P16INK4a upregulation mediated by TBK1 induces retinal ganglion cell senescence in ischemic injury

Cell Death Dis. 2017 Apr 20;8(4):e2752. doi: 10.1038/cddis.2017.169.

Abstract

Glaucoma is a leading cause of irreversible blindness worldwide that is characterized by progressive retinal ganglion cell (RGC) death. However, RGC senescence as a phase before RGC death, and the mechanism of RGC senescence remains unclear. Here, we demonstrate that TANK-binding protein 1 (TBK1) is upregulated in acute IOP elevation-induced ischemic retinas mouse model. Moreover, pre-treatment with the TBK1 inhibitor BX-795 reduced p16INK4a (p16) expression and RGC senescence. Upregulation of TBK1 via plasmid transfection increased Akt phosphorylation at Ser473 and Bmi1 phosphorylation. The Akt inhibitor MK-2206 decreased the expression of p16 and Bmi1 serine phosphorylation. A Bmi1 Ser316 mutation also attenuated TBK1-induced p16 upregulation. Finally, silencing of TBK1 via shRNA knockdown reduced the expression of p16 as well as Akt and Bmi1 phosphorylation, reducing RGC senescence in vivo. These data suggest that acute IOP elevation-induced ischemia increases TBK1 expression, which then increases p16 expression through the Akt- Bmi1 phosphorylation pathway. This study therefore elucidates a novel mechanism whereby TBK1 regulates p16 expression and RGC senescence, suggesting a potential novel treatment strategy for minimizing RGC senescence in retinal ischemia and glaucoma.

MeSH terms

  • Animals
  • Cellular Senescence* / drug effects
  • Cyclin-Dependent Kinase Inhibitor p16 / genetics*
  • Cyclin-Dependent Kinase Inhibitor p16 / metabolism
  • Disease Models, Animal
  • Gene Knockdown Techniques
  • Intraocular Pressure / drug effects
  • Ischemia / enzymology*
  • Ischemia / pathology*
  • Ischemia / physiopathology
  • Models, Biological
  • Phosphorylation / drug effects
  • Polycomb Repressive Complex 1 / metabolism
  • Protein Serine-Threonine Kinases / metabolism*
  • Proto-Oncogene Proteins / metabolism
  • Proto-Oncogene Proteins c-akt / metabolism
  • Pyrimidines / pharmacology
  • RNA, Small Interfering / metabolism
  • Retinal Ganglion Cells / drug effects
  • Retinal Ganglion Cells / enzymology*
  • Retinal Ganglion Cells / pathology*
  • Signal Transduction / drug effects
  • Thiophenes / pharmacology
  • Tumor Suppressor Protein p53 / metabolism
  • Up-Regulation* / drug effects

Substances

  • BX795
  • Bmi1 protein, mouse
  • Cyclin-Dependent Kinase Inhibitor p16
  • Proto-Oncogene Proteins
  • Pyrimidines
  • RNA, Small Interfering
  • Thiophenes
  • Tumor Suppressor Protein p53
  • Polycomb Repressive Complex 1
  • Tbk1 protein, mouse
  • Protein Serine-Threonine Kinases
  • Proto-Oncogene Proteins c-akt