CD33 Antibody - #DF6789

Sialic-acid-binding immunoglobulin-like lectin (Siglec) that plays a role in mediating cell-cell interactions and in maintaining immune cells in a resting state. Preferentially recognizes and binds alpha-2,3- and more avidly alpha-2,6-linked sialic acid-bearing glycans. Upon engagement of ligands such as C1q or syalylated glycoproteins, two immunoreceptor tyrosine-based inhibitory motifs (ITIMs) located in CD33 cytoplasmic tail are phosphorylated by Src-like kinases such as LCK. These phosphorylations provide docking sites for the recruitment and activation of protein-tyrosine phosphatases PTPN6/SHP-1 and PTPN11/SHP-2. In turn, these phosphatases regulate downstream pathways through dephosphorylation of signaling molecules. One of the repressive effect of CD33 on monocyte activation requires phosphoinositide 3-kinase/PI3K.

Glycosylated. Glycosylation at Asn-100 is critical for regulating ligand recognition.

Phosphorylation of Tyr-340 is involved in binding to PTPN6 and PTPN11. Phosphorylation of Tyr-358 is involved in binding to PTPN6. LCK phosphorylates Tyr-340 efficiently and Tyr-358 to a lesser extent.

Cell membrane>Single-pass type I membrane protein.

Peroxisome.
Note: CD33m isoform does not localize to cell surfaces but instead accumulates in peroxisomes.

Monocytic/myeloid lineage cells. In the brain, CD33 is mainly expressed on microglial cells.

Homodimer; disulfide-linked. Interacts with PTPN6/SHP-1 and PTPN11/SHP-2 upon phosphorylation. Interacts with C1QA (via C-terminus); this interaction activates CD33 inhibitory motifs.

Contains 2 copies of a cytoplasmic motif that is referred to as the immunoreceptor tyrosine-based inhibitor motif (ITIM). This motif is involved in modulation of cellular responses. The phosphorylated ITIM motif can bind the SH2 domain of several SH2-containing phosphatases.

Belongs to the immunoglobulin superfamily. SIGLEC (sialic acid binding Ig-like lectin) family.