Abstract
COVID-19 is a globally infectious viral epidemic of great public health concern caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Angiotensin-converting enzyme 2 (ACE2) plays its role as the receptor for SARS-CoV-2 through binding with S protein and the binding results in ACE2 expression decrease. The change of ACE2 is supposed to elicit a series of cellular and molecular events. Other than as the receptor, ACE2's roles on infection by regulating other molecules need to be further studied during SARS-CoV-2 infection. In the present study, we established the ACE2 knockdown model using Vero E6 cells to study how ACE2 influenced the downstream signaling molecules. Analysis of transcriptome sequencing discovered that ACE2 alteration per se caused the alteration of immune factors, including some related to the viral infection-related signaling pathways. We found that ACE2 silencing induced the reduced interferon-induced transmembrane protein 3 (IFITM3) expression. Overexpression of IFITM3 promoted the SARS-CoV-2 pseudovirus infection of Vero E6 cells lacking the ACE2. It indicates that ACE2 can affect IFITM3 expression and function to affect the SARS-CoV-2 infection. Our results reveal possible mechanisms influencing SARS-CoV-2 infectivity and contribute to explaining the rapid spread and pathogenesis especially in the case of ACE2 low expression.