Membrane phosphoinositides, and in particular phosphatidylinositol (4,5)-bisphosphate (PIP2), have been shown to be important for the function of the five members of the KCNQ channel family (KCNQ1-5). In general, our studies have primarily focussed on their actions on KCNQ1. KCNQ1 combines with the auxiliary subunit KCNE1 to form a heteromultimeric channel complex which underlies the cardiac delayed rectifier current IKs. The activity of this channel can be regulated through Gq/11-coupled receptors and downstream phospholipase-C (PLC) activation. The activation of PLC leads to IKs channel inactivation and it is now thought that this occurs due to the hydrolysis of plasma membrane bound PIP2. In detail, the depletion of PIP2 leads to channel inactivation by acting to slow the rate of channel activation and increase the rate of channel deactivation and these effects combine to result in a large shift in the voltage dependence of channel activation (V0.5) towards depolarised potentials. Although PIP2 acutely modulates IKs channel function, the nature of the molecular interactions and the specific residues involved in the binding of PIP2 to this channel had not been established. Using a combination of biochemical and electrophysiological techniques we have identified that a cluster of basic residues (Lys-354, Lys-358, Arg-360 and Lys-362), located just after the S6 domain in the proximal C-terminus, are crucial for the binding of a range of anionic phospholipids, including PIP2. The mutation of these charged residues to alanine, singly or in combination, results in a loss of binding to anionic phospholipids and acts to mimic the electrophysiological effects of PIP2 depletion on channel function by causing a positive shift in the V0.5. Our data also suggest that the two middle residues (Lys-358 and Arg-360), which form the core of the charge cluster, appear to be particularly important as their mutation in combination results in a complete loss of binding to PIP2 (and a range of other phosphoinositides) and a dramatic shift (~+60 mV) in the V0.5. Given that the charged residues we have identified in KCNQ1 appear in general to be well conserved in homologous positions in the other members of the KCNQ family it raises the possibility that the effects of PIP2 on these channels could also be mediated through similarly located charge clusters. To investigate this possibility we have recently, in collaboration, analysed whether the mutation, to alanine, of homologous residues in KCNQ2 acts to alter this channels response to PIP2. Interestingly, the mutation of Arg-325 (which is homologous to Arg-360 in KCNQ1) results in a ~60% reduction in current density, without change in the V0.5, and an approximately eight-fold reduction in the sensitivity of the channel to activation by an exogenously applied water soluble derivative of PIP2. In summary, we have identified that charged residues located in the proximal C-terminus of KCNQ1 and in a homologous region in KCNQ2 are involved in regulating the response of these channels to PIP2. Whether the actions of PIP2 on the remaining members of the KCNQ family are mediated through similarly located charge clusters remains to be determined.