Thiomyristoyl peptides as cell-permeable Sirt6 inhibitors

Abstract

Sirtuins regulate a variety of biological pathways and inhibitors of sirtuins have been actively pursued as tool compounds to study sirtuin biology and as potential therapeutics. Here we demonstrate that thiomyristoyl peptides are potent and cell-permeable inhibitors of Sirt6, one of the seven human sirtuins, and will serve as starting point for the development of more specific Sirt6 inhibitors.

A SIRT2-Selective Inhibitor Promotes c-Myc Oncoprotein Degradation and Exhibits Broad Anticancer Activity

“…Thioacyl lysine peptides can react with NAD in the sirtuin active site, forming a relatively stable intermediate that inhibits sirtuin (Figure 1A) (Fatkins et al, 2006; Hawse et al, 2008; Smith and Denu, 2007). Recent studies suggested that different sirtuins may have different acyl group specificity (Du et al, 2011; Feldman et al, 2013; et al, 2013a; Zhu et al, 2012), which can be utilized to design inhibitors specific for different sirtuins (He et al, 2012; He et al, 2014). To target the sirtuins that can recognize aliphatic acyl groups, we synthesized four thioacyl lysine compounds, TA (thioacetyl) (Suzuki et al, 2009), TB (thiobutyryl), TH (thioheptanoyl), and TM (thiomyristoyl) (Figure 1B), and then analyzed their ability to inhibit different sirtuins.…”

“…Similarly, TM, but not M, increased the level of α-tubulin acetylation in MDA-MB-231 cells based on immunofluorescence imaging (Figure 4F). SIRT2 has been reported to be not only a deacetylase, but also a defatty-acylase (He et al, 2014; Liu et al, 2014), so we further examined the effect of TM on the defatty-acylase activity of SIRT2 in cells. Metabolic labeling of fatty-acylated proteins revealed that SIRT2 KD (Figure S4B) but not TM (Figure S4C) was able to elevate the fatty-acylation levels of many proteins, suggesting that in cells TM is a potent inhibitor of SIRT2 deacetylase but not defatty-acylase.…”

“…Some sirtuins, such as SIRT5 (Du et al, 2011) and SIRT6 (Jiang et al, 2013), prefer to hydrolyze other acyl lysine modifications. Perhaps more surprising is the fact that even the well-studied deacetylases (SIRT1, SIRT2, and SIRT3) can remove long chain fatty acyl groups efficiently (He et al, 2014; Liu et al, 2014). Although the exact substrate proteins for the defatty-acylase activity of SIRT2 remain to be identified, our preliminary studies showed that the fatty-acylation levels of many proteins were elevated when SIRT2 was knocked down (Figure S4B), but not when SIRT2 inhibitor TM was used (Figure S4C).…”

“…In contrast, SIRT2 was also observed to have tumor promoting activity in several studies (Chen et al, 2013; Liu et al, 2013; McGlynn et al, 2014; Soung et al, 2014; Yang et al, 2013; Zhao et al, 2014; Zhao et al, 2013). Moreover, several SIRT2 inhibitors have also been reported to have anticancer effects (Cheon et al, 2015; He et al, 2014; Heltweg et al, 2006; Hoffmann et al, 2014; Kim et al, 2011b; Mahajan et al, 2014; McCarthy et al, 2013; Neugebauer et al, 2008; Rotili et al, 2012; Zhang et al, 2009). However, the moderate potency and specificity of the existing sirtuin inhibitors are insufficient to draw conclusions about the anticancer potential of sirtuin inhibition.…”

Development of Activity-Based Chemical Probes for Human Sirtuins

“…Results from other groups and our own lab indicate that thiosuccinyllysine peptides inhibit SIRT5 55 and thiomyristoyllysine peptides inhibit SIRT6. 56 Based on the prototype probe 1, additional probes with thiosuccinyllysine and thiomyristoyllysine warheads were synthesized to target SIRT5 and SIRT6 (probe 5 and 6, Figure 6A). Indeed, probe 5 with the thiosuccinyl warhead selectively inhibits SIRT5 with an IC 50 of 3.2 ± 0.4 μ M (Table 1).…”