βA3/A1-crystallin regulates apical polarity and EGFR endocytosis in retinal pigmented epithelial cells

Commun Biol. 2021 Jul 8;4(1):850. doi: 10.1038/s42003-021-02386-6.

Abstract

The retinal pigmented epithelium (RPE) is a monolayer of multifunctional cells located at the back of the eye. High membrane turnover and polarization, including formation of actin-based apical microvilli, are essential for RPE function and retinal health. Herein, we demonstrate an important role for βA3/A1-crystallin in RPE. βA3/A1-crystallin deficiency leads to clathrin-mediated epidermal growth factor receptor (EGFR) endocytosis abnormalities and actin network disruption at the apical side that result in RPE polarity disruption and degeneration. We found that βA3/A1-crystallin binds to phosphatidylinositol transfer protein (PITPβ) and that βA3/A1-crystallin deficiency diminishes phosphatidylinositol 4,5-biphosphate (PI(4,5)P2), thus probably decreasing ezrin phosphorylation, EGFR activation, internalization, and degradation. We propose that βA3/A1-crystallin acquired its RPE function before evolving as a structural element in the lens, and that in the RPE, it modulates the PI(4,5)P2 pool through PITPβ/PLC signaling axis, coordinates EGFR activation, regulates ezrin phosphorylation and ultimately the cell polarity.

Publication types

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

MeSH terms

  • Animals
  • Cell Polarity / genetics
  • Cell Polarity / physiology*
  • Cytoskeletal Proteins / metabolism
  • Endocytosis*
  • Epithelial Cells / metabolism*
  • Epithelial Cells / ultrastructure
  • ErbB Receptors / metabolism*
  • Humans
  • Mice
  • Mice, Knockout
  • Phosphatidylinositol 4,5-Diphosphate / metabolism
  • Phospholipid Transfer Proteins / metabolism
  • Phosphorylation
  • Protein Binding
  • Retinal Pigment Epithelium / cytology
  • Retinal Pigment Epithelium / metabolism*
  • beta-Crystallin A Chain / genetics
  • beta-Crystallin A Chain / metabolism*

Substances

  • Cryba1 protein, mouse
  • Cytoskeletal Proteins
  • Phosphatidylinositol 4,5-Diphosphate
  • Phospholipid Transfer Proteins
  • beta-Crystallin A Chain
  • ezrin
  • ErbB Receptors