Receptors

Specific Receptors

In humans, the viral protein binds to the receptor called angiotensin-converting enzyme 2 (ACE2).
An enzyme called TMPRSS2, which is another human protein, helps activate the viral “spike” protein to allow it to enter the host cell.
To infect the host cell, it required a combination of the certain receptor protein to bind to and the activation protein

ACE2 (angiotensin-converting enzyme 2) functions as the receptor for SARS-CoV-2 and is a stabilizer for neutral amino acid transporters. There is evidence that ACE2 has a role in protecting against cardiovascular disease, and when ACE2 is lost, it can lead to “functional deterioration of the heart, and progression of cardiac, renal, and vascular pathologies.” It also controls intestinal inflammation and diarrhea, and acts on other vasoactive peptides that regulate blood pressure & flexibility of the myocardium
TMPRSS2 is known to activate influenza virus, but this enzyme has also been found in human seminal prostasomes, which indicate that it may help regulate sperm function (although that is not completely proven, just a theory). It is also the primary activation enzyme for SARS-CoV-2.
These receptors are primarily found in the type II pneumocytes of the lungs, the goblet secretory cells in the nasal passages, and the absorptive enterocytes in the intestines