Abstract 4475: SMYD2 inhibitor BAY-598 reveals the giant scaffold AHNAK as a novel multi-methylated substrate

Abstract

Abstract The SET and MYND domain-containing protein 2 (SMYD2) has been reported to mono-methylate several lysine residues on histone and non-histone proteins. Overexpression of SMYD2 has been reported in cancer cell lines as well as in esophageal squamous cell carcinoma (ESCC), bladder carcinoma, gastric cancer and pediatric acute lymphoblastic leukemia patients and correlates with lower survival rates. Although several studies uncovered important roles of SMYD2 in promoting tumorgenesis by protein methylation of key proteins (e.g. p53, PTEN, Rb, PARP), the biology of SMYD2 and its possible role in cancer biology is still far from being fully understood. Therefore, we employed the SMYD2 inhibitor BAY-598 (AACR-2015 abstract 2829, publication in preparation), and used proteomics to find novel substrates of SMYD2 in cancer cells. We confirmed with both BAY-598 and by knockdown experiments that the giant scaffold protein AHNAK is a novel major substrate of SMYD2. Different studies have tried to decipher the function of AHNAK in normal and diseased tissues. AHNAK forms multi-protein complexes acting as a structural scaffold involved in different processes, including calcium channel regulation, cell contact signaling, migration, and tumor metastasis. Interestingly, we found AHNAK to be mono-methylated by SMYD2 on multiple sites in its central repeated domain as well as on its C-terminal domain. BAY-598 potently inhibited methylation at these sites on AHNAK. To further determine the prevalence of AHNAK methylation, we analyzed different cancer cell lines and tissues from mice. AHNAK methylation correlated with SMYD2 expression, but not with AHNAK expression, suggesting tissue-specific regulation of AHNAK methylation by SMYD2. In summary, the novel finding of AHNAK regulation by methylation further complements the understanding of the roles of SMYD2 in cancer biology and underlines the utility of using probe inhibitors like BAY-598 to explore potential therapeutic targets in cancer. Citation Format: Erik Eggert, Timo Stellfeld, Daniel Korr, Carlo Stresemann. SMYD2 inhibitor BAY-598 reveals the giant scaffold AHNAK as a novel multi-methylated substrate. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4475.