Electrifying Phosphatases

Richard Horn^*

Department of Physiology, Institute of Hyperexcitability, Jefferson Medical College, 1020 Locust Street, Philadelphia, PA 19107, USA.

Summary: Ci-VSP, a recently described protein with sequence similarity to both the voltage-sensing domain of a voltage-gated potassium channel and the phosphatase PTEN, functions as a transmembrane phosphoinositide phosphatase that is regulated by changes in voltage across the plasma membrane. Ci-VSP dephosphorylated phosphatidylinositol-3,4,5-trisphosphate [PtdIns(3,4,5)P₃] in vitro, exhibited capacitative currents that resembled ion channel gating currents, and, when coexpressed with potassium channels that are regulated by PtdIns(4,5)P₂, conferred sensitivity of potassium current amplitude to prolonged changes in membrane potential. How the voltage-sensing (VS) domain of Ci-VSP communicates with the phosphatase domain, and how the VS domain moves its charges across the membrane electric field in the absence of a transmembrane pore domain, remain to be determined.

*E-mail: richard.horn{at}jefferson.edu

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