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Murine notch homologs (N1-4) undergo presenilin-dependent proteolysis

M T Saxena1, E H Schroeter, J S Mumm

  • 1Department of Molecular Biology and Pharmacology, Washington University School of Medicine, 660 South Euclid Ave., St. Louis, MO 63110, USA.

The Journal of Biological Chemistry
|August 24, 2001
PubMed

Insights

Extracellularly truncated Notch proteins are substrates for presenilin-dependent gamma-secretase activity, similar to Notch1. This conserved proteolysis mechanism allows Notch intracellular domains to activate gene transcription, expanding known gamma-secretase substrates.

Area of Science:

  • Molecular Biology
  • Cell Signaling
  • Proteolysis

Background:

  • Oncogenic Notch receptors (Notch1, Notch2, Notch4) suggest conserved proteolysis in Notch signaling.
  • Presenilin-dependent gamma-secretase activity is crucial for Notch signaling pathway.
  • Previous studies identified limited gamma-secretase substrates.

Purpose of the Study:

  • To investigate if extracellularly truncated Notch homologs are substrates for presenilin-dependent gamma-secretase.
  • To identify conserved features of the cleavage site across different Notch homologs.
  • To determine the functional consequence of Notch proteolysis on nuclear translocation and transcriptional activity.

Main Methods:

  • Biochemical assays to test gamma-secretase activity on truncated Notch proteins.
  • Analysis of amino acid sequence and position at the cleavage site.
  • Nuclear translocation assays for cleaved Notch intracellular domains.
  • Reporter gene assays to measure transactivating potential.

Main Results:

  • Extracellularly truncated Notch1, Notch2, and Notch4 are substrates for presenilin-dependent gamma-secretase.
  • A conserved P1' valine at the cleavage site is critical for gamma-secretase activity.
  • Cleaved Notch intracellular domains translocate to the nucleus and bind to CSL.
  • All four Notch proteins exhibit presenilin-dependent transactivating potential.

Conclusions:

  • This study identifies three new gamma-secretase substrates, increasing the total to five.
  • The findings highlight conserved mechanisms of Notch proteolysis and gamma-secretase activity.
  • The functional redundancy among Notch proteins mediated by gamma-secretase activity remains to be fully elucidated.

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