Cell vesicle trafficking and bacterial protein toxins

An intense trafficking of proteins, peptides, lipids and small molecules takes place in and out of the cell as well as inside the cell between the various cell organelles and compartments. Several protein toxins have been devised by bacteria with the scope of interfering with vesicular trafficking inside cells. Clostridial neurotoxins affect mainly the highly regulated fusion of small vesicles, containing neurotransmitters and hormones, with the plasma membrane. They cleave the three SNARE proteins: VAMP, SNAP-25 and syntaxin, and this selective proteolysis results in a blockade of exocytosis. The Helicobacter pylori cytotoxin is implicated in the pathogenesis of gastroduodenal ulcers. It causes a progressive and extensive vacuolation of cells followed by necrosis, consequent to a cytotoxin induced alteration of membrane trafficking at late endocytic stages. Vacuoles originate from extensive membrane fusion between internal and external membranes of late endosomes and lysosomes in a rab7 dependent process. Vacuoles swell because they are acidic and accumulate membrane permeant amines.