title: Elimination of host cell PtdIns(4,5)P(2) by bacterial SigD promotes membrane fission during invasion by Salmonella.
abstract: Salmonella invades mammalian cells by inducing membrane ruffling and macropinocytosis through actin remodelling. Because phosphoinositides are central to actin assembly, we have studied the dynamics of phosphatidylinositol-4,5-bisphosphate (PtdIns(4,5)P(2)) in HeLa cells during invasion by Salmonella typhimurium. Here we show that the outermost parts of the ruffles induced by invasion show a modest enrichment in PtdIns(4,5)P(2), but that PtdIns(4,5)P(2) is virtually absent from the invaginating regions. Rapid disappearance of PtdIns(4,5)P(2) requires the expression of the Salmonella phosphatase SigD (also known as SopB). Deletion of SigD markedly delays fission of the invaginating membranes, indicating that elimination of PtdIns(4,5)P(2) may be required for rapid formation of Salmonella-containing vacuoles. Heterologous expression of SigD is sufficient to promote the disappearance of PtdIns(4,5)P(2), to reduce the rigidity of the membrane skeleton, and to induce plasmalemmal invagination and fission. Hydrolysis of PtdIns(4,5)P(2) may be a common and essential feature of membrane fission during several internalization processes including invasion, phagocytosis and possibly endocytosis.
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism*; D000818:Animals; D019556:COS Cells; D002451:Cell Compartmentation / Q000502:physiology; D002462:Cell Membrane / Q000378:metabolism* / Q000648:ultrastructure; D012321:DNA-Directed RNA Polymerases / Q000172:deficiency* / Q000235:genetics; D004548:Elasticity; D005057:Eukaryotic Cells / Q000166:cytology / Q000378:metabolism* / Q000382:microbiology; D006367:HeLa Cells; D006801:Humans; D007150:Immunohistochemistry; D018613:Microscopy, Confocal; D010587:Phagocytosis / Q000502:physiology; D019269:Phosphatidylinositol 4,5-Diphosphate; D018129:Phosphatidylinositol Phosphates / Q000172:deficiency*; D010873:Pinocytosis / Q000502:physiology; D017346:Protein Serine-Threonine Kinases; D017434:Protein Structure, Tertiary / Q000502:physiology; D021381:Protein Transport / Q000502:physiology; D011518:Proto-Oncogene Proteins / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt; D011993:Recombinant Fusion Proteins; D012480:Salmonella Infections / Q000378:metabolism* / Q000503:physiopathology; D012486:Salmonella typhimurium / Q000378:metabolism* / Q000472:pathogenicity; D012808:Sigma Factor / Q000172:deficiency* / Q000235:genetics; D010738:Type C Phospholipases / Q000378:metabolism; D014617:Vacuoles / Q000378:metabolism / Q000648:ultrastructure
chemical_list: D019269:Phosphatidylinositol 4,5-Diphosphate; D018129:Phosphatidylinositol Phosphates; D011518:Proto-Oncogene Proteins; D011993:Recombinant Fusion Proteins; D012808:Sigma Factor; D017346:Protein Serine-Threonine Kinases; D051057:Proto-Oncogene Proteins c-akt; C081775:RNA polymerase sigma 70; D012321:DNA-Directed RNA Polymerases; D010738:Type C Phospholipases