Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a secreted protein that controls plasma LDL cholesterol levels by posttranslational regulation of the LDL receptor (LDLR). Previously, we showed that PCSK9 binds specifically to an EGF-like repeat (EGF-A) in LDLR and reroutes the receptor from endosomes to lysosomes rather than to the cell surface. Here, we defined the regions in LDLR and PCSK9 that are required for receptor degradation and examined the relationship between PCSK9 binding and LDLR conformation. Addition of PCSK9 to cultured hepatocytes promoted degradation of WT LDLR and of receptors lacking up to four ligand binding domains, EGF-B or the clustered O-linked sugar region. In contrast, LDLRs lacking the entire ligand binding domain or the ␤-propeller domain failed to be degraded, although they bound and internalized PCSK9. Using gel filtration chromatography, we assessed the effects of PCSK9 binding on an acid-dependent conformational change that happens in the extracellular domain of the LDLR. Although PCSK9 prevented the reduction in hydrodynamic radius of the receptor that occurs at a reduced pH, the effect was not sufficient for LDLR degradation. A truncated version of PCSK9 containing the prodomain and the catalytic domain, but not the C-terminal domain, bound the receptor but did not stimulate LDLR degradation. Thus, domains in both the LDLR and PCSK9 that are not required for binding (or internalization) are essential for PCSK9-mediated degradation of the LDLR.cholesterol ͉ proprotein convertase ͉ ␤-propeller ͉ endocytosis P lasma levels of LDL cholesterol are directly related to the risk of coronary atherosclerosis. The tight association between LDL levels and ischemic heart disease is illustrated by the fact that all monogenic forms of severe hypercholesterolemia are accompanied by premature coronary atherosclerosis. The major pathway for removal of LDL from the circulation is by LDL receptor (LDLR)-mediated endocytosis in the liver. Mutations in the LDLR (1), the ligand for the LDLR (apolipoprotein B-100) (2), or an LDLR adaptor protein (ARH/LDLRAP) (3) all cause hypercholesterolemia by reducing the clearance of circulating LDL. In 2003, a third form of autosomal-dominant hypercholesterolemia was identified that is caused by selected missense mutations in proprotein convertase subtilisin/kexin type 9 (PCSK9) (4).PCSK9 is a 692-aa secreted glycoprotein composed of a 22-aa signal sequence, a prodomain, a catalytic domain that resembles the proteinase K family of subtilisin-like serine proteases, and a cysteine-and histidine-rich C-terminal domain that is unique to this member of the proprotein convertase family (5). In the endoplasmic reticulum, PCSK9 undergoes autocatalytic cleavage between residues 151 and 152 (5, 6), releasing the N-terminal prodomain, which remains noncovalently attached to the catalytic domain, physically shielding the catalytic triad as the protein transits through the secretory pathway (7,8). PCSK9 circulates in the blood (9) and binds the extracellular domain ...

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In this paper, the transmission evolution process based on life-cycle model is proposed, which includes five stages: Producing, Outbreak, Spread, Remission and Termination. It constructs the information transmission model of product quality and safety based on the media influence. And finally the computational result is presented, which show that the proposed model is effective and feasible.

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