Cyclic adenosine 3',5'-monophosphate increases the open probability of potassium channels in activated human T cells

• Published in: The Journal of immunology (1950) Vol. 157; no. 3; pp. 1080 - 1086
• Main Authors: Oleson, DR, DeFelice, LJ, Quinn, MF, Donahoe, RM
• Format: Journal Article
• Language: English
• Published: United States Am Assoc Immnol 01.08.1996
• Subjects: 1-Methyl-3-isobutylxanthine - pharmacology; Adenosine Triphosphate - pharmacology; Calcium - metabolism; Charybdotoxin - pharmacology; Cyclic AMP - pharmacology; Electrophysiology; Humans; Kinetics; Lymphocyte Activation - drug effects; Potassium - metabolism; Potassium Channels - drug effects; Potassium Channels - metabolism; Sodium - metabolism; T-Lymphocytes - drug effects; T-Lymphocytes - immunology; T-Lymphocytes - metabolism
• ISSN: 0022-1767; 1550-6606
• DOI: 10.4049/jimmunol.157.3.1080

In the present report we describe a cAMP-responsive K channel in activated human T cells. Single channel events were recorded using the patch-clamp technique in cell-attached-patch configuration. The channel was K selective, as determined by reversal potentials under different K gradients, and displayed voltage-independent gating. When the applied potential (Vp) was equal to zero, the conductance of the channel was 21.8 +/- 0.9 pS with 150 mM K in the electrode. Typical patches contained between two and seven channels that were relatively quiet, or silent, before agonist stimulation. Adenosine (20-30 microM) increased the average open time probability from 0.017 +/- 0.008 to 0.108 +/- 0.054 over a period of 108 s. Subsequent addition of the phosphodiesterase inhibitor Ro 20-1724 (0.5 mM) increased the probability of being in the open state to 1.155 +/- 0.407 over a period of 180 s. Channel kinetics were well described by assuming two open and two closed states. Exponential time constants for the open states were 0.51 +/- 0.06 and 4.34 +/- 0.31 ms, and closed state time constants were 0.58 +/- 0.05 and 10.1 3 +/- 2.32 ms. In addition, extracellular ATP (0.3-1.0 mM) decreased channel activity. Moreover, Rp-cAMP (0.5-1.0 mM), an antagonist that specifically blocks the ability of cAMP to bind and activate protein kinase A, failed to inhibit adenosine- and Ro 20-1724-induced increases in channel activity, implying a direct action of cAMP on channel gating.