Generation of a recombinant apolipoprotein E variant with improved biological functions: hydrophobic residues (LEU-261, TRP-264, PHE-265, LEU-268, VAL-269) of apoE can account for the apoE-induced hypertriglyceridemia.
To identify the residues in the carboxyl-terminal region 260-299 of human apolipoprotein E (apoE) that contribute to hypertriglyceridemia, two sets of conserved, hydrophobic amino acids between residues 261 and 283 were mutated to alanines, and recombinant adenoviruses expressing these apoE mutants were generated. Adenovirus-mediated gene transfer of apoE4-mut1 (apoE4 (L261A, W264A, F265A, L268A, V269A)) in apoE-deficient mice (apoE(-/-)) corrected plasma cholesterol levels and did not cause hypertriglyceridemia. In contrast, gene transfer of apoE4-mut2 (apoE4 (W276A, L279A, V280A, V283A)) did not correct hypercholesterolemia and induced mild hypertriglyceridemia. ApoE-induced hyperlipidemia was corrected by co-infection with a recombinant adenovirus expressing human lipoprotein lipase. Both apoE4 mutants caused only a small increase in hepatic very low density lipoprotein-triglyceride secretion. Density gradient ultracentrifugation analysis of plasma and electron microscopy showed that wild-type apoE4 and apoE4-mut2 displaced apoA-I from the high density lipoprotein (HDL) region and promoted the formation of discoidal HDL, whereas the apoE4-mut1 did not displace apoA-I from HDL and promoted the formation of spherical HDL. The findings indicate that residues Leu-261, Trp-264, Phe-265, Leu-268, and Val-269 of apoE are responsible for hypertriglyceridemia and also interfere with the formation of HDL. Substitutions of these residues by alanine provide a recombinant apoE form with improved biological functions.
Kypreos
Kyriakos E
KE
Molecular Genetics, Department of Medicine, Boston University School of Medicine, Boston, Massachusetts 02118, USA.
van Dijk
Ko W
KW
Havekes
Louis M
LM
Zannis
Vassilis I
VI
D000818:Animals; D001057:Apolipoproteins E / Q000008:administration & dosage / Q000235:genetics*; D002784:Cholesterol / Q000097:blood; D005260:Female; D006801:Humans; D015228:Hypertriglyceridemia / Q000209:etiology / Q000235:genetics*; D008075:Lipoproteins, HDL / Q000096:biosynthesis; D008079:Lipoproteins, VLDL / Q000378:metabolism; D008099:Liver / Q000378:metabolism; D051379:Mice; D018345:Mice, Knockout; D016297:Mutagenesis, Site-Directed; D020125:Mutation, Missense; D010446:Peptide Fragments / Q000008:administration & dosage / Q000235:genetics; D011994:Recombinant Proteins; D019076:Transgenes; D014280:Triglycerides / Q000378:metabolism
D001057:Apolipoproteins E; D008075:Lipoproteins, HDL; D008079:Lipoproteins, VLDL; D010446:Peptide Fragments; D011994:Recombinant Proteins; D014280:Triglycerides; C030106:very low density lipoprotein triglyceride; D002784:Cholesterol