Title

Modular nature of the main domains in voltage sensitive phosphatases

ORCiD

Carlos A. Villalba-Galea: 0000-0002-6489-4651

Document Type

Poster

Conference Title/Conference Publication

Biophysical Journal

Organization

Biophysical Society 54th Annual Meeting

Location

San Francisco, CA

Conference Dates

February 20-24, 2010

Date of Presentation

2-20-2010

ISSN

0006-3495

Volume

98

Issue

3, Supplement 1

DOI

10.1016/j.bpj.2009.12.1700

First Page

313a

Abstract

Voltage Sensitive Phosphatases (VSPs) constitute a family of enzymes controlled by membrane potential. Its members have a Voltage Sensing Domain (VSD) in the N-terminus and a Phosphatase Domain (PD) in their C-terminus, both connected by a Phospholipid Binding Motif (PBM). Remarkably, N- and C-terminal domains display high homology to two different types of proteins. The VSD of VSPs resembles the VSD of voltage gated channels; while their PD shares a striking homology to the tumor suppressor phosphoinositide phosphatase PTEN. This feature of VSPs makes them look like natural chimeras. Recently, it has been shown that the catalytic activity of Ci-VSP, a member of the VSP family, depends on the binding of the PBM onto the membrane, which is, in turn, controlled by the membrane potential-driven movement of the VSD. For PTEN, it is known that the binding of PTEN onto the plasma membrane mediated by its N-terminus is sine qua non for enzymatic activity.Based on this similarity, we built a chimera by replacing the PD of Ci-VSP by PTEN. This chimera, Ci-VSPTEN, was successfully expressed in Xenopus oocytes and displayed sensing currents resembling those observed in Ci-VSP. As for its enzymatic characteristics, Ci-VSPTEN was expressed in CHO cells and its activity tested by measuring membrane association of GFP-tagged phosphoinositide sensors by TIRF microscopy. Depolarization-induced decline in membrane fluorescence indicated that Ci-VSPTEN has voltage dependent PI(3,4,5)P3 3’-phosphatase activity. Because the binding of the PBM induces an allosteric activation of PTEN, these observations strongly support the idea that the binding of the PBM onto the membrane is a key step in the activation of Ci-VSP. In a broader view, these results show that the VSD and the PD of Ci-VSP, and presumably other VSPs, are naturally modular. (Support: GM030376, DFG OL240/2)

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