Quantitative analysis of mammalian GIRK2 channel regulation by G proteins, PIP2 and Na+ in a reconstituted system

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Abstract

GIRK channels control spike frequency in atrial pacemaker cells and inhibitory potentials in neurons. By directly responding to G proteins, PIP₂ and Na⁺, GIRK is under the control of multiple signaling pathways. In this study, the mammalian GIRK2 channel has been purified and reconstituted in planar lipid membranes and effects of Gα, Gβγ, PIP₂ and Na⁺ analyzed. Gβγ and PIP₂ must be present simultaneously to activate GIRK2. Na⁺ is not essential but modulates the effect of Gβγ and PIP₂ over physiological concentrations. Gα_i1(GTPγS) has no effect, whereas Gα_i1(GDP) closes the channel through removal of Gβγ. In the presence of Gβγ, GIRK2 opens as a function of PIP₂ mole fraction with Hill coefficient 2.5 and an affinity that poises GIRK2 to respond to natural variations of PIP₂ concentration. The dual requirement for Gβγ and PIP₂ can help to explain why GIRK2 is activated by G_i/o, but not G_q coupled GPCRs.

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Weiwei Wang

The Rockefeller University, Howard Hughes Medical Institute, New York, United States

Competing interests
The authors declare that no competing interests exist.
Matthew R Whorton

The Rockefeller University, Howard Hughes Medical Institute, New York, United States

Competing interests
The authors declare that no competing interests exist.
Roderick MacKinnon

The Rockefeller University, Howard Hughes Medical Institute, New York, United States

For correspondence
mackinn@rockefeller.edu

Competing interests
The authors declare that no competing interests exist.

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