Pharmacological activation of the ryanodine receptor in Jurkat T-lymphocytes.
1 Recently, we provided evidence for cyclic adenosine 5'-diphosphate-ribose, cADP-ribose, as a second messenger in Jurkat T-lymphocytes upon stimulation of the T-cell receptor/CD3- complex (Guse et al., 1999). cADP-ribose mobilizes Ca2+ from an intracellular Ca2+ store which is sensitive to caffeine and gated by the ryanodine receptor/Ca2+ release channel. In the present study we investigated the ability of the trypanocidal drug, suramin, to activate the ryanodine receptor of T-cells. Since suramin cannot permeate the plasma membrane, it was necessary to microinject the drug into Fura-2 loaded T-lymphocytes. 2 In a dose dependent manner suramin increased the intracellular Ca2+ concentration. The dose-response curve is very steep and calculates for an EC50 of 7. 6+/-2.9 mM suramin in the injection pipette. 3 Co-injection of the selective ryanodine receptor inhibitor ruthenium red completely abolished the suramin induced Ca2+ transient. This finding allows for the conclusion that the IP3-receptor sensitive Ca2+ pool is not the primary target of the suramin induced Ca2+ transient. 4 Furthermore, Ins(1,4,6)PS3, an antagonist of the InsP3-receptor could not suppress the suramin-induced Ca2+ signal. The suramin induced Ca2+ transients declined very slowly; however, in the presence of Ins(1,4,6)PS3 this decay was accelerated. In addition, suramin did not interact with the cADP-ribose binding site of the ryanodine receptor of T-cells. 5 In conclusion, suramin is found to be an agonist for the T-cell ryanodine receptor as previously found for the cardiac and skeletal muscle isoform. Therefore, suramin can be designated a universal ryanodine receptor agonist.
Hohenegger
M
M
Pharmacological Institute, University of Vienna, Waehringerstr.13a, A-1090 Vienna, Austria. martin.hohenegger@univie.ac.at
Berg
I
I
Weigl
L
L
Mayr
G W
GW
Potter
B V
BV
Guse
A H
AH
D000246:Adenosine Diphosphate Ribose / Q000031:analogs & derivatives / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism; D036563:Cyclic ADP-Ribose / Q000037:antagonists & inhibitors; D004305:Dose-Response Relationship, Drug; D006801:Humans; D015544:Inositol 1,4,5-Trisphosphate / Q000031:analogs & derivatives / Q000494:pharmacology; D019169:Jurkat Cells; D008845:Microinjections; D009946:Organothiophosphorus Compounds / Q000494:pharmacology; D019837:Ryanodine Receptor Calcium Release Channel / Q000187:drug effects* / Q000378:metabolism; D013498:Suramin / Q000494:pharmacology; D013601:T-Lymphocytes / Q000187:drug effects* / Q000378:metabolism
C403087:8-methoxy cyclic adenosine 5'-diphosphate ribose; D009946:Organothiophosphorus Compounds; D019837:Ryanodine Receptor Calcium Release Channel; C086879:inositol 1,4,6-trisphosphorothioate; D036563:Cyclic ADP-Ribose; D000246:Adenosine Diphosphate Ribose; D013498:Suramin; D015544:Inositol 1,4,5-Trisphosphate; D002118:Calcium