SummaryThe functions of the putative cadaverine transport protein CadB were studied in Escherichia coli . CadB had both cadaverine uptake activity, dependent on proton motive force, and cadaverine excretion activity, acting as a cadaverine-lysine antiporter. The Km values for uptake and excretion of cadaverine were 20.8 and 303 m m m m M respectively. Both cadaverine uptake and cadaverine-lysine antiporter activities of CadB were functional in cells. Cell growth of a polyaminerequiring mutant was stimulated slightly at neutral pH by the cadaverine uptake activity and greatly at acidic pH by the cadaverine-lysine antiporter activity. At acidic pH, the operon containing cadB and cadA , encoding lysine decarboxylase, was induced in the presence of lysine. This caused neutralization of the extracellular medium and made possible the production of CO 2 and cadaverine and aminopropylcadaverine instead of putrescine and spermidine. The induction of the cadBA operon also generated a proton motive force. When the cadBA operon was not induced, the expression of the speF-potE operon, encoding inducible ornithine decarboxylase and a putrescine-ornithine antiporter, was increased. The results indicate that the cadBA operon plays important roles in cellular regulation at acidic pH.

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Cycling of polyamines (spermine and spermidine) in the brain was examined by measuring polyamine transport in synaptic vesicles, synaptosomes and glial cells, and the release of spermine from hippocampal slices. It was found that membrane potential-dependent polyamine transport systems exist in synaptosomes and glial cells, and a proton gradientdependent polyamine transport system exists in synaptic vesicles. The glial cell transporter had high affinities for both spermine and spermidine, whereas the transporters in synaptosomes and synaptic vesicles had a much higher affinity for spermine than for spermidine. Polyamine transport by synaptosomes was inhibited by putrescine, agmatine, histidine, and histamine. Transport by glial cells was also inhibited by these four compounds and additionally by norepinephrine. On the other hand, polyamine transport by synaptic vesicles was inhibited only by putrescine and histamine. These results suggest that the polyamine transporters present in glial cells, neurons, and synaptic vesicles each have different properties and are, presumably, different molecular entities. Spermine was found to be accumulated in synaptic vesicles and was released from rat hippocampal slices by depolarization using a high concentration of KCl. Polyamines, in particular spermine, may function as neuromodulators in the brain.

Properties of a membrane protein encoded byPolyamines, which are essential for cell growth, are regulated by biosynthesis, degradation, and transport (1-3). As for polyamine transport, properties of three polyamine transport systems were clarified by cloning the genes for these systems from Escherichia coli in our laboratory (4 -7). Two of them were spermidine-preferential and putrescine-specific uptake systems, in which ATP was necessary as the energy source. The third system was involved in the excretion of putrescine by a putrescine-ornithine antiporter activity. In eukaryotic cells,

It is well known that the addition of spermine or spermidine to culture medium containing ruminant serum inhibits cellular proliferation. This effect is caused by the products of oxidation of polyamines that are generated by serum amine oxidase. Among the products, we found that acrolein is a major toxic compound produced from spermine and spermidine by amine oxidase. We then analysed the level of polyamines (putrescine, spermidine and spermine) and amine oxidase activity in plasma of patients with chronic renal failure. It was found that the levels of putrescine and the amine oxidase activity were increased, whereas spermidine and spermine were decreased in plasma of patients with chronic renal failure. The levels of free and protein-conjugated acrolein were also increased in plasma of patients with chronic renal failure. An increase in putrescine, amine oxidase and acrolein in plasma was observed in all cases such as diabetic nephropathy, chronic glomerulonephritis and nephrosclerosis. These results suggest that acrolein is produced during the early stage of nephritis through kidney damage and also during uraemia through accumulation of polyamines in blood due to the decrease in their excretion into urine.

The DNA double-strand breaks (DSBs) repair pathway has been implicated in maintaining genomic integrity via suppression of chromosomal rearrangements. DNA-dependent protein kinase (DNA-PK) has an important role with DNA DSBs repair. In this study, 93 of untreated cancer patients and 41 of cancer-free healthy volunteers were enrolled. Peripheral blood was collected, separated and centrifuged; DNA-PK activity was measured by DNA-pull-down assay. The expressions of DNA-PKcs, Ku70 and Ku86 were examined by RT-PCR assay and western blotting. Chromosomal aberrations were examined by cytogenetic methods. DNA-PK activities of peripheral blood lymphocytes (PBL) in patients with uterine cervix or breast cancer were significantly lower than those in normal volunteers. Age and smoking had no association with DNA-PK activity, whereas DNA-PK activity and the expression of Ku70, Ku86 and DNA-PKcs in RT-PCR were interrelated. A similar tendency was seen in western blot assay but less clear than in RT-PCR. Therefore, the association between DNA-PK activity and expression of DNA-PK in protein level could not be concluded. The frequency of chromosome aberration, such as dicentric chromosomes and excess fragment increased as the DNA-PK activity decreased. In conclusion, DNA-PK activity is associated with chromosomal instability. DNA-PK activity in PBL is associated with risk of breast and uterine cervix cancer. DNA-PK activity in PBL can be used to select individuals for whom an examination should be performed because of their increased susceptibility to breast and uterine cervix cancer.

The regulation of polyamine transport by antizyme, a protein that is involved in the rapid degradation of ornithine decarboxylase (ODC), was studied in FM3A mouse cells overproducing ODC. Both artificial (Z1) and natural antizymes not only inhibited polyamine uptake but also stimulated polyamine excretion. The properties of the polyamine transporter regulated by antizyme were characterized. The uptake of radiolabelled polyamines was inhibited by excess acetylpolyamines and a protonophore, CCCP (carbonyl cyanide m-chlorophenylhydrazone), whereas the excretion of radiolabelled polyamines was stimulated