Cationic domain 141-150 of apoE covalently linked to a class A amphipathichelix enhances atherogenic lipoprotein metabolism in vitro and in vivo

We previously showed(l) that a peptide,Ac-hE18A-NH2, in which the arginine- lich heparin-binding domain of apolipoprotein E (apoE) [residues 141-150] ( LRKLRKRLLR), covalently linked to 18A (DWLKAFYDKVAEKLKEAF; a class A amphip athic helix with high lipid affinity), enhanced LDL uptake and clearance, B ecause VLDL and remnants contain more cholesterol per particle than LDL, en hanced hepatic clearance of VLDL could lead to an effective lowering of pla sma cholesterol. Therefore, in the present article we compared the ability of this peptide to mediate/facilitate the uptake and degradation of LDL and VLDL in HepG2 cells. The peptide Ac-hE18A-NH2, but not Ac-18A-NH2, enhance d the uptake of LDL by HepG2 cells 5-fold and its degradation 2-fold. The a ssociation of the peptides with VLDL resulted in the displacement of native apoE; however, only Ac-hE18A-NH2 but: not Ac-18A-NH2 caused markedly enhan ced uptake (6-fold) and degradation (3-fold) of VLDL, Ac-hE18A-NH2 also enh anced the uptake (15-fold) and degradation (2-fold) of trypsinized VLDL Sf 100-400 (containing no immuno-detectable apoE), indicating that the peptide restored the cellular interaction of VLDL in the absence of its essential native ligand (apoE), Pretreatment of HepG2s with heparinase and heparitina se abrogated all peptide-mediated enhanced cellular activity, implicating a role for cell-surface heparan sulfate proteoglycans (HSPG). Intravenous ad ministration of Ac-hE18A-NH2 into apoE gene knockout mice reduced plasma ch olesterol by 88% at 6 h and 30% at 24 h after injection, We conclude that t his dual-domain peptide associates with LDL and VLDL and results in rapid h epatic uptake via a HSPG-facilitated pathway. - Datta, G., D. W. Garber, B. H. Chung, M. Chaddha, N. Dashti, W. A. Bradley, S. H. Gianturco, and G. M. Anantharamaiah. Cationic domain 141-150 of apoE covalently linked to a cla ss A amphipathic helix enhances atherogenic lipoprotein metabolism in vitro and in vivo.