SARS-CoV-2 enters host respiratory epithelial cells after its spike protein binds ACE2. Which host factor primes the spike protein by proteolytic cleavage to enable membrane fusion?

• A ADAM17
• B Cathepsin L exclusively, with no other protease involved
• C Neuraminidase
• D Furin and TMPRSS2 ✓

Explanation

The SARS-CoV-2 spike is activated by cleavage at the S1/S2 boundary and the S2 site; host furin accomplishes this during biosynthesis and transmembrane serine protease TMPRSS2 further primes the spike at the cell surface, permitting fusion with the plasma membrane. Neuraminidase is an influenza viral enzyme, not a host factor. ADAM17 sheds ACE2 but does not activate the spike, and cathepsins act in endosomes as an alternative route rather than exclusively.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.