| Budget Amount *help |
¥3,600,000 (Direct Cost: ¥3,600,000)
Fiscal Year 2006: ¥1,600,000 (Direct Cost: ¥1,600,000)
Fiscal Year 2005: ¥2,000,000 (Direct Cost: ¥2,000,000)
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| Research Abstract |
We have previously shown that endothelin (ET)-B receptor stimulation increased neural progenitor proliferation in part via G_<i2> in extracellular matrix molecule-dependent manner. Neural progenitor cells cultured in the presence of ET differentiated into neurons, glial cells and smooth muscle cells (SMCs). In the present study, we first investigated the mechanism of ET-induced differentiation into SMCs. ET effectively promoted expression of SMC-specific proteins in the presence of TGF-β, which is also produced by endothelial cells. Experiments using smooth muscle actin (SMA) promoter-luciferase reporter assay indicated that separate signaling pathways of G protein and TGF-β cooperatively promote expression of SMC-specific proteins in neural progenitor cells.
Next we investigated whether G_<q/11> is also involved in ET-stimulated proliferation and how G_i and G_<q/11> regulate ERK pathway and enhancement of integrin signaling. An inhibitor of G_<q/11> YM-254890, as well as pertussis toxin partially inhibited ET-stimulated phosphorylation of Raf-1 and ERK. ET stimulated protein kinase C (PKC), which was inhibited by YM-254890, while pertussis toxin attenuated ET-induced Ras activation. On the other hand, pertussis toxin and YM-254890 partially inhibited ET-stimulated phosphorylation of FAK and paxillin, and a PKC inhibitor and down-regulation of PKC prevented ET-induced phosphorylation of these protein. A Src family kinase inhibitor, PP2, blocked ET-stimulated phosphorylation of paxillin without effect on ERK. Taken together, ET activates PKC mainly via G_<q/11> and consequently stimulates ERK cascade in cooperation with Ras pathway stimulated by G_i. PKC seems to increase tyrosine phosphorylation of paxillin via Src family kinase to enhance integrin signals, which further increase DNA synthesis and proliferation.
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