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Tyrosine kinases modulate K⁺ channel gating in mouse Schwann cells

Asher Peretz, Alexander Sobko and Bernard Attali

The whole-cell configuration of the patch-clamp technique and immunoprecipitation experiments were used to investigate the effects of tyrosine kinases on voltage-dependent K⁺ channel gating in cultured mouse Schwann cells.

Genistein, a broad-spectrum tyrosine kinase inhibitor, markedly reduced the amplitude of a slowly inactivating delayed-rectifier current (I_K) and, to a lesser extent, that of a transient K⁺ current (I_A). Similar results were obtained on I_K with another tyrosine kinase inhibitor, herbimycin A. Daidzein, the inactive analogue of genistein, was without effect.

Unlike herbimycin A, genistein produced additional effects on I_A by profoundly affecting its gating properties. These changes consisted of slower activation kinetics with an increased time to peak, a positive shift in the voltage dependence of activation (by +30 mV), a decrease in the steepness of activation gating (9 mV per e-fold change) and an acceleration of channel deactivation.

The steepness of the steady-state inactivation was increased by genistein treatment, while the recovery from inactivation was not significantly altered.

The action of genistein on voltage-dependent K⁺ (Kv) currents was accompanied by a decrease in tyrosine phosphorylation of Kv1.4 as well as Kv1.5 and Kv2.1 encoding transient and slowly inactivating delayed-rectifier K⁺ channel subunits, respectively.

In conclusion, the present study shows that tyrosine kinases markedly affect the amplitude of voltage-dependent K⁺ currents in Schwann cells and finely tune the gating properties of the transient K⁺ current component I_A. These modulations may be functionally relevant in the control of K⁺ channel activity during Schwann cell development and peripheral myelinogenesis.

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