ARF4 and infection: Since ARNO has been shown to activate Arf3 and Arf6 in vitro (Frank et al., 1998; Meacci et al., 1997), we examined whether any additional Arf GTPases promote invasion by depleting Arf3, Arf4, Arf5, and Arf6 individually by siRNA transfection of HeLa cells 72 hr before infection with WT Salmonella (Figure S2B).