Staphylococcal enterotoxin-B (SEB) alters [14C]-choline transport and phosphatidylcholine metabolism in cultured human kidney proximal tubular cells.
We studied the effects of SEB on [14C]-choline transport and metabolism of choline containing phospholipids in cultured human kidney proximal tubular (PT) cells. SEB increased the uptake of [14C]-choline in PT cells as a function of toxin concentration, incubation time, and pH. The maximum increase in uptake (3.5-5-fold compared to control) was observed at a toxin concentration of 10 micrograms/10(4) cells, at 4 h and at pH 7.4. Two toxins structurally related to SEB, Staphylococcal enterotoxin-A and toxic shock toxin (TST-1) failed to alter [14C]-choline uptake in PT cells, a finding which indicates that SEB-mediated alteration in choline uptake in PT cells has high specificity. We found that SEB markedly and significantly increased the incorporation of [14C]-choline into phosphatidylcholine, Iysophosphatidylcholine and sphingomyelin, but not into phosphatidylethanolamine. Maximum increase in the incorporation of [14C]-choline into phosphatidylcholine (3-fold compared to control) was observed at 4 h after incubation with toxin. In contrast, SEB did not alter the incorporation of [14C]-choline in phosphatidylethanolamine. The cellular level of phosphatidylcholine was also increased (2-fold compared to control) in PT cells incubated with SEB. This was accompanied by a 3-to-4-fold increase in CTP; phosphocholine, cytidyltransferase activity. In sum, SEB specifically stimulates phosphatidylcholine synthesis in PT cells by increasing choline uptake or by activating CTP: phosphocholine, cytidyltransferase, or both. We believe this is the first-ever report indicating that a toxin can increase phosphatidylcholine synthesis.(ABSTRACT TRUNCATED AT 250 WORDS)
Khullar
M
M
Department of Pediatrics, Johns Hopkins University, School of Medicine, Baltimore, Maryland 21287-3654, USA.
Chatterjee
S
S
D001693:Biological Transport, Active / Q000187:drug effects; D002478:Cells, Cultured; D002794:Choline / Q000378:metabolism*; D019916:Choline-Phosphate Cytidylyltransferase; D004768:Enterotoxins / Q000633:toxicity*; D006801:Humans; D007687:Kidney Tubules, Proximal / Q000187:drug effects* / Q000378:metabolism*; D007700:Kinetics; D009713:Nucleotidyltransferases / Q000378:metabolism; D010713:Phosphatidylcholines / Q000378:metabolism*; D010743:Phospholipids / Q000378:metabolism; D013211:Staphylococcus aureus; D013395:Sucrose / Q000378:metabolism; D013696:Temperature
D004768:Enterotoxins; D010713:Phosphatidylcholines; D010743:Phospholipids; C031818:enterotoxin B, staphylococcal; D013395:Sucrose; D009713:Nucleotidyltransferases; D019916:Choline-Phosphate Cytidylyltransferase; D002794:Choline