title: Regulatory effects of peptides from the pro and catalytic domains of proprotein convertase subtilisin/kexin 9 (PCSK9) on low-density lipoprotein receptor (LDL-R).
abstract: BACKGROUND
  Proprotein convertase subtilisin/kexin 9 (PCSK9) is a proteinase K subtype of mammalian subtilases collectively called PCSKs. PCSK9 upregulates plasma-cholesterol level by degrading low-density lipoprotein receptor (LDL-R). As a result, PCSK9 is a major target for intervention of hypercholesterolemia and in this regard PCSK9- inhibitors may find useful therapeutic and biochemical applications.
  
  
  OBJECTIVE
  Our objective is to develop short peptide based PCSK9 inhibitors from its own pro and/or catalytic domains.
  
  
  RESULTS
  Using human (h) hepatic HepG2 and Huh7 cells we showed that the acidic N-terminal hPCSK(931-60), 31-40 and the mid-basic hPCSK(991-120) peptides derived from hPCSK9-prodomain significantly enhanced LDL-R level without altering PCSK9 content. Moreover, the physiologically relevant phoshpho-Ser47 and sulpho-Y38 containing hPCSK(931-60) peptides diminished LDL-R level suggesting that such posttranslational modifications in the prodomain lead to gain of PCSK9- functional activity. These modifications are thus expected to lead to even higher level of plasma cholesterol. As expected, addition of purified recombinant-PCSK9 to the culture medium decreased LDL-R level which can be restored back by exogenous addition of hPCSK(931-40), (31-60) or (91-120) peptides. Using a series of truncated peptides, we identified the most potent LDL-R promoting activity to reside within the prodomain sequence hPCSK(931-37). Two catalytic domain peptides hPCSK(9181-200) and hPCSK(9368-390), containing proposed LDL-R interacting sites have been shown to diminish LDL-R level.
  
  
  CONCLUSIONS
  Our study concludes that specific peptides from pro- and catalytic domains of hPCSK9 can regulate LDL-R in cell based assay and may be useful for development of novel therapeutics for cholesterol regulation.
authors.affiliation: Chronic Diseases Program, Regional Protein Chemistry Center, Ottawa Hospital Research Institute, 725 Parkdale Av, Ottawa, Ontario, Canada.
authors.forename: H
authors.initials: H
authors.lastname: Palmer-Smith
authors.forename: A
authors.initials: A
authors.lastname: Basak
mesh_terms: D000595:Amino Acid Sequence; D020134:Catalytic Domain; D045744:Cell Line, Tumor; D002942:Circular Dichroism; D006801:Humans; D008969:Molecular Sequence Data; D010455:Peptides / Q000138:chemical synthesis / Q000494:pharmacology*; D000071449:Proprotein Convertase 9; D043484:Proprotein Convertases; D017433:Protein Structure, Secondary; D017434:Protein Structure, Tertiary; D011973:Receptors, LDL / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D012697:Serine Endopeptidases / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism; D015842:Serine Proteinase Inhibitors / Q000138:chemical synthesis / Q000494:pharmacology*
chemical_list: D010455:Peptides; D011973:Receptors, LDL; D011994:Recombinant Proteins; D015842:Serine Proteinase Inhibitors; C472125:PCSK9 protein, human; D000071449:Proprotein Convertase 9; D043484:Proprotein Convertases; D012697:Serine Endopeptidases