Progress of Niemann-Pick type C1 Like 1 on cholesterol metabolism / 生理学报

The polytopic transmembrane protein, Niemann-Pick type C1 Like 1 (NPC1L1), is the key point of exogenous cholesterol absorption and plays an important role in cholesterol metabolism. However, the molecular mechanism of NPC1L1's role in cholesterol uptake remains unclear. NPC1L1 expression is highly regulated by a variety of molecular actors. Nuclear receptors regulate NPC1L1 expression through its promoter region. Polyunsaturated fatty acids down-regulates NPC1L1 expression by the way of sterol regulatory element binding protein 2 (SREBP2). In addition, curcumin and sphingosine-phosphate take part in the regulation of NPC1L1 expression. NPC1L1 has been recognized as an essential protein for sterol absorption and is the molecular target of ezetimibe. Moreover, inhibition of the expression of NPC1L1 has been shown to have beneficial effects on components of the metabolic syndrome. The recent progress in the structure, function and regulation of NPC1L1 is reviewed.

Current Progress in ATP-binding Cassette Transporter Al / 生物化学与生物物理进展

ATP-binding cassette transporter Al (ABCAl) is a kind of membrane intergrate protein and may have multiple and diverse functions. It mediates the cellular efflux of phospholipids and cholesterol to lipid-poor apolipoproteinA- Ⅰ (apoA- Ⅰ ) and plays a significant role in high density lipoprotein (HDL) metabolism. Mutations in human ABCAl cause severe HDL deficiencies characterized by the virtual absence of apoA- Ⅰ and HDL and prevalent atherosclerosis. ABCAl expression is highly regulated and implies a variety of molecular actors. All of the nuclear receptors which involve in regulation of ABCAl expression act via the DR4 element in the ABCAl promoter. cAMP up-regulates ABCAl expression by acting both at the transcriptional and translational level. Cytokines have been shown to exert pleiotropic and antinomic effects on ABCAl transcription, In addition to these, some of enzymes and proteins such as protein kinase A, protein kinase CK2, cathepsin D are involved in the regulation of ABCAl expression. The recent progress in the structure, function and regulation of ABCAl transporter is reviewed.