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Biochemical and cellular characterization of Kidney-type glutaminase with their interaction partners

Author(s):
Emerson Rodrigo Machi Gomes
Total Authors: 1
Document type: Master's Dissertation
Institution: Universidade Estadual de Campinas (UNICAMP). Faculdade de Ciências Médicas
Defense date:
Examining board members:
Ana Carolina Migliorini Figueira; Wilson Nadruz Junior
Advisor: Sandra Martha Gomes Dias
Abstract

Tumor cells have an increased metabolic autonomy compared to non-transformed cells, metabolizing nutrients and incorporating them through pathways that support cell growth and proliferation. The focus of this study was the glutaminase enzyme, which processes glutamine to glutamate for subsequent production of alpha-ketoglutarate, by the glutamate dehydrogenase enzyme, replenishing TCA cycle and bearing its function and the generation of metabolites essential for the synthesis of macromolecules. The gene GLS1 codes for the isoforms kidney-type glutaminase (KGA) and glutaminase C (GAC). These proteins exhibit other domains besides the catalytic, and in the case of KGA, ankirin repeats, known to be involved in protein-protein contacts. The goal of this project was to investigate potential interacting partners of KGA and contextualize the interaction within the metabolic demands of tumor cells. A candidate initially evaluated, the Aldolase A, was not confirmed as a partner of interaction. Another candidate, the BNIP-H, despite having been shown to interact with the KGA in nervous cells, showed no evidence of interaction with KGA in one tested breast cancer cell lines. Finally, yeast two-hybrid studies revealed the nuclear receptor peroxisome proliferator-activated receptor gamma (PPARγ) as a strong interaction partner candidate. We mapped the domains responsible for the interaction between these two proteins, also by two-hybrid and identified the LBD domain of PPARγ as involved in the interaction. The same studies with KGA fragments, although incomplete, showed that the interaction did not involve the carboxy-terminal domain of the enzyme. KGA and PPARγ proteins were expressed in E. coli, purified and their interaction was analyzed by pull-down, fluorescence anisotropy, electrophoresis under native conditions, gel filtration chromatography and crosslinking. The assays indicated that the interaction is favored by the presence of the reaction product glutamate and has a Kd of 4,6 ± 0,5 μM and disfavored by phosphate. Immunogold labeling followed by transmission electron microscopy of SKBR3 cells revealed a curious nuclear staining pattern probably heterochromatic of KGA. Immunofluorescence confocal microscopy showed that both proteins co-localize in the cytoplasm but not in the nucleus. Moreover, it was found that in HEK 293T cells, the presence of KGA decreases PPARγ ability of inducing transactivation of a reporter gene, while PC3 cell overexpressing KGA have low levels of protein expression ACADL target this receptor. Likewise, activity in vitro assays in the presence of KGA showed that PPAR receptor inhibits the glutaminase activity. Our results demonstrate the in vitro interaction between proteins KGA-PPARγ and the potential functional influence that these proteins exerts on each other. Given the involvement of both proteins in the tumor growth, it is speculated that this interaction may have impact on the development of cancer. (AU)

FAPESP's process: 10/13992-3 - Biochemical and cellular characterization of the Kidney-Type Glutaminase in complex with its partners
Grantee:Emerson Rodrigo Machi Gomes
Support type: Scholarships in Brazil - Master