RT Journal Article
SR Electronic
T1 Involvement of ASIP/PAR-3 in the promotion of epithelial tight junction formation
JF Journal of Cell Science
JO J. Cell Sci.
FD The Company of Biologists Ltd
SP 2485
OP 2495
VO 115
IS 12
A1 Hirose, Tomonori
A1 Izumi, Yasushi
A1 Nagashima, Yoji
A1 Tamai-Nagai, Yoko
A1 Kurihara, Hidetake
A1 Sakai, Tatsuo
A1 Suzuki, Yukari
A1 Yamanaka, Tomoyuki
A1 Suzuki, Atsushi
A1 Mizuno, Keiko
A1 Ohno, Shigeo
YR 2002
UL http://jcs.biologists.org/content/115/12/2485.abstract
AB The mammalian protein ASIP/PAR-3 interacts with atypical protein kinase C isotypes (aPKC) and shows overall sequence similarity to the invertebrate proteins C. elegans PAR-3 and Drosophila Bazooka, which are crucial for the establishment of polarity in various cells. The physical interaction between ASIP/PAR-3 and aPKC is also conserved in C. elegans PAR-3 and PKC-3 and in Drosophila Bazooka and DaPKC. In mammals, ASIP/PAR-3 colocalizes with aPKC and concentrates at the tight junctions of epithelial cells, but the biological meaning of ASIP/PAR-3 in tight junctions remains to be clarified. In the present study, we show that ASIP/PAR-3 staining distributes to the subapical domain of epithelial cell-cell junctions, including epithelial cells with less-developed tight junctions, in clear contrast with ZO-1, another tight-junction-associated protein, the staining of which is stronger in cells with well-developed tight junctions. Consistently, immunogold electron microscopy revealed that ASIP/PAR-3 concentrates at the apical edge of tight junctions, whereas ZO-1 distributes alongside tight junctions. To clarify the meaning of this characteristic localization of ASIP, we analyzed the effects of overexpressed ASIP/PAR-3 on tight junction formation in cultured epithelial MDCK cells. The induced overexpression of ASIP/PAR-3, but not its deletion mutant lacking the aPKC-binding sequence, promotes cell-cell contact-induced tight junction formation in MDCK cells when evaluated on the basis of transepithelial electrical resistance and occludin insolubilization. The significance of the aPKC-binding sequence in tight junction formation is also supported by the finding that the conserved PKC-phosphorylation site within this sequence, ASIP-Ser827, is phosphorylated at the most apical tip of cell-cell contacts during the initial phase of tight junction formation in MDCK cells. Together, our present data suggest that ASIP/PAR-3 regulates epithelial tight junction formation positively through interaction with aPKC.