Mannose Receptor glycoprotein ligands in A549 cells

The macrophage mannose receptor (CD206, MR) is an endocytic lectin receptor which plays an important role in homeostasis and innate immunity. The MR contains C-type lectin domains (CTLD) whose specificity for endogenous glycans and glycoprotein ligands have not been well studied. To gain more insights into the recognition by the MR, we used the murine MR CTLD 4-7 coupled to the Fc-part of IgG (MR-Fc) to investigate its glycan and glycoprotein recognition. As lung cancer tissue and the lung cancer cell line A549 showed intense MR-Fc binding, we further investigated the MR glycoprotein ligands in those cells by immunoprecipitation and glycoproteomic analysis. All enriched glycoproteins, of which 42 were identified, contained pauci- or oligomannose N-glycans, confirming the microarray results. Our study demonstrates that the MR CTLD4-7 is highly selective for pauci- and oligomannosidic N-glycans, structures that are often elevated in tumor cells, and suggest a potential role for the MR in tumor biology.