Acts as an activating receptor in myeloid cells and mast cells. (Microbial infection) Acts as a functional murine norovirus (MNV) receptor. Primary determinant of MNV species tropism and is sufficient to render cells permissive to infection by MNV. Can render nonmurine mammalian cells susceptible to MNV infection (PubMed:27681626, PubMed:27540007). Interacts with FCER1G. Expressed in dendritic cells, macrophages and granulocytes. Present on the surface of granulocytes and monocytes/macrophages (at protein level). O-glycosylated. Belongs to the CD300 family.