Characterization of the interaction between anthrax toxin and its cellular receptors.
Mutations in capillary morphogenesis gene 2 (CMG2), one of the two closely related proteins that act as anthrax toxin receptors, cause two rare human autosomal recessive conditions, juvenile hyaline fibromatosis (JHF) and infantile systemic hyalinosis (ISH). Here we demonstrate that CMG2 proteins with certain JHF- and ISH-associated single amino acid substitutions in their von Willebrand factor A domain or transmembrane region do not function as anthrax toxin receptors. However, an ISH-associated CMG2 variant having a truncated cytosolic domain does still function as an anthrax receptor, and in fact makes cells hyper-sensitive to toxin, distinguishing the roles of CMG2 in physiology and anthrax pathology. Site-specific mutagenesis was used to characterize the role that domain 2 of the anthrax toxin protective antigen (PA) plays in interaction with CMG2, focusing on the interaction between the PA 2beta(3)-2beta(4) loop and a pocket (Glu-122 pocket) adjacent to the metal ion-dependent adhesion site in CMG2. Substitutions that disrupted the salt bridge between PA Arg-344 and CMG2 Glu-122 decreased the affinity of PA to CMG2 three- to fourfold. Furthermore, mutation of CMG2 Tyr-119 (within the Glu-122 pocket) to His lowered the pH threshold for PA prepore-to-pore conversion in the endocytic pathway.
Liu
Shihui
S
Bacterial Toxins and Therapeutics Section, Laboratory of Bacterial Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA. shliu@niaid.nih.gov
Leung
Howard J
HJ
Leppla
Stephen H
SH
D000818:Animals; D000942:Antigens, Bacterial / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001427:Bacterial Toxins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D001665:Binding Sites; D016466:CHO Cells; D006224:Cricetinae; D003412:Cricetulus; D006801:Humans; D007700:Kinetics; D008565:Membrane Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D018000:Receptors, Peptide / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D013329:Structure-Activity Relationship; D014162:Transfection
C447150:ANTXR2 protein, human; D000942:Antigens, Bacterial; D001427:Bacterial Toxins; D008565:Membrane Proteins; D018000:Receptors, Peptide; C030325:anthrax toxin; C070309:anthrax toxin receptors