An Evolutionary Insertion in the Mxra8 Receptor-Binding Site Confers Resistance to Alphavirus Infection and Pathogenesis

Abstract

Highlights d An insertion in Bovinae Mxra8 sterically blocks alphavirus binding and infection d The sequence insertion evolved in the Miocene epoch at least 5 million years ago d Loss of the insertion in Mxra8 in several Bovinae restores alphavirus infection d Introduction of the insertion into Mxra8 of mice prevents alphavirus pathogenesis

A molecular understanding of alphavirus entry

“…Natural resistance-associated macrophage protein (NRAMP) proteins are divalent metal ion transporters that have been proposed as receptors for SINV in both insect and mammalian cells [ 85 ]. Gene silencing of dNRAMP (the Drosophila gene) resulted in decreased infection for both cell culture-adapted and wild-type SINV strains in fruit flies [ 86 ]. As transfection of SINV RNA directly into Drosophila cells bypassed a requirement for dNRAMP, this protein was hypothesized to function during alphavirus entry.…”

“…Evolutionary and functional analyses established that most members of the Bovinae subfamily have a 15-amino-acid insertion in the Mxra8 ectodomain that blocks CHIKV binding. Introduction of this sequence into murine Mxra8 abolishes binding to virus particles and reduces CHIKV pathogenesis in vivo, whereas removal of the insertion in Bovinae Mxra8 enhances binding and infection [ 86 ]. This insertion likely evolved approximately 5 million years ago in the Miocene epoch [ 86 ], which could suggest that sequence acquisition was driven by positive selection against a primordial alphavirus.…”

“…Introduction of this sequence into murine Mxra8 abolishes binding to virus particles and reduces CHIKV pathogenesis in vivo, whereas removal of the insertion in Bovinae Mxra8 enhances binding and infection [ 86 ]. This insertion likely evolved approximately 5 million years ago in the Miocene epoch [ 86 ], which could suggest that sequence acquisition was driven by positive selection against a primordial alphavirus. As alphaviruses are believed to have evolved much more recently (approximately 10,000 years ago) [ 91 ], this idea remains speculative.…”

The CD147 Protein Complex Is Involved in Entry of Chikungunya Virus and Related Alphaviruses in Human Cells

“…MXRA8 was previously identified as a receptor for alphaviruses including CHIKV ( Zhang et al, 2018 , 2019 ; Basore et al, 2019 ; Song et al, 2019 ; Kim et al, 2020 ). Because both MXRA8 and CD147 isoform 2 carry two immunoglobulin-like domains and one transmembrane region, we wondered if any homology in amino acid sequence or protein structure could be found between these two proteins.…”

“…Different experimental approaches have been applied previously to identify entry factors like MXRA8, PHB and ATP5B ( Wintachai et al, 2012 ; Fongsaran et al, 2014 ; Zhang et al, 2018 ), responsible for CHIKV binding to and entry in human and mosquito cells. So far only for MXRA8 a direct interaction with the CHIKV envelope proteins was shown, so MXRA8 can be considered as the first bonafide CHIKV receptor ( Zhang et al, 2018 , 2019 ; Basore et al, 2019 ; Song et al, 2019 ; Kim et al, 2020 ). However because the previously identified entry factors and receptor (e.g., MXRA8) are not expressed on all susceptible and permissive cell types, the process of CHIKV entry and the receptor complexes engaged are still incompletely understood.…”