A difference in inward rectification and polyamine block and permeation between the Kir2.1 and Kir3.1/Kir3.4 K+ channels

Samy M.Y. Makary, Tom W. Claydon, Decha Enkvetchakul, Colin G. Nichols, Mark R. Boyett

Research output: Contribution to journalArticlepeer-review

13 Scopus citations

Abstract

Inward rectification is caused by voltage-dependent block of the channel pore by intracellular Mg2+ and polyamines such as spermine. In the present study, we compared inward rectification in the Kir3.1/Kir3.4 channel, which underlies the cardiac current IK,ACh, and the Kir2.1 channel, which underlies the cardiac current IK,1. Sustained outward current at potentials positive to the K+ reversal potential was observed through Kir3.1/Kir3.4, but not Kir2.1, demonstrating that Kir3.1/Kir3.4 exhibits weaker inward rectification than Kir2.1. We show that Kir3.1/Kir3.4 is more sensitive to extracellular spermine block than Kir2.1, and that intracellular and extracellular polyamines can permeate Kir3.1/Kir3.4, but not Kir2.1, to a limited extent. We describe a simple kinetic model in which polyamines act as permeant blockers of Kir3.1/Kir3.4, but as relatively impermeant blockers of Kir2.1. The model shows the difference in sensitivity to extracellular spermine block, as well as the difference in the extent of inward rectification between the two channels. This suggests that Kir3.1/Kir3.4 exhibits weaker inward rectification than Kir2.1 because of the difference in the balance of polyamine block and permeation of the two channels.

Original languageEnglish
Pages (from-to)749-766
Number of pages18
JournalJournal of Physiology
Volume568
Issue number3
DOIs
StatePublished - Nov 1 2005

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