Abstracts of papers (2006)
Last Update: 12/08/2006
Abstracts of papers (2006)
[2006-1] Matsumoto, K. et al., Heterocycles 67, 361-367 (2006)
The title compound was prepared from [alpha]-tert-butyl N[alpha]-tert-butoxycarbonyl-L-glutamate (Boc-Glu-OBu-t) by N-alkylation of 3-methylpyridine after one carbon-elongation through six
steps.
[2006-2] Igarashi, K. and Kashiwagi, K., J. Biochem. 139, 11-16 (2006)
We have recently proposed an idea to explain how polyamines enhance cell growth in Escherichia coli. Since most polyamines exist as polyamine-RNA complexes, our idea is that
polyamines stimulate several kinds of protein synthesis which are important
for cell growth at the level of translation. We found that synthesis of
oligopeptide binding protein (OppA), which is important for nutrient supply,
adenylate cyclase (Cya), RNA polymerase sigma(38) subunit (RpoS), transcription
factor of iron transport operon (FecI), and transcription factor of growth-related
genes including rRNA and some kinds of tRNA synthesis (Fis) was enhanced
by polyamines at the level of translation. We proposed that a group of
genes whose expression is enhanced by polyamines at the level of translation
be referred to as a "polyamine modulon." By DNA microarray, we
found that 309 of 2,742 mRNA species were up-regulated by polyamines. Among
the 309 up-regulated genes, transcriptional enhancement of at least 58
genes might be attributable to increased levels of the transcription factors
Cya, RpoS, FecI, and Fis. This unifying molecular mechanism is proposed
to underlie the physiological role of polyamines in controlling the growth
of Escherichia coli .
[2006-3] Nishimura, K. et al., J. Biochem. 139, 81-90 (2006)
Changes in polyamine levels during aging were measured in 3-, 10- and 26-week-old female mice. The level of polyamines in pancreas, brain, and uterus was maintained during these periods. The level of spermidine slightly decreased in intestine, and decreased significantly in thymus, spleen, ovary, liver, stomach, lung, kidney, heart and muscle during these periods. In skin, the level of spermidine was maximal in 10-week-old mice and markedly reduced in 26-week-old mice. The results suggest that maintenance of polyamine levels may play important roles in the function of the pancreas, brain and uterus in 3- to 26-week-old mice. We next looked for polyamine-rich food materials as a dietary source of polyamines. Foods found to be rich in polyamines included wheat germ, rice bran, black rice, Philippine mango, green pepper, Japanese pumpkin, nuts, fermented pickles, pond smelt, turban shell viscera, whelk viscera, salted salmon roe, salted cod roe, beef intestine (boiled) and liver of eel, beef, pork and chicken; and, as previously reported, soybean, fermented soybean (natto), mushrooms, orange and green tea leaf. These results offer useful information
when it becomes necessary to ingest polyamines from food.
[2006-4] Higashi, K. et al., J. Biol. Chem. 281, 9527-9537 (2006)
Polypeptide release factor 2 (RF2) in Escherichia coli is known to be synthesized by a +1 frameshift at the 26th UGA codon of RF2 mRNA. Polyamines were found to stimulate the +1 frameshift of RF2 synthesis, an effect that was reduced by excess RF2. Polyamine stimulation of +1 frameshift of RF2 synthesis was observed at the early logarithmic phase, which is the important phase in determination of the overall rate of cell growth. A Shine-Dalgarno-like sequence was necessary for an efficient +1 frameshift of RF2 synthesis, but not for polyamine stimulation. Spectinomycin, tetracycline, streptomycin, and neomycin reduced polyamine stimulation of the +1 frameshift of RF2 synthesis. The results suggest that a structural change of the A site on 30 S ribosomal subunits is important for polyamine stimulation of the +1 frameshift. The level of mRNAs of ribosomal proteins and elongation factors having UAA as termination codon was enhanced by polyamines, and OppA synthesis from OppA mRNA having UAA as termination codon was more enhanced by polyamines than that from OppA mRNA having a UGA termination codon. Furthermore, synthesis of ribosomal protein L20 and elongation factor G from the mRNAs having a UAA termination codon was enhanced by polyamines at the level of translation and transcription. The results suggest that some protein synthesis from mRNAs having a UAA termination codon is enhanced at the level of translation through polyamine stimulation of +1 frameshift of RF2 synthesis. It is concluded that prfB encoding RF2 is a new member of the polyamine modulon.
[2006-5] Igarashi, K., Yakugaku Zasshi 126, 455-471 (2006) (in Japanese)
Polyamines (putrescine, spermidine, and spermine) are essential for normal
cell growth. The polyamine level in cells is regulated by biosynthesis,
degradation, and transport. The role of antizyme on polyamine biosynthesis
and transport in mammalian cells and characteristics of polyamine transport
in Escherichia coli and yeast are described briefly in this review. In addition, the effects
of polyamines on protein synthesis and the NMDA receptor are outlined.
Finally, the correlation between acrolein produced from polyamines by polyamine
oxidase and chronic renal failure and brain stroke is summarized. Increased
levels of polyamine oxidase and acrolein are good markers of chronic renal
failure and brain stroke.
[2006-6] Soksawatmaekhin, W. et al., J. Biol. Chem. 281, 29213-29220 (2006)
Amino acid residues involved in cadaverine uptake and cadaverine-lysine
antiporter activity were identified by site-directed mutagenesis of the
CadB protein. It was found that Tyr(73), Tyr(89), Tyr(90), Glu(204), Tyr(235),
Asp(303), and Tyr(423) were strongly involved in both uptake and excretion
and that Tyr(55), Glu(76), Tyr(246), Tyr(310), Cys(370), and Glu(377) were
moderately involved in both activities. Mutations of Trp(43), Tyr(57),
Tyr(107), Tyr(366), and Tyr(368) mainly affected uptake activity, and Trp(41),
Tyr(174), Asp(185), and Glu(408) had weak effects on uptake. The decrease
in the activities of the mutants was reflected by an increase in the Km value. Mutation of Arg(299) mainly affected excretion, suggesting that
Arg(299) is involved in the recognition of the carboxyl group of lysine.
These results indicate that amino acid residues involved in both uptake
and excretion, or solely in excretion, are located in the cytoplasmic loops
and the cytoplasmic side of transmembrane segments, whereas residues involved
in uptake were located in the periplasmic loops and the transmembrane segments.
The SH group of Cys(370) seemed to be important for uptake and excretion,
because both were inhibited by the existence of Cys(125), Cys(389), or
Cys(394) together with Cys(370). The relative topology of 12 transmembrane
segments was determined by inserting cysteine residues at various sites
and measuring the degree of inhibition of transport through crosslinking
with Cys(370). The results suggest that a hydrophilic cavity is formed
by the transmembrane segments II, III, IV, VI, VII, X, XI, and XII.
[2006-7] Khan, N. A. et al., J. Lipid Res. 47, 2306-2313 (2006)
Docosahexaenoic acid (DHA), a PUFA of the n-3 family, inhibited the growth
of FM3A mouse mammary cancer cells by arresting their progression from
the late-G(1) to the S phase of the cell cycle. DHA upregulated p27(Kip1)
levels by inhibiting phosphorylation of mitogen-activated protein (MAP)
kinases, i.e., ERK1/ERK2. Indeed, inhibition of ERK1/ERK2 phosphorylation
by DHA, U0126 [chemical MAPK extracellularly signal-regulated kinase kinase
(MEK) inhibitor], and MEK(SA) (cells expressing dominant negative constructs
of MEK) resulted in the accumulation of p27(Kip1). MAP kinase (MAPK) inhibition
by DHA did not increase p27(Kip1) mRNA levels. Rather, this fatty acid
stabilized p27(Kip1) contents and inhibited MAPK-dependent proteasomal
degradation of this protein. DHA also diminished cyclin E phosphorylation,
cyclin-dependent kinase-2 (CDK2) activity, and phosphorylation of retinoblastoma
protein in these cells. Our study shows that DHA arrests cell growth by
modulating the phosphorylation of cell cycle-related proteins.
[2006-8] Eto, S. et al., Tohoku J. Exp. Med. 210, 145-151 (2006)
Polyamines play an essential role in the growth and differentiation of mammalian cells. The depletion of intracellular polyamines results in the suppression of growth. Proliferation of glomerular mesangial cells (MC) is the most common pathologic change in many forms of glomerulonephritis. Agmatine is a metabolite of arginine via arginine decarboxylase (ADC), highly expressed in the kidney, and unique in its capacity to suppress intracellular polyamine levels required for proliferation. As agmatine enters mammalian cells via the polyamine transport system, its antiproliferative effects may preferentially target cells with increased proliferative kinetics. In the present study, we evaluated the antiproliferative effects of agmatine on human MC in vitro. MC proliferation was stimulated with 20% fetal bovine serum (FBS) or platelet-derived growth factor (PDGF-BB, 20 ng/ml). Cell proliferation was measured using the (4.3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide) (MTT) proliferation assay. Intracellular polyamine levels were assayed by high performance liquid chromatography, and cell death was assessed by cellular DNA fragmentation enzyme-linked immunosorbent assay. The MTT proliferation assay showed that agmatine significantly suppressed proliferation of human MC treated with 20% FBS or 5% FBS + PDGF as compared to human MC treated with 5% FBS. Polyamine levels were markedly lower in cells treated with agmatine, and proliferation was rescued by administration of putrescine. The fragmented DNA was hardly detected in agmatine-treated human MC. In summary, human MC stimulated to increase their proliferative kinetics are significantly more sensitive to the antiproliferative effects of agmatine than normally cultured cells. Suppressed proliferation of the agmatine-treated human MC is not due to increased cell death. These results suggest that agmatine is a promising drug candidate for the treatment of human mesangial proliferative glomerulonephritis.
[2006-9] Igarashi, K. et al., Amino Acids 31, 477-483 (2006)
The levels of polyamines (putrescine, spermidine and spermine) and polyamine oxidase in plasma of patients with chronic renal failure were determined. The level of putrescine was increased but the level of spermine was decreased in the plasma of these patients. The patients also had increased plasma polyamine oxidase activity leading to increased degradation of spermine. As acrolein was a major toxic compound produced from spermine by polyamine oxidase, the levels of free and protein-conjugated acrolein in plasma were also measured. Acrolein levels were enhanced in plasma of patients with chronic renal failure. The accumulated acrolein found as protein conjugates was equivalent to 170 [micro]M, which was about 5-fold higher than in plasma of normal subjects. It was found that acrolein is mainly produced by spermine oxidase in plasma. An increase in putrescine, spermine oxidase and acrolein in plasma was observed in all cases such as diabetic nephropathy, chronic glomerulonephritis and nephrosclerosis. After patients with chronic renal failure had undergone hemodialysis, their levels of plasma polyamines, spermine oxidase and acrolein returned towards normal. It is likely that acrolein produced from spermine accumulates in the blood due to decreased excretion into urine and may function as a uremic "toxin".
[2006-Book1] Igarashi, K., and Kashiwagi, K., Chapter 25 in"Polyamine Cell Signaling" pp. 433-448 (2006)
[Concluding Remarks and Future Perspectives]
In E. coli, some properties of the subunits of ABC transporters (substrate-binding
protein, PotD and PotF, and ATPase, PotA) have been clarified. However,
the properties of transmembrane proteins, such as PotB and PotC, still
remain to be clarified. We hope that in the near future how the four subunits
of the ABC transporter function together in polyamine transport will be
clarified. Elucidation of the polyamine-binding site on PotD and PotF led
to the identification of amino acid residues crucial for polyamine binding
to the N-methyl-D-aspartate subtype of glutamate receptors. As for the polyamine transport
proteins consisting of 12 transmembrane segments linked by hydrophobic
segments of variable length with the NH2- and COOH-termini located in the
cytoplasm (PotE and CadB), the physiological functions and amino acids
residues involved in the activity have been elucidated. The tertiary structure
of PoE and CadB will be clarified soon.
In eukaryotes, some properties of polyamine excretion proteins are clarified in yeast. All of those have 12 transmembrane segments. Thus the structure and functions of these proteins will be elucidated, referring to the information on PotE and CadB. However, the properites of polyamine uptake proteins are still unclear, although it is clear that polyamine uptake is negatively regulated by AZ. The demonstration of polyamine uptake through endocytosis mediated by glypican-1 is interesting. Nevertheless, it is still important to look for polyamine-specific transporters in eukaryotes.
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