Host-primed Ebola virus GP exposes a hydrophobic NPC1 receptor-binding pocket, revealing a target for broadly neutralizing antibodies

Bornholdt ZA, Ndungo E, Fusco L, Flyak AI, Crowe JE Jr, Chandran K and Saphire EO. 2016. mBio 7:02154-15.

[doi: 10.1128/mBio.02154-15]  [Download PDF]


The filovirus surface glycoprotein (GP) mediates viral entry into host cells. Following viral
internalization into endosomes, GP is cleaved by host cysteine proteases to expose a receptor binding site (RBS) otherwise hidden from immune surveillance. Here we present the crystal
structure of proteolytically cleaved Ebola virus GP to a resolution of 3.3 Å. We use this structure
in conjunction with functional analysis of a large panel of pseudotyped viruses bearing mutant
GP proteins to map the Ebola virus GP endosomal RBS at molecular resolution. Our studies
indicate that binding of GP to its endosomal receptor Niemann-Pick C1 occurs in two distinct
stages: initial electrostatic interactions, followed by specific interactions with a hydrophobic
trough exposed on the endosomally cleaved GP1 subunit. Finally, we demonstrate that
monoclonal antibodies targeting the filovirus RBS neutralize all known filovirus GPs, making
this conserved pocket a promising target for the development of pan-filovirus therapeutics.


Ebola virus uses its glycoprotein GP to enter new host cells. During entry, GP must be cleaved
by human enzymes in order for receptor binding to occur. Here we provide the crystal structure
of the cleaved form of Ebola virus GP We demonstrate that cleavage exposes a site at the top of
GP and demonstrate that this site binds the critical domain C of the receptor, termed Niemann
Pick C1, NPC1. We perform mutagenesis to find parts of the site essential for binding NPC1 and
map distinct roles for an upper, charged crest and lower, hydrophobic rough in cleaved GP. We
find that this three-dimensional site is conserved across the filovirus family and that antibody
directed against this site is able to bind cleaved GP form every filovirus tested and neutralize
viruses bearing those GPs.