| Budget Amount *help |
¥3,730,000 (Direct Cost: ¥3,400,000、Indirect Cost: ¥330,000)
Fiscal Year 2007: ¥1,430,000 (Direct Cost: ¥1,100,000、Indirect Cost: ¥330,000)
Fiscal Year 2006: ¥1,200,000 (Direct Cost: ¥1,200,000)
Fiscal Year 2005: ¥1,100,000 (Direct Cost: ¥1,100,000)
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| Research Abstract |
Fibroblast growth factor (FGF)-2, a potent angiogenic factor that is involved in tumor invasion and angiogenesis, is known to be released extracellularly by a non-classical secretory pathway. Recently it has become clear that Epstein-Barrvirus, specifically its oncoprotein LMP1, can induce expression of angiogenic factors. Among these factors is FGF-2. LMP1 not only promotes expression of FGF-2, but also the release extracellularly of its 18-kDa isoform. We analyzed the mechanism of FGF-2 release induced by LMP1. Confocal immunofluorescence microscopy revealed colocalization of FGF-2 with LMP1 in small dots also stained positively for CD63 and cathepsin.D, markers of late endosomes or multivesicular bodies. Biochemical analysis and immunoelectron microscopy of purified exosomal fractions from cotransfected cells demonstrated increased release of exosomes and the concentration of LMP I and FGF-2 in these structures. Moreover, cotransfection appeared to induce partial redistribution of the Na/K-ATPase, which participates in FGF-2 release, from the plasma membrane to the intracellular LMPI/FGF-2 positive dots. Treatment with ouabain, which inhibits Na/K-ATPage activity, partially suppressed FGF-2 secretion via exosomes in a dose-dependent manner. The results suggest that exosomes may represent a previously unrecognized mechanism for FGF-2 release mediated by LMP1, and that this pathway, at least in part, involves the activity of Na/K-ATPase.
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