Characterization of the role of EGF-A of low density lipoprotein receptor in PCSK9 binding.
Proprotein convertase subtilisin kexin-like 9 (PCSK9) promotes the degradation of low density lipoprotein receptor (LDLR) and plays an important role in regulating plasma LDL-cholesterol levels. We have shown that the epidermal growth factor precursor homology domain A (EGF-A) of the LDLR is critical for PCSK9 binding at the cell surface (pH 7.4). Here, we further characterized the role of EGF-A in binding of PCSK9 to the LDLR. We found that PCSK9 efficiently bound to the LDLR but not to other LDLR family members. Replacement of EGF-A in the very low density lipoprotein receptor (VLDLR) with EGF-A of the LDLR promoted the degradation of the mutant VLDLR induced by PCSK9. Furthermore, we found that PCSK9 bound to recombinant EGF-A in a pH-dependent manner with stronger binding at pH 6.0. We also identified amino acid residues in EGF-A of the LDLR important for PCSK9 binding. Mutations G293H, D299V, L318D, and L318H reduced PCSK9 binding to the LDLR at neutral pH without effect at pH 6.0, while mutations R329P and E332G reduced PCSK9 binding at both pH values. Thus, our findings reveal that EGF-A of the LDLR is critical for PCSK9 binding at the cell surface (neutral pH) and at the acidic endosomal environment (pH 6.0), but different determinants contribute to efficient PCSK9 binding in different pH environments.
['Gu|Hong-mei|HM|', 'Adijiang|Ayinuer|A|', 'Mah|Matthew|M|', 'Zhang|Da-wei|DW|']
D000595:Amino Acid Sequence D000818:Animals D019556:COS Cells D002522:Chlorocebus aethiops D017124:Conserved Sequence D004815:Epidermal Growth Factor D006801:Humans D006863:Hydrogen-Ion Concentration D008969:Molecular Sequence Data D009154:Mutation D000071449:Proprotein Convertase 9 D043484:Proprotein Convertases D011485:Protein Binding D011498:Protein Precursors D017434:Protein Structure, Tertiary D059748:Proteolysis D011973:Receptors, LDL D012697:Serine Endopeptidases
proprotein convertase subtilisin kexin-like 9 epidermal growth factor precursor homology domain A ligand binding