Novel processing of Notch 1 within its intracellular domain by a cysteine protease

Angeliki Fassa, Loukia Parisiadou, Nikolaos K. Robakis, Spiros Efthimiopoulos*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

1 Scopus citations


In order to study N1 processing, we expressed human N1 (hN1) in HEK293 cells (293-hN1). Following Western blot analysis of 293-hN1 extracts, we detected, in addition to full-length hN1 and the N1 extracellular domain truncated form (N1-TM), a novel extracellular domain truncated form of hN1 with a COOH-terminal deletion, designated hN1-TMΔCT. Treatment of cells with the γ-secretase inhibitor L-685,458 resulted in an accumulation of hN1-TMΔCT suggesting that this fragment is a γ-secretase substrate. To identify the proteolytic activity(ies) that generates hN1-TMΔCT, we treated 293-hN1 cells with inhibitors of proteasome, calpains, caspases, serine and cysteine proteases. Despite the presence of a caspase-3 cleavage site within hN1 intracellular domain, none of the caspase inhibitors inhibited hN1-TMΔCT production. The proteasomal inhibitors used had also no effect. Incubation of cells with the cysteine protease inhibitor E64d resulted in the accumulation of hN1-TM and the inhibition of hN1-TMΔCT production suggesting a precursor-product relationship and that a cysteine protease is involved. Similarly, treatment of cells expressing amyloid precursor protein or E-cadherin with E-64d resulted in the accumulation of COOH-terminal fragments suggesting that these proteins are also processed within their intracellular domain by a cysteine protease. Processing towards hN1-TMΔCT requires maturation and transport of hN1 to the cell surface since treatment with brefeldin A inhibited its production and resulted in accumulation of hN1. Processing of hN1 within its intracellular domain could generate fragments that can exert novel functions and/or interfere with the function of hN1 intracellular domain.

Original languageEnglish (US)
Pages (from-to)148-155
Number of pages8
JournalNeurodegenerative Diseases
Issue number2-3
StatePublished - Jun 2007


  • Alzheimer's disease
  • Cysteine protease
  • Notch 1
  • Postsynaptic densities
  • Presenilin
  • Presynaptic terminals

ASJC Scopus subject areas

  • Neurology
  • Clinical Neurology


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