Skip to main page content
U.S. flag

An official website of the United States government

Dot gov

The .gov means it’s official.
Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you’re on a federal government site.

Https

The site is secure.
The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

Access keys NCBI Homepage MyNCBI Homepage Main Content Main Navigation
Comparative Study
. 2007 Jul 13;282(28):20502-12.
doi: 10.1074/jbc.M701634200. Epub 2007 May 10.

Effects of pH and low density lipoprotein (LDL) on PCSK9-dependent LDL receptor regulation

Timothy S Fisher  1 , Paola Lo Surdo, Shilpa Pandit, Marco Mattu, Joseph C Santoro, Doug Wisniewski, Richard T Cummings, Alessandra Calzetta, Rose M Cubbon, Paul A Fischer, Anil Tarachandani, Raffaele De Francesco, Samuel D Wright, Carl P Sparrow, Andrea Carfi, Ayesha Sitlani
Affiliations
Free article
Comparative Study

Effects of pH and low density lipoprotein (LDL) on PCSK9-dependent LDL receptor regulation

Timothy S Fisher et al. J Biol Chem. .
Free article

Abstract

Mutations within PCSK9 (proprotein convertase subtilisin/kexin type 9) are associated with dominant forms of familial hyper- and hypocholesterolemia. Although PCSK9 controls low density lipoprotein (LDL) receptor (LDLR) levels post-transcriptionally, several questions concerning its mode of action remain unanswered. We show that purified PCSK9 protein added to the medium of human endothelial kidney 293, HepG2, and Chinese hamster ovary cell lines decreases cellular LDL uptake in a dose-dependent manner. Using this cell-based assay of PCSK9 activity, we found that the relative potencies of several PCSK9 missense mutants (S127R and D374Y, associated with hypercholesterolemia, and R46L, associated with hypocholesterolemia) correlate with LDL cholesterol levels in humans carrying such mutations. Notably, we found that in vitro wild-type PCSK9 binds LDLR with an approximately 150-fold higher affinity at an acidic endosomal pH (K(D) = 4.19 nm) compared with a neutral pH (K(D) = 628 nm). We also demonstrate that wild-type PCSK9 and mutants S127R and R46L are internalized by cells to similar levels, whereas D374Y is more efficiently internalized, consistent with their affinities for LDLR at neutral pH. Finally, we show that LDL diminishes PCSK9 binding to LDLR in vitro and partially inhibits the effects of secreted PCSK9 on LDLR degradation in cell culture. Together, the results of our biochemical and cell-based experiments suggest a model in which secreted PCSK9 binds to LDLR and directs the trafficking of LDLR to the lysosomes for degradation.

PubMed Disclaimer

Similar articles

See all similar articles

Cited by

See all "Cited by" articles

Publication types

MeSH terms