Nucleolin Acts as a Scavenger Receptor for Acetylated Low-Density Lipoprotein on Macrophages

Abstract

Although macrophage phagocytoses modified low-density lipoprotein (LDL), excessive accumulation of modified LDL induces macrophage foam cell formation, which is a feature of atherosclerotic plaque. Thus, the identification of scavenger receptor for modified LDL will provide better understanding of an atherosclerotic event. We recently showed that nucleolin expressed on macrophages acts as a scavenger receptor for various endogenous discarded products. Here, we investigated whether or not nucleolin is involved in the uptake of acetylated LDL (AcLDL). In contrast to normal LDL, AcLDL directly bound to immobilized nucleolin. AcLDL exhibited a higher affinity for macrophages than normal LDL. This binding of AcLDL was inhibited by anti-nucleolin antibody and antineoplastic guanine-rich oligonucleotide (AGRO), a nucleolinspecific oligonucleotide aptamer. In addition, AcLDL exhibited a higher affinity for HEK cells transfected with nucleolin than those without. Further, intracellular accumulation of AcLDL was also inhibited by antinucleolin antibody. The results of this study suggest that nucleolin expressed on macrophages is a receptor for AcLDL.Key words nucleolin; macrophage; acetylated low-density lipoprotein (AcLDL); scavenger receptor Low-density lipoprotein (LDL) elevates cholesterol deposits in macrophage foam cells, which are involved in the development of atherosclerotic lesions.1) As the uptake of normal LDL via its receptor is controlled by feedback regulation, excess levels of LDL-derived cholesterol in macrophages might be attributed to modifications of LDL such as oxidation, acetylation, and aggregation.2) Scavenger receptors (SRs) and other unknown receptors account for up to 95% of the uptake of modified LDL.

Arginine-Rich Cell-Penetrating Peptides Require Nucleolin and Cholesterol-Poor Subdomains for Translocation across Membranes

“…Moreover, we were able to pinpoint cell-surface nucleolin as one candidate protein required for the translocation of arginine-rich CPPs across membranes, since downregulation of nucleolin by siRNA (Figure B,C, Figure S6B) or blocking it with specific antibody on the GPMVs suppressed the accumulation of arginine-rich CPPs into the vesicles (Figure S6C). Nucleolin is an abundant protein that mostly resides in the nucleolus of mammalian cells; however, several reports have demonstrated that in some cells, mostly in cancerous ones, nucleolin is also targeted to the cell surface where it, among other functions, acts as a binding partner or a low-affinity coreceptor for several viruses ,, and lipoproteins. , In addition, the cellular uptake of a few synthetic compounds such as the guanosine-rich aptamer AS1411 − and pentameric pseudopeptide HB-19 ,, is mediated by nucleolin that localizes on the cell surface. Indeed, nucleolin has several regions and modifications that might attract cationic CPPs.…”

Fine Tuning of Phosphorothioate Inclusion in 2′-O-Methyl Oligonucleotides Contributes to Specific Cell Targeting for Splice-Switching Modulation

“…Furthermore, Ncl was reported to act as a scavenger receptor for acetylated low-density lipoproteins on macrophages (Canton et al, 2013;Ezzat et al, 2015;Miki et al, 2015), and other receptor proteins may be involved in signalosomes. Thus, it is possible that Ncl interacts with 2OMePS, leading to reduced 2OMePS activity upon diminishing of a particular 2OMe-binding protein.…”

Anti-nucleolin aptamer AS1411: an advancing therapeutic

“…This can be done with various receptors, one of which is nucleolin. Nucleolin is used in microglia recognition of amyloid beta peptide 1–42 ( Ozawa et al, 2013 ), macrophage recognition of maleyated bovine serum albumin, and acetylated low-density lipoprotein ( Miki et al, 2015 ; Miki et al, 2015 ), to name a few. After recognition, there is the process of internalization through cytoskeleton rearrangement and, ultimately, degradation ( Uribe-Querol and Rosales, 2020 ).…”