Characteristics of Angiotensin I-converting enzyme 2, type II transmembrane serine protease 2 and 4 in tree shrew indicate it as a potential animal model for SARS-CoV-2 infection

Abstract

Angiotensin I-converting enzyme 2 (ACE2), type II transmembrane serine protease 2 and 4 (TMPRSS2 and TMPRSS4) are important receptors for SARS-CoV-2 infection. In this study, the full-length tree shrewACE2 gene was cloned and sequenced, and its biological information was analyzed. The expression levels of ACE2, TMPRSS2 and TMPRSS4 in various tissues or organs of the tree shrew were detected. The results showed that the full-length ACE2 gene in tree shrews was 2,786 bp, and its CDS was 2,418 bp, encoding 805 amino acids. Phylogenetic analysis based on the CDS of ACE2 revealed that tree shrews were more similar to rabbits (85.93%) and humans (85.47%) but far from mice (82.81%) and rats (82.58%). In silico analysis according to the binding site of SARS-CoV-2 with the ACE2 receptor of different species predicted that tree shrews had potential SARS-CoV-2 infection possibility, which was similar to that of rabbits, cats and dogs but significantly higher than that of mice and rats. In addition, various tissues or organs of tree shrews expressed ACE2, TMPRSS2 and TMPRSS4. Among them, the kidney most highly expressed ACE2, followed by the lung and liver. The esophagus, lung, liver, intestine and kidney had relatively high expression levels of TMPRSS2 and TMPRSS4. In general, we reported for the first time the expression of ACE2, TMPRSS2 and TMPRSS4 in various tissues or organs in tree shrews. Our results revealed that tree shrews could be used as a potential animal model to study the mechanism underlying SARS-CoV-2 infection.

Keywords: ACE2; TMPRSS2; TMPRSS4; Tree shrew; tissue expression.

Graphical abstract

Figure 1.

Comparison of the ACE2 amino-acid sequences of tree shrew with other species

Figure 2.

Phylogenetic tree of ACE2 protein sequence in different species

Figure 3.

Tertiary structure prediction of ACE2 protein for tree shrews and human

Figure 4.

Differences of the key regions of ACE2 combined with SARS-CoV between tree shrew and human

Figure 5.

Differences of the key regions of ACE2 combined with SARS-CoV2 between tree shrew and human

Figure 6.

Expression of ACE2 gene in different tissues of tree shrew

Figure 7.

Expression of TMPRSS2 and TMPRSS4 gene in different tissues of tree shrew

Figure 8.

Western Blot expression levels of the Tree shrew ACE2, TMPRSS2 and TMPRSS4 proteins in different tissues. (a) WB result of ACE2 in different tissues of tree shrew; (b) WB result of TMPRSS2 in different tissues of tree shrew; (c) WB result of TMPRSS4 in different tissues of tree shrew. Each experiment had three repetitions