Pore-forming subunit of a voltage-gated ion channel required for sensory perception of sweet, bitter and umami tastes (By similarity). Specifically present in type II taste bud cells, where it plays a central role in sweet, bitter and umami taste perception by inducing ATP release from the cell, ATP acting as a neurotransmitter to activate afferent neural gustatory pathways (By similarity). Together with CALHM3, forms a fast-activating voltage-gated ATP-release channel in type II taste bud cells (TBCs) (By similarity). Acts both as a voltage-gated and calcium-activated ion channel: mediates neuronal excitability in response to changes in extracellular Ca(2+) concentration (PubMed:22711817, PubMed:23300080). Has poor ion selectivity and forms a wide pore (around 14 Angstroms) that mediates permeation of Ca(2+), Na(+) and K(+), as well as permeation of monovalent anions (PubMed:22711817). Acts as an activator of the ERK1 and ERK2 cascade (PubMed:23345406). Triggers endoplasmic reticulum stress by reducing the calcium content of the endoplasmic reticulum (PubMed:21574960). May indirectly control amyloid precursor protein (APP) proteolysis and aggregated amyloid-beta (Abeta) peptides levels in a Ca(2+) dependent manner (PubMed:18585350). Inhibited by Gd(3+), Ruthenium Red, and Zn(2+) and partially inhibited by 2-aminoethoxydiphenyl borate. Homohexamer. Associates with CALHM3 as a pore-forming subunit in an hetero-hexameric channel complex (By similarity). Colocalizes with HSPA5 at the endoplasmic reticulum (PubMed:18585350). Localizes to the basolateral membrane of epithelial cells including taste cells (By similarity). Predominantly expressed in adult brain. Detected also in retinoic acid-differentiated SH-SY5Y cells. Specifically expressed in circumvallate taste bud cells. Leu-86 causes a dysregulation of Ca(2+) homeostasis and amyloid precursor protein (APP) metabolism and has been suggested to be a risk factor for the development of Alzheimer disease (PubMed:18585350, PubMed:20061624, PubMed:20164592). However, this association with Alzheimer disease could not be confirmed in a number of studies performed in different populations (PubMed:19472444, PubMed:19070563, PubMed:19191331, PubMed:19191332, PubMed:19545933, PubMed:19655363, PubMed:21378601). According to a meta-analysis study, Leu-86 is likely not a genetic determinant of Alzheimer disease but may modulate age of onset by interacting with the effect of the APOE*4 allele of the APOE gene (PubMed:20847397). Belongs to the CALHM family.