Dual roles of CXCR4 (C-X-C motif chemokine receptor 4) in promoting entry of ebolavirus and targeting excessive glycoprotein for reticulophagic degradation to facilitate viral fitness.

Ebola virus disease (EVD) caused by Zaire Ebolavirus (EBOV) infection is a major threat to public health in Africa and even worldwide, due to its extremely high mortality rate. However, there are still no effective antiviral therapies that can completely cure EVD. A comprehensive understanding of virus-host interactions would be beneficial for developing new antiviral agents. Here, we showed that CXCR4-induced macroautophagy/autophagy and was internalized to endosomes by interacting with glycoprotein (GP) on viral particles during EBOV infection; this promoted the EBOV attachment and entry, which was reduced by CXCR4 antagonist and neutralizing antibody. We also found that CXCR4 increased EBOV replication by downregulating cytotoxic GP to promote viral fitness instead of influencing the assembly of viral factory. Mechanistically, excessive EBOV GP could hijack CXCR4 sorting and transporting pathways by their interactions with HGS, one of the key components of the ESCRT machinery; subsequently GP could be carried back to the endoplasmic reticulum by CXCR4, where the E3 ubiquitin ligase RNF185 was recruited to polyubiquitinate GP in a K27- and K63-linked manner. Finally, polyubiquitinated GP was degraded in lysosomes via reticulophagy by interacting with RETREG1 (reticulophagy regulator 1), in an ATG3- and ATG5-dependent manner. Our findings revealed dual roles of CXCR4 in regulation of EBOV life cycle, either acting as an entry factor by interacting with GP on viral particles to facilitate viral entry or targeting excessive GP for reticulophagic degradation, providing new evidence that EBOV hijacked the host vesicular transportation system through efficient virus-host interactions to facilitate viral fitness.Abbreviations: Baf A1: bafilomycin A(1); BDBV: Bundibugyo Ebolavirus; CHX: cycloheximide; CXCR4: C-X-C motif chemokine receptor 4; CLEC4M/DC-SIGNR: C type lectin domain family 4 member M; EBOV: Zaire Ebolavirus; EEA1: early endosome antigen 1; ER: endoplasmic reticulum; ERAD: ER-associated degradation; ESCRT: endosomal sorting complex required for transport; EVD: Ebolavirus disease; HAVCR1/TIM-1: hepatitis A virus cellular receptor 1; GP: glycoprotein; HGS: hepatocyte growth factor-regulated tyrosine kinase substrate; HIV: human immunodeficiency virus; IFL: internal fusion loop; ITCH/AIP4: itchy E3 ubiquitin protein ligase; LAMP: lysosomal associated membrane protein; LC-MS/MS: liquid chromatography mass spectrometry; PDIs: protein disulfide isomerases; RBD: receptor binding domain; RESTV: Reston Ebolavirus; RETREG1: reticulophagy regulator 1; RNF185: ring finger protein 185; SQSTM1/p62: sequestosome 1; SUDV: Sudan Ebolavirus; TAFV: Taï Forest Ebolavirus; TRIM21: tripartite motif containing 21; trVLPs: transcription- and replication-competent virus-like particles; Ub: ubiquitin.