HRT1 modulates vascular smooth muscle cell proliferation and apoptosis

Biochem Biophys Res Commun. 2003 Aug 29;308(3):596-601. doi: 10.1016/s0006-291x(03)01453-0.


The Notch signaling pathway plays vital roles in vascular development and homeostasis. However, the functional role of HRT1, a primary downstream effector of Notch signaling in VSMC, is poorly characterized. In the present study, we postulated that HRT1 plays fundamental roles in modulating VSMC fate. To test the hypothesis that HRT1 is coupled to growth regulation, we generated VSMC lines constitutively overexpressing HRT1 (HRT1SMC) and demonstrated an exaggerated growth behavior compared to its control cell line. The lack of cell cycle arrest at confluence in HRT1SMC was associated with an attenuated up-regulation of the cell cycle inhibitor, p21(WAF1/CIP1). We further established that both transient and constitutive HRT1 signaling promoted VSMC survival in response to serum deprivation and pro-apoptotic Fas ligand. Resistance to apoptosis was associated with the induction of Akt expression/activity, a well-described anti-apoptotic mediator. Overall, these findings provide initial evidence that HRT1 functions as a critical determinant of VSMC proliferation and survival.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Apoptosis*
  • Basic Helix-Loop-Helix Transcription Factors
  • Cell Division
  • Cell Line
  • Cell Survival
  • Cells, Cultured
  • Cyclin-Dependent Kinase Inhibitor p21
  • Cyclins / metabolism
  • Muscle, Smooth, Vascular / cytology
  • Muscle, Smooth, Vascular / metabolism*
  • Protein-Serine-Threonine Kinases*
  • Proto-Oncogene Proteins / metabolism
  • Proto-Oncogene Proteins c-akt
  • Rats
  • Repressor Proteins / physiology*
  • Signal Transduction


  • Basic Helix-Loop-Helix Transcription Factors
  • Cdkn1a protein, rat
  • Cyclin-Dependent Kinase Inhibitor p21
  • Cyclins
  • Hairy, HRT1 protein
  • Proto-Oncogene Proteins
  • Repressor Proteins
  • Akt1 protein, rat
  • Protein-Serine-Threonine Kinases
  • Proto-Oncogene Proteins c-akt