Differential basolateral–apical distribution of scavenger receptor, class B, type I in cultured cells and the liver

Stefanie Fruhwürth, Werner J. Kovacs, Robert Bittman, Simon Messner, Clemens Röhrl, Herbert Stangl

Research output: Contribution to journalArticlepeer-review

6 Citations (Scopus)

Abstract

The high-density lipoprotein (HDL) receptor, scavenger receptor class B, type I (SR-BI), mediates selective cholesteryl ester uptake into the liver, which finally results in cholesterol secretion into the bile. Despite several reports, the distribution of hepatic SR-BI between the sinusoidal and canalicular membranes is still under debate. We present immunohistological data using specific markers showing that the bulk of SR-BI is present in sinusoidal membranes and, to a lesser extent, in canalicular membranes in murine and human liver sections. In addition, SR-BI was detected in preparations of rat liver canalicular membranes. We also compared the in vivo findings to HepG2 cells, a widely used in vitro hepatocyte model. Interestingly, SR-BI was enriched in bile canalicular-like (BC-like) structures in polarized HepG2 cells, which were cultivated either conventionally to form a monolayer or in Matrigel to form three-dimensional structures. Fluorescently labeled HDL was transported into close proximity of BC-like structures, whereas HDL labeled with the fluorescent cholesterol analog BODIPY-cholesterol was clearly detected within these structures. Importantly, similarly to human and mouse liver, SR-BI was localized in basolateral membranes in three-dimensional liver microtissues from primary human liver cells. Our results demonstrate that SR-BI is highly enriched in sinusoidal membranes and is also found in canalicular membranes. There was no significant basolateral–apical redistribution of hepatic SR-BI in fasting and refeeding experiments in mice. Furthermore, in vitro studies in polarized HepG2 cells showed explicit differences as SR-BI was highly enriched in BC-like structures. These structures are, however, functional and accumulated HDL-derived cholesterol. Thus, biological relevant model systems should be employed when investigating SR-BI distribution in vitro.

Original languageEnglish
Pages (from-to)645-655
Number of pages11
JournalHistochemistry and Cell Biology
Volume142
Issue number6
DOIs
Publication statusPublished - Dec 2014
Externally publishedYes

Keywords

  • BODIPY-cholesterol
  • Canalicular membranes
  • Cholesterol
  • HDL
  • HepG2
  • SR-BI
  • Humans
  • Mice, Inbred C57BL
  • Scavenger Receptors, Class B/metabolism
  • Male
  • Blotting, Western
  • Hep G2 Cells
  • Animals
  • Cell Membrane/metabolism
  • Liver/metabolism
  • Fluorescent Antibody Technique
  • Mice

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