Intracellular Ca2+ pools in Jurkat T-lymphocytes.
Jurkat T-lymphocytes comprise at least four intracellular Ca2+ pools. Pool I was agonist-sensitive and contained 23 +/- 8% (n = 18) of the total Ca(2+)-storage capacity, as shown in intact cells in the presence of EGTA. The time courses of the agonist-induced formation of Ins(1,4,5)P3 and of the Ca2+ release from pool I were nearly superimposable, indicating that the agonist-sensitive pool I is emptied by Ins(1,4,5)P3. Likewise, in permeabilized cells, the size of the Ins(1,4,5)P3-sensitive Ca2+ pool I was 27 +/- 11% (n = 14). Pool II contained 26 +/- 5% (n = 9) of intracellularly stored Ca2+ and was liberated by thapsigargin, an inhibitor of the endoplasmic-reticulum (ER) Ca(2+)-ATPase. Addition of thapsigargin before addition of agonist abolished the agonist-induced Ca2+ release in both intact and permeabilized cells, indicating that pool I is a subcompartment of the ER Ca2+ pool. The content of this ER Ca2+ pool (pools I and II) amounted to 51 +/- 15% (n = 9) in intact cells and 49 +/- 16% (n = 16) in permeabilized cells. Caffeine released Ca2+ even when the ER pool (pools I and II) was emptied by previous addition of thapsigargin, indicating the presence of a third pool independent of pools I and II. Pool III contained 23 +/- 6% (n = 8) in intact cells, but 41 +/- 8% (n = 5) in permeabilized cells. The remaining intracellularly stored Ca2+ was released by addition of the Ca2+ ionophore ionomycin. This fourth pool contained 27 +/- 8% (n = 9) in intact cells, but less than 10% in permeabilized cells. The size of pool III was increased when pools I and II were emptied before addition of caffeine, whereas the size of pool IV was decreased under such conditions. In conclusion, this first comprehensive description of intracellular Ca2+ pools in Jurkat T-lymphocytes demonstrates the presence of four different Ca2+ pools, provides estimates of their sizes and describes relationships between each other. Release of Ca2+ from pool I [Ins(1,4,5)P3-sensitive] has previously been shown to play a major role in T-cell activation, whereas the physiological role of pools II-IV remains to be established.
Guse
A H
AH
Clinical Research Unit for Rheumatology/Immunology, University of Erlangen-Nürnberg, Germany.
Roth
E
E
Emmrich
F
F
D000911:Antibodies, Monoclonal; D017252:CD3 Complex / Q000276:immunology / Q000502:physiology; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism* / Q000494:pharmacology; D000252:Calcium-Transporting ATPases / Q000037:antagonists & inhibitors; D002460:Cell Line; D004533:Egtazic Acid / Q000494:pharmacology; D004721:Endoplasmic Reticulum / Q000378:metabolism; D015544:Inositol 1,4,5-Trisphosphate / Q000378:metabolism / Q000494:pharmacology; D015759:Ionomycin / Q000494:pharmacology; D007700:Kinetics; D013601:T-Lymphocytes / Q000187:drug effects / Q000378:metabolism*; D013729:Terpenes / Q000494:pharmacology; D019284:Thapsigargin
D000911:Antibodies, Monoclonal; D017252:CD3 Complex; D013729:Terpenes; D002110:Caffeine; D004533:Egtazic Acid; D015759:Ionomycin; D019284:Thapsigargin; D015544:Inositol 1,4,5-Trisphosphate; D000252:Calcium-Transporting ATPases; D002118:Calcium