Mouse anti-beta subunit of coatomer, anti-zeta subunit of coatomer, mouse anti-myc (9E10), sheep anti-TGN46, rabbit anti-Giantin antibodies have been described previously 21 (link). Rabbit anti-myc antibody (#2278S), rabbit anti-cdc42 antibody (#2462S), and mouse anti-β-actin antibody (#3700P) were obtained (Cell Signaling). All secondary antibodies were also obtained (Jackson ImmunoResearch Laboratory).