Roles of a serine/threonine-specific phosphatase in steroid receptor function

Lead Research Organisation: University of Dundee
Department Name: College of Life Sciences

Abstract

Glucocorticoids are widely used for the treatment of inflammatory and autoimmune diseases, but their use is limited by side effects, which include fat deposits and impaired use of blood sugar. The protein within tissues, which binds the glucocorticoids is the glucocorticoid receptor, but its interactions with other proteins and how the glucocortcoid receptor complexes regulate cell function are incompletely understood. My recent research has shown that a protein phosphatase, called Ppp5, which removes phosphate from proteins, may be crucial for the normal function of the glucocorticoid receptor in vivo. The aims of this project are to employ tissues from a mouse model that I have made in which Ppp5 does not work. This new mouse line provides an important and unique opportunity to understand how Ppp5 controls the body's response to glucocorticoids.

Technical Summary

Abstract of Research
Glucocorticoids are widely used to treat inflammatory and autoimmune disorders, but their use is limited by side effects, which include metabolic derangements such as central adiposity, glucose intolerance and insulin resistance. Glucocorticoids bind to the glucocorticoid receptor (GR), their mechanisms of action and cell-type specific signalling are only partially understood. GR complexes are thought to comprise a receptor polypeptide, heat shock protein (Hsp) 90 and one of four tetratricopeptide repeat (TPR) proteins that include protein phosphatase, Ppp5. The latter is the only phosphatase encoded by the human genome that contains a TPR domain. Other laboratories have reported that Ppp5 interacts with the GR and, based on overexpression and RNA knockdown studies, they have reported that Ppp5 modulates GR function. I have recently developed a mouse line in which wild type Ppp5 is replaced by a catalytically inactive mutant, Ppp5KI, and the aim of the project to exploit this new powerful knock-in model to establish the role that Ppp5 plays in regulating GR function in vivo in order to ascertain whether modulating Ppp5 activity by a pharmaceutical may be useful.

Publications

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Title Antibodies 
Description Antibodies have been raised, which recognize mouse protein phosphatase 5 (Ppp5/PP5). 
Type Of Material Antibody 
Year Produced 2011 
Provided To Others? Yes  
Impact The antibodies enable the expression levels and interactions of Ppp5 in the transgenic mouse to be ascertained. 
 
Title Mouse model (Ppp5KI) 
Description Mouse model in which the gene expressing the protein phosphatase Ppp5 is replaced by a gene expressing Ppp5 in which aspartic acid 274 is replaced by alanine. Ppp5Asp274Ala is essentially inactive (expressing <0.3 % of the wild type enzyme activity). 
Type Of Material Model of mechanisms or symptoms - mammalian in vivo 
Year Produced 2014 
Provided To Others? Yes  
Impact The Ppp5KI mouse model exhibits decreased weight gain compared with controls, alteration of glucocorticoid receptor function and decreased abdominal adipose tissue. 
 
Description Assessment of mouse phenotype by magnetic resonance imaging 
Organisation University of Dundee
Department Biological Chemistry and Drug Discovery (BCDD)
Country United Kingdom 
Sector Academic/University 
PI Contribution The mouse model was provided by my research and my postdoctoral research assistant performed the biochemical and cell culture experiments. and we discussed the interpretation of the data.
Collaborator Contribution Collaborator provided the experimental procedure and expertise for analysis of the mouse model by magnetic resonance imaging.
Impact The studies strongly supported initial dissection indicating decreased weight of fat pads in the mutant mouse .
Start Year 2010