For primary antibodies, rabbit polyclonal antiserum against Erv41, Erv46, and Och1 (Otte et al., 2001 ); Yet3 (Wilson and Barlowe, 2010 (link)); Fpr2; and Gls1 (Shibuya et al., 2015 (link)) has been described previously. Mouse monoclonal antibody HA.11 against the hemagglutinin epitope was purchased from BioLegend (San Diego, CA) and used for co-IPs and detection of HA-tagged proteins by immunoblot. Primary antibodies were used at 1:1000 dilutions except for anti-Fpr2 and anti-HA, which were used at 1:500 and 1:2000 dilutions, respectively. For secondary antibodies, two different systems were used. First, horseradish peroxidase–linked anti-rabbit and anti-mouse antibodies (GE Healthcare) were used at 1:10,000 dilutions. Blots were developed with SuperSignal West Pico Chemiluminescent substrate (Thermo Fisher Scientific), imaged using a G:Box Chemi XR5 (Syngene), and quantified with GeneTools image analysis software (Syngene). Alternatively, IRDye cross-linked anti-rabbit and anti-mouse antibodies (LI-COR Biosciences) were used at 1:10,000 dilutions. Blots were imaged with an Odyssey CLx imager (LI-COR Biosciences) and quantified with Image Studio Lite (LI-COR Biosciences).