Membrane-associated GRP78 helps subgroup J avian leucosis virus enter cells

We previously identified chicken Annexin A2 (chANXA2) as a novel receptor for retrovirus avian leucosis virus subgroup J (ALV-J), using a DF1 cell line expressing the viral envelope (env) protein. To further probe whether other proteins participate in virus infection, we investigated several host proteins from co-immunoprecipitation with the DF1 cell line expressing viral env. Mass spectrometry analysis indicates that the chicken glucose-regulation protein 78 (chGRP78) of the DF1 membrane interacted with the ALV-J env protein. The results revealed that antibodies or siRNA to chGRP78 significantly inhibited ALV-J infection and replication, and over-expression of chGRP78 enabled the entry of ALV-J into non-susceptible cells. Taken together, these results are the first to report that chGRP78 functions to help ALV-J enter cells.