| Budget Amount *help |
¥17,170,000 (Direct Cost: ¥15,400,000、Indirect Cost: ¥1,770,000)
Fiscal Year 2007: ¥7,670,000 (Direct Cost: ¥5,900,000、Indirect Cost: ¥1,770,000)
Fiscal Year 2006: ¥9,500,000 (Direct Cost: ¥9,500,000)
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| Research Abstract |
The lipid kinase phosphatidylinositol 4-phosphate 5-kinase (PIP5K) phosphorylates phosphatidylinositol 4-phosphate to produce phosphatidylinositol 4,5-bisphosphate (PIP2), which functions as a lipid signaling molecule. Three isozymes for mammalian PIP5K, α β and γ, and three splicing variants of γ type of PIP5K, γ635, γ661 and γ687, have been identified. We have been investigating activation mechanisms and physiological functions of each PIP5K isozyme to understand the molecular multiplicity of PIP5K. During 2 years of this project, we obtained the results described below.
1. Specific partner protein of PIP5K γ661
PIP5K γ661 of PIP5K isozymes and splicing variants, was found to specifically interact with and is activated by the adaptor complex AP-2 in mouse hippocampal neurons. Furthermore, it was found that the interaction of these molecules is absolutely required for the clathrin-dependent synaptic vesicle endocytosis induced by depolarization, in mouse hippocampal neurons.
2. Specific partner protein of PIP5Kβ
PIP5Kβ of PIP5K isozymes specifically interact with KIF2A. The interaction stimulated PIP5Kβ kinase activity and microtubule depolymerizing activity of KIF2A. Finally, the interaction of these two molecules was found to negatively regulate axonal outgrowth of mouse hippocampal neurons.
3. PIP5K binding site for its activator ARF6
The small G protein ARF6 activates PIP5K. We identified that ARF6 binds to the kinase core domain of PIP5K, which is highly conserved among PIP5K isozymes.
4. Preparation and analysis of PIP5K α knockout mice
We prepared PIP5K α knockout mice, which have not yet been reported. These mice were apparently healthy and any defects were not observe.
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