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Emerging Concepts in Ion Channel Biophysics
Poster Abstracts
72
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.