SARS-CoV-2 uses which host cell receptor for primary attachment, and which viral protein mediates this interaction after priming by a host serine protease?

• A CD4 receptor — S protein after priming by furin
• B ACE2 receptor — N (nucleocapsid) protein after priming by cathepsin B/L
• C DC-SIGN receptor — S protein after priming by trypsin
• D ACE2 receptor — S (spike) protein RBD after priming by TMPRSS2 ✓

Explanation

SARS-CoV-2 spike (S) protein receptor-binding domain (RBD) binds to angiotensin-converting enzyme 2 (ACE2) on host cells. Cell entry requires proteolytic priming of the S protein at the S1/S2 and S2' cleavage sites. TMPRSS2 (transmembrane serine protease 2), expressed on respiratory epithelial cells, is the primary host protease responsible for S protein priming at the cell surface, enabling membrane fusion for direct cell entry. Alternatively, endosomal cathepsins B/L can prime the S protein in the endosomal pathway. The unique furin cleavage site (PRRAR) at S1/S2 in SARS-CoV-2 (absent in SARS-CoV-1) enhances cell-to-cell spread. TMPRSS2 inhibitors (camostat mesylate) were investigated therapeutically.

Reference: Ananthanarayan & Paniker's Textbook of Microbiology, 11th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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