HeLa (H1, #CRL-1958), HT-29 (#HTB-38), CHO-C6, and 293T (#CRL-3216) cells were originally obtained from ATCC. They tested negative for mycoplasma contamination, but have not been authenticated. Huh7 and Huh7 LDLR−/− cells were kindly provided by Y. Matsuura36 (link). The following mouse monoclonal antibodies were purchased from the indicated vendors: RAC1 (23A8, Abcam), non-glucosylated RAC1 (Clone 102, BD Biosciences), β-actin (AC-15, Sigma), and HS (F58–10E4, mouse IgM, Amsbio). Rabbit monoclonal IgG against LDLR (EP1553Y) was purchased from Abcam. Chicken polyclonal IgY (#753A) against TcdA was purchased from List Biological Labs. Statistical analysis was performed using OriginPro 8 (V8.0724, OriginLab Corp.) software.