Table 4. Selected Human Proteins Involved in SARS-CoV-2 Infection.

protein target	acronym	role in SARS-CoV-2 infection	COVID-19 clinical trial?a
Host Cell Proteins Involved in Viral Entrance
angiotensin-converting enzyme 243	ACE2	cell surface receptor for S protein	yes
furin44,45	FURIN	cleaves S protein to expose S2 domain needed for virus-plasma membrane fusion	no
transmembrane serine proteinase 27	TMPRSS2	cleaves S protein to expose S2 domain needed for virus-plasma membrane fusion	yes
CD147/basigin39,40	BSG	alternative cell surface receptor for S protein	yes
cathepsin L7,41	CTSL	cleaves S protein to expose S2 domain needed for virus-endosomal membrane fusion	no
phosphatidylinositol inositol kinase PIKfyve41	PIKFYVE	involved in phosphoinositide metabolism, regulates endosomal dynamics; may be involved in facilitating SARS-CoV-2 entry	no
Host Proteins Involved in Viral RNA/Protein Synthesis Processes
inosine monophosphate dehydrogenase IMPDH25,52	IMPDH2	binds to NSP14; involved in guanine nucleotide metabolism	no
translation initiation factor eIF-4A5,53	EIF4A1	binds to NSP2; involved in viral protein translation	no
translation initiation factor eIF-1A5	EIF1AX	involved in viral protein translation	yes
translocon protein Sec615,54	SEC61A, SEC61B	involved in viral protein insertion into endoplasmic reticulum	no
splicing factor SF3B155	SF3B1	altered expression in SARS-CoV-2 infection	no
Host Proteins Involved in Inflammatory Response
protein kinase JAK1 and JAK246,47	JAK1/JAK2	involved in cytokine signaling	yes
interleukin 648	IL6	involved in cytokine storm	yes
complement C349	C3	early complement factor that mediates inflammation and lung injury in COVID-19	yes
chemokine receptor CCR115	CCR1	involved in cytokine signaling	no
chemokine CXCL1050	CXCL10	involved in cytokine signaling
neutrophil extracellular traps42,51	N.A.	increased levels in COVID-19 patients, excessive amounts trigger inflammation and blood clotting	yes

^aClinical trial data was obtained as of 5/21/2020 from www.ClinicalTrials.gov. “Yes” in the table includes trials with the following status: “Not Yet Recruiting”, “Recruiting”, “Enrolling”, “Active”, or “Completed”.