title: The beta-VLDL receptor pathway of murine P388D1 macrophages.
abstract: Very low density lipoproteins Sf 100-400 (VLDL1) from hypertriglyceridemic (HTG) subjects and chylomicrons cause receptor-mediated lipid engorgement in unstimulated macrophages in vitro via the beta-VLDL receptor pathway. We now report that the murine macrophage P388D1 cell line possesses the characteristics of the beta-VLDL receptor pathway observed previously in freshly isolated resident murine peritoneal macrophages or human monocyte-macrophages. HTG-VLDL1 isolated from the plasma of subjects with hypertriglyceridemia types 3, 4, and 5 interact with P388D1 macrophages in a high-affinity, curvilinear manner. beta-VLDL, HTG-VLDL1, chylomicrons, and thrombin-treated HTG-VLDL1 (which do not bind to the LDL receptor) compete efficiently and similarly for the uptake and degradation of HTG-VLDL1. LDL and acetyl LDL do not compete, indicating that uptake of HTG-VLDL1 is via neither the LDL receptor nor the acetyl LDL receptor. Binding of thrombin-treated HTG-VLDL1 to the beta-VLDL receptor indicates that the thrombin-accessible apoE, which is absolutely required for interaction of HTG-VLDL Sf greater than 60 with the LDL receptor, is not required for binding to the beta-VLDL receptor. The uptake and degradation of 125I-labeled HTG-VLDL1 is suppressed up to 80-90% by preincubation of the cells with sterols, acetyl LDL, or beta-VLDL, indicating that this process is not via the irrepressible chylomicron remnant (apoE) receptor. Chylomicrons, HTG-VLDL1, and thrombin-treated HTG-VLDL1-but not normal VLDL1, beta-VLDL, LDL, or acetyl LDL-produce massive triglyceride accumulation (10-20-fold mass increases in 4 hr) in P388D1 macrophages.(ABSTRACT TRUNCATED AT 250 WORDS)
mesh_terms: D000818:Animals; D001667:Binding, Competitive; D002460:Cell Line; D002914:Chylomicrons / Q000378:metabolism; D006801:Humans; D006953:Hyperlipoproteinemia Type IV / Q000097:blood; D007700:Kinetics; D008079:Lipoproteins, VLDL / Q000097:blood / Q000378:metabolism*; D008264:Macrophages / Q000032:analysis / Q000378:metabolism*; D051379:Mice; D011973:Receptors, LDL / Q000378:metabolism*; D014280:Triglycerides / Q000378:metabolism
chemical_list: D002914:Chylomicrons; D008079:Lipoproteins, VLDL; D011973:Receptors, LDL; D014280:Triglycerides; C036053:VLDL receptor