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Jajoo S, Mukherjea D, Pingle S, Sekino Y, Ramkumar V: Induction of adenosine A1 receptor expression by pertussis toxin via an adenosine 5'-diphosphate ribosylation-independent pathway. J Pharmacol Exp Ther. 2006 Apr;317(1):1-10. Epub 2005 Dec 1.
Pertussis toxin ADP ribosylates G (i) and G (o) transducing proteins and functionally uncouples adenosine A (1) receptor (A (1) AR) from its effectors. We hypothesized that this loss in receptor coupling could lead to de novo A (1) AR synthesis by the cell in a futile attempt to re-establish normal receptor function. To test this hypothesis, we used hamster ductus deferens tumor (DDT (1) MF-2) cells, a cell culture model for studying A (1) AR, and showed that pertussis toxin (100 ng/ml) produced a time-dependent loss in A (1) AR-G (i) interaction and abolished A (1) AR activation of extracellular signal-regulated kinase 1/2. Interestingly, pertussis toxin increased the expression of A (1) AR, as measured by real-time polymerase chain reaction, immunocytochemistry, and [(3) H] cyclopentyl-1,3-dipropylxanthine (DPCPX) binding, suggesting a compensatory response to G (i) protein inactivation. DDT (1) MF-2 cells exposed to pertussis toxin demonstrated nuclear factor kappaB (NF-kappaB) activation within 30 min of exposure, a time point that preceded the loss of function of the A (1) AR. Inhibition of NF-kappaB attenuated the increase in A (1) AR induced by pertussis toxin. Cells exposed to B-oligomer subunit of pertussis toxin, devoid of significant ADP ribosyltransferase activity, showed increased A (1) AR protein expression, preceded by activation of NF-kappaB. B-Oligomer increased intracellular Ca (2+) in DDT (1) MF-2 cells. Chelation of intracellular Ca (2+) with 1,2-bis (2-aminophenoxy) ethane-N,N,N',N'-tetraacetic acid or inhibition of protein kinase C (PKC) with bisindolylmaleimide hydrochloride reduced the activation of NF-kappaB and [(3) H] DPCPX binding. We conclude that pertussis toxin promotes de novo A (1) AR synthesis by activating NF-kappaB through an ADP ribosylation-independent mechanism involving intracellular Ca (2+) release and PKC activation. |
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