CIB2 regulates mTORC1 signaling and is essential for autophagy and visual function

Nat Commun. 2021 Jun 23;12(1):3906. doi: 10.1038/s41467-021-24056-1.

Abstract

Age-related macular degeneration (AMD) is a multifactorial neurodegenerative disorder. Although molecular mechanisms remain elusive, deficits in autophagy have been associated with AMD. Here we show that deficiency of calcium and integrin binding protein 2 (CIB2) in mice, leads to age-related pathologies, including sub-retinal pigment epithelium (RPE) deposits, marked accumulation of drusen markers APOE, C3, Aβ, and esterified cholesterol, and impaired visual function, which can be rescued using exogenous retinoids. Cib2 mutant mice exhibit reduced lysosomal capacity and autophagic clearance, and increased mTORC1 signaling-a negative regulator of autophagy. We observe concordant molecular deficits in dry-AMD RPE/choroid post-mortem human tissues. Mechanistically, CIB2 negatively regulates mTORC1 by preferentially binding to 'nucleotide empty' or inactive GDP-loaded Rheb. Upregulated mTORC1 signaling has been implicated in lymphangioleiomyomatosis (LAM) cancer. Over-expressing CIB2 in LAM patient-derived fibroblasts downregulates hyperactive mTORC1 signaling. Thus, our findings have significant implications for treatment of AMD and other mTORC1 hyperactivity-associated disorders.

Publication types

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

MeSH terms

  • Animals
  • Autophagy / genetics*
  • COS Cells
  • Calcium-Binding Proteins / deficiency
  • Calcium-Binding Proteins / genetics*
  • Cells, Cultured
  • Chlorocebus aethiops
  • Disease Models, Animal
  • HEK293 Cells
  • Humans
  • Lysosomes / metabolism
  • Macular Degeneration / genetics
  • Macular Degeneration / pathology
  • Mechanistic Target of Rapamycin Complex 1 / genetics*
  • Mechanistic Target of Rapamycin Complex 1 / metabolism
  • Mice
  • Mice, Knockout
  • Retina / metabolism
  • Retinal Pigment Epithelium / metabolism*
  • Signal Transduction / genetics*

Substances

  • Calcium-Binding Proteins
  • Cib2 protein, mouse
  • Mechanistic Target of Rapamycin Complex 1