Illustration of the calcium homeostasis modulator 1 (CALHM1) channel in its open state. This pore-forming transmembrane protein is found in nerve cells and taste buds where it regulates cellular levels of calcium ions (Ca2+) and modulates electrical excitability. It has also been shown to influence processing of amyloid precursor protein to amyloid beta. Plaques of amyloid beta in the brain are characteristic of Alzheimer's disease.