Notch signalling is a key intercellular communication mechanism that is essential for cell specification and tissue patterning, and which coordinates critical steps of blood vessel growth1,2,3 . Although subtle alterations in Notch activity suffice to elicit profound differences in endothelial behaviour and blood vessel formation2,3 , little is known about the regulation and adaptation of endothelial Notch responses. Here we report that the NAD+-dependent deacetylase SIRT1 acts as an intrinsic negative modulator of Notch signalling in endothelial cells. We show that acetylation of the Notch1 intracellular domain (NICD) on conserved lysines controls the amplitude and duration of Notch responses by altering NICD protein turnover. SIRT1 associates with NICD and functions as a NICD deacetylase, which opposes the acetylation-induced NICD stabilization. Consequently, endothelial cells lacking SIRT1 activity are sensitized to Notch signalling, resulting in impaired growth, sprout elongation and enhanced Notch target gene expression in response to DLL4 stimulation, thereby promoting a non-sprouting, stalk-cell-like phenotype. In vivo, inactivation of Sirt1 in zebrafish and mice causes reduced vascular branching and density as a consequence of enhanced Notch signalling. Our findings identify reversible acetylation of the NICD as a molecular mechanism to adapt the dynamics of Notch signalling, and indicate that SIRT1 acts as rheostat to fine-tune endothelial Notch responses.
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We are thankful to F. W. Alt, R. Kopan, Z. Lou, E. Seto, S. L. Berger, S. Diane Hayward, S. McMahon, G. Thurston and N. D. Lawson for reagents and to I. Dikic for comments. This work was supported by grants from the DFG (PO1306/1-1, SFB 834/A6 and Exc 147/1). F.D. was supported by the Interuniversity Attraction Poles Program–Belgian Science Policy (IUAP-BELSPO PVI/28). R.M. is supported by the Sidney Kimmel Cancer Research Foundation, a New Investigator Grant from the Massachusetts Life Sciences Center, an AFAR Research Grant and NIH grants (R01DK088190-01A1 and R01GM093072-01). H.G. is supported by Cancer Research UK, the European Molecular Biology Organisation Young Investigator Programme, and The Lister Institute of Preventive Medicine. H.G. and K.B. are supported by the Fondation Leducq Transatlantic Network of Excellence ARTEMIS. C.A.F. is supported by the Marie Curie FP7 People initiative. G.D. and M.M. thank F. Pezzimenti for fish care and technical help, and AIRC (Associazione Italiana per la Ricerca sul Cancro) for financial support.
The authors declare no competing financial interests.
This file contains Supplementary Figures 1-16 with legends. (PDF 24705 kb)
This movie shows simulation of a Sirt1 wild-type vessel. Tip cell selection occurs fast, movie represents 1 hour and 52 minutes (450 model time steps). Colour indicates NICD levels, purple - low, green – high (MOV 1098 kb)
This movie shows simulation of a Sirt1-deficient vessel. Tip cell selection occurs slowly after initial oscillations in NICD levels. Colour indicates NICD levels, purple - low, green - high. (MOV 2410 kb)
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Journal of Cellular Physiology (2019)
International Journal of Molecular Sciences (2019)
Frontiers in Genetics (2019)
Biochimica et Biophysica Acta (BBA) - Molecular Cell Research (2019)
Developmental Biology (2019)