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

We have further shown that in SARS-CoV–infected Vero E6 epithelial cells, PALS1 protein is enriched at the ERGIC/Golgi region, where E proteins accumulate (Figure 3). We argue that in these cells, PALS1 trafficking is altered through mis-targeting to/or retention at the ERGIC/Golgi site. Conversely, the tight junction protein ZO-1 was maintained at cell–cell contact domains in SARS-CoV–infected cells, indicating the specificity of PALS1 mislocation. Additionally, in Vero E6 cells transiently expressing EYFP-PALS1 and E, we observed that these proteins also colocalized in the perinuclear region (Supplemental Figure S1). Interestingly, we observed that morphogenesis of MDCKII cysts is significantly disrupted when E is expressed (Figure 5 and Supplemental Figure S3). However, polarity was not affected at the time of analysis, as indicated by the apical distribution of GP135, ZO-1, PALS1, and CRB3 (Figure 5 and Supplemental Figure S3). Strikingly, similar findings were observed when E (ΔPBM) was expressed, but not a control HcRed protein (data not shown). Correct tissue morphogenesis is a very sensitive marker, which depends on intact polarity (Schlüter and Margolis, 2009) but also on cdc42-dependent spindle morphology (Jaffe et al., 2008; Qin et al., 2010) independently from tight junction formation. It is possible that E interacts with a cellular pathway that regulates cyst morphogenesis, independently of its PBM. It is reasonable to postulate that E contains more than one region that interacts with host cell factors. It is indeed well known that pathogens usually develop several strategies to ensure their optimal adaptation/interaction/virulence within the host cell environment.