Phosphoinositide phosphatases: emerging roles as voltage sensors?

During a genomic survey of the transparent sea squirt (Ciona intestinalis), Murata et al. discovered a gene that encodes a protein containing homologous sequences to both a CX(5)R phosphatase and an ion channel. The authors named the novel protein, C. intestinalis voltage-sensor-containing phosphatase, Ci-VSP. The N terminus of Ci-VSP appears to function as a voltage-gated sensor; the C terminus functions as a phosphoinositide phosphatase. The authors suggest that when the N-terminal voltage sensor is activated, this in turn activates the phosphatase, which converts PI(3,4,5)P(3) to PI(4,5)P(2). Localized changes in membrane PI(4,5)P(2) levels could then serve to either positively or negatively regulate a variety of ion transporters and channels.