mannosereceptor

The mannose receptor, also known as CD206 or MRC1, is a type I transmembrane protein that belongs to the C-type lectin receptor family. It is expressed mainly on professional phagocytes such as macrophages and dendritic cells, including liver Kupffer cells and splenic macrophages, as well as some endothelial cells. The receptor binds carbohydrate ligands bearing terminal mannose, fucose, or N-acetylglucosamine, which are common on microbial glycoproteins and on aged or misfolded self glycoproteins.

Structure and ligands: The receptor features a stalk or neck region that allows oligomerization, followed by a cluster of C-type lectin carbohydrate recognition domains, an optional collagen-like region, a transmembrane domain, and a cytoplasmic tail with endocytic motifs that direct internalization. This arrangement enables high-avidity binding to multivalent ligands and rapid uptake. Ligand binding includes a broad range of pathogens and glycoproteins that display mannose- or fucose-containing residues.

Functions: Mannose receptor mediates endocytosis and phagocytosis of bound ligands, delivering them to endosomes for degradation or processing. It participates in clearance of circulating glycoproteins and in presentation of antigen to CD4+ T cells, influencing adaptive immunity. Receptor engagement can modulate cytokine production, often contributing to anti-inflammatory responses and immune tolerance under certain conditions.

Clinical and research relevance: The receptor contributes to host defense by mediating uptake of pathogens with mannose-rich surfaces. Its expression and function are being explored for targeted drug delivery to macrophages and for vaccine strategies. Alterations in MR expression have been studied in various diseases, including infectious, inflammatory, and metabolic conditions.