Phosphoinositide 3-kinase δ inactivation prevents vitreous-induced activation of AKT/MDM2/p53 and migration of retinal pigment epithelial cells

J Biol Chem. 2019 Oct 18;294(42):15408-15417. doi: 10.1074/jbc.RA119.010130. Epub 2019 Aug 29.

Abstract

Phosphoinositide 3-kinases (PI3Ks) are a family of lipid kinases that play a critical role in transmitting signals from cell-surface molecules to intracellular protein effectors. Key PI3Ks include PI3Kα, PI3Kβ, and PI3Kδ, which are regulated by receptors. The signaling pathway comprising the PI3Ks, along with a Ser/Thr kinase (AKT), a proto-oncogene product (mouse double minute (MDM)2), and a tumor suppressor protein (p53), plays an essential role in experimental proliferative vitreoretinopathy (PVR), which is a fibrotic blinding eye disorder. However, which PI3K isoforms are involved in PVR is unknown. A major characteristic of PVR is the formation of epi (or sub)-retinal membranes that consist of extracellular matrix and cells, including retinal pigment epithelium (RPE) cells, glial cells, and macrophages. RPE cells are considered key players in PVR pathogenesis. Using immunoblotting and immunofluorescence analyses, we herein provide the evidence that PI3Kδ is highly expressed in human RPEs when it is primarily expressed in leukocytes. We also found that PI3Kδ inactivation through two approaches, CRISPR/Cas9-mediated depletion and a PI3Kδ-specific inhibitor (idelalisib), not only blocks vitreous-induced activation of AKT and MDM2 but also abrogates a vitreous-stimulated decrease in p53. Furthermore, we demonstrate that PI3Kδ inactivation prevents vitreous-induced proliferation, migration, and contraction of human RPEs. These results suggest that PI3Kδ may represent a potential therapeutic target for RPE-related eye diseases, including PVR.

Keywords: Akt PKB; migration; mouse double minute 2 homolog (MDM2); p53; phosphatidylinositide 3-kinase (PI 3-kinase).

Publication types

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

MeSH terms

  • Cell Movement
  • Cell Proliferation
  • Class I Phosphatidylinositol 3-Kinases / genetics
  • Class I Phosphatidylinositol 3-Kinases / metabolism*
  • Epithelial Cells / cytology
  • Epithelial Cells / metabolism
  • Humans
  • Proto-Oncogene Mas
  • Proto-Oncogene Proteins c-akt / genetics
  • Proto-Oncogene Proteins c-akt / metabolism*
  • Proto-Oncogene Proteins c-mdm2 / genetics
  • Proto-Oncogene Proteins c-mdm2 / metabolism*
  • Retinal Pigment Epithelium / cytology
  • Retinal Pigment Epithelium / enzymology
  • Retinal Pigment Epithelium / metabolism*
  • Signal Transduction
  • Tumor Suppressor Protein p53 / genetics
  • Tumor Suppressor Protein p53 / metabolism*
  • Vitreous Body / enzymology
  • Vitreous Body / metabolism*

Substances

  • MAS1 protein, human
  • Proto-Oncogene Mas
  • Tumor Suppressor Protein p53
  • Proto-Oncogene Proteins c-mdm2
  • Class I Phosphatidylinositol 3-Kinases
  • PIK3CD protein, human
  • Proto-Oncogene Proteins c-akt