Effects of site specific phosphorylation on the structure and functions of the glucocorticoid receptor

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Effects of site specific phosphorylation on the structure and functions of the glucocorticoid receptor

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Title: Effects of site specific phosphorylation on the structure and functions of the glucocorticoid receptor
Author: Anna Magdalena Stwora de Garza
Abstract: Ligand dependant transcription factors, like nuclear hormone receptors (NHRs), are capable of exerting transcriptional regulation in the nucleus in response to various intra- and extracellular signals. Transcription factors contain segments that are intrinsically disordered (ID) under native conditions. Posttranslational modifications, such as phosphorylation, affect protein stability and activity of proteins. Conformational changes of such disordered domains have been shown to facilitate binding of one or more coregulatory proteins. The glucocorticoid receptor (GR) belongs to the NHR super family and contains such an ID domain in its N-terminal region, the AF1. This transactivation domain must interact with co-regulators for optimal activity and contains most of the conserved phosphorylation sites (S203, S211, and S226) in the human GR. Published data has linked site-specific phosphorylation of the GR to physiological functions of the GR in a leukemia cell line model (5). This project’s aims were to study how site-specific phosphorylation affects the structure and function of the glucocorticoid receptor. The aims of the project were: 1) to test the effect of site-specific phosphorylation on the conformation of the recombinant AF1 domain of the human GR, 2) to test the effects of site-specific phosphorylation on the interactions of AF1 with specific coregulatory proteins and the subsequent changes in transcriptional activity in CV-1 cells, and 3) to test if site-specific phosphorylation of the GR is controlled by MAPK activity and if this phosphorylation is sufficient to restore lost GR function in refractory hematological malignancies. \r\n We show for the first time, that ID AF1 domain of glucocorticoid receptor (GR) adopts a functionally folded conformation due to site-specific (S211) phosphorylation by p38 MAPK that we have earlier shown to be involved in the apoptotic and gene-inductive events initiated by GR. These conformational changes are important for AF1s interaction with coregulatory proteins, and subsequent GRE mediated transcriptional activity of the GR. \r\n Finally, these conformational changes are important for AF1s interaction with coregulatory proteins, and subsequent GRE mediated transcriptional activity of the GR. This activating phosphorylation, specifically S211, is controlled by balanced MAPK activity in in vitro cell line models providing and additional mechanism for resistance. Where phosphorylated p38 levels are high relative to low ERK and JNK activity levels. Further suggesting that p38 MAPK activity plays a role in structural and functional consequences of the GR. \r\n
URI: http://hdl.handle.net/2152.3/296
Date: 2008-09-04

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