Characterization of the cell membrane-associated products of the Neuregulin 4 gene

Oncogene. 2008 Jan 24;27(5):715-20. doi: 10.1038/sj.onc.1210689. Epub 2007 Aug 6.

Abstract

The NRG4 gene is a member of a family of four genes that encode a class of epidermal growth factors. This gene has been reported to express a protein designated here as NRG4A1. We describe here a novel splice variant of the NRG4 gene, NRG4A2, which encodes a C-terminal region containing a predicted type I PDZ-binding peptide. Both NRG4A1 and NRG4A2 were shown to be expressed on the cell surface, as expected by the presence of a predicted transmembrane sequence, and were modified at a single N-linked glycosylation site in the extracellular domain. Significant stabilization of expression of both proteins was seen in the presence of the proteosome inhibitor MG-132 suggesting that they are normally degraded by this system. N-terminal cleavage was inhibited in both isotypes by the broad-spectrum matrix metalloproteinase inhibitor, galardin (GM 6001). A glycosylated, secreted form of NRG4A1 was detected in the cell medium which showed biological activity in two assays, phosphorylation of the HER4 receptor and stimulation of neurite formation in PC-12 cells stably expressing HER4. Transfection and expression of green fluorescent protein-tagged proteins and immunofluorescent staining with specific anti-peptide antibodies showed that NRG4A1 is localized to membrane ruffles, while NRG4A2 has a more punctate membrane distribution.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Base Sequence
  • Breast Neoplasms / pathology
  • Cell Membrane / chemistry
  • Dipeptides / pharmacology
  • Enzyme Inhibitors / pharmacology
  • ErbB Receptors / metabolism
  • Humans
  • Leupeptins / pharmacology
  • Molecular Sequence Data
  • Neuregulins / analysis
  • Neuregulins / genetics*
  • Neuregulins / metabolism*
  • Phosphorylation
  • Protein Isoforms
  • Receptor, ErbB-4
  • Reverse Transcriptase Polymerase Chain Reaction
  • Sequence Alignment
  • Tumor Cells, Cultured

Substances

  • Dipeptides
  • Enzyme Inhibitors
  • Leupeptins
  • N-(2(R)-2-(hydroxamidocarbonylmethyl)-4-methylpentanoyl)-L-tryptophan methylamide
  • Neuregulins
  • Protein Isoforms
  • neuregulin-4
  • ERBB4 protein, human
  • ErbB Receptors
  • Receptor, ErbB-4
  • benzyloxycarbonylleucyl-leucyl-leucine aldehyde