Acute suppression of inwardly rectifying Kir2.1 channels by direct tyrosine kinase phosphorylation

Signaling via cytosolic and receptor tyrosine kinases is associated with ce ll growth and differentiation but also targets onto transmitter receptors a nd ion channels. Here, regulation by tyrosine kinase (TK) activity was inve stigated for inwardly rectifying K+ (Kir2.1) channels that control membrane excitability in many central neurons. In mammalian tsA-201 cells, the memb rane-permeable protein tyrosine phosphatase inhibitor, perorthovanadate (10 0 mu M), suppressed currents through recombinant Kir2.1 channels by 60 +/- 20%, Coapplication of the TK inhibitor genistein (100 mu M:) completely abo lished this effect. Native Kir2.1 channels in rat basophilic leukocytes wer e affected by manipulation of the TK and protein tyrosine phosphatase activ ity in a qualitatively similar manner. Site mutation of a tyrosine consensu s residue for TK phosphorylation in the C-terminal domain of Kir2.1 generat ed channel properties indistinguishable from wild-type Kir2.1 channels. How ever, Kir2.1Y242F channels were no longer suppressed following exposure to perorthovanadate, indicating that the channel is a direct substrate for TKs . After coexpression of nerve growth factor receptor with Kir2.1 channels i n tsA-201 cells and Xenopus oocytes, the activity of Kir2.1 was rapidly sup pressed by applied nerve growth factor (0.5 mu g/ml) by 31 +/- 10 and 21 +/ - 15%, respectively, Acute inhibition was also evoked by epidermal growth f actor and insulin via endogenous insulin receptors, indicating that Kir2.1 channels may serve as a general target for neurotrophic growth factors in t he brain.