Lipid raft proteome reveals ATP synthase complex in the cell surface.
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 alpha and beta 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.
Bae
Tae-Jung
TJ
Graduate School of Life Sciences and Biotechnology, Korea University, Seoul, Korea.
Kim
Min-Sik
MS
Kim
Jun-Woo
JW
Kim
Bong-Woo
BW
Choo
Hyo-Jung
HJ
Lee
Joong-Won
JW
Kim
Ki-Bum
KB
Lee
Chang Seok
CS
Kim
Ji-Hyun
JH
Chang
Sun Young
SY
Kang
Chang-Yuil
CY
Lee
Sang-Won
SW
Lee
Song-Won
SW
Ko
Young-Gyu
YG
D000595:Amino Acid Sequence; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism*; D002853:Chromatography, Liquid; D045304:Cytochromes c; D008099:Liver / Q000378:metabolism; D008297:Male; D013058:Mass Spectrometry; D021962:Membrane Microdomains / Q000378:metabolism*; D008565:Membrane Proteins; D025261:Mitochondrial Proton-Translocating ATPases / Q000378:metabolism*; D008969:Molecular Sequence Data; D020543:Proteome / Q000378:metabolism*; D051381:Rats
D008565:Membrane Proteins; D020543:Proteome; C106354:flotillins; D045304:Cytochromes c; C497342:ATP synthase beta subunit, rat; D025261:Mitochondrial Proton-Translocating ATPases