Degradation of newly synthesized ApoB-48 PathwayStep1215 PathwayStep1216 PathwayStep1211 PathwayStep1212 PathwayStep1213 PathwayStep1214 PathwayStep1210 PathwayStep1208 PathwayStep1209 PathwayStep1206 PathwayStep1207 PathwayStep1205 Exocytosis of nascent chylomicrons ApoB-48 + 40 triacylglycerol + 60 phospholipid => ApoB-48:TG:PL complex ApoB-48:TG:PL complex + 100 triacylglycerols + ApoA-I + ApoA-IV => nascent chylomicron chylomicron remnant:apoE complex + LDLR => chylomicron remnant:apoE:LDLR complex chylomicron remnant:apoE:LDLR complex [plasma membrane] => chylomicron remnant:apoE:LDLR complex [clathrin-coated vesicle] (LDLRAP1-dependent) TG-depleted chylomicron + spherical HDL => chylomicron remnant + spherical HDL:apoA-I:apoA-II:apoA-IV:apoC-II:apoC-III chylomicron remnant + apoE => chylomicron remnant:apoE complex nascent chylomicron + spherical HDL:apoC-II:apoC-III:apoE =>spherical HDL + chylomicron chylomicron => TG-depleted chylomicron + 50 long-chain fatty acids + 50 diacylglycerols chylomicron remnant:apoE:LDLR complex => chylomicron remnant:apoE + LDLR chylomicron remnant:apoE:LDLR complex [coated vesicle membrane] => chylomicron remnant:apoE:LDLR complex [endosome membrane] Chylomicron-mediated lipid transport Authored: D'Eustachio, P, 2007-04-30 14:19:38 Chylomicrons transport triacylglycerol, phospholipid, and cholesterol derived from dietary lipid from the small intestine to other tissues of the body. Each chylomicron assembles around a single molecule of apolipoprotein B-48 (Phillips et al. 1997) which at the time the particle leaves the intestine and enters the lymphatic circulation is complexed with >200,000 molecules of triacylglycerol (TG), ~35,000 of phospholipid, ~11,000 of cholesterol ester, ~8,000 of free cholesterol, ~60 copies of apolipoprotein A-I, ~15 copies of apolipoprotein A-IV, and copies of apolipoprotein A-II (Bhattacharya and Redgrave 1981; Havel and Kane 2001). As chylomicrons circulate in the body, they acquire molecules of apolipoproteins C and E, and through interaction with endothelial lipases can lose a large fraction of their triacylglycerol. These changes convert them to chylomicron remnants which bind to LDL receptors, primarily on the surfaces of liver cells, clearing them from the circulation. This whole sequence of events is rapid: the normal lifespan of a chylomicron is 30 - 60 minutes (Havel and Kane 2001). Edited: D'Eustachio, P, 2006-02-20 18:35:05 GENE ONTOLOGYGO:0042157 ISBN0079130356 Pubmed7288288 Pubmed9215545 Reactome Database ID Release 43174800 Reactome, http://www.reactome.org ReactomeREACT_6841