title: ER-stress-inducible Herp, facilitates the degradation of immature nicastrin.
abstract: BACKGROUND
  Herp is an endoplasmic reticulum (ER)-stress-inducible membrane protein harboring an ubiquitin-like domain (ULD). However, its biological functions are not fully understood. Here, we examined the role of Herp in the degradation of γ-secretase components.
  
  
  METHODS
  Effects of ULD-lacking Herp (ΔUb-Herp) expression on the degradation of γ-secretase components were analyzed.
  
  
  RESULTS
  The cellular expression of ΔUb-Herp was found to inhibit the degradation of overexpressed immature nicastrin and full-length presenilin. The mechanisms underlying Herp-mediated nicastrin degradation was further analyzed. We found that immature nicastrin accumulates in the ER of ΔUb-Herp overexpressing cells or Herp-deficient cells more than that in the ER of wild-type cells. Further, ΔUb-Herp expression inhibited nicastrin ubiquitination, suggesting that the ULD of Herp is likely involved in nicastrin ubiquitination. Co-immunoprecipitation study showed that Herp as well as ΔUb-Herp potentially interacts with nicastrin, mediating nicastrin interaction with p97, which functions in retranslocation of misfolded proteins from the ER to the cytosol.
  
  
  CONCLUSIONS
  Thus, Herp is likely involved in degradation of immature nicastrin by facilitating p97-dependent nicastrin retranslocation and ubiquitination.
  
  
  CONCLUSIONS
  We suggest that Herp could play a role in the elimination of the excess unassembled components of a multimeric complex.
authors: Department of Biology, Faculty of Sciences, Kyushu University Graduate School, Fukuoka 812-8581, Japan.
authors: Toshihiro
authors: T
authors: Marutani
authors: Tomoji
authors: T
authors: Maeda
authors: Chiaki
authors: C
authors: Tanabe
authors: Kun
authors: K
authors: Zou
authors: Wataru
authors: W
authors: Araki
authors: Koichi
authors: K
authors: Kokame
authors: Makoto
authors: M
authors: Michikawa
authors: Hiroto
authors: H
authors: Komano