The Journal of Immunology, Vol 157, Issue 3 1080-1086, Copyright © 1996 by American Association of Immunologists

ARTICLES

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

DR Oleson, LJ DeFelice, MF Quinn and RM Donahoe
Department of Psychiatry and Behavioral Sciences, Emory University School of Medicine, Atlanta, GA 30322, USA.

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.