title: LRP5 and LRP6 are not required for protective antigen-mediated internalization or lethality of anthrax lethal toxin.
abstract: Anthrax toxin (AnTx) plays a key role in the pathogenesis of anthrax. AnTx is composed of three proteins: protective antigen (PA), edema factor, and lethal factor (LF). PA is not toxic but serves to bind cells and translocate the toxic edema factor or LF moieties to the cytosol. Recently, the low-density lipoprotein receptor-related protein LRP6 has been reported to mediate internalization and lethality of AnTx. Based on its similarity to LRP6, we hypothesized that LRP5 may also play a role in cellular uptake of AnTx. We assayed PA-dependent uptake of anthrax LF or a cytotoxic LF fusion protein (FP59) in cells and mice harboring targeted deletions of Lrp5 or Lrp6. Unexpectedly, we observed that uptake was unaltered in the presence or absence of either Lrp5 or Lrp6 expression. Moreover, we observed efficient PA-mediated uptake into anthrax toxin receptor (ANTXR)-deficient Chinese hamster ovary cells (PR230) that had been stably engineered to express either human ANTXR1 or human ANTXR2 in the presence or absence of siRNA specific for LRP5 or LRP6. Our results demonstrate that neither LRP5 nor LRP6 is necessary for PA-mediated internalization or lethality of anthrax lethal toxin.
authors.affiliation: Laboratory of Cancer and Developmental Cell Biology, Van Andel Research Institute, Grand Rapids, Michigan, United States of America.
authors.forename: John J
authors.initials: JJ
authors.lastname: Young
authors.forename: Jennifer L
authors.initials: JL
authors.lastname: Bromberg-White
authors.forename: Cassandra
authors.initials: C
authors.lastname: Zylstra
authors.forename: Joseph T
authors.initials: JT
authors.lastname: Church
authors.forename: Elissa
authors.initials: E
authors.lastname: Boguslawski
authors.forename: James H
authors.initials: JH
authors.lastname: Resau
authors.forename: Bart O
authors.initials: BO
authors.lastname: Williams
authors.forename: Nicholas S
authors.initials: NS
authors.lastname: Duesbery
mesh_terms: D000818:Animals; D000881:Anthrax / Q000209:etiology / Q000503:physiopathology / Q000517:prevention & control; D000942:Antigens, Bacterial / Q000276:immunology / Q000378:metabolism / Q000502:physiology*; D001408:Bacillus anthracis / Q000276:immunology*; D001427:Bacterial Toxins / Q000378:metabolism*; D001692:Biological Transport / Q000502:physiology; D016466:CHO Cells; D002478:Cells, Cultured; D006224:Cricetinae; D003412:Cricetulus; D004705:Endocytosis / Q000502:physiology; D005786:Gene Expression Regulation; D006801:Humans; D026502:LDL-Receptor Related Proteins / Q000235:genetics / Q000502:physiology*; D060492:Low Density Lipoprotein Receptor-Related Protein-5; D060488:Low Density Lipoprotein Receptor-Related Protein-6; D051379:Mice; D018345:Mice, Knockout; D034741:RNA, Small Interfering / Q000494:pharmacology
chemical_list: D000942:Antigens, Bacterial; D001427:Bacterial Toxins; D026502:LDL-Receptor Related Proteins; C555482:LRP5 protein, human; C555475:LRP6 protein, human; D060492:Low Density Lipoprotein Receptor-Related Protein-5; D060488:Low Density Lipoprotein Receptor-Related Protein-6; C555483:Lrp5 protein, mouse; C555476:Lrp6 protein, mouse; D034741:RNA, Small Interfering; C030325:anthrax toxin