Fig. 4: LILRB1 plays an important role in LDL uptake.

a, b Products of immunoprecipitation by anti-IgG and anti-LILRB1 antibodies were sent for mass spectrum analysis. Potential LILRB1 interacting proteins detected by MS were analyzed with Gene Ontology (GO) enrichment analysis. Enriched Pathways involved in metabolisms are shown. c Immunoprecipitation of LILRB1 (left panel) and FLAG-LDLRAP1 (right panel) in 293 T cells overexpressing LILRB1 and FLAG-LDLRAP1 showing the binding of LILRB1 and FLAG-LDLRAP1. d, f Immunoprecipitation of endogenously expressed LILRB1 in ARP-1 cells showing the binding of LILRB1 and LDLRAP1 (d) and LILRB1 and LDLR (f). e Immunoprecipitation of LILRB1 (left panel) and LDLR (right panel) in 293 T cells overexpressing LILRB1 and LDLR showed the binding of LILRB1 and LDLR. g–j Representative fluorescent confocal images showing the co-localization of LILRB1 and LDLRAP1 (g), co-localization of LILRB1 and LDLR (h), co-localization of LILRB1, LDLRAP1 and LDLR (i), and co-localization of LILRB1 and LDL (j) in ARP-1 cells or MOLP-8 cells. k, l CTR-KD or LILRB1-KD MM cells were cultured in FBS-free medium for 24 h and then incubated with chemically modified LDL labeled with red fluorescence for 2 h. The uptake of LDL by CTR-KD or LILRB1-KD MM cells was measured by flow cytometry (k). Representative fluorescent confocal images showing LDL uptake ability of CTR-KD or LILRB1-KD MM cells (l). m, o Uptake of LDL/cholesterol was detected by the changes of extracellular LDL/cholesterol concentrations in the supernatant of CTR-KD and LILRB1-KD ARP-1 cells (m), as well as CTR and LILRB1-OE MM.1 R cells (o), by fluorescence microplate reader. (n, p) Intracellular cholesterol concentrations of CTR-KD and LILRB1-KD ARP-1 cells (n), as well as CTR and LILRB1-OE MM.1 R cells (p), were detected with fluorescence microplate reader. For (c–j, l), the independent experiments were repeated three times and the representative images are shown. For (k, m–p), n = 3, independent experimental repeats; data are summary of three independent experiments and shown as mean ± SD. Statistical significance was determined by two-tailed Student t-test. Source data are provided as a Source Data file.