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Research Papers
Stoichiometry of Kir channels with phosphatidylinositol bisphosphate
Taihao Jin, Jin Liang Sui, Avia Rosenhouse-Dantsker, Kim Chan, Lily Jan and Diomedes E. Logothetis
volume 2 | issue 1
January/February 2008Subscribe to this journal for $79/year
Phosphatidylinositol bisphosphate (PIP2) is the most abundant phosphoinositide in the plasma membranes of cells and its interaction with many ion channel proteins has proven to be a critical factor enabling ion channel gating. All members of the inwardly rectifying potassium (Kir) channel family depend on PIP2 for their activity, displaying distinct affinities and stereospecificities of interaction with the phosphoinositide. Here, we explored the stoichiometry of Kir channels with PIP2. We first showed that PIP2 regulated the activity of Kir3.4 channels mainly by altering their bursting behavior. Detailed burst analysis indicates that the channels assumed up to four open states and a connectivity of four between open and closed states depending on the available PIP2 levels. Moreover, by controlling the number of PIP2-sensitive subunits in the stoichiometry of a tetrameric Kir2.1 channel, we showed that characteristic channel activity was obtained when at least two wild-type subunits were present. Our studies support a kinetic model for gating of Kir channels by PIP2, where each of the four open states corresponds to the channel activated by one to four PIP2 molecules.
Authors
Taihao Jin
UCSF
Jin Liang Sui
Mount Sinai School of Medicine, New York, NY
Avia Rosenhouse-Dantsker
Mount Sinai School of Medicine, New York, NY
Kim Chan
Case Western Reserve University
Lily Jan
Diomedes E. Logothetis
Mount Sinai School of Medicine, New York, NY