Endophilin-1 regulates blood-brain barrier permeability by controlling ZO-1 and occludin expression via the EGFR-ERK1/2 pathway

Brain Res. 2014 Jul 21:1573:17-26. doi: 10.1016/j.brainres.2014.05.022. Epub 2014 May 20.

Abstract

The blood-brain barrier (BBB) plays a pivotal role in maintenance and regulation of the neural microenvironment. Brain endothelial cells (BECs), held together by tight junctions (TJs), have a primary role in restricting the permeability of the BBB. Endophilin-1 is a multifunctional protein that influences epithelial growth factor receptor (EGFR) endocytosis and degradation and plays an important role in regulating the glomerular filtration barrier in the kidney. Endophilin-1 likely plays a similar role in controlling BBB permeability. In this study, we therefore analyzed the expression and function of endophilin-1 in the human BEC line hCMEC/D3. Our results show that endophilin-1 over-expression reduced the expression of the TJ-associated proteins ZO-1 and occludin and increased the paracellular permeability of hCMEC/D3 cells, whereas silencing of endogenous endophilin-1 yielded the opposite results. Over-expression of ZO-1 and occludin prevented the increase in permeability induced by endophilin-1 over-expression, whereas down-regulation of ZO-1 and occludin prevented the reduction in permeability induced by endophilin-1 silencing. Co-localization and co-immunoprecipitation experiments suggested that endophilin-1 interacts with the EGFR. The levels of EGFR and its downstream effector phosphorylated extracellular signal-regulated kinase 1/2 (p-ERK1/2) are significantly decreased when endophilin-1 is over-expressed. Conversely, endophilin-1 down-regulation led to markedly increased levels of these proteins. In addition, the reduced permeability induced by endophilin-1 down-regulation was blocked by AG1478 and PD98059, inhibitors of EGFR and ERK1/2, respectively. Up-regulation of ZO-1 and occludin was blocked by the EGFR and ERK1/2 inhibitors. These results suggest that endophilin-1 regulates BBB permeability by controlling ZO-1 and occludin expression via the EGFR-ERK1/2 pathway in BECs.

Keywords: Blood–brain barrier permeability; Endophilin-1; Epithelial growth factor receptor; Extracellular signal-regulated kinases; Tight junction.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acyltransferases / genetics
  • Acyltransferases / metabolism*
  • Blood-Brain Barrier / drug effects
  • Blood-Brain Barrier / physiology*
  • Blotting, Western
  • Capillary Permeability / drug effects
  • Capillary Permeability / physiology*
  • Cell Line
  • Electric Impedance
  • ErbB Receptors / metabolism
  • Fluorescent Antibody Technique
  • Gene Expression Regulation
  • Humans
  • Immunoprecipitation
  • MAP Kinase Signaling System / drug effects
  • MAP Kinase Signaling System / physiology
  • Occludin / metabolism*
  • Tight Junction Proteins / metabolism
  • Transfection
  • Zonula Occludens-1 Protein / metabolism*

Substances

  • OCLN protein, human
  • Occludin
  • TJP1 protein, human
  • Tight Junction Proteins
  • Zonula Occludens-1 Protein
  • Acyltransferases
  • 2-acylglycerophosphate acyltransferase
  • EGFR protein, human
  • ErbB Receptors