Fig. 5.

PIP₂ transient signaling. A, In the proposed model, PIP₂ dissociates from K_ir and diffuses laterally in the plasma membrane. G proteins activate lipid-hydrolyzing enzymes that deplete PIP₂ from the plasma membrane or laterally redistribute PIP₂ into distinct lipid micro domains (e.g. lipid rafts). Dynamic PIP₂ signaling gives rise to a transient inactivation of K_ir that contributes to an action potential. B, PIP₂ degradation products are taken up by endocytosis and PIP₂ resynthesis returns the cell to a resting state.