Methylmercury fractionation in muscle and liver tissue of Cichla monoculus from the middle Rio Negro/Amazonas: Study of mercury and selenium interactions using a metalloproteomic approach.

• Grant number: 25/04676-6
• Support Opportunities: Scholarships in Brazil - Doctorate
• Start date: December 01, 2025
• End date: November 30, 2028
• Field of knowledge: Agronomical Sciences - Fishery Resources and Fishery Engineering - Inland Water Fishery Resources
• Principal Investigator: Pedro de Magalhães Padilha
• Grantee: Joyce Andrade da Silva
• Host Institution: Instituto de Biociências (IBB). Universidade Estadual Paulista (UNESP). Campus de Botucatu. Botucatu , SP, Brazil

Abstract

The presence of selenium (Se) can mitigate the deleterious effects of mercury species (HgEPs) in fish. However, the physiological aspects and macromolecular mechanisms related to HgEPs toxicity and the mitigating effect of Se have not been fully elucidated. Therefore, this research proposal aims to investigate changes in the muscle and liver proteome of Cichla monoculus from the middle Rio Negro/Amazonas region to understand HgEPs toxicity and the protective role of Se, with an emphasis on methylmercury (MeHg). This will be achieved using speciation analysis and a metalloproteomics approach. Hg speciation analysis in the muscle, liver, and protein fractions of Cichla monoculus will be performed by graphite furnace atomic absorption spectrometry (GFAAS). The muscle and liver proteomes will be fractionated by two-dimensional electrophoresis (2D PAGE), followed by the mapping of HgEPs in protein spots using GFAAS. Protein spots associated with Hg and Se will then be characterized by liquid chromatography tandem mass spectrometry (LC-MS/MS). Protein abundance analysis will be conducted using Shotgun-LC-MS/MS to identify differentially expressed Hg/Se-metal binding proteins. Additionally, the enzymatic activities of CAT, SOD, and GPx, as well as the concentration of LOOH, will be determined to assess oxidative stress. Finally, ontological analysis of the Hg/Se-metal binding proteins using the STRING software will enable the categorization of biological processes, functions, and cellular compartments. We hope to identify potential biomarkers of mercury toxicity and the mitigating effect of Se in Cichla monoculus.