An). The PTX-resistant YFP-G i2 C352I construct was created by site-directed mutagenesis using standard methods. Red fluorescent protein (RFP)-Lifeact and green fluorescent protein (GFP)-Lifeact were kindly provided by Michael Sixt. For CXCR4-YFP, YFP was fused to the C-terminus of human CXCR. Elmo1-GFP (kindly provided by Kodi S. Ravichandran), Ags3-RFP (22), AGS4-GFP and LGN-GFP (kindly provided