Effects of modulators of adenylyl cyclase on interleukin-2 production, cytosolic Ca2+ elevation, and K+ channel activity in Jurkat T cells.
We have studied the effects of prostaglandin E2 (PGE2) and cholera toxin, two modulators of adenylyl cyclase, and 8-bromo cAMP (8-BrcAMP) on various parameters of lymphocyte activation using the human T cell line Jurkat. Our results show that PGE2 and cholera toxin inhibit, in a dose-related manner, the phytohemagglutinin (PHA)-dependent production of interleukin 2 by these cells. The data are consistent with the interpretation that the inhibition is due to an intracellular increase in cAMP, since the metabolically stable 8-BrcAMP analog produced the same inhibitory effect. However, PGE2 or 8-BrcAMP did not interfere with the PHA-induced elevation in the cytosolic concentration of Ca2+, suggesting that changes in the intracellular concentration of cAMP does not affect the internal release or the influx of Ca2+. In contrast, cholera toxin prevented the Ca2+ response of Jurkat cells to PHA. We studied the effects of PGE2, cholera toxin, and 8-BrcAMP on the amplitude of the K+ outward current using the patch clamp technique in the whole cell configuration. Results showed that PGE2, 8-BrcAMP, and cholera toxin inhibited K+ channel activity. For instance, the amplitude of the outward K+ current was reduced to 43 +/- 19%, 50 +/- 26%, and 46 +/- 16% of control values in the case of cells perfused in the presence of PGE2, 8-BrcAMP, and cholera toxin, respectively. Blocking K+ channels with tetraethylammonium ions did not prevent the characteristic Jurkat Ca2+ response to PHA. Our observations that cAMP inhibits K+ channel activity in a T cell line provide an additional explanation for its reported inhibition of lymphocyte activation. Increasing the intracellular concentration of cAMP may result in reduction of K+ movements and in negative modulation of signal transduction via G-proteins as previously suggested. These two effects could act in synergy to impair signal transduction.
Bastin
B
B
Department of Biochemistry, Faculty of Medicine, University of Sherbrooke, Quebec, Canada.
Payet
M D
MD
Dupuis
G
G
D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology; D000262:Adenylyl Cyclases / Q000378:metabolism; D002118:Calcium / Q000378:metabolism*; D002460:Cell Line; D002772:Cholera Toxin / Q000494:pharmacology; D003600:Cytosol / Q000378:metabolism; D015232:Dinoprostone / Q000494:pharmacology; D006801:Humans; D066298:In Vitro Techniques; D007376:Interleukin-2 / Q000096:biosynthesis*; D008213:Lymphocyte Activation; D010835:Phytohemagglutinins / Q000494:pharmacology; D011188:Potassium / Q000502:physiology; D015221:Potassium Channels / Q000502:physiology*; D013601:T-Lymphocytes / Q000502:physiology*; D013757:Tetraethylammonium Compounds / Q000494:pharmacology
D007376:Interleukin-2; D010835:Phytohemagglutinins; D015221:Potassium Channels; D013757:Tetraethylammonium Compounds; D015124:8-Bromo Cyclic Adenosine Monophosphate; D002772:Cholera Toxin; D000262:Adenylyl Cyclases; D015232:Dinoprostone; D011188:Potassium; D002118:Calcium