Expression of the ATP-binding cassette membrane transporter, ABCG2, in human and rodent brain microvessel endothelial and glial cell culture systems

Pharm Res. 2007 Jul;24(7):1262-74. doi: 10.1007/s11095-007-9244-1. Epub 2007 Mar 23.

Abstract

Purpose: The function of ABCG2 (BCRP), a member of the ATP-binding cassette (ABC) superfamily of membrane-associated drug transporters, at the blood-brain barrier remains highly controversial. This project investigates the functional expression of endogenous ABCG2 in cultures of human and rodent brain cellular compartments.

Materials and methods: RT-PCR, western blot and fluorescent immunocytochemical analyses were performed on ABCG2-overexpressing human breast cancer (MCF-MX100) cells, human and rat brain microvessel endothelial (HBEC and RBE4, respectively), and rat glial cells.

Results: RT-PCR analysis detected ABCG2 mRNA in all the cell culture systems. Western blot analysis with anti-ABCG2 monoclonal BXP-21 antibody detected a robust band at approximately 72 kDa in the ABCG2-overexpressing MCF-MX100 cell line, whereas low expression was found in human and rat brain cell systems. Immunofluorescence microscopy detected predominant plasma membrane localization of ABCG2 in MCF-MX100 cells but weak signal in all brain cellular compartments. In the presence of ABCG2 inhibitors, the accumulation of (3)H-mitoxantrone and pheophorbide A, two established ABCG2 substrates, was significantly increased in MCF-MX100 cells but not in the human and rodent brain cell culture systems.

Conclusions: Our data show low endogenous ABCG2 protein expression, localization and activity in cultures of human and rat brain microvessel endothelial and glial cells.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • ATP Binding Cassette Transporter, Subfamily G, Member 2
  • ATP-Binding Cassette Transporters / antagonists & inhibitors
  • ATP-Binding Cassette Transporters / genetics
  • ATP-Binding Cassette Transporters / metabolism*
  • Animals
  • Animals, Newborn
  • Astrocytes / drug effects
  • Astrocytes / metabolism*
  • Blotting, Western
  • Brain / blood supply*
  • Breast Neoplasms / genetics
  • Breast Neoplasms / metabolism*
  • Breast Neoplasms / pathology
  • Cell Line, Tumor
  • Chlorophyll / analogs & derivatives
  • Chlorophyll / metabolism
  • Endothelial Cells / drug effects
  • Endothelial Cells / metabolism*
  • Female
  • Fluorescent Antibody Technique, Indirect
  • Humans
  • Indoles / pharmacology
  • Microcirculation / cytology
  • Microcirculation / metabolism
  • Microglia / drug effects
  • Microglia / metabolism*
  • Mitoxantrone / metabolism
  • Neoplasm Proteins / antagonists & inhibitors
  • Neoplasm Proteins / genetics
  • Neoplasm Proteins / metabolism*
  • RNA, Messenger / metabolism
  • Rats
  • Rats, Wistar
  • Reverse Transcriptase Polymerase Chain Reaction
  • Time Factors
  • Transfection
  • Tritium

Substances

  • ABCG2 protein, human
  • ATP Binding Cassette Transporter, Subfamily G, Member 2
  • ATP-Binding Cassette Transporters
  • Abcg2 protein, rat
  • Indoles
  • Neoplasm Proteins
  • RNA, Messenger
  • Tritium
  • Chlorophyll
  • Mitoxantrone
  • tryptoquivaline
  • pheophorbide a