Molecular characterization of proprotein convertase subtilisin/kexin type 9-mediated degradation of the LDLR

Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a secreted protein that promotes degradation of cell surface LDL receptors (LDLRs) in selected cell types. Here we used genetic and pharmacological inhibitors to define the pathways involved in PCSK9-mediated LDLR degradation. Inactivating mut...

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Bibliographic Details
Published in:Journal of lipid research 2012-09, Vol.53 (9), p.1932-1943
Main Authors: Wang, Yan, Huang, Yongcheng, Hobbs, Helen H., Cohen, Jonathan C.
Format: Article
Language:English
Subjects:
autophagy
Cell Line
cholesterol
Clathrin - metabolism
Endocytosis
endosomes
Fibroblasts - cytology
Humans
low density lipoprotein receptor
lysosomes
Lysosomes - metabolism
Proprotein Convertase 9
Proprotein Convertases - metabolism
Proteasome Endopeptidase Complex - metabolism
Proteolysis
Receptors, LDL - metabolism
Serine Endopeptidases - metabolism
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Summary:Proprotein convertase subtilisin/kexin type 9 (PCSK9) is a secreted protein that promotes degradation of cell surface LDL receptors (LDLRs) in selected cell types. Here we used genetic and pharmacological inhibitors to define the pathways involved in PCSK9-mediated LDLR degradation. Inactivating mutations in autosomal recessive hypercholesterolemia (ARH), an endocytic adaptor, blocked PCSK9-mediated LDLR degradation in lymphocytes but not in fibroblasts. Thus, ARH is not specifically required for PCSK9-mediated LDLR degradation. Knockdown of clathrin heavy chain with siRNAs prevented LDLR degradation. In contrast, prevention of ubiquitination of the LDLR cytoplasmic tail, inhibition of proteasomal activity, or disruption of proteins required for lysosomal targeting via macroautophagy (autophagy related 5 and 7) or the endosomal sorting complex required for trafficking (ESCRT) pathway (hepatocyte growth factor-regulated Tyr-kinase substrate and tumor suppressor gene 101) failed to block PCSK9-mediated LDLR degradation. These findings are consistent with a model in which the LDLR-PCSK9 complex is internalized via clathrin-mediated endocytosis and then routed to lysosomes via a mechanism that does not require ubiquitination and is distinct from the autophagy and proteosomal degradation pathways. Finally, the PCSK9-LDLR complex appears not to be transported by the canonical ESCRT pathway.
ISSN:0022-2275
1539-7262
DOI:10.1194/jlr.M028563