GSK-3β Localizes to the Cardiac Z-Disc to Maintain Length Dependent Activation

Abstract

Background: Altered kinase localization is gaining appreciation as a mechanism of cardiovascular disease. Previous work suggests GSK-3β (glycogen synthase kinase 3β) localizes to and regulates contractile function of the myofilament. We aimed to discover GSK-3β’s in vivo role in regulating myofilament function, the mechanisms involved, and the translational relevance. Methods: Inducible cardiomyocyte-specific GSK-3β knockout mice and left ventricular myocardium from nonfailing and failing human hearts were studied. Results: Skinned cardiomyocytes from knockout mice failed to exhibit calcium sensitization with stretch indicating a loss of length-dependent activation (LDA), the mechanism underlying the Frank-Starling Law. Titin acts as a length sensor for LDA, and knockout mice had decreased titin stiffness compared with control mice, explaining the lack of LDA. Knockout mice exhibited no changes in titin isoforms, titin phosphorylation, or other thin filament phosphorylation sites known to affect passive tension or LDA. Mass spectrometry identified several z-disc proteins as myofilament phospho-substrates of GSK-3β. Agreeing with the localization of its targets, GSK-3β that is phosphorylated at Y216 binds to the z-disc. We showed pY216 was necessary and sufficient for z-disc binding using adenoviruses for wild-type, Y216F, and Y216E GSK-3β in neonatal rat ventricular cardiomyocytes. One of GSK-3β’s z-disc targets, abLIM-1 (actin-binding LIM protein 1), binds to the z-disc domains of titin that are important for maintaining passive tension. Genetic knockdown of abLIM-1 via siRNA in human engineered heart tissues resulted in enhancement of LDA, indicating abLIM-1 may act as a negative regulator that is modulated by GSK-3β. Last, GSK-3β myofilament localization was reduced in left ventricular myocardium from failing human hearts, which correlated with depressed LDA. Conclusions: We identified a novel mechanism by which GSK-3β localizes to the myofilament to modulate LDA. Importantly, z-disc GSK-3β levels were reduced in patients with heart failure, indicating z-disc localized GSK-3β is a possible therapeutic target to restore the Frank-Starling mechanism in patients with heart failure.

Small Angle X-ray Diffraction as a Tool for Structural Characterization of Muscle Disease

“…X-ray diffraction has been an important tool in the ongoing quest to understand the structural basis of LDA [ 21 , 42 , 75 , 163 , 169 , 170 , 171 ]. At this time, the detailed mechanism underlying LDA has not been resolved [ 172 ] with seemingly contradictory findings being reported in intact rat myocardium [ 21 , 75 , 169 ] and skinned porcine myocardium [ 42 ]. For a discussion of these current controversies see reference [ 172 ].…”

“…At this time, the detailed mechanism underlying LDA has not been resolved [ 172 ] with seemingly contradictory findings being reported in intact rat myocardium [ 21 , 75 , 169 ] and skinned porcine myocardium [ 42 ]. For a discussion of these current controversies see reference [ 172 ]. A detailed review of the work up to this point is, therefore, beyond the scope of this review article.…”

Combinatorial miRNA1a/15b interference drives adult cardiac regeneration

“…S14D heatmap encompass miR-1a/15b regulated genes that are unaffected or only mildly altered (and below the significance threshold) upon treatment with miR-1a LNAs or miR-15b LNAs individually. Many of the genes within this Unique subgroup are characterized by a role in inducing cardiomyocyte de-differentiation, early cardiac development and remodeling comprising of genes such as T-Box Transcription Factor 20 (TBX20) 38,39 , PR-Domain Zinc Finger Protein 16 (PRDM16) 40 , ADP-Ribosylhydrolase Like 1 (ADPRHL1) 41 , Glycogen Synthase Kinase 3 Beta (GSK3B) 42 , Fibroblast Growth Factor Receptor Substrate 2 (FRS2) 43 , Sorbin And SH3 Domain Containing 2 (SORBS2) 44 , WW Domain Containing Transcription Regulator 1 (WWTR1) 45 and SRY-Box Transcription Factor 9 (SOX9) 46 ( Fig. S14D ).…”

Actin-Binding LIM 1 (ABLIM1) Inhibits Glioblastoma Progression and Serves as a Novel Prognostic Biomarker

“…Additionally, ABLIM1 may interact with GSK-3 β signaling pathways. A recent study demonstrated that GSK-3 β could bind ABLIM1 and modulate its function in cardiovascular cells [ 27 ]. Since the Wnt-GSK-3 β signaling pathway is well known for its tumor-related function, GSK-3 and ABLIM1 probably interact with malignancies.…”