Calcium homeostasis modulator 1 (CALHM1) is a cerebral Ca²⁺ channel component responsible for controlling intracellular Ca²⁺ levels and Ab metabolism. CALHM1 is a three transmembrane glycoprotein, mostly localized to the endoplasmic reticulum (ER) although it can be detected at the plasma membrane. A functional channel is formed by multiple subunits which has some structural similarities to the NMDA receptor. It is expressed in all brain regions.