Compared to other tissues, SARS-CoV-2 receptor ACE2 detected in the lungs and respiratory tract is rare
As we adjust to a world altered by the coronavirus pandemic, researchers continue to refine our understanding of the disease. SARS-CoV-2 virus particles gain entry into cells by latching onto a surface protein, angiotensin-converting enzyme 2 (ACE2), whose usual function is to break down angiotensin II, a large protein involved in many processes, including inflammation. A recent study confirmed ACE2 is present in a wide range of tissues, from the eye to the small intestine (pictured, with ACE2 in brown), but found it surprisingly rare in the lungs and respiratory tract. This apparent paradox suggests changes in ACE2 expression may underpin infection: initial virus entry, perhaps in the upper airways, could trigger upregulation of ACE2 in the lungs, which are then severely affected. Smoking might also increase ACE2 expression, so further investigating the early stages of SARS-CoV-2 infection could help identify high-risk patients, and generally inform better prevention and treatment.
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