CDK5-Mediated Hyperphosphorylation of SIRT1 Contributes to the Development of Endothelial Senescence and Atherosclerosis
Background—Endothelial senescence represents one of the major characteristics of vascular aging and promotes the development of atherosclerosis. SIRT1 is a NAD-dependent deacetylase possessing anti-aging activities. During the occurrence of endothelial senescence, both the expression and activity of SIRT1 are down-regulated. The present study was designed to investigate the molecular mechanisms contributing to the loss-of-SIRT1 function in senescent endothelial cells.
Methods and Results—After repetitive passages, primary cultures of porcine aortic endothelial cells (PAECs) exhibited a severe senescence phenotype. Western blotting revealed that phosphorylation of SIRT1 at serine 47 (S47) was significantly enhanced in senescent endothelial cells. S47 phosphorylation was stimulated by agents promoting senescence and attenuated by drugs with anti-senescence properties. Mutation of S47 to non-phosphorable alanine (S47A) enhanced, whereas replacing S47 with phospho-mimicking aspartic acid (S47D) abolished the anti-senescent, growth-promoting and LKB1-downregulating actions of SIRT1. Phosphorylation at S47 was critically involved in the nuclear retention of SIRT1, but abolished its association with the telomeric repeat-binding factor 2-interacting protein 1 (TERF2IP). Cyclin-dependent kinase 5 (CDK5) was identified as a SIRT1 kinase modulating S47 phosphorylation. Knocking down or inhibition of CDK5 reduced the number of senescent endothelial cells, promoted nuclear exportation of SIRT1 and attenuated the expression of inflammatory genes in PAECs. The truncated regulatory subunit of CDK5, P25, accumulated in senescent PAECs and atherosclerotic aortae. Chronic treatment with roscovitine (CDK5 inhibitor) blocked the development of cellular senescence and atherosclerosis in aortae of hypercholesterolemic ApoE-/- mice.
Conclusions—CDK5-mediated hyperphosphorylation of SIRT1 facilitates the development of endothelial senescence and atherosclerosis.
- Received May 16, 2012.
- Accepted June 22, 2012.
- Copyright © 2012, American Heart Association, Inc. All rights reserved. Unauthorized use prohibited