRACT: It is generally accepted that the lysosomal compartment plays an important role in the degradation of cellular components. In this communication we discuss various experimental models which have been used to study mechanisms of intralysosomal degradation and also discuss the evidence obtained in support of the following proposals: 1. The autophagosomes can be isolated into high purity and are the subcellular locus of induced protein degradation. 2. Different membrane components such as proteins and lipids are degraded at different rates inside the lysosomes. Intralysosomal hydrolysis is not the rate limiting step in degradation. 3. Lysosomes take up soluble material in vitro by invagination and pinching off of their membranes (microautophagy). 4. Secretory vesicles can degrade their secretory contents by fusing with the lysosomes.
    Virchows Archiv B Cell Pathology 02/1981; 36(2-3):219-34. DOI:10.1007/BF02912068
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    ABSTRACT: The rate of initiation of protein synthesis in mammalian cells in culture is regulated by the availability of essential amino acids. Previous reports have suggested that this effect is mediated by changes in the ratio of uncharged to charged tRNA species in these cells. We have investigated this possibility by examining the formation of 40-S subunit. Met-tRNAf ribosomal initiation complexes in extracts of Ehrlich ascites tumour cells; this is the stage in initiation previously shown to be regulated in response to lysine starvation of the intact cells. These results suggest that amino acid starvation regulates the formation of 40-S polypeptide chain initiation complexes in mammalian cells by a mechanism which is not influenced by the rate of protein synthesis and does not directly involve uncharged tRNA.
    European Journal of Biochemistry 04/1982; 122(3):519-26. DOI:10.1111/j.1432-1033.1982.tb06468.x · 3.58 Impact Factor
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    ABSTRACT: The effects of amino acid deprivation and treatment with amino alcohols upon the growth, viability, and susceptibility to methotrexate (MTX) cytotoxicity were examined in BALB/3T3 cells and their virally transformed counterparts, SV-T2 cells. Cells were deprived of either histidine or tyrosine plus phenylalanine, or they were treated with amino alcohol analogues of histidine and tyrosine (histidinol and tyrosinol). When incubated in medium lacking histidine and supplemented with dialyzed serum (histidine-deficient medium), the BALB/3T3 cells remained viable for at least 3 days, but they ceased logarithmic growth, and the cell number reached an early plateau. In contrast, the SV-T2 cells continued to divide in histidine-deficient medium. Neither cell line ceased division in medium deficient in both phenylalanine and tyrosine. Incubation of the BALB/3T3 cells with 1.5 mM histidinol or 1.0 mM tyrosinol caused an early plateau similar to the effect of histidine deprivation. SV-T2 cells were not affected by these concentrations of histidinol or tyrosinol, but growth was arrested at higher concentrations. Any of the conditions used which caused a plateau in the number of BALB/3T3 cells substantially protected the treated cells from cell death caused by MTX. Therefore, pretreatment of BALB/3T3 cells with histidine deprivation, 1.5 mM histidinol, or 1.0 mM tyrosinol protected this cell line against MTX-induced cell death, while the same pretreatment conditions failed to protect SV-T2 cells. (SV-T2 cells were protected by 4.0 mM histidinol.) Thus, the ability of MTX to kill cells in vitro can be selectively modified by conditions which protect cells which retain normal growth control characteristics, but which do not protect virally transformed cells.
    Cancer Research 11/1983; 43(10):4703-8. · 9.28 Impact Factor
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