The alpha 2-macroglobulin receptor/low density lipoprotein receptor-related protein binds and internalizes Pseudomonas exotoxin A.
The alpha 2-macroglobulin receptor/low density lipoprotein receptor-related protein (alpha 2 MR/LRP) is a large cell-surface glycoprotein consisting of a 515-kDa and an 85-kDa polypeptide; this receptor is thought to be responsible for the binding and endocytosis of activated alpha 2-macroglobulin and apoE-enriched beta-very low density lipoprotein. A similar high molecular weight glycoprotein has been identified as a potential receptor for Pseudomonas exotoxin A (PE). We demonstrate that the alpha 2 MR/LRP and the PE-binding glycoprotein have a similar mobility upon sodium dodecyl sulfate-polyacrylamide gel electrophoresis and are immunologically indistinguishable. Furthermore, affinity-purified alpha 2 MR/LRP binds specifically to PE but not to a mutant toxin defective in its ability to bind cells. The 39-kDa receptor-associated protein, which blocks binding of ligands to alpha 2 MR/LRP, also prevents binding and subsequent toxicity of PE for mouse fibroblasts. The concentration of receptor-associated protein that was required to reduce binding and toxicity to 50% was approximately 14 nM, a value virtually identical to the KD measured for the interaction of receptor-associated protein with the purified receptor. Overall, the studies strongly suggest that the alpha 2 MR/LRP is responsible for internalizing PE.
Kounnas
M Z
MZ
Biochemistry Laboratory, American Red Cross, Rockville, Maryland 20855.
Morris
R E
RE
Thompson
M R
MR
FitzGerald
D J
DJ
Strickland
D K
DK
Saelinger
C B
CB
D036002:ADP Ribose Transferases; D000595:Amino Acid Sequence; D000818:Animals; D001427:Bacterial Toxins / Q000378:metabolism*; D002478:Cells, Cultured; D004591:Electrophoresis, Polyacrylamide Gel; D005098:Exotoxins / Q000378:metabolism*; D005347:Fibroblasts / Q000166:cytology; D006801:Humans; D026503:Low Density Lipoprotein Receptor-Related Protein-1; D051379:Mice; D008969:Molecular Sequence Data; D011550:Pseudomonas aeruginosa / Q000378:metabolism*; D011971:Receptors, Immunologic / Q000378:metabolism*; D037521:Virulence Factors; D000097668:Pseudomonas aeruginosa Exotoxin A
D036002:ADP Ribose Transferases; D001427:Bacterial Toxins; D005098:Exotoxins; D026503:Low Density Lipoprotein Receptor-Related Protein-1; D011971:Receptors, Immunologic; D037521:Virulence Factors; D000097668:Pseudomonas aeruginosa Exotoxin A