Siglec-7

Sialic Acid Binding Ig Like Lectin 7 (Siglec-7, also known as p75/AIRM1 or CD328) is a surface inhibitory receptor belonging to a family of Sialic acid recognizing Immunoglobulin-like Lectins (Siglecs) that is expressed on natural killer (NK) cells and monocytes. In line with most inhibitory receptors, Siglec-7 is characterized by Ig-like domains in the extracellular portion and a classical ITIM, together with an ITIM-like domain, in its cytoplasmic tail.
Siglec-7 plays an important role in inhibitory signal transducing through sialic acids (Sia)-dependent-binding. The interaction between Siglec-7 and Sia can reduce the cytotoxicity of NK cells towards the target cells through the ITIM recruiting SHP-1/2, blocking signal conduction pathway, and playing negative regulation. Siglec-7 can regulate immune responses contributing to immune tolerance, however, it can also decrease anti-tumor immunity on account of the aberrant expression of sialylated glycans on the surface of malignant cells of different histotypes [e.g., AML, CLL, melanoma, renal cell carcinoma, colon adenocarcinoma]. Therefore, Siglec-7 acts as an attractive immune checkpoint that can be targeted to enhance anti-tumor responses.