Emerging Concepts in Ion Channel Biophysics

Emerging Concepts in Ion Channel Biophysics

Poster Abstracts

20-POS Board 20 New Insights in the Kinetics of the Kir2.1 Inward Rectifier Potassium Channel Miguel Cuaxospa-Blancas 1 , Ramón Latorre 2 , Ubaldo García 1 . 1 Centro de Investigación y de Estudios Avanzados del IPN, Mexico City, Mexico, 2 University of Valparaiso, Valparaiso, Chile. The Kir2.1 inward rectifier potassium channel belongs to the family known as IRK channels which have been considered as the principal players in the mechanism that permits buffering external potassium concentration, setting the resting membrane potential and modulating the action potential wave form. Several reports have shown that the Kir2.1 channel expression regulates specific aspects in the cell-excitability behavior in cardiac and skeletal muscles, and in the forebrain. Exist evidence corresponding to the single-channels kinetics of homomeric Kir2.1 channel, where authors show that the channel goes through various sub-states of conductance, which are so small that they do not represent any statistical difference. Using cell-attached and inside-out patches from HEK293 cells, we provide new insights which allow us to show that Kir2.1 channel not only presents the occurrence of three open-states of subconductance but also this kinetical behavior is often stable and long lasting, with very low probability of visiting the closed-state. Another special feature we could confirm is that Kir2.1 channel shows burst of activity mainly between the two largest states of subconductance and not in the same way between the closed-state and the smallest state of subconductance. Finally, we performed similar experiments in cells previously incubated with 100 µM of PIP2 and the occurrence of states of subconductance was almost abolished, which suggests that the affinity of PIP2 to its specific binding-site is directly related with the prevention of the appearance of sublevels of conduction.

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