The SARS Coronavirus E Protein Interacts with PALS1 and Alters Tight Junction Formation and Epithelial Morphogenesis

Teoh, Kim-Tat; Siu, Yu-Lam; Chan, Wing-Lim; Schlüter, Marc A.; Liu, Chia-Jen; Peiris, J. S. Malik; Bruzzone, Roberto; Margolis, Benjamin; Nal, Béatrice

At 2 h post-calcium switch, in HA-E (wt) monolayers, PALS1 appeared in confocal sections as a discontinuous line around cells, indicating that TJ might not be mature. Conversely, in HA-E (ΔPBM) cells PALS1 was uniformly present at cell-cell contacts. This result explains the significantly different TER values between the two cell lines at this time point (100 vs. 450 Ω/cm2, Figure 8A). At 8 and 24 h, although TER values of both cell lines were similar (400–500 and 100–120 Ω/cm2, respectively), differences could be observed. At 8 h, gaps between cells were occasionally observed close to round cells with high cytoplasmic PALS1 expression and so more frequently for the MDCKII eGFP-PALS1 HA-E (wt) cell line (Figure 8B, panel c). At 24 h, cells were in contact with each others. At this time, more round cells with higher expression of E (wt) and cytoplasmic localization of PALS1 were seen (Figure 8B, panel e, red arrow). PALS1 was mainly at apical cell–cell contacts in MDCKII eGFP-PALS1 HA-E (ΔPBM) cells, although cells had an irregular shape. This irregular shape was also observed in both cell lines at 120 h post-calcium switch.