Proteomic Profiling of Cytosolic Glutathione Transferases from Three Bivalve Species: Corbicula fluminea, Mytilus galloprovincialis and Anodonta cygnea

José Martins,Vítor Vasconcelos,Hugo Osório,Rute Da Fonseca,Alexandre Campos

doi:10.3390/ijms15021887

Abstract

Suspension-feeding bivalves are considered efficient toxin vectors with a relative insensitivity to toxicants compared to other aquatic organisms. This fact highlights the potential role of detoxification enzymes, such as glutathione transferases (GSTs), in this bivalve resistance. Nevertheless, the GST system has not been extensively described in these organisms. In the present study, cytosolic GSTs isoforms (cGST) were surveyed in three bivalves with different habitats and life strategies: Corbicula fluminea, Anodonta cygnea and Mytilus galloprovincialis. GSTs were purified by glutathione-agarose affinity chromatography, and the collection of expressed cGST classes of each bivalve were identified using a proteomic approach. All the purified extracts were also characterized kinetically. Results reveal variations in cGST subunits collection (diversity and properties) between the three tested bivalves. Using proteomics, four pi-class and two sigma-class GST subunits were identified in M. galloprovincialis. C. fluminea also yielded four pi-class and one sigma-class GST subunits. For A. cygnea, two mu-class and one pi-class GST subunits were identified, these being the first record of GSTs from these freshwater mussels. The affinity purified extracts also show differences regarding enzymatic behavior among species. The variations found in cGST collection and kinetics might justify diverse selective advantages for each bivalve organism.

Highlights

Aquatic organisms are recurrently exposed to numerous environmental contaminants
The knowledge of the diversity of GSTs expressed can be explored in order to identify the specific isoforms involved, individually or not, in xenobiotic transformation and degradation
Superfamily in three different bivalve mollusks with diverse life strategies and habitats. Marine mussels, such as M. galloprovincialis, are suspension feeders commonly living in dense masses at the intertidal and subtidal level of coastal waters and estuaries [27]

Summary

Introduction

Aquatic organisms are recurrently exposed to numerous environmental contaminants. Bivalves, as sessile filter-feeding organisms, are one of the most threatened organisms by these environmental stressors. Glutathione transferases (GSTs) play a significant role in cellular defense against chemically-induced toxicity. Drug-metabolizing enzymes belonging to the GST superfamily are multifunctional phase II proteins primarily involved in the cellular detoxification of both endogenous and exogenous compounds [1]. The GST defensive system acts mainly by catalyzing the conjugation of the thiol group of reduced glutathione (GSH) with the electrophilic sites of noxious compounds [2]. This represents the first step of the mercapturic acid detoxification pathway, resulting in more water soluble peptide derivatives than the parent toxin [3].

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Conclusion