Key points are not available for this paper at this time.
Proprotein convertase subtilisin/kexin type 9 (PCSK9), a member of the proteinase K subfamily of subtilases, promotes internalization and degradation of low density lipoprotein receptors (LDLRs) after binding the receptor on the surface of hepatocytes. PCSK9 has autocatalytic activity that releases the prodomain at the N terminus of the protein. The prodomain remains tightly associated with the catalytic domain as the complex transits the secretory pathway. It is not known whether enzymatic activity is required for the LDLR-reducing effects of PCSK9. Here we expressed the prodomain together with a catalytically inactive protease domain in cells and purified the protein from the medium. The ability of the catalytically inactive PCSK9 to bind and degrade LDLRs when added to culture medium of human hepatoma HepG2 cells at physiological concentrations was similar to that seen using wild-type protein. Similarly, a catalytic-dead version of a gain-of-function mutant, PCSK9(D374Y), showed no loss of activity compared with a catalytically active counterpart; both proteins displayed ∼10-fold increased activity in degradation of cell surface LDLRs compared with wild-type PCSK9. We conclude that the ability of PCSK9 to degrade LDLRs is independent of catalytic activity and suggest that PCSK9 functions as a chaperone to prevent LDLR recycling and/or to target LDLRs for lysosomal degradation. Proprotein convertase subtilisin/kexin type 9 (PCSK9), a member of the proteinase K subfamily of subtilases, promotes internalization and degradation of low density lipoprotein receptors (LDLRs) after binding the receptor on the surface of hepatocytes. PCSK9 has autocatalytic activity that releases the prodomain at the N terminus of the protein. The prodomain remains tightly associated with the catalytic domain as the complex transits the secretory pathway. It is not known whether enzymatic activity is required for the LDLR-reducing effects of PCSK9. Here we expressed the prodomain together with a catalytically inactive protease domain in cells and purified the protein from the medium. The ability of the catalytically inactive PCSK9 to bind and degrade LDLRs when added to culture medium of human hepatoma HepG2 cells at physiological concentrations was similar to that seen using wild-type protein. Similarly, a catalytic-dead version of a gain-of-function mutant, PCSK9(D374Y), showed no loss of activity compared with a catalytically active counterpart; both proteins displayed ∼10-fold increased activity in degradation of cell surface LDLRs compared with wild-type PCSK9. We conclude that the ability of PCSK9 to degrade LDLRs is independent of catalytic activity and suggest that PCSK9 functions as a chaperone to prevent LDLR recycling and/or to target LDLRs for lysosomal degradation. Secretory proprotein convertase (PC) 4The abbreviations used are: PC, proprotein convertase; ER, endoplasmic reticulum; LDL, low density lipoprotein; LDLR, LDL receptor; HEK, human embryonic kidney; N.D., not detected. enzymes are structurally related to the bacterial subtilisin-like serine protease kexin found in yeast. There are nine subtilisin-like serine proteinases in mammals designated PC1/3, PC2, furin, PC4, PC5/6, PACE4, PC7, S1P (site-1 protease), and PCSK9 (proprotein convertase subtilisin/kexin type 9) (1Seidah N.G. Prat A. J. Mol. Med. 2007; (, in press)PubMed Google Scholar). PCs share a general structure that consists of a signal sequence followed by a prodomain, a conserved subtilisin-like catalytic domain, and a variable C-terminal domain (2Seidah N.G. Chretien M. Curr. Opin. Biotechnol. 1997; 8: 602-607Crossref PubMed Scopus (241) Google Scholar, 3Seidah N.G. Benjannet S. Wickham L. Marcinkiewicz J. Jasmin S.B. Stifani S. Basak A. Prat A. Chretien M. Proc. Natl. Acad. Sci. U. S. A. 2003; 100: 928-933Crossref PubMed Scopus (933) Google Scholar). All family members except PC2 undergo autocatalytic cleavage in the endoplasmic reticulum (ER), releasing the prodomain (4Benjannet S. Rondeau N. Paquet L. Boudreault A. Lazure C. Chretien M. Seidah N.G. Biochem. J. 1993; 294: 735-743Crossref PubMed Scopus (173) Google Scholar, 5Molloy S.S. Thomas L. VanSlyke J.K. Stenberg P.E. Thomas G. EMBO J. 1994; 13: 18-33Crossref PubMed Scopus (420) Google Scholar, 6Nakayama K. Biochem. J. 1997; 327: 625-635Crossref PubMed Scopus (705) Google Scholar). PC1/3, PC2, furin, PC4, PC5/6, PACE4, and PC7 cleave at single or paired basic amino acids with the general sequence (K/R)-(Xn)-(K/R)↓. S1P and PCSK9 cleave after non-basic amino acids in the motifs RXX(L/K)↓ (7Cheng D. Espenshade P.J. Slaughter C.A. Jaen J.C. Brown M.S. Goldstein J.L. J. Biol. Chem. 1999; 274: 22805-22812Abstract Full Text Full Text PDF PubMed Scopus (66) Google Scholar) and (V/I) FAQ↓ (8Naureckiene S. Ma L. Sreekumar K. Purandare U. Lo C.F. Huang Y. Chiang L.W. Grenier J.M. Ozenberger B.A. Jacobsen J.S. Kennedy J.D. DiStefano P.S. Wood A. Bingham B. Arch. Biochem. Biophys. 2003; 420: 55-67Crossref PubMed Scopus (137) Google Scholar, 9Benjannet S. Rhainds D. Essalmani R. Mayne J. Wickham L. Jin W. Asselin M.C. Hamelin J. Varret M. Allard D. Trillard M. Abifadel M. Tebon A. Attie A.D. Rader D.J. Boileau C. Brissette L. Chretien M. Prat A. Seidah N.G. J. Biol. Chem. 2004; 279: 48865-48875Abstract Full Text Full Text PDF PubMed Scopus (515) Google Scholar), respectively. The prodomain serves a dual function, assisting in both the proper folding of the protease domain and the regulation of catalytic activity (6Nakayama K. Biochem. J. 1997; 327: 625-635Crossref PubMed Scopus (705) Google Scholar, 10Baker D. Shiau A.K. Agard D.A. Curr. Opin. Cell Biol. 1993; 5: 966-970Crossref PubMed Scopus (154) Google Scholar, 11Anderson E.D. Molloy S.S. Jean F. Fei H. Shimamura S. Thomas G. J. Biol. Chem. 2002; 277: 12879-12890Abstract Full Text Full Text PDF PubMed Scopus (107) Google Scholar). Autocatalytic cleavage of the zymogen in the ER is required for transport from this compartment (4Benjannet S. Rondeau N. Paquet L. Boudreault A. Lazure C. Chretien M. Seidah N.G. Biochem. J. 1993; 294: 735-743Crossref PubMed Scopus (173) Google Scholar, 5Molloy S.S. Thomas L. VanSlyke J.K. Stenberg P.E. Thomas G. EMBO J. 1994; 13: 18-33Crossref PubMed Scopus (420) Google Scholar, 6Nakayama K. Biochem. J. 1997; 327: 625-635Crossref PubMed Scopus (705) Google Scholar). The excised prodomain remains noncovalently associated with the protein and inhibits aberrant protease activity (6Nakayama K. Biochem. J. 1997; 327: 625-635Crossref PubMed Scopus (705) Google Scholar, 11Anderson E.D. Molloy S.S. Jean F. Fei H. Shimamura S. Thomas G. J. Biol. Chem. 2002; 277: 12879-12890Abstract Full Text Full Text PDF PubMed Scopus (107) Google Scholar). In most PCs, the prodomain undergoes a second proteolytic processing event that relieves inhibition and unmasks enzymatic activity in the appropriate compartment (11Anderson E.D. Molloy S.S. Jean F. Fei H. Shimamura S. Thomas G. J. Biol. Chem. 2002; 277: 12879-12890Abstract Full Text Full Text PDF PubMed Scopus (107) Google Scholar). Protein substrates are known for eight of the nine subtilisinlike serine proteinases. Cleavage of the substrates generally results in the production of mature bioactive proteins as well as processing intermediates or, occasionally, the inactivation of the cleaved protein (12Seidah N.G. Khatib A.M. Prat A. Biol. Chem. 2006; 387: 871-877Crossref PubMed Scopus (85) Google Scholar). The only subtilisin-like serine proteinase without an identified protein substrate is PCSK9. Like the other PCs, PCSK9 is synthesized as an inactive proenzyme and contains a triad of residues (Asp186, His226, and Ser386) that are required for catalytic activity (3Seidah N.G. Benjannet S. Wickham L. Marcinkiewicz J. Jasmin S.B. Stifani S. Basak A. Prat A. Chretien M. Proc. Natl. Acad. Sci. U. S. A. 2003; 100: 928-933Crossref PubMed Scopus (933) Google Scholar). The ∼74-kDa precursor form of PCSK9 undergoes intramolecular autocatalytic cleavage in the ER, which produces a 14-kDa prodomain and a ∼60-kDa catalytic fragment (8Naureckiene S. Ma L. Sreekumar K. Purandare U. Lo C.F. Huang Y. Chiang L.W. Grenier J.M. Ozenberger B.A. Jacobsen J.S. Kennedy J.D. DiStefano P.S. Wood A. Bingham B. Arch. Biochem. Biophys. 2003; 420: 55-67Crossref PubMed Scopus (137) Google Scholar, 9Benjannet S. Rhainds D. Essalmani R. Mayne J. Wickham L. Jin W. Asselin M.C. Hamelin J. Varret M. Allard D. Trillard M. Abifadel M. Tebon A. Attie A.D. Rader D.J. Boileau C. Brissette L. Chretien M. Prat A. Seidah N.G. J. Biol. Chem. 2004; 279: 48865-48875Abstract Full Text Full Text PDF PubMed Scopus (515) Google Scholar). The cleaved prodomain remains associated with the catalytic domain forming a complex that is transported to the Golgi apparatus and subsequently secreted (3Seidah N.G. Benjannet S. Wickham L. Marcinkiewicz J. Jasmin S.B. Stifani S. Basak A. Prat A. Chretien M. Proc. Natl. Acad. Sci. U. S. A. 2003; 100: 928-933Crossref PubMed Scopus (933) Google Scholar, 9Benjannet S. Rhainds D. Essalmani R. Mayne J. Wickham L. Jin W. Asselin M.C. Hamelin J. Varret M. Allard D. Trillard M. Abifadel M. Tebon A. Attie A.D. Rader D.J. Boileau C. Brissette L. Chretien M. Prat A. Seidah N.G. J. Biol. Chem. 2004; 279: 48865-48875Abstract Full Text Full Text PDF PubMed Scopus (515) Google Scholar). Several studies have shown that the secreted mature form of PCSK9 contains an intact prodomain, with no evidence of secondary proteolytic processing (9Benjannet S. Rhainds D. Essalmani R. Mayne J. Wickham L. Jin W. Asselin M.C. Hamelin J. Varret M. Allard D. Trillard M. Abifadel M. Tebon A. Attie A.D. Rader D.J. Boileau C. Brissette L. Chretien M. Prat A. Seidah N.G. J. Biol. Chem. 2004; 279: 48865-48875Abstract Full Text Full Text PDF PubMed Scopus (515) Google Scholar, 13Lagace T.A. Curtis D.E. Garuti R. McNutt M.C. Park S.W. Prather H.B. Anderson N.N. Ho Y.K. Hammer R.E. Horton J.D. J. Clin. Investig. 2006; 116: 2995-3005Crossref PubMed Scopus (532) Google Scholar, 14Cunningham D. Danley D.E. Geoghegan K.F. Griffor M.C. Hawkins J.L. Subashi T.A. Varghese A.H. Ammirati M.J. Culp J.S. Hoth L.R. Mansour M.N. McGrath K.M. Seddon A.P. Shenolikar S. Stutzman-Engwall K.J. Warren L.C. Xia D. Qiu X. Nat. Struct. Mol. Biol. 2007; 14: 413-419Crossref PubMed Scopus (365) Google Scholar). Much attention has been focused on the biological role and potential substrates of PCSK9 since the discovery that gain-of-function mutations in PCSK9 cause an autosomal dominant form of familial hypercholesterolemia (15Abifadel M. Varret M. Rabes J-P. Ouguerram K. Devillers M. Cruaud C. Benjannet S. Wickham L. Erlich D. Villéger L. Farnier M. Beucler I. Bruckert E. Chambaz J. Chanu B. Lecerf J.-M. Luc G. Moulin P. Weissenbach J. Prat A. Krempf M. Junien C. Seidah N.G. Boileau C. Nat. Genet. 2003; 34: 154-156Crossref PubMed Scopus (2221) Google Scholar). Studies in mice in which PCSK9 was overexpressed demonstrated that PCSK9 mediates the destruction of LDL receptor (LDLR) protein in liver, the primary receptor responsible for LDL cholesterol clearance from plasma (9Benjannet S. Rhainds D. Essalmani R. Mayne J. Wickham L. Jin W. Asselin M.C. Hamelin J. Varret M. Allard D. Trillard M. Abifadel M. Tebon A. Attie A.D. Rader D.J. Boileau C. Brissette L. Chretien M. Prat A. Seidah N.G. J. Biol. Chem. 2004; 279: 48865-48875Abstract Full Text Full Text PDF PubMed Scopus (515) Google Scholar, 16Maxwell K.N. Breslow J.L. Proc. Natl. Acad. Sci. U. S. A. 2004; 101: 7100-7105Crossref PubMed Scopus (514) Google Scholar, 17Park S.W. Moon Y-A. Horton J.D. J. Biol. Chem. 2004; 279: 50630-50638Abstract Full Text Full Text PDF PubMed Scopus (434) Google Scholar, 18Lalanne F. Lambert G. Amar M.J.A. Chetiveaux M. Zair Y. Jarnoux A-L. Ouguerram K. Friburg J. Seidah N.G. Brewer Jr., H.B. Krempf M. Costet P. J. Lipid Res. 2005; 46: 1312-1319Abstract Full Text Full Text PDF PubMed Scopus (86) Google Scholar). Conversely, humans with loss-of-function mutations in PCSK9 have lower plasma LDL cholesterol levels, and PCSK9 knock-out mice have increased LDLR protein expression in liver (19Cohen J. Pertsemlidis A. Kotowski I.K. Graham R. Garcia C.K. Hobbs Nat. Genet. 2005; PubMed Scopus Google Scholar, S. Curtis D.E. Garuti R. Anderson N.N. Y. Ho Y.K. Hammer R.E. Moon Y-A. Horton J.D. Proc. Natl. Acad. Sci. U. S. A. 2005; PubMed Scopus Google Scholar). The from humans and the in studies in mice that PCSK9 the of the the by which PCSK9 this is only is with the secreted form of PCSK9 binding to the LDLR and in degradation of the receptor T.A. Curtis D.E. Garuti R. McNutt M.C. Park S.W. Prather H.B. Anderson N.N. Ho Y.K. Hammer R.E. Horton J.D. J. Clin. Investig. 2006; 116: 2995-3005Crossref PubMed Scopus (532) Google Scholar, J. Mol. Genet. 2006; PubMed Scopus Google Scholar). T.A. Garuti R. M. Horton J.D. J.C. Hobbs J. Biol. Chem. 2007; Full Text Full Text PDF PubMed Scopus Google Scholar) the binding of PCSK9 in the LDLR to the of the domain and showed that PCSK9 binding to this is required for LDLR degradation. the secreted form of PCSK9 to the complex T.A. Curtis D.E. Garuti R. McNutt M.C. Park S.W. Prather H.B. Anderson N.N. Ho Y.K. Hammer R.E. Horton J.D. J. Clin. Investig. 2006; 116: 2995-3005Crossref PubMed Scopus (532) Google Scholar). binding and internalization of PCSK9 and the LDLR are required for PCSK9 to degradation of the is not known whether PCSK9 catalytically in the to cleave the LDLR or an protein that LDLR of the catalytic activity using results in PCSK9 in the ER or in folding of the protein. we have this by the prodomain and an inactive catalytic domain in in cells and the protein complex from the medium. this we evidence that PCSK9 catalytic activity is not required for PCSK9 to bind and degrade LDLRs in human hepatoma HepG2 of and PCSK9 of are in the and of with PCSK9 cells using cells P.J. Proc. Natl. Acad. Sci. U. S. A. PubMed Scopus Google Scholar) with the prodomain and the other a catalytic of the are in the and from with human PCSK9 Y. T.A. L. Horton J.D. J.C. Hobbs J. Genet. 2006; Full Text Full Text PDF PubMed Scopus Google Scholar). human PCSK9 prodomain purified from was used to in the prodomain of PCSK9. used are in the PCSK9 cells with PCSK9 and proteins as T.A. Curtis D.E. Garuti R. McNutt M.C. Park S.W. Prather H.B. Anderson N.N. Ho Y.K. Hammer R.E. Horton J.D. J. Clin. Investig. 2006; 116: 2995-3005Crossref PubMed Scopus (532) Google Scholar). of purified human LDLR was as T.A. Curtis D.E. Garuti R. McNutt M.C. Park S.W. Prather H.B. Anderson N.N. Ho Y.K. Hammer R.E. Horton J.D. J. Clin. Investig. 2006; 116: 2995-3005Crossref PubMed Scopus (532) Google Scholar) using the in the the family of serine autocatalytic cleavage of the prodomain is required for the secretory pathway. the conserved serine of the catalytic triad in PCSK9 autocatalytic cleavage in of the protein the ER (8Naureckiene S. Ma L. Sreekumar K. Purandare U. Lo C.F. Huang Y. Chiang L.W. Grenier J.M. Ozenberger B.A. Jacobsen J.S. Kennedy J.D. DiStefano P.S. Wood A. Bingham B. Arch. Biochem. Biophys. 2003; 420: 55-67Crossref PubMed Scopus (137) Google Scholar, 17Park S.W. Moon Y-A. Horton J.D. J. Biol. Chem. 2004; 279: 50630-50638Abstract Full Text Full Text PDF PubMed Scopus (434) Google Scholar). whether catalytic activity is required for PCSK9 to an was to secreted catalytically inactive PCSK9. expression was that the signal and prodomain of PCSK9 followed by a second expression was that the signal and C-terminal of PCSK9 followed by a The cells to whether the PCSK9 expressed in and secreted from the shown in the prodomain and catalytic expressed in the cells of only when both The ability to PCSK9 by the prodomain and catalytic fragment of PCSK9 a to amino residues of the catalytic triad to whether catalytic activity was required for PCSK9 cell was subsequently that expressed the or a protein an for the serine at of the catalytic amino the autocatalytic cleavage of PCSK9 (3Seidah N.G. Benjannet S. Wickham L. Marcinkiewicz J. Jasmin S.B. Stifani S. Basak A. Prat A. Chretien M. Proc. Natl. Acad. Sci. U. S. A. 2003; 100: 928-933Crossref PubMed Scopus (933) Google Scholar, 17Park S.W. Moon Y-A. Horton J.D. J. Biol. Chem. 2004; 279: 50630-50638Abstract Full Text Full Text PDF PubMed Scopus (434) Google Scholar). cell of the purified protein to binding and for proteins purified using the as T.A. Curtis D.E. Garuti R. McNutt M.C. Park S.W. Prather H.B. Anderson N.N. Ho Y.K. Hammer R.E. Horton J.D. J. Clin. Investig. 2006; 116: 2995-3005Crossref PubMed Scopus (532) Google Scholar). that the catalytic fragment and prodomain with both proteins expressed in the and are secreted together in a similar to that of the wild-type PCSK9 purified from cells with a single the PCSK9 protein. The to serine at of the purified protein was by using not evidence that the produces a catalytically inactive protein was from the using an that the at the terminus of the of purified PCSK9 or using an or prodomain that only the the that the wild-type cleave the from the prodomain and the The sequence of the cleavage in was by and was found to at the at which the prodomain is cleaved from PCSK9 We whether the secreted proteins bind to the LDLR by using purified LDLR protein. that the purified and proteins the LDLR with similar to that with purified PCSK9 protein from a single the protein. We whether catalytic activity was required for PCSK9 to degrade LDLRs when added to the medium of HepG2 cells in medium to LDLR expression T.A. Curtis D.E. Garuti R. McNutt M.C. Park S.W. Prather H.B. Anderson N.N. Ho Y.K. Hammer R.E. Horton J.D. J. Clin. Investig. 2006; 116: 2995-3005Crossref PubMed Scopus (532) Google Scholar). with purified the surface proteins of the cells with a and using LDLRs in and cell surface LDLRs by and T.A. Curtis D.E. Garuti R. McNutt M.C. Park S.W. Prather H.B. Anderson N.N. Ho Y.K. Hammer R.E. Horton J.D. J. Clin. Investig. 2006; 116: 2995-3005Crossref PubMed Scopus (532) Google Scholar). The of and cell surface PCSK9 by and using an that only added PCSK9. that PCSK9 purified from the (PCSK9), and in the of LDLRs on the cell surface at concentrations without cell surface the receptor in PCSK9 was in in a was not the cell surface proteins that most of the PCSK9 been catalytically inactive PCSK9 to degrade LDLRs at a similar to that found in human plasma T.A. Curtis D.E. Garuti R. McNutt M.C. Park S.W. Prather H.B. Anderson N.N. Ho Y.K. Hammer R.E. Horton J.D. J. Clin. Investig. 2006; 116: 2995-3005Crossref PubMed Scopus (532) Google Scholar). results that catalytic activity of PCSK9 is not required to degrade LDLRs when PCSK9 is added to HepG2 mutations in human PCSK9 identified that in a gain-of-function and hypercholesterolemia (15Abifadel M. Varret M. Rabes J-P. Ouguerram K. Devillers M. Cruaud C. Benjannet S. Wickham L. Erlich D. Villéger L. Farnier M. Beucler I. Bruckert E. Chambaz J. Chanu B. Lecerf J.-M. Luc G. Moulin P. Weissenbach J. Prat A. Krempf M. Junien C. Seidah N.G. Boileau C. Nat. Genet. 2003; 34: 154-156Crossref PubMed Scopus (2221) Google Scholar). gain-of-function PCSK9 PCSK9(D374Y), to the LDLR with and is ∼10-fold active in LDLRs the wild-type protein T.A. Curtis D.E. Garuti R. McNutt M.C. Park S.W. Prather H.B. Anderson N.N. Ho Y.K. Hammer R.E. Horton J.D. J. Clin. Investig. 2006; 116: 2995-3005Crossref PubMed Scopus (532) Google Scholar, 14Cunningham D. Danley D.E. Geoghegan K.F. Griffor M.C. Hawkins J.L. Subashi T.A. Varghese A.H. Ammirati M.J. Culp J.S. Hoth L.R. Mansour M.N. McGrath K.M. Seddon A.P. Shenolikar S. Stutzman-Engwall K.J. Warren L.C. Xia D. Qiu X. Nat. Struct. Mol. Biol. 2007; 14: 413-419Crossref PubMed Scopus (365) Google Scholar). the that binding of PCSK9 to LDLR, not catalytic is required for PCSK9 to degrade the LDLR is the of the the catalytically inactive increased binding and degradation this an cell was that expressed PCSK9 in and that both the and mutations in the catalytic fragment The binding of the was by The of for the LDLR was similar to that of the both of which an for LDLR the wild-type PCSK9 protein. added to the medium of HepG2 cells at the of wild-type the and the proteins to degrade the LDLRs on the cell surface and the that the binding of PCSK9 to the LDLR the degradation of the LDLR a that not proteolytic activity of PCSK9. In this we that a in PCSK9 that catalytic activity not with the of the protein to the ability to bind to the LDLR or to the destruction of LDLRs when added to the medium of HepG2 results a in which PCSK9 to the LDLR, which the LDLR to the for degradation or the recycling of the receptor in a that is independent of catalytic activity of the protein. that other PCs, PCSK9 is as a subtilisin-like serine protease in that the protein a biological that is independent of proteolytic Studies have demonstrated that PCSK9 and the LDLR and that the of PCSK9 with the cell surface and internalization is the of LDLRs T.A. Curtis D.E. Garuti R. McNutt M.C. Park S.W. Prather H.B. Anderson N.N. Ho Y.K. Hammer R.E. Horton J.D. J. Clin. Investig. 2006; 116: 2995-3005Crossref PubMed Scopus (532) Google Scholar, T.A. Garuti R. M. Horton J.D. J.C. Hobbs J. Biol. Chem. 2007; Full Text Full Text PDF PubMed Scopus Google Scholar). In both proteins to a and internalization is required for PCSK9 to LDLR protein this activity is in the of autosomal hypercholesterolemia an protein required in for LDLR internalization in T.A. Curtis D.E. Garuti R. McNutt M.C. Park S.W. Prather H.B. Anderson N.N. Ho Y.K. Hammer R.E. Horton J.D. J. Clin. Investig. 2006; 116: 2995-3005Crossref PubMed Scopus (532) Google Scholar, T.A. Garuti R. M. Horton J.D. J.C. Hobbs J. Biol. Chem. 2007; Full Text Full Text PDF PubMed Scopus Google Scholar). as PCSK9 is a member of the proteinase K subfamily of serine that PCSK9 cleaved the LDLR, which degradation. second was that PCSK9 cleaved as protein that the destruction of The of that catalytic activity is not required for PCSK9 to the destruction of LDLRs when added to HepG2 The of the that binding of PCSK9 to the LDLR is to target LDLRs for the catalytic in the protein not the ∼10-fold activity of the protein T.A. Curtis D.E. Garuti R. McNutt M.C. Park S.W. Prather H.B. Anderson N.N. Ho Y.K. Hammer R.E. Horton J.D. J. Clin. Investig. 2006; 116: 2995-3005Crossref PubMed Scopus (532) Google Scholar). the that the gain-of-function of is a of increased for the studies have that cleavage of PCSK9 is required for the protein to secreted from cells (9Benjannet S. Rhainds D. Essalmani R. Mayne J. Wickham L. Jin W. Asselin M.C. Hamelin J. Varret M. Allard D. Trillard M. Abifadel M. Tebon A. Attie A.D. Rader D.J. Boileau C. Brissette L. Chretien M. Prat A. Seidah N.G. J. Biol. Chem. 2004; 279: 48865-48875Abstract Full Text Full Text PDF PubMed Scopus (515) Google Scholar). We have found that catalytically inactive are a of PCSK9 is secreted the medium. The secreted catalytically inactive protein was purified and in as in and the PCSK9 protein not bind to the LDLR LDLRs in HepG2 cells not cleavage of the prodomain required for PCSK9 to a that mediates LDLR The of that the PCSK9 prodomain is of a chaperone in as by the ER and of and the ability of the protein to bind to the has been shown that active in cells by the of the prodomain and a fragment the prodomain on (11Anderson E.D. Molloy S.S. Jean F. Fei H. Shimamura S. Thomas G. J. Biol. Chem. 2002; 277: 12879-12890Abstract Full Text Full Text PDF PubMed Scopus (107) Google Scholar). In the of the ability of the prodomain to in for studies of the of catalytic on LDLR degradation independent of effects on PCSK9 in the secretory pathway. The structure of PCSK9 was at D. Danley D.E. Geoghegan K.F. Griffor M.C. Hawkins J.L. Subashi T.A. Varghese A.H. Ammirati M.J. Culp J.S. Hoth L.R. Mansour M.N. McGrath K.M. Seddon A.P. Shenolikar S. Stutzman-Engwall K.J. Warren L.C. Xia D. Qiu X. Nat. Struct. Mol. Biol. 2007; 14: 413-419Crossref PubMed Scopus (365) Google Scholar). The prodomain to an target that is found in the of other proprotein and is the of a second cleavage event that results in and of the The of a target in the prodomain of PCSK9 has been as evidence that catalytic activity not in the of PCSK9 D. Danley D.E. Geoghegan K.F. Griffor M.C. Hawkins J.L. Subashi T.A. Varghese A.H. Ammirati M.J. Culp J.S. Hoth L.R. Mansour M.N. McGrath K.M. Seddon A.P. Shenolikar S. Stutzman-Engwall K.J. Warren L.C. Xia D. Qiu X. Nat. Struct. Mol. Biol. 2007; 14: 413-419Crossref PubMed Scopus (365) Google Scholar). The studies evidence that added PCSK9 LDLRs in a that LDLR binding not catalytic Studies by K.N. Breslow J.L. Proc. Natl. Acad. Sci. U. S. A. 2005; PubMed Scopus Google Scholar) showed that of PCSK9 in HepG2 cells degradation of LDLRs in a and N. D.A. Tebon A. Benjannet S. Hamelin J. P.S. Attie A.D. Prat A. Seidah N.G. 2007; 8: PubMed Scopus Google Scholar) have that the proteins in the ER and in the Golgi apparatus in hepatocytes. The results of studies not the that PCSK9 in a that catalytic (19Cohen J. Pertsemlidis A. Kotowski I.K. Graham R. Garcia C.K. Hobbs Nat. Genet. 2005; PubMed Scopus Google Scholar) that of a in PCSK9 that LDL cholesterol by In a mutations in PCSK9 LDL cholesterol by which was associated with a in the of of in J.C. E. Hobbs N. J. Med. 2006; PubMed Scopus Google Scholar). In that loss-of-function mutations in PCSK9 to have a J.C. E. Hobbs N. J. Med. 2006; PubMed Scopus Google Scholar). from humans with loss-of-function mutations in PCSK9 PCSK9 as a potential target for the of hypercholesterolemia and suggest that of the protease of The of a for PCSK9 catalytic activity in LDLRs has for the of PCSK9 It has been shown that LDLR not when a catalytically that is not secreted is expressed in liver S.W. Moon Y-A. Horton J.D. J. Biol. Chem. 2004; 279: 50630-50638Abstract Full Text Full Text PDF PubMed Scopus (434) Google Scholar) or in liver cells the suggest that of PCSK9 catalytic activity have to in the ER to PCSK9 ability to LDLR protein We W. H. and for of the J. L. Goldstein and M. S. Brown for and Y. K. Ho and for in Anderson and with
McNutt et al. (Thu,) studied this question.
Synapse has enriched 5 closely related papers on similar clinical questions. Consider them for comparative context: