GSK3β mediates muscle pathology in myotonic dystrophy
Karlie Jones, Christina Wei, Polina Iakova, Enrico Bugiardini, Christiane Schneider-Gold, Giovanni Meola, James Woodgett, James Killian, Nikolai A. Timchenko, Lubov T. Timchenko
Karlie Jones, Christina Wei, Polina Iakova, Enrico Bugiardini, Christiane Schneider-Gold, Giovanni Meola, James Woodgett, James Killian, Nikolai A. Timchenko, Lubov T. Timchenko
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Research Article Muscle biology

GSK3β mediates muscle pathology in myotonic dystrophy

Abstract

Myotonic dystrophy type 1 (DM1) is a complex neuromuscular disease characterized by skeletal muscle wasting, weakness, and myotonia. DM1 is caused by the accumulation of CUG repeats, which alter the biological activities of RNA-binding proteins, including CUG-binding protein 1 (CUGBP1). CUGBP1 is an important skeletal muscle translational regulator that is activated by cyclin D3–dependent kinase 4 (CDK4). Here we show that mutant CUG repeats suppress Cdk4 signaling by increasing the stability and activity of glycogen synthase kinase 3β (GSK3β). Using a mouse model of DM1 (HSALR), we found that CUG repeats in the 3′ untranslated region (UTR) of human skeletal actin increase active GSK3β in skeletal muscle of mice, prior to the development of skeletal muscle weakness. Inhibition of GSK3β in both DM1 cell culture and mouse models corrected cyclin D3 levels and reduced muscle weakness and myotonia in DM1 mice. Our data predict that compounds normalizing GSK3β activity might be beneficial for improvement of muscle function in patients with DM1.

Authors

Karlie Jones, Christina Wei, Polina Iakova, Enrico Bugiardini, Christiane Schneider-Gold, Giovanni Meola, James Woodgett, James Killian, Nikolai A. Timchenko, Lubov T. Timchenko

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Figure 5

Inhibition of GSK3β activity corrects cyclin D3 levels in CUG-expressing CHO cells.

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Inhibition of GSK3β activity corrects cyclin D3 levels in CUG-expressing...
(A) Accumulation of mutant CUG repeats elevates active GSK3β and reduces cyclin D3. Western blot analysis of cytoplasmic protein extracts from CHO double-stable CUG-expressing monoclonal cells before addition of Dox (time 0) and at different time points after Dox addition (shown on the top) with antibodies to total GSK3β, p-Y216–GSK3β, total cyclin D3, and β-actin. (B) Ratios of GSK3β and cyclin D3 signals to β-actin (y axis), based on protein expression in A. The standard deviations represent values of 3 experiments. The x axis shows time after Dox addition (in hours). (C) GSK3β is increased at early time points after Dox treatment. Proteins were isolated in 1–7 hours after Dox addition and analyzed by Western blotting with antibodies to total GSK3β and β-actin. (D) The ratios of GSK3β signals to β-actin signals of protein expression shown in C are presented in the y axis. The x axis shows time points after Dox addition. The standard deviations show values of 3 experiments. (E) Lithium normalizes cyclin D3 levels in CUG-expressing CHO cells. Western blot analysis of the protein extracts isolated as described in A, but cells after Dox addition were treated with 20 μM LiCl for 7 hours. (F) Ratios of GSK3β and cyclin D3 signals observed in E to β-actin (y axis). The x axis shows time after Dox addition (in hours). Standard deviations based on 3 repeats are shown.