Self-assembly of HEK cell-secreted ApoE particles resembles ApoE enrichment of lipoproteins as a ligand for the LDL receptor-related protein.
Recent studies have shown that the lipidation and assembly state of apolipoprotein E (apoE) determine receptor recognition and amyloid-beta peptide (Abeta) binding. We previously demonstrated that apoE secreted by HEK cells stably expressing apoE3 or apoE4 (HEK-apoE) binds Abeta and inhibits Abeta-induced neurotoxicity by an isoform-specific process that requires apoE receptors. Here we characterized the structure of HEK-apoE assemblies and determined their receptor binding specificity. By chromatography, HEK-apoE elutes in high molecular mass fractions and is the size of plasma HDL, consistent with a multiprotein assembly. No lipid was associated with these apoE assemblies. Several methods for analyzing receptor binding indicate that HEK-apoE is a ligand for low-density lipoprotein (LDL) receptor-related protein (LRP) but not the LDL receptor. This suggests that self-assembly of apoE may induce a functional conformation necessary for binding to LRP. Our results indicate that, in addition to lipid content, the assembly state of apoE influences Abeta binding and receptor recognition.
LaDu
Mary Jo
MJ
Department of Anatomy and Cell Biology, University of Illinois at Chicago, Chicago, Illinois 60612, USA.
Stine
W Blaine
WB
Narita
Masaaki
M
Getz
Godfrey S
GS
Reardon
Catherine A
CA
Bu
Guojun
G
D000818:Animals; D053318:Apolipoprotein E3; D053327:Apolipoprotein E4; D001057:Apolipoproteins E / Q000737:chemistry* / Q000378:metabolism* / Q000648:ultrastructure; D002460:Cell Line; D002850:Chromatography, Gel; D005347:Fibroblasts / Q000378:metabolism; D006801:Humans; D007457:Iodine Radioisotopes; D008024:Ligands; D026503:Low Density Lipoprotein Receptor-Related Protein-1 / Q000737:chemistry / Q000378:metabolism*; D051379:Mice; D011485:Protein Binding; D011973:Receptors, LDL / Q000378:metabolism; D014461:Ultracentrifugation
D053318:Apolipoprotein E3; D053327:Apolipoprotein E4; D001057:Apolipoproteins E; D007457:Iodine Radioisotopes; D008024:Ligands; D026503:Low Density Lipoprotein Receptor-Related Protein-1; D011973:Receptors, LDL