Level of receptor-associated protein moderates cellular susceptibility to pseudomonas exotoxin A.
Pseudomonas exotoxin A (PE) enters mammalian cells via a receptor-mediated endocytic pathway. The initial step in this pathway is binding to the multiligand receptor termed the alpha 2-macroglobulin receptor/low-density lipoprotein receptor-related protein (LRP). Binding of toxin, and of the many other ligands that bind to LRP, is blocked by the addition of a 39-kDa receptor-associated protein (RAP). Here we show that approximately 40% of the cell-associated LRP is on the surface of toxin-sensitive mouse LM fibroblasts and thus accessible for toxin internalization. The remainder is located intracellularly, primarily in the Golgi region. Mammalian cells exhibit a wide range of sensitivity to PE. To investigate possible reasons for this, we examined the expression levels of both LRP and RAP. Results from a variety of cell lines indicated that there was a positive correlation between LRP expression and toxin sensitivity. In the absence of LRP, cells were as much as 200-fold more resistant to PE compared with sensitive cells. A second group of resistant cells expressed LRP but had a high level of RAP. Thus, a toxin-resistant phenotype would be expected when cells expressed either low levels of LRP or high levels of LRP in the presence of high levels of RAP. We hypothesize that RAP has a pivotal role in moderating cellular susceptibility to PE.
Mucci
D
D
Department of Molecular Genetics, University of Cincinnati, College of Medicine, Ohio 45267, USA.
Forristal
J
J
Strickland
D
D
Morris
R
R
Fitzgerald
D
D
Saelinger
C B
CB
D036002:ADP Ribose Transferases; D000818:Animals; D001427:Bacterial Toxins; D016466:CHO Cells; D002352:Carrier Proteins / Q000378:metabolism; D002451:Cell Compartmentation; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D002522:Chlorocebus aethiops; D006224:Cricetinae; D004351:Drug Resistance; D004492:Edetic Acid / Q000494:pharmacology; D005098:Exotoxins / Q000633:toxicity*; D006023:Glycoproteins / Q000378:metabolism; D006801:Humans; D066298:In Vitro Techniques; D026563:LDL-Receptor Related Protein-Associated Protein; D026503:Low Density Lipoprotein Receptor-Related Protein-1; D051379:Mice; D011971:Receptors, Immunologic / Q000378:metabolism*; D014709:Vero Cells; D037521:Virulence Factors; D000097668:Pseudomonas aeruginosa Exotoxin A
D036002:ADP Ribose Transferases; D001427:Bacterial Toxins; D002352:Carrier Proteins; D004492:Edetic Acid; D005098:Exotoxins; D006023:Glycoproteins; D026563:LDL-Receptor Related Protein-Associated Protein; D026503:Low Density Lipoprotein Receptor-Related Protein-1; D011971:Receptors, Immunologic; D037521:Virulence Factors; D000097668:Pseudomonas aeruginosa Exotoxin A