Shaker-related Kv1.3 channels are the most prevalent and widely studied ion channels in normal human T Lymphocytes (TL) as well as in certain T cell lines, such as Jurkat cells. This review focuses on modulatoty effects of intracellular cAMP on the activity of the channels. Available data provide evidence that: 1) intracellular cAMP directly activates a novel class of charybdotoxin-insensitive voltage-independent cAMP-gated K+ channels, but not the Kv1.3 channels both in quiescent and activated human T Lymphocytes, 2) intracellular cAMP reduces the Kv1.3 channel activity by protein kinase A - dependent channel phosphorylation in Jurkat TL cell line, 3) intracellular cAMP does not affect the activity of Kv1.3 channels in normal human T Lymphocytes. The apparently different effects of intracellular cAMP on Kv1.3 channels expressed in normal and Jurkat TL may reflect differences in the biochemical microenvironment as well as in an expression of auxiliary channel subunits in both cell types. A more complete biochemical characterisation of the Kv1.3 channel microenvironment and the channel-associated subunits in different T cell subtypes will be necessary to further elucidate this problem.
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