Calsyntenin-3 (CST-3; also CDH-11 and Alcadein-beta) is a 160 kDa member of the Alcadein family of molecules. It is expressed on the membranes of GABAergic neurons and in the granules of anterior pituitary secretory cells. Calsyntenin-3 is a calcium-binding protein that is proposed to regulate post-synaptic signaling, plus participate in the formation of a membrane-associated APP-X11L-CST-3 complex that blocks APP cleavage.
Mature human CST-3 is a 937 amino acid (aa) type I transmembrane protein. It contains two cadherin domains (aa 29 - 246) in the extracellular region, and an 87 aa cytoplasmic tail. Cleavage presumably occurs, generating a soluble 120 kDa ECD. One splice event shows a 34 aa substitution for the N-terminal 21 amino acids. Over aa 21 - 849, human CST-3 shares 97% aa identity with mouse CST-3.