Abstract
Gamma-secretase-like proteolysis at site 3 (S3), within the transmembrane domain, releases the Notch intracellular domain (NICD) and activates CSL-mediated Notch signaling. S3 processing occurs only in response to ligand binding; however, the molecular basis of this regulation is unknown. Here we demonstrate that ligand binding facilitates cleavage at a novel site (S2), within the extracellular juxtamembrane region, which serves to release ectodomain repression of NICD production. Cleavage at S2 generates a transient intermediate peptide termed NEXT (Notch extracellular truncation). NEXT accumulates when NICD production is blocked by point mutations or gamma-secretase inhibitors or by loss of presenilin 1, and inhibition of NEXT eliminates NICD production. Our data demonstrate that S2 cleavage is a ligand-regulated step in the proteolytic cascade leading to Notch activation.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Amino Acid Sequence
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Amyloid Precursor Protein Secretases
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Conserved Sequence
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Cysteine / genetics
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Disintegrins / metabolism
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Drosophila Proteins*
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Endopeptidases / metabolism*
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Ligands
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Membrane Proteins / genetics
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Membrane Proteins / metabolism*
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Metalloendopeptidases / metabolism
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Mutation
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Peptide Fragments / genetics
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Peptide Fragments / metabolism*
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Presenilin-1
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Protein Processing, Post-Translational*
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Receptor, Notch1
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Receptors, Cell Surface / genetics
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Receptors, Cell Surface / metabolism*
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Signal Transduction
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Transcription Factors*
Substances
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Disintegrins
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Drosophila Proteins
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Ligands
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Membrane Proteins
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Peptide Fragments
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Presenilin-1
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Receptor, Notch1
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Receptors, Cell Surface
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Transcription Factors
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Amyloid Precursor Protein Secretases
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Endopeptidases
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KUZ protein, Drosophila
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Metalloendopeptidases
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Cysteine