title: Dual modes of membrane binding direct pore formation by Streptolysin O.
abstract: Effector translocation is central to the virulence of many bacterial pathogens, including Streptococcus pyogenes, which utilizes the cholesterol-dependent cytolysin Streptolysin O (SLO) to translocate the NAD(+) glycohydrolase SPN into host cells during infection. SLO's translocation activity does not require host cell membrane cholesterol or pore formation by SLO, yet SLO does form pores during infection via a cholesterol-dependent mechanism. Although cholesterol was considered the primary receptor for SLO, SLO's membrane-binding domain also encodes a putative carbohydrate-binding site, implicating a potential glycan receptor in binding and pore formation. Analysis of carbohydrate-binding site SLO mutants and carbohydrate-defective cell lines revealed that glycan recognition is involved in SLO's pore formation pathway and is an essential step when SLO is secreted by non-adherent bacteria, as occurs during lysis of erythrocytes. However, SLO also recognizes host cell membranes via a second mechanism when secreted from adherent bacteria, which requires co-secretion of SPN but not glycan binding by SLO. This SPN-mediated membrane binding of SLO correlates with SPN translocation, and requires SPN's non-enzymatic domain, which is predicted to adopt the structure of a carbohydrate-binding module. SPN-dependent membrane binding also promotes pore formation by SLO, demonstrating that pore formation can occur by distinct pathways during infection.
authors.affiliation: Department of Molecular Microbiology, Washington University School of Medicine, Saint Louis, MO, 63110-1093, USA.
authors.forename: Cara C
authors.initials: CC
authors.lastname: Mozola
authors.affiliation: Department of Molecular Microbiology, Washington University School of Medicine, Saint Louis, MO, 63110-1093, USA.
authors.forename: Michael G
authors.initials: MG
authors.lastname: Caparon
mesh_terms: D000818:Animals; D001424:Bacterial Infections / Q000378:metabolism; D001426:Bacterial Proteins / Q000737:chemistry / Q000378:metabolism; D016466:CHO Cells; D050260:Carbohydrate Metabolism; D002462:Cell Membrane / Q000378:metabolism*; D002784:Cholesterol / Q000378:metabolism; D003412:Cricetulus; D004926:Escherichia coli / Q000166:cytology / Q000378:metabolism; D006461:Hemolysis; D009154:Mutation; D009244:NAD+ Nucleosidase / Q000235:genetics / Q000378:metabolism; D011485:Protein Binding; D021381:Protein Transport; D013297:Streptococcus pyogenes / Q000166:cytology* / Q000378:metabolism; D013301:Streptolysins / Q000737:chemistry / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D013301:Streptolysins; C025964:streptolysin O; D002784:Cholesterol; D009244:NAD+ Nucleosidase