Abstract
Sirtuin 1 (SIRT1), an NAD+-dependent deacetylase, is a crucial regulator that produces multiple physiological benefits, such as the prevention of cancer and age-related diseases. SIRT1 is activated by sirtuin-activating compounds (STACs). Here, we report that quercetin 3,5,7,3′,4′-pentamethyl ether (KPMF-8), a natural STAC from Thai black ginger Kaempferia parviflora, interacts with SIRT1 directly and stimulates SIRT1 activity by enhancing the binding affinity of SIRT1 with Ac-p53 peptide, a native substrate peptide without a fluorogenic moiety. The binding affinity between SIRT1 and Ac-p53 peptide was enhanced 8.2-fold by KPMF-8 but only 1.4-fold by resveratrol. The specific binding sites of KPMF-8 to SIRT1 were mainly localized to the helix2–turn–helix3 motif in the N-terminal domain of SIRT1. Intracellular deacetylase activity in MCF-7 cells was promoted 1.7-fold by KPMF-8 supplemented in the cell medium but only 1.2-fold by resveratrol. This work reveals that KPMF-8 activates SIRT1 more effectively than resveratrol does.
Highlights
Sirtuin 1 (SIRT1), an NAD+-dependent deacetylase, is a crucial regulator that produces multiple physiological benefits, such as the prevention of cancer and age-related diseases
To confirm the stimulating activity of KPMF-8 on SIRT1 activity reported by Nakata et al (2014), we performed catalytic reactions with recombinant full-length SIRT1 using Ac-p53-AMC peptide (Fig. 1a, b) in the presence of 2–10 μM KPMF-8 in vitro
This binding affinity increased roughly 1.4-fold in the presence of 0.2 mM resveratrol (KD = 38.8 μM; Fig. 4d). This binding affinity increased more dramatically in the presence of 0.2 mM KPMF-8 (KD = 6.67 μM; Fig. 4c), about 8-fold. These results indicate that KPMF-8 is much more efficient than resveratrol in enhancing SIRT1–Ac-p53 peptide binding, which explains why KPMF-8 showed more activation of SIRT1 deacetylase activity
Summary
Sirtuin 1 (SIRT1), an NAD+-dependent deacetylase, is a crucial regulator that produces multiple physiological benefits, such as the prevention of cancer and age-related diseases. Several classes of plant polyphenols, with modifications at the B ring 4′ position, such as butein, isoliquiritigenin, and quercetin, were confirmed to stimulate SIRT1 activity[6] Some of these natural compounds, such as resveratrol and piceatannol, were reported to prolong lifespan in yeast, metazoans and mice by acting on SIRT1 enzyme and other target proteins like cyclooxygenases, lipooxygenases and MAPK family proteins. In light of skepticism about other controversial STACs, further study is required to determine the followings: (1) whether KPMF-8 directly interacts with SIRT1, (2) whether KPMF-8 activates SIRT1 towards the native substrate, and (3) whether KPMF-8 can penetrate the cell membrane and accelerate intracellular deacetylase activity within the cellular environment These basic in vitro studies on intermolecular interactions/recognitions are necessary and will yield important results before the potential pharmaceutical role of KPMF-8 can be tested in animal models and humans. KPMF-8 significantly increases intracellular deacetylase activity in MCF-7 cells
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