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[The family of HDL receptor]
1Jikei University School of Medicine, Internal Medicine (III).
Several HDL binding proteins have recently cloned and their roles in HDL metabolism have been gradually elucidated. HBP (vigilin), which lacks a transmembrane domain, is responsive to cell cholesterol levels, however, its physiological roles remain unknown. SR-B1, a member of the class B scavenger receptor, has been reported to bind with not only oxidized LDL but also HDL. The level of SR-B1 expression correlates with both the selective cholesterol transfer into cells and cholesterol efflux from cells. These data suggest that SR-B1 plays important roles in steroid hormone production. HB2 shows high sequence homology with ALCAM (activated leukocyte-cell adhesion molecule). When overexpressed with HB2, HDL binding is increased in the cells. After PMA-induced differentiation of monocytes into macrophages, HB2 mRNA is elevated, which correlates with increased binding of HDL, but is down-regulated by cholesterol loading of macrophages. However, physiological role of HB2 also remains unknown.
Several HDL binding proteins have recently cloned and their roles in HDL metabolism have been gradually elucidated. HBP (vigilin), which lacks a transmembrane domain, is responsive to cell cholesterol levels, however, its physiological roles remain unknown. SR-B1, a member of the class B scavenger receptor, has been reported to bind with not only oxidized LDL but also HDL. The level of SR-B1 expression correlates with both the selective cholesterol transfer into cells and cholesterol efflux from cells. These data suggest that SR-B1 plays important roles in steroid hormone production. HB2 shows high sequence homology with ALCAM (activated leukocyte-cell adhesion molecule). When overexpressed with HB2, HDL binding is increased in the cells. After PMA-induced differentiation of monocytes into macrophages, HB2 mRNA is elevated, which correlates with increased binding of HDL, but is down-regulated by cholesterol loading of macrophages. However, physiological role of HB2 also remains unknown.