Occludin expression and tight junction strand formation during replicative DNA synthesis in primary cultures of rat hepatocytes

Autor: Takashi Kojima, Michio Mori, Masao Yamamoto, Yohichi Mochizuki, Yasuo Kokai, Norimasa Sawada
Rok vydání: 1998
Předmět:
Zdroj: Medical Electron Microscopy. 31:169-176
ISSN: 1860-1499
0918-4287
Popis: Occludin, an integral membrane protein, is a candidate for forming the functional intercellular seal of the tight junction. In the present study, we examined the changes of occludin expression and tight junction strand in the cultured hepatocytes. In L-15 medium containing EGF with 2% DMSO and 10−7M glucagon, the great majority of the cells were quiescent. Under this condition, occludin immunoreactivity was observed at cell-to-cell contacts. Tight junction strands formed well-developed networks in freeze-fracture replicas. When the cells entered S phase of the cell cycle, occludin immunoreactivity and the number of tight junction strands decreased. By contrast, when DNA synthesis was then inhibited by readdition of DMSO and glucagon, occludin immunoreactivity and the number of tight junction strands were restored. Regardless of DNA synthesis, however, there was no significant decrease in the protein and mRNA levels of occludin. These changes of occludin immunoreactivity were correlated to the organization of actin filaments. On the other hand, no change of ZO-1 immunoreactivity was observed. These results suggested that tight junctions of cultured hepatocytes regulated in a cell cycle-dependent fashion and correlated with the organization of circumferential actin bundles.
Databáze: OpenAIRE
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