Anoctamin (ANO or TMEM16) is a family of 10 membrane proteins. This family is named so because these channels are selective to ANions and have eight (OCT) transmembrane domains. Also, these channels are subject to glycosylation in their extracellular loops and have both intracellular N- and C-termini¹. Members of this family are expressed in a broad range of different organisms ranging from mammals, flies, worms, plants and yeast¹. Alternative splicing is known to affect these channels and regarding their oligomerization state, homedimerization has been observed although when heterologously expressed, these channels may hetero oligomerize².

Ano1 (or TMEM16A, DOG1 and others) the first member to be identified was found to be a Ca²⁺-activated Cl^- channel^3-5 therefore other members are likely to also be Cl^- channels. These channels are expressed in many different tissues: bronchiolar epithelial cells, pancreatic acinar cells, proximal kidney tubule epithelium, retina, dorsal root ganglia and submandibular gland¹. In fact, Ano1 gained a lot of attention as its activation may serve as a therapeutic treatment for cystic fibrosis since it is also expressed in the airways⁶. These Ca²⁺-activated Cl^- channels are believed to play a role in development as knockout of Ano1 in mice causes abnormal development of the trachea⁷. Ano2 (TMEM16B) has been shown to mediate Ca²⁺-activated Cl^- current in olfactory epithelium and photoreceptor synapses^2,8,9.

Although relatively newly discovered channels, they are being discovered in many medical indications. Ano1 has become a marker in gastrointestinal tumors as its expression is significantly upregulated^10,11. Similarly, Ano1 is also highly expressed in other carcinomas^12,13.