Autosomal dominant hypercholesterolemia (ADH; OMIM144400), a risk factor for coronary heart disease, is characterized by an increase in low-density lipoprotein cholesterol levels that is associated with mutations in the genes LDLR (encoding low-density lipoprotein receptor) or APOB (encoding apolipoprotein B). We mapped a third locus associated with ADH, HCHOLA3 at 1p32, and now report two mutations in the gene PCSK9 (encoding proprotein convertase subtilisin/kexin type 9) that cause ADH. PCSK9 encodes NARC-1 (neural apoptosis regulated convertase), a newly identified human subtilase that is highly expressed in the liver and contributes to cholesterol homeostasis.

Background: Severe acute respiratory syndrome (SARS) is caused by a newly discovered coronavirus (SARS-CoV). No effective prophylactic or post-exposure therapy is currently available.

Seven secretory mammalian kexin-like subtilases have been identified that cleave a variety of precursor proteins at monobasic and dibasic residues. The recently characterized pyrolysin-like subtilase SKI-1 cleaves proproteins at nonbasic residues. In this work we describe the properties of a proteinase K-like subtilase, neural apoptosis-regulated convertase 1 (NARC-1), representing the ninth member of the secretory subtilase family. Biosynthetic and microsequencing analyses of WT and mutant enzyme revealed that human and mouse pro-NARC-1 are autocatalytically and intramolecularly processed into NARC-1 at the (Y,I)VV(V,L)(L,M)2 motif, a site that is representative of its enzymic specificity. In vitro peptide processing studies and͞or Ala substitutions of the P1-P5 sites suggested that hydrophobic͞aliphatic residues are more critical at P1, P3, and P5 than at P2 or P4. NARC-1 expression is highest in neuroepithelioma SK-N-MCIXC, hepatic BRL-3A, and in colon carcinoma LoVo-C5 cell lines. In situ hybridization and Northern blot analyses of NARC-1 expression during development in the adult and after partial hepatectomy revealed that it is expressed in cells that have the capacity to proliferate and differentiate. These include hepatocytes, kidney mesenchymal cells, intestinal ileum, and colon epithelia as well as embryonic brain telencephalon neurons. Accordingly, transfection of NARC-1 in primary cultures of embryonic day 13.5 telencephalon cells led to enhanced recruitment of undifferentiated neural progenitor cells into the neuronal lineage, suggesting that NARC-1 is implicated in the differentiation of cortical neurons.cleavage specificity ͉ hypercholesterolemia ͉ neurogenesis ͉ hepatogenesis

A recombinant vaccinia virus vector was used to coexpress the two candidate mouse prohormone convertases, PC1 and PC2, together with mouse proopiomelanocortin (POMC) in the constitutively secreting cell line BSC-40 and in the endocrine tissue-derived cell lines PC12 and AtT-20, which exhibit regulated secretion. Monitoring of POMC processing demonstrated the distinct cleavage specificities of PCi and PC2, since in the cell lines analyzed (i) PCi cleaves POMC into corticotropin and fB-lipotropin, (ii) PC2 cleaves POMC into (3-endorphin, an N-terminally extended corticotropin containing the joining peptide, and either aMSH or desacetyl-aMSH, and (iii) PC2 cleaves POMC at the five pairs of basic residues analyzed, whereas PC1 cleaves two of them preferentially, suggesting that PC2 has a broader spectrum of activity than PC1. These data are consistent with our hypothesis on the physiological role of PCi and PC2 as distinct proprotein convertases acting alone or together to produce a set of tissuespecific maturation products in the brain and in peripheral tissues.Limited proteolysis of inactive precursors at pairs of basic residues or, less frequently, at single basic amino acids (1, 2) is a general mechanism by which the cell produces a variety of active proteins and peptides. Until recently, the molecular nature of the processing enzyme(s) was not identified except for the yeast pro-a mating factor precursor, where a subtilisin-like serine proteinase called KEX2 was proven to be the physiological convertase (3). In the last year, different groups obtained the complete cDNA structures of three distinct candidate mammalian convertases, furin (4), PC1 (5, 6), and PC2 (5, 7). The putative convertase function of these proteins was largely based on sequence homology with KEX2 (8, 9) and on their tissue and cellular distribution, especially for PC1 and PC2 (5, 6). Here we show that the expression of PC1 or PC2 by vaccinia virus (VV) recombinants results in the production of distinct proteolytic enzymes in three cell lines: the mouse pituitary corticotroph line AtT-20 and two that do not express these enzymes endogenously, the African green monkey kidney epithelial cell line BSC-40 and the rat pheochromocytoma cell line PC12. These proteinases cleave proopiomelanocortin (POMC) into the same set of distinct peptides known to be produced in vivo in the hypothalamus, adenohypophysis (AP), and pars intermedia of the pituitary, including adrenocorticotropin (ACTH), p-lipotropin (,8LPH), ,f-endorphin (f3End), and a-melanotropin (aMSH) or desacetyl-aMSH.MATERIALS AND METHODS Ws. Purified recombinant VVs using the full-length mouse (i) PC1 and mPC2 cDNA inserts (5, 6) (VV:mPC1 and VV:mPC2) were prepared as described (10). VV:POMC (mouse) was a gift of G. Thomas (Vollum Institute, Portland, OR).Northern Blot Analysis. Total RNA was prepared as described (11). The [a-32P]UTP-labeled cRNA probes were generated from cDNA sequences of mPC1 (6) and mPC2 (5) inserted in plasmid Rc/CMV vector (Invitrogen, San Diego) and linearized...