Effects of BAG2 and DNAJB6 chaperones on protein degradation in cell models of neurodegenerative diseases

Author(s)

Raquel de Souza Lima

• Document type: Master's Dissertation
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Instituto de Biociências (IBIOC/SB)
• Defense date: 2019-09-18

Examining board members

Merari de Fatima Ramires Ferrari; Marcela Bermudez Echeverry; Marilene Hohmuth Lopes; Luis Eduardo Soares Netto

• Advisor: Merari de Fatima Ramires Ferrari

Abstract

Aging is a worldwide issue and the understanding of the molecular and cellular events associated to this process are crucial for the study of age-related diseases, such as neurodegenerative disorders. The aim of this project was to evaluate the autophagy process in the sporadic neurodegenerative diseases, and also to verify the modulatory aspects of BAG2 and DNAJB6 chaperones upon degradation of specific substrates in different cell models. Rotenone treatment led to autophagy dysfunction prior protein aggregation in hippocampal cells. Experiments using SH-SY5Y cells revealed that rotenone treatment caused tau protein dysfunction associated to a decrease in Pink1 and Parkin protein levels that are fundamental for mitochondrial degradation. Chaperones are an essential component of protein quality control systems. Chaperones act to facilitate protein folding, transport across membranes, remodeling, disaggregation, refolding and/or degradation of clients. BAG2 transfection increased p52/SQSTM1 protein levels in cells from hippocampus and locus coeruleus, which may indicate a role of this cochaperone to specific substrates degradation, interestingly; an opposite result was achieved with the SH-SY5Y differentiated cells, suggesting that BAG2 presents different functions depending on the region, cell type and substrate analyzed. To verify this hypothesis, BAG2 was co-transfected with the ?-synuclein (wild-type, and the A53T mutant) in SH-SY5Y cells. BAG2 overexpression was able to decrease only the A53T protein levels in the differentiated cells, supporting the different role of BAG2 in neuron-like cells. DNAJB6 chaperone was efficient in modulating ?-synuclein protein levels modified with an arginine in the N-terminus region of the protein. This specific result points to a role of the DNAJB6 chaperone in the Nend rule pathway together with the importance of the S/T rich region of the DNAJB6 to the substrate recognition (AU)

• FAPESP's process: 16/04409-9 - Analysis of autophagy and the role of co-chaperone bag-2 upon protein aggregates in neurodegenerative diseases
• Grantee: Raquel de Souza Lima
• Support Opportunities: Scholarships in Brazil - Master