Journal de bioanalyse et de biomédecine

Hepatic Endosome Protein Profiling in Apolipoprotein E Deficient Mice Expressing Apolipoprotein B48 but not B100

Abstract

AnShu Chen, ZhongMao Guo, LiChun Zhou and Hong Yang

Liver cells absorb apolipoprotein (Apo) B48-carrying lipoproteins in ApoE’s absence, albeit not as ef fi ciently as the ApoE-mediated process. Our objective was to identify differentially expressed hepatic endosome proteins in mice expressing ApoB48 but lacking ApoE and ApoB100 expression ( ApoE -/- /B48/48 ). We puri fi ed early and late endosomes from ApoE -/- /B48/48 and wild-type mouse’s livers. In ApoE -/- /B48/48 mouse’s hepatic endosomes, proteomic analysis revealed elevated protein levels of major urinary protein 6 (MUP), calreticulin, protein disul fi de isomerases (PDI) A1, and A3. These proteins are capable of interacting with lipids/lipoproteins and triggering receptor- mediated endocytosis. In addition, hepatic endosomes from ApoE -/- /B48/48 mice exhibited signi fi cantly reduced protein levels of haptoglobin, hemopexin, late endosome/lysosome interacting protein, cell division control protein 2 homolog, γ -soluble Nethylmaleimide- sensitive factor attachment protein, vacuolar ATP synthase catalytic subunit A1, dipeptidyl peptidases II, cathepsin B, D, H, and Z. These proteins participate in plasma heme clearance, receptor-mediated signaling, membrane fusion, endosomal/lysosomal acidi fi cation, and protein degradation. The signi fi cance of increasing endosomal MUP, calreticulin and PDIs in ApoE -/- /B48/48 mouse liver cells is not clear; however, reducing endosomal/ lysosomal membrane proteins and hydrolases might be, at least partially, responsible for the retarded clearance of plasma ApoB-carrying lipoproteins in ApoE -/- /B48/48 mice.