Lysine methyltransferase SMYD2 promotes cyst growth in autosomal dominant polycystic kidney disease
Linda Xiaoyan Li, Lucy X. Fan, Julie Xia Zhou, Jared J. Grantham, James P. Calvet, Julien Sage, Xiaogang Li
Linda Xiaoyan Li, Lucy X. Fan, Julie Xia Zhou, Jared J. Grantham, James P. Calvet, Julien Sage, Xiaogang Li
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Research Article Genetics Nephrology

Lysine methyltransferase SMYD2 promotes cyst growth in autosomal dominant polycystic kidney disease

Abstract

Autosomal dominant polycystic kidney disease (ADPKD) is driven by mutations in PKD1 and PKD2 genes. Recent work suggests that epigenetic modulation of gene expression and protein function may play a role in ADPKD pathogenesis. In this study, we identified SMYD2, a SET and MYND domain protein with lysine methyltransferase activity, as a regulator of renal cyst growth. SMYD2 was upregulated in renal epithelial cells and tissues from Pkd1-knockout mice as well as in ADPKD patients. SMYD2 deficiency delayed renal cyst growth in postnatal kidneys from Pkd1 mutant mice. Pkd1 and Smyd2 double-knockout mice lived longer than Pkd1-knockout mice. Targeting SMYD2 with its specific inhibitor, AZ505, delayed cyst growth in both early- and later-stage Pkd1 conditional knockout mouse models. SMYD2 carried out its function via methylation and activation of STAT3 and the p65 subunit of NF-κB, leading to increased cystic renal epithelial cell proliferation and survival. We further identified two positive feedback loops that integrate epigenetic regulation and renal inflammation in cyst development: SMYD2/IL-6/STAT3/SMYD2 and SMYD2/TNF-α/NF-κB/SMYD2. These pathways provide mechanisms by which SMYD2 might be induced by cyst fluid IL-6 and TNF-α in ADPKD kidneys. The SMYD2 transcriptional target gene Ptpn13 also linked SMYD2 to other PKD-associated signaling pathways, including ERK, mTOR, and Akt signaling, via PTPN13-mediated phosphorylation.

Authors

Linda Xiaoyan Li, Lucy X. Fan, Julie Xia Zhou, Jared J. Grantham, James P. Calvet, Julien Sage, Xiaogang Li

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Figure 6

Synergistic effects exist among SMYD2, STAT3, and the p65 subunit of NF-κB in Pkd1 mutant renal epithelial cells.

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Synergistic effects exist among SMYD2, STAT3, and the p65 subunit of NF-...
(A) The interaction between STAT3 and p65 was disrupted in Smyd2-knockdown Pkd1-homozygous PN24 cells as examined by co-IP with either anti-STAT3 or anti-p65 antibody, and the methylation of STAT3 and p65 was also decreased in these cells. (B) Inhibition of STAT3 with its inhibitor S3I-201 disrupted the interaction between SMYD2 and NF-κB p65, and decreased p65 methylation and phosphorylation in Pkd1-homozygous PN24 cells. (C) Inhibition of NF-κB with its inhibitor BAY-11-7085 disrupted the interaction between SMYD2 and STAT3, and decreased STAT3 methylation and phosphorylation in Pkd1-homozygous PN24 cells. (D) Potential working models of the synergistic effect among SMYD2, STAT3, and p65. The interaction between SMYD2 and STAT3 may facilitate the recruitment of NF-κB to this complex, leading to the methylation (me) and phosphorylation of NF-κB (left panel); and the interaction between SMYD2 and NF-κB may facilitate the recruitment of STAT3 to this complex, leading to the methylation and phosphorylation of STAT3 (right panel), in Pkd1 mutant renal epithelial cells. (E and F) Stimulation with cytokines IL-6 (E) and TNF-α (F) induced SMYD2 expression in a time-dependent manner in mIMCD3 cells. (G and H) Western blot analysis of SMYD2 expression in the presence of the STAT3 inhibitor S3I-201 (G) or NF-κB inhibitor BAY-11-7085 (H) in Pkd1-null MEK cells. SMYD2 expression was decreased in Pkd1-null MEK cells treated with these inhibitors in a dose-dependent manner. (I) STAT3 and p65 bound to the promoter of Smyd2. ChIP-qPCR assay was performed with anti-STAT3 antibody, anti-p65 antibody, or normal rabbit IgG in Pkd1-null MEK cells. Anti-H3K4me2 antibody was used as a positive control.