Table 1.

ACE2 and B⁰AT1 Tissue Expression

Protein	Organ or tissue expression	Cell type	Assay	Involvement with COVID-19	Author (year)
ACE2	Esophagus	Epithelial cells	scRNA-seq	Contributes to virus spread and immunopathology in airways and intestinal system	Zou et al. (2020) [11]
	Intestine	Enterocytes and intestinal villi	scRNA-seq	Indicates an intrinsic susceptibility of intestine to SARS-CoV-2 infection and replication	Zou et al. (2020) [11], Hamming et al. (2004) [10]
	Oral cavity	Epithelial cells	RNA-seq	Potential route of SARS-CoV-2 infection	Xu et al. (2020) [19], Zou et al. (2020) [11]
	Stomach	Epithelial cells	scRNA-seq	Potential route of SARS-CoV-2 infection	Zou et al. (2020) [11]
	Intestine	Enterocytes and intestinal villi	Western blot	Modulates the diarrhea that occurs in up to 39% of COVID-19 cases	Jando et al. (2017) [20]
B0AT1	Intestine	Enterocytes and intestinal villi	Western blot	Modulates the diarrhea that occurs in up to 39% of COVID-19 cases	Jando et al. (2017) [20]

ACE2, angiotensin-converting enzyme 2; COVID-19, coronavirus disease; scRNA, single cell RNA; SARS-CoV-2, severe acute respiratory syndrome coronavirus 2.