A comparative analysis of the expression of key proteins involved in the entry of coronavirus into different types of cell cultures

The expression of specific receptors and proteases in each cell type determines the relative preference for different modes of SARS-CoV-2 entry. This includes entry through TMPRSS2-mediated fusion of the viral and host cell membranes, as well as entry through endocytosis, which involves the activity of cathepsin L. Cathepsin L is responsible for cleaving the viral S protein, and its expression level can affect the efficiency of viral entry. The expression level of mRNA for three key proteins involved in SARS CoV-2 entry into host cells (ACE2 receptor, TMPRSS2 serine protease, and cathepsin L) was assessed in human cell lines from various tissues (n=5), and in cell lines derived from the kidneys of different animal species (n=7). The highest level of ACE2 gene expression was observed in the human colon adenocarcinoma cell line Caco-2, and in the Vero and VeroE6 cells (derived from African green monkey kidneys), the expression of this gene was more than four times higher than in the other studied animal cell lines. Among human cell lines, the highest level of TMPRSS2 gene expression was observed in HEK293T (embryonic kidney) and Caco-2 cells, and among animal cell cultures, it was seen in MDBK (domestic bovine kidney) cells. The maximum level of CTSL mRNA expression was found in A549 (human lung cancer) cells. These findings are important for selecting a model system to study the pathways used by the virus to enter target cells and to investigate various aspects of SARS-CoV-2’s interaction with cells.

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