Salmonella induces the formation of filamentous structures containing lysosomal membrane glycoproteins in epithelial cells

Abstract

Salmonella species invade and replicate within epithelial cells in membrane-bound vacuoles. In this report we show that upon infection of HeLa epithelial cells, Salmonella typhimurium residues in vacuoles that contain lysosomal membrane glycoproteins (lgps). Four to six hours after invasion, intracellular bacteria induce the formation of stable filamentous structures containing lgps that are connected to the bacteria-containing vacuoles. Formation of these lgp-rich structures requires viable intracellular bacteria and is blocked by inhibitors of vacuolar acidification. These structures are not present in uninfected cells or in cells infected with another invasive bacteria, Yersinia enterocolitica. Tracers added to the extracellular medium are not delivered to the Salmonella-induced filaments, suggesting that these structures are different from previously described tubular lysosomes. Initiation of intracellular bacterial replication correlates with formation of these lgp-containing filaments. Certain avirulent Salmonella mutants that are defective for intracellular replication fail to induce formation of these structures. These observations suggest that Salmonella-induced filaments containing lgps are linked to intracellular bacterial replication.