title: The role of Siglec-1 and SR-BI interaction in the phagocytosis of oxidized low density lipoprotein by macrophages.
abstract: BACKGROUND
  Macrophages play a proatherosclerotic role in atherosclerosis via oxLDL uptake. As an adhesion molecular of I-type lectins, Siglec-1 is highly expressed on circulating monocytes and plaque macrophages of atherosclerotic patients, but the exact role of Siglec-1 has not been elucidated.
  
  
  METHODS
  In this study, oxLDL was used to stimulate Siglec-1 and some oxLDL receptors (SR-BI, CD64, CD32B, LOX-1 and TLR-4) expression on bone marrow-derived macrophages, whereas small interfering RNA was used to down-regulate Siglec-1. Meanwhile, an ELISA-based assay for Siglec-1-oxLDL interaction was performed, and co-immunoprecipitation (co-IP) and laser scanning confocal microscopy (LSCM) were used to determine the role of Siglec-1 in oxLDL uptake by macrophages.
  
  
  RESULTS
  We found that oxLDL could up-regulate the expression of various potential oxLDL receptors, including Siglec-1, in a dose-dependent manner. Moreover, down-regulation of Siglec-1 could attenuate oxLDL uptake by Oil red O staining. LSCM revealed that Siglec-1 and CD64/SR-BI may colocalize on oxLDL-stimulated macrophage surface, whereas co-IP showed that Siglec-1 and SR-BI can be immunoprecipitated by each other. However, no direct interaction between Siglec-1 and oxLDL was found in the in vitro protein interaction system.
  
  
  CONCLUSIONS
  Thus, Siglec-1 can interact with SR-BI in the phagocytosis of oxLDL by macrophages, rather than act as an independent receptor for oxLDL.
authors.affiliation: Department of Laboratory Medicine, Chengdu Military General Hospital, Chengdu, China.
authors.forename: Yi-song
authors.initials: YS
authors.lastname: Xiong
authors.forename: Juan
authors.initials: J
authors.lastname: Yu
authors.forename: Chang
authors.initials: C
authors.lastname: Li
authors.forename: Lin
authors.initials: L
authors.lastname: Zhu
authors.forename: Li-juan
authors.initials: LJ
authors.lastname: Wu
authors.forename: Ren-qian
authors.initials: RQ
authors.lastname: Zhong
mesh_terms: D000818:Animals; D050197:Atherosclerosis / Q000235:genetics / Q000378:metabolism / Q000473:pathology; D002478:Cells, Cultured; D005786:Gene Expression Regulation / Q000235:genetics; D008077:Lipoproteins, LDL / Q000235:genetics / Q000378:metabolism*; D008264:Macrophages / Q000378:metabolism* / Q000473:pathology; D051379:Mice; D010587:Phagocytosis; D051122:Scavenger Receptors, Class B / Q000235:genetics / Q000378:metabolism*; D063267:Sialic Acid Binding Ig-like Lectin 1 / Q000235:genetics / Q000378:metabolism*
chemical_list: D008077:Lipoproteins, LDL; C454739:Scarb1 protein, mouse; D051122:Scavenger Receptors, Class B; D063267:Sialic Acid Binding Ig-like Lectin 1; C571167:Siglec1 protein, mouse; C099252:oxidized low density lipoprotein