Expression of human scavenger receptor B1 on and in human platelets.
OBJECTIVE
The abundance of HDL particles correlates inversely with the incidence of coronary heart disease. The human scavenger receptor B1 (hSR-B1/CLA-1) is a receptor for HDL. Expression of hSR-B1/CLA-1 mRNA and protein in human platelets was determined using reverse transcriptase-polymerase chain reaction and Western blot, respectively. Presence of the protein on the surface of platelets was shown using flow cytometry.


RESULTS
Immunochemical staining for hSR-B1/CLA-1 showed that it was expressed in megakaryocytes, the platelet precursors of human bone marrow. These findings prompted us to ask whether hSR-B1/CLA-1 was differentially expressed on platelets obtained from patients with atherosclerotic disease compared with those in control subjects. Our findings showed that abundance of hSR-B1/CLA-1 was significantly reduced on the surface of platelets from patients with atherosclerotic disease. The reduced levels of hSR-B1/CLA-1 were associated with increased cholesterol ester content in platelets from patients with atherosclerotic disease compared with control subjects. A negative correlation existed between hSR-B1/CLA-1 expression and platelet aggregation. In summary, our studies show that the HDL receptor hSR-B1/CLA-1 is expressed in platelets and their precursor, the megakaryocyte. The levels of hSR-B1/CLA-1 expression correlate inversely with cholesterol ester content and platelet aggregation.


CONCLUSIONS
These findings suggest that determining the level of hSR-B1/CLA-1 expression on the platelets may be a useful clinical marker for atherosclerotic diseases.
Imachi
Hitomi
H
First Department of Internal Medicine, Central Laboratory, Kagawa Medical University, 1750-1, Miki-cho, Kita-gun, Kagawa, 761-0793, Japan.
Murao
Koji
K
Cao
Wenming
W
Tada
Satoshi
S
Taminato
Tomohiko
T
Wong
Norman C W
NC
Takahara
Jiro
J
Ishida
Toshihiko
T
D000328:Adult; D000368:Aged; D001161:Arteriosclerosis / Q000097:blood*; D015415:Biomarkers; D001792:Blood Platelets / Q000737:chemistry*; D018955:CD36 Antigens / Q000097:blood* / Q000235:genetics; D002462:Cell Membrane / Q000737:chemistry; D002478:Cells, Cultured; D002784:Cholesterol / Q000378:metabolism; D002788:Cholesterol Esters / Q000097:blood; D005260:Female; D006801:Humans; D008297:Male; D008533:Megakaryocytes / Q000737:chemistry; D008565:Membrane Proteins; D008875:Middle Aged; D010974:Platelet Aggregation; D012333:RNA, Messenger / Q000097:blood; D011971:Receptors, Immunologic; D018110:Receptors, Lipoprotein; D051116:Receptors, Scavenger; D051122:Scavenger Receptors, Class B; D014162:Transfection
D015415:Biomarkers; D018955:CD36 Antigens; D002788:Cholesterol Esters; D008565:Membrane Proteins; D012333:RNA, Messenger; D011971:Receptors, Immunologic; D018110:Receptors, Lipoprotein; D051116:Receptors, Scavenger; C454739:Scarb1 protein, mouse; D051122:Scavenger Receptors, Class B; D002784:Cholesterol