Award Date

5-1-2015

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry and Biochemistry

First Committee Member

Ronald K. Gary

Second Committee Member

Bryan L. Spangelo

Third Committee Member

Balakrishnan Naduvalath

Fourth Committee Member

Ernesto Abel-Santos

Fifth Committee Member

Helen J. Wing

Number of Pages

277

Abstract

Glycogen Synthase Kinase-3β (GSK-3β) is an important serine/threonine kinase that phosphorylates/regulates diverse and metabolically important proteins. Some of the important substrates of GSK-3β are glycogen synthase, tau, β-catenin, cyclin D1, axin, c-jun, c-myc, Heat Shock Factor–1, BCL-3, CREB, Histone H1.5, mdm2, p21 (CIP1), pyruvate dehydrogenase and many more. De-regulation of GSK-3β has been implicated in diseases like cancer, Alzheimer’s disease, bipolar disorder and type 2 diabetes mellitus. Currently, GSK-3β is one of the most widely studied proteins and there is a great interest in developing potent and efficient GSK-3β-inhibitors for research as well as therapeutic purposes. We demonstrate that beryllium in the form of BeSO4 salt is a much more potent GSK-3β-inhibitor compared to LiCl.

We observed that one of the unique properties of beryllium is its modus operandi to regulate the inhibitory Ser-9 phosphorylation of GSK-3β in a cell type specific manner. Our study for the first time validates the potential of beryllium to function as a biologically relevant GSK-3β-inhibitor. Beryllium induces a decrease in the phosphorylation of glycogen synthase in cultured NIH/3T3 cells. This decrease in phosphorylated form of glycogen synthase demonstrates the ability of beryllium to inhibit GSK-3β’s kinase activity in treated cells. One of the most important substrates in relation to GSK-3β’s inhibition is β-catenin – one of the downstream effector molecules of the Wnt signaling pathway. Our results in NIH/3T3 and A172 cells indicate that beryllium has minimal effect on Wnt signaling/ β-catenin pathway compared to other established GSK-3β-inhibitors. The minimal effect of beryllium at physiologically effective concentrations on Wnt signaling/β-catenin pathway indicates that it could be a more pathway specific inhibitor. One of the most intriguing discoveries of our study has been the lithium induced increase in the phosphorylated form of β-catenin, which is against the “accepted dogma”. Here we propose an alternative model explaining the regulation of the Wnt/β-catenin signaling pathway by lithium.

Use of GSK-3β-inhibitors for therapeutic purposes presents the risk of inducing cancer in patients due to accumulation of β-catenin, an oncogene activator. The unique ability of beryllium to repress the kinase activity of GSK-3β without inducing a heavy nuclear localization of β-catenin might provide an opportunity to develop a potentially potent, efficient, pathway-specific and biologically active GSK-3β inhibitor with minimal adverse effects.

Keywords

Beryllium; Beryllium compounds; β-Catenin; Catenin; Glycogen synthase kinase-3; Glycogen Synthase Kinase - 3β; Lithium; Lithium chloride; Ser-9 phosphorylation; Phosphorylation; Protein-tyrosine kinase – Inhibitors; Serine

Disciplines

Biochemistry | Chemistry

Language

English


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