Specific Rab GTPase-activating proteins define the Shiga toxin and epidermal growth factor uptake pathways

R ab family guanosine triphosphatases ( GTPases) together with their regulators define specific pathways of membrane traffic within eukaryotic cells. In this study, we have investigated which Rab GTPase-activating proteins ( GAPs) can interfere with the trafficking of Shiga toxin from the cell surface to the Golgi apparatus and studied transport of the epidermal growth factor ( EGF) from the cell surface to endosomes. This screen identifies 6 ( EVI5, RN-tre/USP6NL, TBC1D10A-C, and TBC1D17) of 39 predicted human Rab GAPs as specific regulators of Shiga toxin but not EGF uptake. We show that Rab43 is the target of RN- tre and is required for Shiga toxin uptake. In contrast, RabGAP- 5, a Rab5 GAP, was unique among the GAPs tested and reduced the uptake of EGF but not Shiga toxin. These results suggest that Shiga toxin trafficking to the Golgi is a multistep process controlled by several Rab GAPs and their target Rabs and that this process is discrete from ligand-induced EGF receptor trafficking.