The ACE2 Receptor for Coronavirus Entry Is Localized at Apical Cell-Cell Junctions of Epithelial Cells

• Published in: Cells (Basel, Switzerland) Vol. 11; no. 4; p. 627
• Main Authors: Rouaud, Florian, Méan, Isabelle, Citi, Sandra
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI AG 11.02.2022; MDPI
• Subjects: ACE2; ADAM17 Protein - metabolism; Adherens Junctions - metabolism; Angiotensin-Converting Enzyme 2 - genetics; Angiotensin-Converting Enzyme 2 - metabolism; Antibodies; Cadherins - metabolism; Cancer; Carrier Proteins - metabolism; CD9 antigen; Cell differentiation; Cell junctions; Cell Line; Cell Membrane Permeability; Cell—Cell junctions; coronavirus; Coronavirus - metabolism; Coronaviruses; Cytokines; Epithelial cells; Epithelial Cells - metabolism; Epithelial Cells - virology; epithelium; Gene expression; Gene Expression - genetics; Immunoblotting; Immunofluorescence; Immunoprecipitation; Intercellular Junctions - metabolism; Intercellular Junctions - virology; Internalization; Localization; Membrane proteins; Microscopy; Middle East respiratory syndrome; mRNA; Proteins; Respiratory diseases; Severe acute respiratory syndrome coronavirus 2; Tetraspanin 29 - metabolism; Tight Junction Proteins - metabolism; Tight junctions; Tight Junctions - metabolism; Transcriptome - genetics; Viruses; United States > US; Switzerland; Germany; ACE2; coronavirus; epithelium; Cell—Cell junctions
• ISSN: 2073-4409; 2073-4409
• DOI: 10.3390/cells11040627

Transmembrane proteins of adherens and tight junctions are known targets for viruses and bacterial toxins. The coronavirus receptor ACE2 has been localized at the apical surface of epithelial cells, but it is not clear whether ACE2 is localized at apical Cell-Cell junctions and whether it associates with junctional proteins. Here we explored the expression and localization of ACE2 and its association with transmembrane and tight junction proteins in epithelial tissues and cultured cells by data mining, immunoblotting, immunofluorescence microscopy, and co-immunoprecipitation experiments. ACE2 mRNA is abundant in epithelial tissues, where its expression correlates with the expression of the tight junction proteins cingulin and occludin. In cultured epithelial cells ACE2 mRNA is upregulated upon differentiation and ACE2 protein is widely expressed and co-immunoprecipitates with the transmembrane proteins ADAM17 and CD9. We show by immunofluorescence microscopy that ACE2 colocalizes with ADAM17 and CD9 and the tight junction protein cingulin at apical junctions of intestinal (Caco-2), mammary (Eph4) and kidney (mCCD) epithelial cells. These observations identify ACE2, ADAM17 and CD9 as new epithelial junctional transmembrane proteins and suggest that the cytokine-enhanced endocytic internalization of junction-associated protein complexes comprising ACE2 may promote coronavirus entry.