A Drosophila model of insulin resistance associated with the human TRIB3 Q/R polymorphism.

Zachary Fischer,Laramie Pence,Anna Shipman,Jin-Yuan Fan,Rahul Das,Samuel Bouyain,Leonard L Dobens

doi:10.1242/dmm.030619

Zachary Fischer, Laramie Pence + Show 5 more

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https://doi.org/10.1242/dmm.030619

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Abstract

ABSTRACTMembers of the Tribbles family of proteins are conserved pseudokinases with diverse roles in cell growth and proliferation. Both Drosophila Tribbles (Trbl) and vertebrate Trib3 proteins bind to the kinase Akt (Akt1) to block its phosphorylation activation and reduce downstream insulin-stimulated anabolism. A single nucleotide polymorphism (SNP) variant in human TRIB3, which results in a glutamine (Q) to arginine (R) missense mutation in a conserved motif at position 84, confers stronger Akt binding, resulting in reduced Akt phosphorylation, and is associated with a predisposition to Type 2 diabetes, cardiovascular disease, diabetic nephropathy, chronic kidney disease and leukemogenesis. Here, we used a Drosophila model to understand the importance of the conserved R residue in several Trbl functions. In the fly fat body, misexpression of a site-directed Q mutation at position R141 resulted in weakened binding to Drosophila Akt (dAkt), leading to increased levels of phospho-dAkt, increased cell and tissue size, and increases in the levels of stored glycogen and triglycerides. Consistent with the functional conservation of this arginine in modulating Akt activity, mouse Trib3 R84 misexpressed in the fly fat body blocked dAkt phosphorylation with a strength similar to wild-type Trbl. Limited mutational analysis shows that the R141 site dictates the strength of Akt binding but does not affect other Trbl-dependent developmental processes, suggesting a specificity that could serve as a drug target for metabolic diseases.

Highlights

Genetics heavily influence susceptibility to insulin resistance syndrome (Bouret et al, 2015; Eckardt et al, 2011; Frayling et al, 2003; Kahn et al, 2014; Mitchell et al, 1994; Weijnen et al, 2002)
It seems more likely that the consequence of the mutation is to alter the binding of Trib3 to a currently unknown protein at this site and an attractive possibility is Akt, which we have shown is a target of Tribbles in fly tissue
We reported previously that fly Trbl has a conserved role in modulating Akt to regulate the insulin signaling pathway (Das et al, 2014) and, here, we extend these data by demonstrating that a conserved site in Trbl corresponding to an single nucleotide polymorphism (SNP) variant R84 in human TRIB3, which is associated with insulin resistance, is important in the modulation of insulin signaling in flies as well (Prudente et al, 2005)

Summary

Introduction

Genetics heavily influence susceptibility to insulin resistance syndrome (including Type 2 diabetes) (Bouret et al, 2015; Eckardt et al, 2011; Frayling et al, 2003; Kahn et al, 2014; Mitchell et al, 1994; Weijnen et al, 2002). *Present address: Department of Biochemistry, College of Agricultural and Life Sciences, University of Wisconsin-Madison, 433 Babcock Drive, Madison, WI 53706, USA Received 10 May 2017; Accepted 5 October 2017 approaches have identified only a few genes that function in insulin responsive cells, a result that could be caused by poor coverage of genetic markers, environmental influences or problems classifying multifactorial diseases (Prudente et al, 2012a; Visscher et al, 2012; Voight et al, 2010; Zeggini et al, 2008). But complex, role of Akt in mediating insulin-regulated cell growth and survival, it is not surprising that aberrant alteration of Akt activity underlies diabetic metabolic disease (reviewed in Zdychová and Komers, 2005)

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