| Budget Amount *help |
¥3,600,000 (Direct Cost: ¥3,600,000)
Fiscal Year 2005: ¥1,400,000 (Direct Cost: ¥1,400,000)
Fiscal Year 2004: ¥2,200,000 (Direct Cost: ¥2,200,000)
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| Research Abstract |
Tight junctions of epithelial and endothelial cell sheets control both paracellular permeability and apicobasal polarity, and dysfunction of tight junctions is considered to cause and/or modify various pathological conditions such as inflammatory bowel disease, vasogenic edema and blood-borne metastasis. Although molecular components of tight junctions and their interactions have been rapidly disclosed, it remains obscure which signals cue tight-junction formation and epithelial polarization.
Mouse F9 embryonal carcinoma cells provide an attractive system for facilitating molecular mechanisms for epithelial morphogenesis, since they have the capability of differentiating into polarized epithelial cells. We previously generated cell line F9 L32T2, which allows sequential inactivation of loxP-flanked genes and tight control of gene expression. Using this line, we showed that two members of the nuclear receptor superfamily, retinoid receptors and hepatocyte nuclear factor (HNF)-4α, triggered not only expression of tight-junction molecules, but also modulation of subcellular distribution of junction and cell polarity proteins, resulting in junction formation and epithelial polarization. We also demonstrated that HNF-4α, like retinoid receptors, up-regulated gene expression of p21^<CIP1/WAF1> and inhibited cell proliferation.
We also developed primary culture of porcine blood-brain barrier endothelial cells, and established an inducible gene expression system in the leaky lung endothelial cell line. Using these cell culture systems, we revealed that that Thr^<203> of claudin-1 and Thr^<207> of claudin-5 were involved in modulation of the endothelial barrier function by MAP kinase and cAMP, respectively. Furthermore, we found that functional gap junctions could be required to maintain the endothelial barrier function.
These findings would contribute to elucidate regulation of epithelial and endothelial barrier in physiological and pathological conditions.
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