Divergent Pseudomonas exotoxin A sensitivity in normal and transformed liver cells is correlated with low-density lipoprotein receptor-related protein expression.
Pseudomonas exotoxin A (PEA) is an extracellular virulence factor produced by the opportunistic human pathogen Pseudomonas aerguinosa. PEA intoxification begins when PEA binds to the low-density lipoprotein receptor-related protein (LRP). The liver is the primary target of systemic PEA, due largely to the high levels of functional LRP expressed by liver cells. Using a 3H-leucine incorporation assay to measure inhibition of protein synthesis we have demonstrated that normal (BNL CL.2) and transformed (BNL 1ME A7R.1) liver cells exhibit divergent PEA sensitivity; with BNL 1ME A7R.1 cells demonstrating greater PEA sensitivity than their non-transformed counterparts. The receptor-associated protein, a LRP antagonist, decreased PEA toxicity in BNL 1ME A7R.1 cells, confirming the importance of the LRP in PEA intoxification in this cell type. Increased PEA sensitivity in BNL 1ME A7R.1 cells was associated with increased functional cell surface LRP expression, as measured by alpha2-macroglobulin binding and internalization studies, and increased LRP mRNA levels, as determined by Northern blot analysis. Interestingly, BNL CL.2 cells were more sensitive than BNL 1ME A7R.1 cells to conjugate and mutant PEA toxins that do not utilize the LRP for cellular entry. These data demonstrate that increased LRP expression is an important mechanism by which PEA sensitivity is increased in BNL 1ME A7R.1 transformed liver cells.
Laithwaite
J E
JE
Department of Biomedical Sciences, University of Guelph, Ontario, N1G 2W1, Guelph, Canada.
Benn
S J
SJ
Marshall
W S
WS
FitzGerald
D J
DJ
LaMarre
J
J
D036002:ADP Ribose Transferases; D000818:Animals; D001427:Bacterial Toxins / Q000737:chemistry / Q000494:pharmacology*; D015152:Blotting, Northern; D002352:Carrier Proteins / Q000378:metabolism; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D005098:Exotoxins / Q000737:chemistry / Q000494:pharmacology*; D005982:Glutathione Transferase / Q000378:metabolism; D022781:Hepatocytes / Q000187:drug effects*; D008024:Ligands; D008099:Liver / Q000187:drug effects*; D051379:Mice; D008807:Mice, Inbred BALB C; D011485:Protein Binding; D011549:Pseudomonas / Q000737:chemistry*; D012333:RNA, Messenger / Q000096:biosynthesis / Q000302:isolation & purification; D011973:Receptors, LDL / Q000096:biosynthesis*; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D016211:Transforming Growth Factor alpha / Q000494:pharmacology; D037521:Virulence Factors; D000097668:Pseudomonas aeruginosa Exotoxin A
D036002:ADP Ribose Transferases; D001427:Bacterial Toxins; D002352:Carrier Proteins; D005098:Exotoxins; D005982:Glutathione Transferase; D008024:Ligands; D012333:RNA, Messenger; D011973:Receptors, LDL; D011993:Recombinant Fusion Proteins; D016211:Transforming Growth Factor alpha; D037521:Virulence Factors; D000097668:Pseudomonas aeruginosa Exotoxin A; C103332:GST-RAP protein, recombinant