Modulation of phospholipase A2 by electrostatic fields and dipole potential of glycosphingolipids in monolayers

Bruno Maggio

doi:10.1016/s0022-2275(20)32128-3

Abstract

Phospholipase A2 activity against mixed monolayers of dilauroylphosphatidic acid or dilauroylphosphatidylcholine with glycosphingolipids can be reversibly modulated by external constant electrostatic fields. The changes of enzymatic activity are correlated to the depolarization or hyperpolarization of the film caused by specific dipolar properties of glycosphingolipids. Hyperpolarizing fields enhance the enzymatic activity against pure dilauroylphosphatidic acid while depolarizing fields induce a decrease of activity. Compared to the pure substrate, the interface of mixed films containing neutral glycosphingolipids or gangliosides is already partially depolarized and the magnitude of activation induced by an external hyperpolarizing field is decreased; conversely, depolarizing fields cause an increased inhibition of activity. Differing from gangliosides, sulfatides bring about a hyperpolarization of the mixed lipid monolayer and external hyperpolarizing or depolarizing fields cause enhanced activation and reduced inhibition, respectively. The effects of glycosphingolipids depend on their relative proportion in the monolayer. Results were similar with dilauroylphosphosphatidylcholine but the field effects were less than half of those found with dilauroylphosphatidic acid. Our work shows that the activity of phospholipase A2 in addition to responding reversibly to external electrostatic fields, is directly modulated by the polarity and magnitude of the lipid polar head group dipole moments.—Maggio, B. Modulation of phospholipase A2 by electrostatic fields and dipole potential of glycosphingolipids in monolayers. J. Lipid Res. 1999. 40: 930–939.

Highlights

Phospholipase A2 activity against mixed monolayers of dilauroylphosphatidic acid or dilauroylphosphatidylcholine with glycosphingolipids can be reversibly modulated by external constant electrostatic fields
The resultant molecular dipole moment of the oligosaccharide moiety of most neutral glycosphingolipids and gangliosides points toward the opposite direction, to that of the hydrocarbon portion, and its Abbreviations: PLA2, phospholipase A2, porcine phospholipase A2 (EC 3.1.1.4); dlPA didocecanoyl-sn-glycero-3phosphatidic acid; dlPG didodecanoyl-snglycero-3-phosphatidylglycerol; dlPC didodecanoyl-sn-glycero-3-phosphocholine; ceramide, N-acyl-sphingosine; GalCer Glc␤1-1ЈCer; asialo-GM1, Gg4Cer, Gal␤13GalNAc ␤1-4-Gal ␤1-4Glc␤1-1ЈCer; Sulf (sulfatide 3 O-SO3-Gal␤1-1ЈCer; GMl Gal␤1-3GalNAc ␤1-4-Gal(3-2␣NeuAc) ␤14Glc␤1-1ЈCer; GDla NeuAc␣2-3Gal␤1-3GalNAc␤1-4Gal(3-2␣NeuAc) ␤1-4Glc␤1-1ЈCer
We previously showed that the activation or inhibition of PLA2 activity by glycosphingolipids was exerted directly at the interfacial level, most probably through changes induced by modification of the substrate intermolecular organization [21, 23, 33]

Summary

Introduction

Phospholipase A2 activity against mixed monolayers of dilauroylphosphatidic acid or dilauroylphosphatidylcholine with glycosphingolipids can be reversibly modulated by external constant electrostatic fields. Evidence has grown steadily showing that constant or alternating electromagnetic fields of different intensity can induce dramatic effects in biosystems [1] This should not be surprising in view of the marked molecular and supramolecular structural anisotropy, which implies electrostatic dipolar anisotropy that is inherent to biological molecules. Oriented polarized molecules when exposed to constant or alternating electrostatic fields can respond with different effects These include dynamic modifications of membrane topology (4 –6), cellular function [7, 8], protein phosphorylation [9], transmembrane fluxes of ions and metabolites [10], as well as activation of membrane enzymes that are naturally part of (or become associated to) a lipid interface in order to exhibit activity [11,12,13,14]. The resultant molecular dipole moment of the oligosaccharide moiety of most neutral glycosphingolipids and gangliosides points toward the opposite direction, to that of the hydrocarbon portion, and its Abbreviations: PLA2, phospholipase A2, porcine phospholipase A2 (EC 3.1.1.4); dlPA (dilauroylphosphatidic acid) didocecanoyl-sn-glycero-3phosphatidic acid; dlPG (dilauroylphosphatidylglycerol) didodecanoyl-snglycero-3-phosphatidylglycerol; dlPC (dipalmitoylphosphatidylcholine) didodecanoyl-sn-glycero-3-phosphocholine; ceramide, N-acyl-sphingosine; GalCer (galactosylceramide) Glc␤1-1ЈCer; asialo-GM1, Gg4Cer, Gal␤13GalNAc ␤1-4-Gal ␤1-4Glc␤1-1ЈCer; Sulf (sulfatide 3 O-SO3-Gal␤1-1ЈCer; GMl (monosialoganglioside) Gal␤1-3GalNAc ␤1-4-Gal(3-2␣NeuAc) ␤14Glc␤1-1ЈCer; GDla (disialoganglioside) NeuAc␣2-3Gal␤1-3GalNAc␤1-4Gal(3-2␣NeuAc) ␤1-4Glc␤1-1ЈCer

Methods

Results

Conclusion