SorLA signaling by regulated intramembrane proteolysis

J Biol Chem. 2006 May 26;281(21):14547-53. doi: 10.1074/jbc.M601660200. Epub 2006 Mar 10.

Abstract

The single-transmembrane receptor SorLA/LR11 contains binding domains typical for lipoprotein receptors and a VPS10 domain, which binds the neuropeptide head-activator. This undecapeptide enhances proliferation of neuronal precursor cells in a SorLA-dependent manner. Using specific inhibitors we found previously that head activator activates shedding of SorLA by the metalloprotease TACE close to the transmembrane domain releasing the large extra-cellular part of the receptor. Here we show that the remaining COOH-terminal membrane fragment of SorLA is processed by gamma-secretase. Inhibition of gamma-secretase by specific inhibitors or overexpression of dominant negative presenilin mutants and knock out of the presenilin genes led to accumulation of the SorLA membrane fragment and also of full-length SorLA in the membrane. In an in vitro assay we observed the gamma-secretase-dependent release of the two soluble cleavage products, the SorLA cytoplasmic domain and the SorLA beta-peptide. These processing steps are reminiscent of a novel signaling pathway that has been described for the notch receptor. Here, the notch cytoplasmic domain is released into the cytoplasm by the gamma-secretase and migrates to the nucleus where it acts as a transcriptional regulator. In parallel we found that a fusion protein of the released cytoplasmic tail of SorLA with EGFP located to the nucleus only if the nuclear localization signal of SorLA was intact. In a reporter gene assay the cytoplasmic domain of SorLA acted as a transcriptional activator indicating that SorLA might directly regulate transcription after activation by gamma-secretase.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Amino Acid Sequence
  • Amyloid Precursor Protein Secretases
  • Aspartic Acid Endopeptidases
  • Cell Nucleus / metabolism
  • Cytoplasm / metabolism
  • Endopeptidases / metabolism
  • Gene Expression Regulation
  • Green Fluorescent Proteins / metabolism
  • Humans
  • LDL-Receptor Related Proteins
  • Membrane Proteins / metabolism
  • Membrane Transport Proteins / metabolism
  • Membrane Transport Proteins / physiology*
  • Molecular Sequence Data
  • Nuclear Localization Signals
  • Peptides / chemistry
  • Presenilin-1
  • Protein Sorting Signals
  • Receptors, LDL / metabolism
  • Receptors, LDL / physiology*
  • Signal Transduction

Substances

  • LDL-Receptor Related Proteins
  • Membrane Proteins
  • Membrane Transport Proteins
  • Nuclear Localization Signals
  • PSEN1 protein, human
  • Peptides
  • Presenilin-1
  • Protein Sorting Signals
  • Receptors, LDL
  • SORL1 protein, human
  • Green Fluorescent Proteins
  • Amyloid Precursor Protein Secretases
  • Endopeptidases
  • Aspartic Acid Endopeptidases
  • BACE1 protein, human