Expression cloning and characterization of a novel glycosylphosphatidylinositol-anchored high density lipoprotein-binding protein, GPI-HBP1.
By expression cloning using fluorescent-labeled high density lipoprotein (HDL), we isolated two clones that conferred the cell surface binding of HDL. Nucleotide sequence of the two clones revealed that one corresponds to scavenger receptor class B, type 1 (SRBI) and the other encoded a novel protein with 228 amino acids. The primary structure of the newly identified HDL-binding protein resembles GPI-anchored proteins consisting of an N-terminal signal sequence, an acidic region with a cluster of aspartate and glutamate residues, an Ly-6 motif highly conserved among the lymphocyte antigen family, and a C-terminal hydrophobic region. This newly identified HDL-binding protein designated GPI-anchored HDL-binding protein 1 (GPI-HBP1), was susceptible to phosphatidylinositol-specific phospholipase C treatment and binds HDL with high affinity (calculated K(d) = 2-3 microg/ml). Similar to SRBI, GPI-HBP1 mediates selective lipid uptake but not the protein component of HDL. Among various ligands for SRBI, HDL was most preferentially bound to GPI-HBP1. In contrast to SRBI, GPI-HBP1 lacked HDL-dependent cholesterol efflux. The GPI-HBP1 transcripts were detected with the highest levels in heart and, to a much lesser extent, in lung and liver. In situ hybridization revealed the accumulation of GPI-HBP1 transcripts in cardiac muscle cells, hepatic Kupffer cells and sinusoidal endothelium, and bronchial epithelium and alveolar macrophages in the lung.
Ioka
Ryoichi X
RX
Tohoku University Gene Research Center, Sendai 981-8555, Japan.
Kang
Man-Jong
MJ
Kamiyama
Shin
S
Kim
Dong-Ho
DH
Magoori
Kenta
K
Kamataki
Akihisa
A
Ito
Yuichiro
Y
Takei
Yumiko A
YA
Sasaki
Masako
M
Suzuki
Takashi
T
Sasano
Hironobu
H
Takahashi
Sadao
S
Sakai
Juro
J
Fujino
Takahiro
T
Yamamoto
Tokuo T
TT
D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D015152:Blotting, Northern; D016466:CHO Cells; D002784:Cholesterol / Q000378:metabolism; D003001:Cloning, Molecular; D006224:Cricetinae; D018076:DNA, Complementary / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D017261:Glycosylphosphatidylinositols / Q000378:metabolism*; D017403:In Situ Hybridization; D007700:Kinetics; D007728:Kupffer Cells; D008024:Ligands; D008075:Lipoproteins, HDL / Q000378:metabolism*; D008099:Liver / Q000378:metabolism; D008168:Lung / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D009206:Myocardium / Q000378:metabolism; D011485:Protein Binding; D017434:Protein Structure, Tertiary; D012333:RNA, Messenger / Q000378:metabolism; D018110:Receptors, Lipoprotein / Q000737:chemistry* / Q000235:genetics*; D013997:Time Factors; D014018:Tissue Distribution; D014162:Transfection
D018076:DNA, Complementary; C472779:GPI-HBP1 protein, mouse; D017261:Glycosylphosphatidylinositols; D008024:Ligands; D008075:Lipoproteins, HDL; D012333:RNA, Messenger; D018110:Receptors, Lipoprotein; D002784:Cholesterol