Figure 1.

The time sequence of tight junction and adherens junction assembly in Ras-transformed MDCK cells after addition of PD98059 for 1 (e–h), 5 (i–l), 10 (m–p), and 20 (q–t) h. Immunofluorescence staining of E-cadherin, occludin, claudin-1, and ZO-1 showed that E-cadherin was hardly expressed in Ras-transformed cells (a), whereas tight junction proteins (b–d) were present in the cytoplasm. After addition of PD98059 for 1 h, occludin, claudin-1, and ZO-1 started to be recruited to the cell–cell contact area (f–h), whereas E-cadherin was not (e). E-cadherin, occludin, claudin-1, and ZO-1 were all gradually localized to the sites of cell–cell contact (i–p). By 20 h of PD98059 treatment, the immunostaining of E-cadherin (q), occludin (r), claudin-1 (s), and ZO-1 (t) at the intercellular junctions was well developed. Bar, 20 μm.