Sorting Tubules Regulate Blood-Brain Barrier Transcytosis

Cell Rep. 2017 Dec 12;21(11):3256-3270. doi: 10.1016/j.celrep.2017.11.055.

Abstract

Transcytosis across the blood-brain barrier (BBB) regulates key processes of the brain, but the intracellular sorting mechanisms that determine successful receptor-mediated transcytosis in brain endothelial cells (BECs) remain unidentified. Here, we used Transferrin receptor-based Brain Shuttle constructs to investigate intracellular transport in BECs, and we uncovered a pathway for the regulation of receptor-mediated transcytosis. By combining live-cell imaging and mathematical modeling in vitro with super-resolution microscopy of the BBB, we show that intracellular tubules promote transcytosis across the BBB. A monovalent construct (sFab) sorted for transcytosis was localized to intracellular tubules, whereas a bivalent construct (dFab) sorted for degradation formed clusters with impaired transport along tubules. Manipulating tubule biogenesis by overexpressing the small GTPase Rab17 increased dFab transport into tubules and induced its transcytosis in BECs. We propose that sorting tubules regulate transcytosis in BECs and may be a general mechanism for receptor-mediated transport across the BBB.

Keywords: blood brain barrier; brain endothelial cells; sorting tubules; super-resolution; transcytosis.

MeSH terms

  • Animals
  • Blood-Brain Barrier / metabolism*
  • Blood-Brain Barrier / ultrastructure
  • Brain / metabolism*
  • Brain / ultrastructure
  • Cytoplasmic Structures / metabolism*
  • Cytoplasmic Structures / ultrastructure
  • Endothelial Cells / metabolism*
  • Endothelial Cells / ultrastructure
  • Female
  • Fluorescent Dyes / chemistry
  • Gene Expression
  • Genes, Reporter
  • Immunoglobulin Fab Fragments / genetics
  • Immunoglobulin Fab Fragments / metabolism
  • Mice
  • Mice, Inbred C57BL
  • Optical Imaging
  • Protein Isoforms / genetics
  • Protein Isoforms / metabolism
  • Protein Transport
  • Receptors, Transferrin / genetics
  • Receptors, Transferrin / metabolism
  • Transcytosis
  • rab GTP-Binding Proteins / genetics
  • rab GTP-Binding Proteins / metabolism*

Substances

  • Fluorescent Dyes
  • Immunoglobulin Fab Fragments
  • Protein Isoforms
  • Receptors, Transferrin
  • Rab17 protein, mouse
  • rab GTP-Binding Proteins