Recombinant SARS-CoV-2 envelope protein traffics to the trans-Golgi network following amphipol-mediated delivery into human cells

Hutchison, James M.; Capone, Ricardo; Luu, Dustin D.; Shah, Karan H.; Hadziselimovic, Arina; Van Horn, Wade D.; Sanders, Charles R.

The SARS-CoV-2 envelope protein (S2-E) is a conserved membrane protein that is important for coronavirus assembly and budding. Here, we describe the recombinant expression and purification of S2-E in amphipol-class amphipathic polymer solutions, which solubilize and stabilize membrane proteins, but do not disrupt membranes. We found that amphipol delivery of S2-E to pre-formed planar bilayers results in spontaneous membrane integration and formation of viroporin cation channels. Amphipol delivery of the S2-E protein to human cells results in plasma membrane integration, followed by retrograde trafficking to the trans-Golgi network (TGN) and accumulation in swollen perinuclear LAMP1-positive vesicles, likely lysosomes. Coronavirus envelope proteins have previously been proposed to manipulate the luminal pH of the TGN, which serves as an accumulation station for progeny coronavirus particles prior to cellular egress via lysosomes. Delivery of S2-E to cells will enable chemical biological approaches for future studies of SARS-CoV-2 pathogenesis and possibly even development of “Trojan Horse” anti-viral therapies. Finally, this work also establishes a paradigm for amphipol-mediated delivery of membrane proteins to cells.