Cd300e, also known as immune receptor expressed by myeloid cells (IREM)-2, is a transmembrane protein belonging to the CD300 glycoprotein family. It functions as an immune-activating receptor, primarily expressed in myeloid cells. Cd300e is involved in regulating oxidative stress, immune cell activation, tissue damage and repair, and lipid metabolism, and is associated with pathways like MicroRNAs in cancers and the Calcium signaling pathway [1,2]. It holds potential as a biomarker for disease diagnosis and treatment in various conditions such as infections, immune disorders, obesity, diabetes, and cancer [1,2].

In a murine breast cancer model, exercise-downregulated Cd300e was found to have a tumor-promoting role, with its upregulation in multiple cancers like myeloma, ovarian, lung, and colorectal cancers correlating with poorer prognostic outcomes [2]. In mice, the ortholog mCd300e was identified as an immune-activating receptor that recognizes sphingomyelin and regulates non-classical and intermediate monocyte functions through FcRγ and DAP12 [3]. In the context of liver cirrhosis, CD300E+ macrophages in a mouse model of carbon tetrachloride-induced cirrhosis promoted liver regeneration after splenectomy [4]. In childhood IgA nephropathy, mizoribine treatment inhibited Dex-induced expression of CD300E in cultured human macrophages, which was associated with halting kidney fibrosis [5].

In conclusion, Cd300e is a significant immune-activating receptor involved in multiple biological processes and disease conditions. Studies using mouse models, such as in cancer, liver cirrhosis, and IgA nephropathy, have revealed its role in disease progression and potential as a therapeutic target. Understanding Cd300e helps in uncovering disease mechanisms and developing targeted therapies for various diseases including cancer, obesity-related disorders, and immune-mediated diseases.