Binding of proprotein convertase subtilisin/kexin type 9 to epidermal growth factor-like repeat A of low density lipoprotein receptor decreases receptor recycling and increases degradation.
Proprotein convertase subtilisin/kexin type 9 (PCSK9) promotes degradation of hepatic low density lipoprotein receptors (LDLR), the major route of clearance of circulating cholesterol. Gain-of-function mutations in PCSK9 cause hypercholesterolemia and premature atherosclerosis, whereas loss-of-function mutations result in hypocholesterolemia and protection from heart disease. Recombinant human PCSK9 binds the LDLR on the surface of cultured hepatocytes and promotes degradation of the receptor after internalization. Here we localized the site of binding of PCSK9 within the extracellular domain of the LDLR and determined the fate of the receptor after PCSK9 binding. Recombinant human PCSK9 interacted in a sequence-specific manner with the first epidermal growth factor-like repeat (EGF-A) in the EGF homology domain of the human LDLR. Similar binding specificity was observed between PCSK9 and purified EGF-A. Binding to EGF-A was calcium-dependent and increased dramatically with reduction in pH from 7 to 5.2. The addition of PCSK9, but not heat-inactivated PCSK9, to the medium of cultured hepatocytes resulted in redistribution of the receptor from the plasma membrane to lysosomes. These data are consistent with a model in which PCSK9 binding to EGF-A interferes with an acid-dependent conformational change required for receptor recycling. As a consequence, the LDLR is rerouted from the endosome to the lysosome where it is degraded.
Zhang
Da-Wei
DW
Departments of Molecular Genetics and Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas 75390.
Lagace
Thomas A
TA
Departments of Molecular Genetics and Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas 75390.
Garuti
Rita
R
Departments of Molecular Genetics and Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas 75390.
Zhao
Zhenze
Z
Departments of Molecular Genetics and Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas 75390.
McDonald
Meghan
M
Departments of Molecular Genetics and Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas 75390.
Horton
Jay D
JD
Departments of Molecular Genetics and Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas 75390.
Cohen
Jonathan C
JC
Departments of Molecular Genetics and Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas 75390; Donald W. Reynolds Cardiovascular Clinical Research Center, University of Texas Southwestern Medical Center, Dallas, Texas 75390. Electronic address: Jonathan.cohen@utsouthwestern.edu.
Hobbs
Helen H
HH
Departments of Molecular Genetics and Internal Medicine, University of Texas Southwestern Medical Center, Dallas, Texas 75390; Donald W. Reynolds Cardiovascular Clinical Research Center, University of Texas Southwestern Medical Center, Dallas, Texas 75390; Howard Hughes Institute, University of Texas Southwestern Medical Center, Dallas, Texas 75390. Electronic address: Helen.hobbs@utsouthwestern.edu.
D000595:Amino Acid Sequence; D000818:Animals; D019556:COS Cells; D002478:Cells, Cultured / Q000378:metabolism; D002522:Chlorocebus aethiops; D004815:Epidermal Growth Factor / Q000378:metabolism*; D022781:Hepatocytes / Q000378:metabolism; D006801:Humans; D008247:Lysosomes / Q000378:metabolism; D008969:Molecular Sequence Data; D000071449:Proprotein Convertase 9; D043484:Proprotein Convertases; D011485:Protein Binding; D011487:Protein Conformation; D011973:Receptors, LDL / Q000378:metabolism*; D011994:Recombinant Proteins / Q000737:chemistry; D012697:Serine Endopeptidases / Q000737:chemistry / Q000502:physiology*; D020860:Subtilisin / Q000502:physiology*
D011973:Receptors, LDL; D011994:Recombinant Proteins; D004815:Epidermal Growth Factor; C472125:PCSK9 protein, human; D000071449:Proprotein Convertase 9; D043484:Proprotein Convertases; D012697:Serine Endopeptidases; D020860:Subtilisin