| Co-Investigator(Kenkyū-buntansha) |
NAKAMURA Keiichiro Kyushu University, Graduate School of Medical Sciences, Associate Prof., 大学院・医学研究院, 助教授 (20172398)
SHIBATA Yosaburo Kyushu University, Graduate School of Medical Sciences, Prof., 大学院・医学研究院, 教授 (90037482)
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| Research Abstract |
Claudin (CL) is an integral membrane protein of tight junction (TJ) and claudin protein family consists of more than 20 isoforms. Morphology and function of TJ vary in epithelia and endothelia in different tissues. It is thought that compositional differences of CLs may affect morphology and function of TJs. Blood brain barrier of embryonic brain is immature but the barrier becomes mature with growth. Thus, we analyzed mRNA expression of CLs by RT-PCR. CL-1, -5, -10, -12, and -15 were expressed in 8-week-old mouse aorta, suggesting that vascular endothelial cells expressed CL-1, -5, -10, -12, and -15. In contrast, CL-1, -5, -10, and -12 were expressed in adult brain but CL-15 was not. Compared with adult brain, much less CL-10 was expressed in embryonic 18-day-old brain. Taken together, brood brain barrier may be different from others because brain endothelial cells expressed CL-10 with growth and did not express CL-15. Next, we introduced claudin-10 or -15 into MDCK cells to examine which type of TJ strand was formed by them. CL-10 formed TJ strand with E-associated particles but CL-15 formed that with P-associated ones. In general, it is thought that E-associated or P-associated particles may be related to leaky or tight TJ, respectively. Our results are not consistent with this hypothesis. However, compositional differences of CLs may be more responsible for morphological and functional of TJs. C-terminus of CL-1 binds to N-terminus of ZO-1, and C-terminus of ZO-1 binds to actin cytoskeketon. To understand the role of this binding between CL-1 and ZO-1, C-terminus mutated claudin-1 which could not bind to ZO-1 was introduced into MDCK cells. Introduced CL-1 formed ectopic TJ strands in laterral plasma membrane. This suggest that the binding between CL-1 and ZO-1 may be important to form TJ strand at the most apical site of lateral plasma membrane.
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