Fig 8.

Model for phosphatidylserine-mediated virus entry enhancing receptor (or PVEER) uptake of virus. (A) Virus buds from cell surface after infection, incorporating GP and PtdSer onto the viral envelope. The glycan cloud formed by extensive GP glycosylation events provides both stability of the GP in its prefusion state and potential steric protection against immune responses to GP residues. (B) Uptake of virus by a neighboring cell. PtdSer on the viral envelope interacts with PVEERs, such as the Gas6/Axl complex and TIM family, which mediate virus internalization. (C) Conditions within the endosome promote GP-dependent fusion events. Within the endosome, low-pH events can lead directly to GP conformational changes or, alternatively, protease processing of the GP, thereby reducing energy barriers required for fusion. Additional factors, such as binding of NPC1 by filovirus GPs, may also be necessary.