| Budget Amount *help |
¥3,400,000 (Direct Cost: ¥3,400,000)
Fiscal Year 1998: ¥600,000 (Direct Cost: ¥600,000)
Fiscal Year 1997: ¥2,800,000 (Direct Cost: ¥2,800,000)
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| Research Abstract |
The purpose of this investigation was to define the possible function of PAF (platelet-ctivating factor) in budding yeast in relation to cell growth regulation.
1.Changes in PAF Production and Distribution of S.cerevisiae cells in Various phase of Life Cycle
We examined the changes of PAF production and its cellular distribution in S.cerevisiae during cell cycle. PAF production of cells was the highest at G_1 phase, and 90 % of PAF was localized in the cell surface. And, we found that the yeast produces PAF in early stage of mating process in response to the mating hormone. Furthermore, STE6 gene disruptant (MAT a cell) was made by using ste6 : URA3, and PAF production and distribution of the disruptant were compared with those of wild type cells. Results indicated that Ste6p encoded by STE6 gene, transport not only lipopeptide mating hormone a-factor, but also lipid mediator PAF.
2.Mechanism of Regulation of Cell Growth by PAF
PAF was added to culture medium and yeast cell growth was monitored. PAF inhibited cell growth dose-ependent manner. We obtained PAP-insensitive mutants, and examined the effects of PAF on the concentration of intracellular cAMP, activities of membrane adenylate cyclase and metabolism of phosphatidyl inositol (cellular IP_3). Results showed that mechanisms of PAF-induced inhibition of cell growth were related to RAS-cAMP pathway and/or the signal transduction mediated by IP_3.
3.Cloning of PAF-ensitive Gene
PAF-sensitive gene, GPR1 was isolated. Gprlp, encoded by GPR1 gene was not PAF receptor, but it is aG-protein coupled receptor which localized at plasma membrane, and regulates the cellular cAMP level in response to the extracellular signal such as glucose.
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