Intermedilysin-receptor interactions during assembly of the pore complex: assembly intermediates increase host cell susceptibility to complement-mediated lysis.
Intermedilysin (ILY) is an unusual member of the family of cholesterol-dependent cytolysins because it binds to human CD59 (hCD59) rather than directly to cholesterol-rich membranes. Binding of ILY to hCD59 initiates a series of conformational changes within the toxin that result in the conversion of the soluble monomer into an oligomeric membrane-embedded pore complex. In this study the association of ILY with its membrane receptor has been examined throughout the assembly and formation of the pore complex. Using ILY mutants trapped at various stages of pore assembly, we show ILY remains engaged with hCD59 throughout the assembly of the prepore oligomer, but it disengages from the receptor upon the conversion to the pore complex. We further show that the assembly intermediates increase the sensitivity of the host cell to lysis by its complement membrane attack complex, apparently by blocking the hCD59-binding site for complement proteins C8alpha and C9.
LaChapelle
Stephanie
S
Department of Microbiology and Immunology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA.
Tweten
Rodney K
RK
Hotze
Eileen M
EM
D000818:Animals; D001430:Bacteriocins / Q000276:immunology / Q000378:metabolism*; D001665:Binding Sites; D018957:CD59 Antigens / Q000378:metabolism*; D016466:CHO Cells; D003185:Complement C8 / Q000378:metabolism*; D003186:Complement C9 / Q000378:metabolism*; D006224:Cricetinae; D003412:Cricetulus; D003603:Cytotoxins / Q000378:metabolism*; D019281:Dimerization; D004910:Erythrocyte Membrane / Q000737:chemistry*; D006461:Hemolysis; D006801:Humans; D047468:Immunoprecipitation; D011485:Protein Binding; D011817:Rabbits
D001430:Bacteriocins; D018957:CD59 Antigens; D003185:Complement C8; D003186:Complement C9; D003603:Cytotoxins; C403910:intermedilysin protein, Streptococcus intermedius; C051590:CD59 protein, human