Functional expression and characterization of the human ABCG1 and ABCG4 proteins: Indications for heterodimerization

Judit Cserepes, Zsófia Szentpétery, László Seres, Csilla Özvegy-Laczka, Thomas Langmann, Gerd Schmitz, Hristos Glavinas, Izabella Klein, László Homolya, András Váradi, Balázs Sarkadi, N. Barry Elkind

Research output: Contribution to journalArticle

69 Citations (Scopus)

Abstract

The closely related human ABC half-transporters, ABCG1 and ABCG4, have been suggested to play an important role in cellular lipid/sterol regulation but no experimental data for their expression or function are available. We expressed ABCG1 and ABCG4 and their catalytic site mutant variants in insect cells, generated specific antibodies, and analyzed their function in isolated membrane preparations. ABCG1 had a high basal ATPase activity, further stimulated by lipophilic cations and significantly inhibited by cyclosporin A, thyroxine or benzamil. ABCG4 had a lower basal ATPase activity which was not modulated by any of the tested compounds. The catalytic site (K-M) mutants had no ATPase activity. Since dimerization is a requirement for half-transporters, we suggest that both ABCG1 and ABCG4 function as homodimers. Importantly, we also found that co-expression of the ABCG4-KM mutant selectively abolished the ATPase activity of the ABCG1 and therefore they most probably also heterodimerize. The heterologous expression, specific recognition, and functional characterization of these transporters should help to delineate their physiological role and mechanism of action.

Original languageEnglish
Pages (from-to)860-867
Number of pages8
JournalBiochemical and biophysical research communications
Volume320
Issue number3
DOIs
Publication statusPublished - Jul 30 2004

Keywords

  • ABC half-transporter
  • ABCG1
  • ABCG4
  • Dominant negative
  • Drug-stimulated ATPase activity
  • Heterodimer
  • Sf9 cells

ASJC Scopus subject areas

  • Biophysics
  • Biochemistry
  • Molecular Biology
  • Cell Biology

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