title: A Subregion of Reelin Suppresses Lipoprotein-Induced Cholesterol Accumulation in Macrophages.
abstract: Activation of apolipoprotein E receptor-2 (apoER2) and very low density lipoprotein receptor (VLDLR) inhibits foam cell formation. Reelin is a ligand of these receptors. Here we generated two reelin subregions containing the receptor binding domain with or without its C-terminal region (R5-6C and R5-6, respectively) and studied the impact of these peptides on macrophage cholesterol metabolism. We found that both R5-6C and R5-6 can be secreted by cells. Purified R5-6 protein can bind apoER2 and VLDLR. Overexpression of apoER2 in macrophages increased the amount of R5-6 bound to the cell surface. Treatment of macrophages with 0.2 μg/ml R5-6 elevated ATP binding cassette A1 (ABCA1) protein level by ~72% and apoAI-mediated cholesterol efflux by ~39%. In addition, the medium harvested from cells overexpressing R5-6 or R5-6C (R5-6- and R5-6C-conditioned media, respectively) also up-regulated ABCA1 protein expression, which was associated with accelerated cholesterol efflux and enhanced phosphorylation of phosphatidylinositol 3 kinase (PI3K) and specificity protein-1 (Sp1) in macrophages. The increased ABCA1 expression and cholesterol efflux by R5-6- and R5-6C-conditioned media were diminished by Sp1 or PI3K inhibitors mithramycin A and LY294002. Further, the cholesterol accumulation induced by apoB-containing, apoE-free lipoproteins was significantly less in macrophages incubated with R5-6- or R5-6C-conditioned medium than in those incubated with control conditioned medium. Knockdown of apoER2 or VLDLR attenuated the inhibitory role of R5-6-conditioned medium against lipoprotein-induced cholesterol accumulation. These results suggest that the reelin subregion R5-6 can serve as a tool for studying the role of apoER2 and VLDLR in atherogenesis.
authors: Department of Physiology, Meharry Medical College, Nashville, Tennessee, United States of America.
authors: Emmanuel U
authors: EU
authors: Okoro
authors: Department of Physiology, Meharry Medical College, Nashville, Tennessee, United States of America; Department of Pathology, Central Hospital of Wuhan, Wuhan City, People's Republic of China.
authors: Hongfeng
authors: H
authors: Zhang
authors: Department of Physiology, Meharry Medical College, Nashville, Tennessee, United States of America.
authors: Zhongmao
authors: Z
authors: Guo
authors: Department of Physiology, Meharry Medical College, Nashville, Tennessee, United States of America; Wuhan University School of Basic Medical Science, Wuhan City, People's Republic of China.
authors: Fang
authors: F
authors: Yang
authors: Department of Physiology, Meharry Medical College, Nashville, Tennessee, United States of America.
authors: Carlie
authors: C
authors: Smith
authors: Department of Physiology, Meharry Medical College, Nashville, Tennessee, United States of America.
authors: Hong
authors: H
authors: Yang
mesh_terms: D064286:ATP Binding Cassette Transporter 1 / Q000378:metabolism; D000818:Animals; D050197:Atherosclerosis / Q000235:genetics / Q000378:metabolism; D001665:Binding Sites; D015816:Cell Adhesion Molecules, Neuronal / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D002460:Cell Line; D002784:Cholesterol / Q000378:metabolism*; D017077:Culture Media, Conditioned / Q000494:pharmacology; D016326:Extracellular Matrix Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D057809:HEK293 Cells; D006801:Humans; D026502:LDL-Receptor Related Proteins / Q000235:genetics / Q000378:metabolism; D008074:Lipoproteins / Q000378:metabolism*; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D009419:Nerve Tissue Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D011973:Receptors, LDL / Q000235:genetics / Q000378:metabolism; D000091042:Reelin Protein; D012697:Serine Endopeptidases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects
chemical_list: D064286:ATP Binding Cassette Transporter 1; D015816:Cell Adhesion Molecules, Neuronal; D017077:Culture Media, Conditioned; D016326:Extracellular Matrix Proteins; D026502:LDL-Receptor Related Proteins; D008074:Lipoproteins; D009419:Nerve Tissue Proteins; D011973:Receptors, LDL; D000091042:Reelin Protein; C036053:VLDL receptor; C098773:low density lipoprotein receptor-related protein 8; D002784:Cholesterol; C000717127:RELN protein, human; C000717128:Reln protein, mouse; D012697:Serine Endopeptidases