PCSK9 Prosegment chimera as novel inhibitors of LDLR degradation

  1. Get@NRC: PCSK9 Prosegment chimera as novel inhibitors of LDLR degradation (Opens in a new window)
DOIResolve DOI: http://doi.org/10.1371/journal.pone.0072113
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Journal titlePLoS ONE
Article numbere72113
Subjectimmunoglobulin G1; low density lipoprotein receptor; PCSK9 inhibitor; proteinase inhibitor; recombinant Fcpro protein; recombinant protein; unclassified drug; amino terminal sequence; article; carboxy terminal sequence; cell strain HEK293; cell strain HepG2; controlled study; down regulation; enzyme active site; enzyme activity; human; human cell; in vitro study; protein binding; protein degradation; protein domain; protein expression; protein function; protein protein interaction; protein secretion
AbstractThe proprotein convertase PCSK9, a target for the treatment of hypercholesterolemia, is a negative regulator of the LDL receptor (LDLR) leading to its degradation in endosomes/lysosomes and up-regulation of plasma LDL-cholesterol levels. The proprotein convertases, a family of nine secretory serine proteases, are first synthesized as inactive zymogens. Except for PCSK9, all other convertases are activated following the autocatalytic excision of their inhibitory N-terminal prosegment. PCSK9 is unique since the mature enzyme exhibits a cleaved prosegment complexed with the catalytic subunit and has no protease activity towards other substrates. Similar to other convertases, we hypothesized that the in trans presence of the PCSK9 prosegment would interfere with PCSK9's activity on the LDLR. Since the prosegment cannot be secreted alone, we engineered a chimeric protein using the Fc-region of human IgG1 fused to the PCSK9 prosegment. The expression of such Fcpro-fusion protein in HEK293 and HepG2 cells resulted in a secreted protein that binds PCSK9 and markedly inhibits its activity on the LDLR. This was observed by either intracellular co-expression of PCSK9 and Fcpro or by an extracellular in vitro co-incubation of Fcpro with PCSK9. Structure-function studies revealed that the inhibitory function of Fcpro does not require the acidic N-terminal stretch (residues 31-58) nor the C-terminal Gln152 of the prosegment. Fcpro likely interacts with the prosegment and/or catalytic subunit of the prosegment≡PCSK9 complex thereby allosterically modulating its function. Our data suggest a novel strategic approach for the design and isolation of PCSK9 inhibitors. © 2013 Luna Saavedra et al.
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AffiliationNational Research Council Canada (NRC-CNRC); NRC Institute for Biological Sciences (IBS-ISB)
Peer reviewedYes
NPARC number21269754
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Record identifiere14dd102-92ae-4cc3-90c3-996e1fa83227
Record created2013-12-13
Record modified2016-05-09
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