Bone Marrow Stromal Cell Antigen 2 (BST2)

Tetherin is a type 2 integral membrane protein, with the N-terminus in the cytoplasm, one membrane spanning domain, and a C-terminus modified by the addition of a glycosyl-phosphatidylinositol (gpi) anchor. When the virion buds from the surface of the cell, one of the tetherin membrane domains is in the new viral membrane, the other remains in the plasma membrane, tethering the virion to the cell. It is antagonized by the viral protein Vpu which is thought to work by targetting tetherin for degredation via the beta-TrCP2 dependent pathway.

Tetherin exists as a dimer on the surface of cells, and prevention of dimerisation by mutating the cystine residues, prevents tetherin from inhibiting virus release, although it is still detectable in the cell.