SP1 (transcription factor Sp1) participates in the transcriptional regulation of Slc2a4 mediated by estrogen receptor ER-alpha in 3T3-L1 adipocytes

Author(s)

João Nilton Barreto Andrade

• Document type: Master's Dissertation
• Press: São Paulo.
• Institution: Universidade de São Paulo (USP). Faculdade de Medicina (FM/SBD)
• Defense date: 2018-05-15

Examining board members

Ubiratan Fabres Machado; Fabiana de Sant'Anna Evangelista; Maria Lucia Cardillo Correa Giannella

• Advisor: Ubiratan Fabres Machado

Abstract

Type 2 diabetes mellitus (T2DM) is characterized by insulin resistance, which can be modulated by estrogen in both females and males. In this process, the glucose transporter GLUT4 (solute carrier family 2 member 4 gene - Slc2a4) plays an important role, since increasing GLUT4 expression improves glycemic control. Estradiol (E2) regulates the expression of Slc2a4, by a mechanism in which estrogen receptors (ERs) play opposite effects: ER-alpha stimulates, whereas ER-beta inhibits the expression. Transcriptional effects of ERs involve co-regulators, notably the transcription factor SP1, a powerful enhancer of Slc2a4. However, the role of SP1 in the ERs-mediated regulation of Slc2a4 is unknown; and that was the aim of the present study. Differentiated adipocytes 3T3-L1 were treated (24 hours) with E2, ER-alpha agonist (PPT) or ER-beta agonist (DPN). It was analyzed: gene expression (RT-qPCR) of Slc2a4 and Sp1; total content o GLUT4 and nuclear content of ER-alpha/beta and SP1 (Western blotting); binding activity of SP1 into Slc2a4 promoter (electrophoretic mobility shift assay); and content of nuclear SP1/ER-alpha complexes (immunoprecipitation). Results confirmed that E2 increases the expression of Slc2a4/GLUT4, by the dominant effect of ER-alpha. The ER-alpha agonist PPT increased the nuclear content of SP1, the interaction of SP1/ER-alpha, and the binding activity of SP1 into the Slc2a4. The agonist DPN evinced that ER-beta activity does not involve the SP1. In conclusion, the enhancer effect of ER-alpha upon Slc2a4 gene expression involves a transactivation mechanism via SP1. This observation point outs the cooperation of ER-alpha/SP1 as a new target for the development of approaches to treat insulin resistance and T2DM (AU)

• FAPESP's process: 15/18715-1 - Participation of the transcription factor SP1 in estradiolinduced regulation of Slc2a4/GLUT4 expression in adipocytes 3T3L1
• Grantee: João Nilton Barreto Andrade
• Support Opportunities: Scholarships in Brazil - Master