Arginine methylation of SIRT7 couples glucose sensing with mitochondria biogenesis (2018)
Figure 5

Figure 5. PRMT6 modulates SIRT7 methylation in an AMPK-dependent manner

A. Glucose depletion reduces SIRT7 methylation. MEF cells stably expressing Flag-SIRT7 were cultured in medium depleted with glucose (12 hrs), FBS (12 hrs) or glutamine (24 hrs). R388 methylation of immunopurified SIRT7 and Ampk phosphorylation were determined by western blot. R388 methylation level was normalized to Flag-SIRT7 (Ratio).

B. Glucose starvation decreases R388 methylation of SIRT7 in a time-dependent manner. MEF cells stably expressing Flag-SIRT7 were cultured in glucose-free media as indicated. R388 methylation level of immunopurified SIRT7 was determined by western blot.

C. Glucose dose-dependently upregulates R388 methylation of SIRT7. MEF cells stably expressing Flag-SIRT7 were cultured with increasing concentrations of glucose as indicated for 12 hrs. R388 methylation of SIRT7 and Ampk phosphorylation were determined by western blot.

D. AICAR treatment decreases R388 methylation of SIRT7. MEF cells stably expressing Flag-SIRT7 were treated with or without AICAR for 12 hrs. R388 methylation of immunoprecipitated SIRT7 was determined by western blot.

E-F. AICAR reduces the percentage of R388-methylated endogenous SIRT7 in MEF cells. R388-methylated endogenous SIRT7 was captured from control and AICAR-treated MEF cells by using R388 site-specific methylation antibody (E). Input, output, and immunoprecipitate were analyzed by western blot to quantify the percentage of R388-methylated protein (F) (mean±SD, n=3 experimental replicates).

G. AMPK deletion increases SIRT7 R388 methylation. Flag-tagged SIRT7 was stably expressed in Ampk wildtype (WT) and Ampk α1/α2 double-knockout (DKO) MEF cells and 293A cells. SIRT7 protein was immunopurified with Flag-beads, R388 methylation was determined by western blot.

H. AMPK is required for glucose starvation-induced R388 hypomethylation of SIRT7. Ampk wildtype (WT) and Ampk α1/α2 double-knockout (DKO) MEF cells stably expressing Flag-SIRT7 were cultured with or without glucose for 12 hrs. SIRT7 was purified with Flag-beads and R388 methylation was determined by western blot.

I. PRMT6 is necessary for AMPK-induced SIRT7 hypomethylation. Flag-tagged SIRT7 was stably expressed in scramble control MEF cells or cells expressing two independent shRNAs targeting Prmt6 (#1 and #2). Cells were cultured with or without glucose for 12 hrs. R388 methylation of immunopurified SIRT7 was determined by western blot.

J. PRMT6 is necessary for AMPK-induced SIRT7 hypomethylation. Wildtype MEFs and Ampk DKO cells were treated with PRMT6i for 24 hrs. SIRT7 was purified by Flag-beads, and R388 methylation of SIRT7 was determined by western blot.

K. Both AICAR treatment and glucose depletion impair the association between Prmt6 and Sirt7. MEF cells were cultured with or without glucose and treated with AICAR as indicated. Co-immunoprecipitation was performed using SIRT7 antibody. Input and immunoprecipitates were analyzed by western blot.

L. R388 methylation of SIRT7 does not modulate its phosphorylation. MEF cells stably expressing Flag-tagged wildtype SIRT7 or RK mutant were treated with PRMT6i (24 hrs) and cultured with or without glucose (12 hrs) as indicated. SIRT7 protein was immunopurified with Flag-beads, R388 methylation and phosphorylation of SIRT7 were determined by western blot.