Isoflurane Enhances the Moonlighting Activity of GAPDH: Implications for GABAA Receptor Trafficking

Andrew J Montalbano,Eugene E Fibuch,Christopher S Theisen,Norbert W Seidler

doi:10.5402/2012/970795

Andrew J Montalbano, Eugene E Fibuch + Show 2 more

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https://doi.org/10.5402/2012/970795

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Abstract

GABAA receptor activity is directly modulated by glyceraldehyde 3-phosphate dehydrogenase (GAPDH), a protein with many nonglycolytic moonlighting functions. In addition to playing a role in the phosphorylation of the receptor, GAPDH may also participate in proper receptor trafficking to the plasma membrane. We previously showed that volatile anesthetics affect GAPDH structure and function that may contribute to the manner by which GAPDH modulates the GABAA receptor. In the current study, GAPDH interacted with engineered phospholipid-containing vesicles, preferring association with phosphatidylserine over phosphatidylcholine. Phosphatidyl-serine is known to participate in membrane trafficking of transport proteins and to play a role in GABAA receptor stability and function. We observed that GAPDH promoted the self-association and fusion of phosphatidyl-serine-rich vesicles as well as decreased membrane fluidity. Isoflurane enhanced each of these GAPDH-mediated events. Isoflurane also increased the binding of GAPDH to the cytoplasmic loop of the GABAA receptor. These observations are consistent with the working model of isoflurane playing a role in the trafficking of membrane proteins. This study is the first to implicate GAPDH and isoflurane in the regulation of GABAA receptor localization, providing insight into the mechanism of action of anesthesia.

Highlights

The activity of the GABAA receptor is modulated directly by glyceraldehyde 3-phosphate dehydrogenase (GAPDH) [1], which participates in the local production of ATP followed by phosphotransferase activity involving the phosphorylation of the cytoplasmic loop of the α-subunit of the GABAA receptor
We examined the interaction of GAPDH with unilamellar vesicles (ULVs) by incubating GAPDH (5 μM) and ULVs (240 μg/mL) briefly (2 min) prior to determining enzyme activity
In the presence of ULVs made from 90% dioleoyl phosphatidylcholine (DOPC) and 10% dioleoyl phosphatidylserine (DOPS), designated as PC-rich vesicles, there was no change in GAPDH enzyme activity with and without ULVs (Figure 1(a))

Summary

Introduction

The activity of the GABAA receptor is modulated directly by glyceraldehyde 3-phosphate dehydrogenase (GAPDH) [1], which participates in the local production of ATP followed by phosphotransferase activity involving the phosphorylation of the cytoplasmic loop of the α-subunit of the GABAA receptor. We previously showed that volatile anesthetics affect GAPDH structure and function [3, 4]. Others have showed that volatile agents influence the oxidoreductase activity of GAPDH [5, 6]. These observations support the concept that volatile anesthetic agents bind to GAPDH. We propose that the binding of anesthetic agents to GAPDH may contribute to the manner by which GAPDH modulates the GABAA receptor

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