Since detergent-resistant lipid rafts are involved in pathogen invasion, cholesterol homeostasis, angiogenesis, neurodegenerative diseases and signal transduction, protein identification in the rafts could provide important information to study their function. Here, we analyzed detergent-resistant raft proteins isolated from rat liver by capillary liquid chromatography-tandem mass spectrometry. Out of 196 proteins identified, 32% belonged to the raft or plasma membrane, 24% to mitochondrial, 20% to microsomal, 7% to miscellaneous, and 17% are unknown proteins. For example, membrane-bound receptors, trimeric GTP-binding proteins, ATP-binding cassette transporters, and glycosylphosphatidylinositol-anchored proteins were identified in this analysis. Unexpectedly, there were many mitochondrial proteins, raising a new issue for the presence of mitochondrial rafts or the localization of mitochondrial proteins into plasma membrane rafts. We confirmed that ATP synthase α and β were expressed on the surface of the plasma membrane in HepG2 hepatocytes by immunofluorescence, cell surface biotinylation, and cellular fractionation. They had two distinct biochemical properties, detergent insolubility and low density, suggesting that the ATP synthase complex might be located in plasma membrane rafts as well as in the mitochondria.
Bibliographical noteFunding Information:
The studies described in this paper were supported by the Polish National Science Centre grants No 2015/17/B/NZ1/02496 (to AS), 2015/18/E/NZ1/00737 (to BK), the European Union's Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement No 665735 (Bio4Med) and by the Nencki Institute of Experimental Biology .
- ATP synthase
- Capillary liquid chromatography-tandem mass spectrometry
- Lipid rafts
ASJC Scopus subject areas
- Molecular Biology