COR1C regulates ARP2/3 complex activity at the endosome bud. (A) Representative images of COS-7 cells cotransfected with COR1A/1B/1C siRNAs to deplete all type I coronins and with mCh-Rab7 (LE, gray), α actin-Halo (green), and ARP3-mNG (magenta). Buds with extended actin (at arrow) were tracked before and after addition of an ARP2/3 complex inhibitor (150 μM CK-666) in merged magnified insets on right (5 × 5 μm). n = 10 cells. (B) Diagram of the ARP3-V5-TurboID biotinylation experiment. HeLa cells were cotransfected with ARP2/3-V5-TurboID and GFP-Rab7, COR1C-GFP, or COR1C-ACT– ΔCC-GFP and treated with biotin, and then biotinylated proteins were bound and eluted from α-biotin beads. (C) Representative V5 and GFP immunoblot from experiment in B shows high levels of biotinylation for full-length COR1C compared with COR1C mutant or Rab7 control. (D) Quantification of immunoblot, as shown in C. Pulldown numbers were calculated by normalizing elute signal with the load signal, performed in triplicate. Statistical analyses were performed with one-way ANOVA, P value from Tukey’s test: ***, P < 0.001. Scale bars for whole cell = 5 μm; insets = 1 μm. Source data are available for this figure: SourceData F4.