Direct inhibition of the cloned Kv1.5 channel by AG-1478, a tyrosine kinase inhibitor.
The action of tyrphostin AG-1478, a potent protein tyrosine kinase (PTK) inhibitor, on rat brain Kv1.5 channels (Kv1.5) stably expressed in Chinese hamster ovary cells was investigated using the whole cell patch-clamp technique. AG-1478 rapidly and reversibly inhibited Kv1.5 currents at 50 mV in a concentration-dependent manner with an IC50 of 9.82 microM. AG-1478 accelerated the decay rate of inactivation of Kv1.5 currents without modifying the kinetics of current activation. Pretreatment with the structurally dissimilar PTK inhibitors (genistein and lavendustin A) had no effect on the AG-1478-induced inhibition of Kv1.5 and did not modify the AG-1478-induced current kinetics. The rate constants for binding and unbinding of AG-1478 were 1.46 microM(-1) x s(-1) and 10.19 s(-1), respectively. The AG-1478-induced inhibition of Kv1.5 channels was voltage dependent, with a steep increase over the voltage range of channel opening. However, the inhibition exhibited voltage independence over the voltage range in which channels are fully activated. AG-1478 produced no significant effect on the steady-state activation or inactivation curves. AG-1478 slowed the deactivation time course, resulting in a tail crossover phenomenon. Inhibition of Kv1.5 by AG-1478 was use dependent. The present results suggest that AG-1478 acts directly on Kv1.5 currents as an open-channel blocker and independently of the effects of AG-1478 on PTK activity.
Choi
Bok Hee
BH
Department of Physiology, College of Medicine, The Catholic University of Korea, Socho-gu, Seoul 137-701, Korea.
Choi
Jin-Sung
JS
Rhie
Duck-Joo
DJ
Yoon
Shin Hee
SH
Min
Do Sik
DS
Jo
Yang-Hyeok
YH
Kim
Myung-Suk
MS
Hahn
Sang June
SJ
D000818:Animals; D016466:CHO Cells; D006224:Cricetinae; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D015870:Gene Expression; D019833:Genistein / Q000494:pharmacology; D051666:Kv1.5 Potassium Channel; D008564:Membrane Potentials / Q000187:drug effects; D018408:Patch-Clamp Techniques; D010636:Phenols / Q000494:pharmacology; D026902:Potassium Channel Blockers; D015221:Potassium Channels / Q000235:genetics / Q000378:metabolism; D024642:Potassium Channels, Voltage-Gated; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors*; D011799:Quinazolines; D051381:Rats; D013997:Time Factors; D014162:Transfection; D020032:Tyrphostins / Q000494:pharmacology*
D004791:Enzyme Inhibitors; C496983:Kcna5 protein, rat; D051666:Kv1.5 Potassium Channel; D010636:Phenols; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D024642:Potassium Channels, Voltage-Gated; D011799:Quinazolines; D020032:Tyrphostins; C101044:RTKI cpd; C062898:lavendustin A; D019833:Genistein; D011505:Protein-Tyrosine Kinases