Abstract
We have measured the activity of the n type K+ channel present in human (Jurkat) T lymphocytes using the patch clamp technique in the whole-cell configuration. We report that protein kinase A (PKA) and protein kinase C (PKC) modulate, in a dual manner, the K+ conductance in these cells. Activation of PKA decreases the amplitude of the current, as previously reported (Bastin, B., Payet, M. D., and Dupuis, G. (1990) Cell. Immunol. 128, 385-399), and this is also the case for 12-O-tetradecanoylphorbol-13-acetate-dependent activation of PKC. In contrast, inhibitors of PKC (H7, staurosporine, polymixin B, and anti-PKC antibody) increase the current amplitude. Of importance, down-regulation of PKC or its inhibition prevented the PKA-dependent inhibition of the K+ channels. Addition of alkaline phosphatase via the patch pipette increased the K+ conductance under basal conditions and reversed the inhibition produced by PKA. The dual modulation of K+ channels in Jurkat T cells is in agreement with the presence of consensus sequences in the primary structure of the n type K+ channel.
Highlights
We demonstrate that the T lymphocyte n type K+ channel (Lewis and Cahalan, 1990)present in Jurkat T cells (Dupuis et al, 1989) is regulated inadual manner by proteinkinase A (PKA) and by protein kinase C (PKC)
Three types of K+ channels have'been described in murine T lymphocytes, the n, n', and 1 types, which can be characterized by their voltage dependence and their responses to pharmacological agents (Gallin, 1991; Lewis and Cahalan, 1990)
The K' current recorded in Jurkat lymphocytes demonstrates all the characteristics of the n type current, i.e. an activation at potentials more positive than -40 mV, usedependent inactivation, and inhibition by triethylammonium salts with a K,/2 of 6 mM (Dupuis et al, 1989)
Summary
We demonstrate that the T lymphocyte n type K+ channel (Lewis and Cahalan, 1990)present in Jurkat T cells (Dupuis et al, 1989) is regulated inadual manner by PKA and by PKC. We present evidence that the previously reported (Bastin et al, 1990) CAMP-dependent inhibition of the K’ conductance in these cells depends on PKC activity andthe probable phosphorylation of the K+channel, since the use of inhibitors of PKC prevents the PKA-dependent negative modulation.
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