Controlling the Activity of a Phosphatase and Tensin Homolog (PTEN) by Membrane Potential

Abstract

The recently discovered voltage-sensitive phosphatases (VSPs) hydrolyze phosphoinositides upon depolarization of the membrane potential, thus representing a novel principle for the transduction of electrical activity into biochemical signals. Here, we demonstrate the possibility to confer voltage sensitivity to cytosolic enzymes. By fusing the tumor suppressor PTEN to the voltage sensor of the prototypic VSP from Ciona intestinalis, Ci-VSP, we generated chimeric proteins that are voltage-sensitive and display PTEN-like enzymatic activity in a strictly depolarization-dependent manner in vivo. Functional coupling of the exogenous enzymatic activity to the voltage sensor is mediated by a phospholipid-binding motif at the interface between voltage sensor and catalytic domains. Our findings reveal that the main domains of VSPs and related phosphoinositide phosphatases are intrinsically modular and define structural requirements for coupling of enzymatic activity to a voltage sensor domain. A key feature of this prototype of novel engineered voltage-sensitive enzymes, termed Ci-VSPTEN, is the novel ability to switch enzymatic activity of PTEN rapidly and reversibly. We demonstrate that experimental control of Ci-VSPTEN can be obtained either by electrophysiological techniques or more general techniques, using potassium-induced depolarization of intact cells. Thus, Ci-VSPTEN provides a novel approach for studying the complex mechanism of activation, cellular control, and pharmacology of this important tumor suppressor. Moreover, by inducing temporally precise perturbation of phosphoinositide concentrations, Ci-VSPTEN will be useful for probing the role and specificity of these messengers in many cellular processes and to analyze the timing of phosphoinositide signaling.