Fig. 1.

PIP₂ lipid regulation of ion channels. A, The chemical structure of plasma membrane PIP₂ is shown with an arachidonyl acyl chain (green) and inositol phosphates at the 4′ and 5′ position (red). B, a cartoon representation of a PIP₂ lipid gated ion channel. PIP₂ is shown bound to a lipid binding site in the transmembrane domain of an ion channel. C, List of ion channels with lipid gating properties. K_ir2.2 and 3.2 are the most clearly “lipid-gated”. A second group appears to be dual regulated, or “PIP₂ modulated”. PIP₂ modulates channel gating, but gating also requires either voltage or a second ligand. A third group of channels behave similar to K_ir but await definitive proof of lipid gating vs. PIP₂ modulation (?). The list of channels is exemplary and not comprehensive.