Immunoproteasome deficiency protects in the retina after optic nerve crush

PLoS One. 2015 May 15;10(5):e0126768. doi: 10.1371/journal.pone.0126768. eCollection 2015.

Abstract

The immunoproteasome is upregulated by disease, oxidative stress, and inflammatory cytokines, suggesting an expanded role for the immunoproteasome in stress signaling that goes beyond its canonical role in generating peptides for antigen presentation. The signaling pathways that are regulated by the immunoproteasome remain elusive. However, previous studies suggest a role for the immunoproteasome in the regulation of PTEN and NF-κB signaling. One well-known pathway upstream of NF-κB and downstream of PTEN is the Akt signaling pathway, which is responsible for mediating cellular survival and is modulated after optic nerve crush (ONC). This study investigated the role of retinal immunoproteasome after injury induced by ONC, focusing on the Akt cell survival pathway. Retinas or retinal pigment epithelial (RPE) cells from wild type (WT) and knockout (KO) mice lacking either one (LMP2) or two (LMP7 and MECL-1) catalytic subunits of the immunoproteasome were utilized in this study. We show that mRNA and protein levels of the immunoproteasome subunits are significantly upregulated in WT retinas following ONC. Mice lacking the immunoproteasome subunits show either a delayed or dampened apoptotic response as well as altered Akt signaling, compared to WT mice after ONC. Treatment of the RPE cells with insulin growth factor-1 (IGF-1) to stimulate Akt signaling confirmed that the immunoproteasome modulates this pathway, and most likely modulates parallel pathways as well. This study links the inducible expression of the immunoproteasome following retinal injury to Akt signaling, which is important in many disease pathways.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cysteine Endopeptidases / genetics
  • Cysteine Endopeptidases / metabolism
  • Epithelial Cells / metabolism
  • Female
  • Insulin-Like Growth Factor I / genetics
  • Insulin-Like Growth Factor I / metabolism
  • Male
  • Mice
  • Mice, Knockout
  • NF-kappa B / genetics
  • NF-kappa B / metabolism
  • Nerve Crush / methods
  • Optic Nerve / metabolism*
  • Oxidative Stress / genetics
  • PTEN Phosphohydrolase / genetics
  • PTEN Phosphohydrolase / metabolism
  • Proteasome Endopeptidase Complex / genetics*
  • Proteasome Endopeptidase Complex / metabolism
  • Proto-Oncogene Proteins c-akt / genetics
  • Proto-Oncogene Proteins c-akt / metabolism
  • Retina / metabolism*
  • Signal Transduction / genetics
  • Up-Regulation / genetics

Substances

  • NF-kappa B
  • LMP-2 protein
  • Insulin-Like Growth Factor I
  • Proto-Oncogene Proteins c-akt
  • PTEN Phosphohydrolase
  • Pten protein, mouse
  • Cysteine Endopeptidases
  • LMP7 protein
  • Proteasome Endopeptidase Complex
  • Psmb10 protein, mouse