Observing rapid phosphatidylinositol 3,4-bisphosphate kinetics during activation of voltage-sensing phosphatase (VSP) in mammalian cells using total internal reflection microscopy at high frame rates.

Abstract

Voltage-sensing phosphatases (VSPs) are PI(4,5)P2/PI(3,4,5)P3-5- and PI(3,4)P2/PI(3,4,5)P3-3-phosphatases consisting of a voltage sensor domain and a catalytic domain (Halaszovich 2009; Kurokawa 2012). Their catalytic activity is controlled by membrane voltage. The effect of VSPs on PI(3,4)P2 is paradox, as it is produced by the 5-phosphatase activity as well as degraded by the 3-phosphatase activity. Grimm & Isacoff (2016) report a transient increase in PI(3,4)P2 immediately after VSP activation in Ciona intestinalis (Ci-) VSP expressing Xenopus leavis oocytes, detectable using a membrane anchored FRET-based PI(3,4)P2 probe, whereas a diffusible, translocating fluorescent probe could not detect the transient.