The function of MSR1 (macrophage scavenger receptor 1, ENSG00000038945) is as follows. Membrane receptor that mediates the binding, endocytosis and phagocytosis of a broad range of ligands. Recognizes and internalizes modified forms of low-density lipoproteins including acetylated LDL (AcLDL) and oxidized LDL (OxLDL), thereby promoting cholesterol uptake and contributing to foam cell formation during atherogenesis (PubMed:2251254, PubMed:34252459). Binds various pathogen-associated and damage-associated molecules, including bacterial cell wall components, apoptotic cell debris and polyanionic ligands, supporting macrophage clearance activity in innate immune defense (PubMed:10722588). Upon stimulation by CpG DNA, mediates activation of LYN, which phosphorylates SYK that is subsequently recruited to endosomal TLR9 to promote downstream TLR9 signaling (PubMed:29057947, PubMed:40980882). {ECO:0000269|PubMed:10722588, ECO:0000269|PubMed:2251254, ECO:0000269|PubMed:29057947, ECO:0000269|PubMed:34252459, ECO:0000269|PubMed:40980882}. [Isoform III]: Does not internalize acetylated LDL. .