Staurosporine directly blocks Kv1.3 channels expressed in Chinese hamster ovary cells

Abstract

The effects of staurosporine (ST), a widely used protein kinase C (PKC) inhibitor, were examined on Kv1.3 channels stably expressed in Chinese hamster ovary (CHO) cells using the whole-cell and excised inside-out configurations of the patch clamp technique. In whole-cell recordings, ST, at external concentrations from 300 nM to 10 microM, accelerated the rate of inactivation of Kv1.3 currents and thereby reduced the current at the end of the depolarizing pulse in a concentration-dependent manner with an IC50 of 1.2 microM. The actions of ST were unaffected by pretreatment with another selective PKC inhibitor, chelerythrine, or by including the PKC pseudosubstrate peptide inhibitor, PKC 19-36, in the intracellular solution. Rp-cAMPS, a specific protein kinase A inhibitor, included in intracellular solution did not affect the effects of ST. Furthermore, the same effects of ST on Kv1.3 were also observed in excised inside-out patches when applied to the internal face of the membrane. These effects were completely reversible upon washing. Current-voltage relations for Kv1.3 currents at the end of voltage steps indicated that ST reduced Kv1.3 currents over a wide voltage range. The blockade exhibited a shallow voltage dependence between -10 mV and +40 mV, increasing at more positive potentials. ST had no effect on the voltage dependence of steady-state inactivation. It reduced the tail current amplitude and slowed the deactivation time course, resulting in a crossover phenomenon. These results suggest that the action of ST on Kv1.3 is independent of PKC and PKA inhibition. ST blocks the open state of Kv1.3 channels to produce an apparent acceleration of the inactivation rate.

Pepstatin A induces extracellular acidification distinct from aspartic protease inhibition in microglial cell lines

“…Several investigators have described differential effects of staurosporine and chelerythrine on cellular function (Barker et al, 1998;Friedrich et al, 1998;Macica et al, 1998;Choi et al, 1999). NHE1 is one of the dominant routes of proton extrusion at plasma membranes (Sangan et al, 2002).…”

The Guanylyl Cyclase Activator YC-1 Directly Inhibits the Voltage-Dependent K+ Channels in Rabbit Coronary Arterial Smooth Muscle Cells

“…For example, the PKC inhibitor bisindolylmaleimide (I) directly blocks stably expressed Kv1.5 channels in Chinese hamster ovary (CHO) cells (13) and Kv channels from freshly isolated coronary and mesenteric arterial smooth muscle cells (14,31). Another PKC inhibitor, staurosporine, also blocks Kv1.3 channels stably expressed in CHO cells (32) and directly blocks the coronary Kv current (10). The PKA inhibitor H-89 blocks Kv channels in coronary smooth muscle cells (33) and Kv1.3 channels expressed in CHO cells (34), independently of PKA inhibition.…”

Direct effect of protein kinase C inhibitors on cardiovascular ion channels

“…Besides cardiovascular ion channels, staurosporine was reported to inhibit the Kv1.3 channel expressed in Chinese hamster ovary (CHO) cells (IC50=1.2 μM) (38). Staurosporine accelerates the inactivation rate of Kv1.3 channel, which implies that it interacts with the open state of the channel.…”