The vacuolating
cytotoxin VacA is a major
virulence factor of Helicobacter pylori, a bacterium responsible for
gastroduodenal ulcers and
cancer. VacA associates with
lipid rafts, is endocytosed, and reaches the late endocytic compartment where it induces vacuolation. We have investigated the endocytic and intracellular trafficking pathways used by VacA, in HeLa and gastric AGS cells. We report here that VacA was first bound to plasma-membrane domains localized above
F-actin structures that were controlled by the Rac1
GTPase. VacA was subsequently pinocytosed by a
clathrin-independent mechanism into cell peripheral early endocytic compartments lacking
caveolin 1, the Rab5 effector early endosomes antigen-1 (EEA1) and
transferrin. These compartments took up fluid-phase (as evidenced by the accumulation of fluorescent
dextran) and
glycosylphosphatidylinositol-anchored
proteins (GPI-APs). VacA pinocytosis was controlled by Cdc42 and did not require cellular
tyrosine kinases,
dynamin 2,
ADP-ribosylating factor 6, or RhoA
GTPase activities. VacA was subsequently routed to EEA1-sorting endosomes and then sorted to late endosomes. During all these different endocytic steps, VacA was continuously associated with
detergent resistant membrane domains. From these results we propose that VacA might be a valuable probe to study raft-associated molecules, pinocytosed by a
clathrin-independent mechanism, and routed to the degradative compartment.