title: Aggregatibacter actinomycetemcomitans leukotoxin requires beta-sheets 1 and 2 of the human CD11a beta-propeller for cytotoxicity.
abstract: Aggregatibacter actinomycetemcomitans leukotoxin (Ltx) is a repeats-in-toxin (RTX) cytolysin that kills human leukocyte function-associated antigen-1 (LFA-1; alpha(L)/beta(2))-bearing cells. In order to determine whether the alpha(L) portion of the heterodimer is involved in Ltx recognition, we transfected human, mouse and bovine alpha(L) cDNAs into J-beta(2).7, an alpha(L)-deficient cell line, and looked for restoration of Ltx susceptibility. Cells expressing either bovine or human alpha(L) in conjunction with human beta(2) were efficiently killed by Ltx, an indication that bovine alpha(L) could substitute for its human counterpart in critical regions used by Ltx for attachment to LFA-1. On the other hand, cells expressing murine alpha(L) and human beta(2) were not susceptible to the lethal effects of Ltx indicating that the toxin recognition sites are not present in the corresponding mouse sequence. To further identify the region(s) of alpha(L) recognized by Ltx, we constructed and evaluated a panel of chimeric human/murine alpha(L) genes in J-beta(2).7 cells. Analysis of the alpha(L) mutant panel showed that the presence of human N-terminal 128 amino acids on a mouse CD11a background, a region that includes beta-sheets 1 and 2 of the beta-propeller of the human alpha(L) chain, was sufficient for Ltx cytolysis.
authors.affiliation: Leon Levy Research Center for Oral Biology, University of Pennsylvania, Philadelphia, PA 19104, USA.
authors.forename: Irene R
authors.initials: IR
authors.lastname: Kieba
authors.forename: Karen P
authors.initials: KP
authors.lastname: Fong
authors.forename: Hsin-Yao
authors.initials: HY
authors.lastname: Tang
authors.forename: Karl E
authors.initials: KE
authors.lastname: Hoffman
authors.forename: David W
authors.initials: DW
authors.lastname: Speicher
authors.forename: Lloyd B
authors.initials: LB
authors.lastname: Klickstein
authors.forename: Edward T
authors.initials: ET
authors.lastname: Lally
mesh_terms: D016976:Aggregatibacter actinomycetemcomitans / Q000378:metabolism*; D000818:Animals; D040881:CD11a Antigen / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D002417:Cattle; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D005098:Exotoxins / Q000494:pharmacology*; D005434:Flow Cytometry; D006801:Humans; D016169:Lymphocyte Function-Associated Antigen-1 / Q000235:genetics / Q000378:metabolism* / Q000502:physiology; D051379:Mice; D018613:Microscopy, Confocal; D011485:Protein Binding / Q000187:drug effects; D017433:Protein Structure, Secondary; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology
chemical_list: D040881:CD11a Antigen; D005098:Exotoxins; D016169:Lymphocyte Function-Associated Antigen-1; D011993:Recombinant Fusion Proteins; C018579:leukotoxin