Helicobacter pylori induces formation of stress fibers and membrane ruffles in AGS cells by rac activation

Helicobacter pylori induces signaling cascades leading to changes in cytosk eleton and an inflammatory response. Information on the morphological chang es and cytoskeletal rearrangements induced by attachment of the bacterium i s contradictory and signal transduction pathways are not well known. Since rho family of small GTPases is known to mediate cytoskeletal response to va rious extracellular stimuli, and is also involved in several other importan t signal transduction pathways, we have investigated the role of rac and cd c42 in H. pylori-induced cytoskeletal changes in cultured carcinoma AGS cel ls. AGS cells grown with serum expressed actin filaments in the form of sho rt stress fibers and thin network at the edges, which were depolymerized by removal of serum. In serum-starved cells both type I and type II strains o f H. pylori induced formation of actin filaments and lamellipodia-like stru ctures. Microinjection of active rac induced similar changes, but injection of inactive rac prevented the effects of H. pylori, while active or inacti ve cdc42 did not have any significant effect. Cytoskeletal effects of H. py lori were inhibited by actinomycin D, but not completely by cycloheximide. These results indicate that rac activation is involved in signal transducti on cascade leading to cytoskeletal reorganization induced by H. pylori and that gene activation and synthesis of new proteins is necessary in this pro cess. (C) 2000 Academic Press.