Figure 1. Acetylation of GSK3β increased in pathological cardiac hypertrophy.

(A) Scatter plot showing cardiac hypertrophy, as measured by Heart weight/Tibia Length (HW/TL) ratio of 8 weeks old 129/Sv mice treated with either vehicle or isoproterenol (ISO) at the dose of 10 mg/kg/day. ISO was continuously infused for 7 days using osmotic mini-pumps. n = 9–10 mice per group. Data is presented as mean ± s.d, *p<0.05. Student’s t test was used to calculate the p values. (B) Scatter plot representing left ventricular posterior wall thickness of 8 weeks old 129/Sv mice treated with either vehicle or ISO at the dose of 10 mg/kg/day. ISO was continuously infused for 7 days using osmotic mini-pumps. n = 6 mice per group. Data is presented as mean ± s.d, *p<0.05. Student’s t test was used to calculate the p values. (C) Scatter plot indicating the contractile functions of heart as represented by ejection fraction of 8 weeks old 129/Sv mice treated with either vehicle or ISO at the dose of 10 mg/kg/day. ISO was continuously infused for 7 days using osmotic mini-pumps. n = 6 mice per group. Data is presented as mean ± s.d, *p<0.05. Student’s t test was used to calculate the p values. (D) Histogram showing GSK3β activity assay in heart lysates of vehicle or ISO-treated 8 weeks old 129/Sv mice. Mice were treated with either vehicle or ISO at the dose of 10 mg/kg/day for 7 days using osmotic mini-pumps. GSK3β was immunoprecipitated from the heart lysates of vehicle or ISO infused mice using anti-GSK3β antibody, clone GSK-4B (Sigma). The immunoprecipitated GSK3β was incubated with the peptide substrate in the presence of γ−³²P-ATP. The incorporation of ³²P into the GSK3β peptide substrate, which contains specific phosphorylation residues of GSK3β was measured. n = 10 mice per group. Data is presented as mean ± s.d, *p<0.05. Student’s t test was used to calculate the p values. (E) Eight weeks old 129/Sv mice were treated with either vehicle or ISO at the dose of 10 mg/kg/day for 7 days using osmotic mini-pumps. GSK3β was immunoprecipitated from the heart lysates of vehicle or ISO infused mice using anti-GSK3β antibody (sc-9166, Santa Cruz Biotechnolgy) and the affinity resin immobilized with protein A/G. Western blotting analysis was performed to detect the levels of GSK3β acetylation (Ac-Lys) by anti-acetyl-lysine antibody. IgG was used as negative control in this assay. Heart tissue lysates (WCL) were probed for indicated proteins by western blotting. ANP was used as a positive control to assess cardiac hypertrophy in ISO infused mice. n = 4 mice per group. # marked western blotting images denotes SIRT2 antibody (#12650; Cell Signaling), used in this assay detects single band. (F) Histogram showing relative acetylated GSK3β in vehicle and ISO-treated mice heart tissues, as measured from Figure 1E. Signal intensities of acetylated GSK3β and GSK3β were measured by densitometry analysis (ImageJ software). n = 4 mice per group. Data is presented as mean ± s.d. *p<0.05. Student’s t test was used to calculate the p values. (G) GSK3β was immunoprecipitated from heart tissues of 8 weeks old 129/Sv mice using anti-GSK3β antibody (sc-9166, Santa Cruz Biotechnology), and the affinity resin with protein A/G immobilized. Western blotting was performed to detect GSK3β interaction with p300 using anti-p300 antibody. IgG was used as a negative control. Whole cell lysates (WCL) were probed for the presence of GSK3β and p300 by western blotting. (H) Co-localization of GSK3β with p300 was assessed in 293 T cells by confocal microscopy. The antibodies used are anti-GSK3β (sc-9166, Santacruz), and p300 (05–257, Millipore). DAPI was used to stain the nucleus. Expanded images (right small boxes) show yellow color in the merge image, indicating the co-localization of GSK3β (Green) and p300 (Red) in the nucleus. (I) In vitro binding assay to test the direct interaction between GSK3β and p300. Recombinant p300 (Millipore # 2273152) was incubated with recombinant GST or GST-GSK3β, purified from E. coli BL21 (DE3) by affinity chromatography using Glutathione Sepharose 4B. (J) Western blotting analysis showing the acetylation and activity of GSK3β in rat neonatal cardiomyocytes infected with adenovirus expressing either luciferase shRNA (control) or p300 shRNA (p300-KD) for 72 hr. Depletion of p300 was confirmed by western blotting. GSK3β was immunoprecipitated from control and p300-KD cells using anti-GSK3β antibody (sc-9166, Santa Cruz Biotechnology) and the affinity resin immobilized with protein A/G. Western blotting was performed to detect acetylation of GSK3β using the anti Ac-Lysine antibody. GSK3β activity was measured by assessing the phosphorylation of glycogen synthase (p–GS). Site-specific antibodies were used to detect the phosphorylation of GSK3β at indicated residues in cardiomyocyte lysates (WCL). (K) Histogram showing the quantification of relative acetylated GSK3β in control and p300 depleted (p300-KD) rat neonatal cardiomyocytes, as measured from Figure 1J. Rat neonatal cardiomyocytes were infected with adenovirus expressing either luciferase shRNA (control) or p300 shRNA (p300-KD) for 72 hr. Signal intensities of acetylated GSK3β and GSK3β were quantified by densitometry analysis (ImageJ software). n = 3 independent experiments. Data is presented as mean ± s.d. *p<0.05. Student’s t test was used to calculate the p values. (L) Histogram depicting the activity of GSK3β in control and p300 depleted (p300-KD) rat neonatal cardiomyocytes, as measured by the ratio of phosphorylation of glycogen synthase vs total glycogen synthase from Figure 1J. Rat neonatal cardiomyocytes were infected with adenovirus expressing either luciferase shRNA (control) or p300 shRNA (p300-KD) for 72 hr. Signal intensities of phospho-glycogen synthase and glycogen synthase were measured by densitometry analysis (ImageJ software). n = 3 independent experiments. Data is presented as mean ± s.d. *p<0.05. Student’s t test was used to calculate the p values. (M) Western blotting analysis showing the acetylation of GSK3β in rat neonatal cardiomyocytes infected with either control (Ad-null) or p300 overexpressing adenovirus (Ad-p300) for 24 hr. Overexpression of p300 was confirmed by western blotting. GSK3β was immunoprecipitated using anti-GSK3β antibody (sc-9166, Santacruz) and the affinity resin with protein A/G immobilized. Site-specific antibodies were used to detect the phosphorylation of GSK3β at indicated residues in cell lysates (WCL). (N) Western blotting analysis showing the activity of GSK3β in rat neonatal cardiomyocytes infected with control (Ad-null) or p300 expressing adenovirus (Ad-p300) for 24 hr. Overexpression of p300 was confirmed by western blotting and the activity of GSK3β was probed by assessing the levels of p-GS and GS by western blotting. (O) Histogram showing the activity of GSK3β in control (Ad-Null) or p300 overexpressing (Ad-p300) rat neonatal cardiomyocytes, as measured by the ratio of phosphorylation of glycogen synthase vs total glycogen synthase from Figure 1N. Signal intensities of phospho-glycogen synthase and glycogen synthase were assessed by densitometry analysis (ImageJ software). n = 3 independent experiments. Data is presented as mean ± s.d. *p<0.05. Student’s t test was used to calculate the p values. (P) In vitro kinase assay showing the activity of acetylated and non-acetylated GSK3β. Human GSK3β with HA tag was overexpressed in HeLa cells by transfection of the plasmid pcDNA3-HA-GSK3β. HA-GSK3β was immunoprecipitated using HA-coupled agarose beads (Sigma-Aldrich) and the HA-GSK3β was acetylated by recombinant p300 (Millipore), in the presence or absence of Acetyl-CoA (Ac-CoA) in HAT buffer. The enzymatic activity of GSK3β was measured against glycogen synthase (GS)-peptide. n = 6 independent experiments. Data is presented as mean ± s.d. *p<0.05. One-way ANOVA was used to calculate the p values.