Connexins and Pannexins

Unless otherwise stated all data on this page refer to the human proteins. Gene information is provided for human (Hs), mouse (Mm) and rat (Rn).


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Gap junctions are essential for many physiological processes including cardiac and smooth muscle contraction, regulation of neuronal excitability and epithelial electrolyte transport [3-5]. Gap junction channels allow the passive diffusion of molecules of up to 1,000 Daltons which can include nutrients, metabolites and second messengers (such as IP3) as well as cations and anions. 21 connexin genes (Cx23, Cx25, Cx26, Cx30, Cx30.2, Cx30.3, Cx31, Cx31.1, Cx31.9, Cx32, Cx36, Cx37, Cx40, Cx40.1, Cx43, Cx45, Cx46, Cx47, Cx50, Cx59, Cx62) and 3 pannexin genes (Px1, Px2, Px3; which are structurally related to the invertebrate innexin genes) code for gap junction proteins in humans. Each connexin gap junction comprises 2 hemichannels or ‘connexons’ which are themselves formed from 6 connexin molecules. The various connexins have been observed to combine into both homomeric and heteromeric combinations, each of which may exhibit different functional properties. It is also suggested that individual hemichannels formed by a number of different connexins might be functional in at least some cells [6]. Connexins have a common topology, with four α-helical transmembrane domains, two extracellular loops, a cytoplasmic loop, and N- and C-termini located on the cytoplasmic membrane face. In mice, the most abundant connexins in electrical synapses in the brain seem to be Cx36, Cx45 and Cx57 [9]. Mutations in connexin genes are associated with the occurrence of a number of pathologies, such as peripheral neuropathies, cardiovascular diseases and hereditary deafness. The pannexin genes Px1 and Px2 are widely expressed in the mammalian brain [10]. Like the connexins, at least some of the pannexins can form hemichannels [3,7].

Channels and Subunits

Cx23 Show summary »

Cx25 Show summary »

Cx26 Show summary »

Cx30 Show summary »

Cx30.2 Show summary »

Cx30.3 Show summary »

Cx31 Show summary »

Cx31.1 Show summary »

Cx31.9 Show summary »

Cx32 Show summary »

Cx36 Show summary »

Cx37 Show summary »

Cx40 Show summary »

Cx40.1 Show summary »

Cx43 Show summary »

Cx45 Show summary »

Cx46 Show summary »

Cx47 Show summary »

Cx50 Show summary »

Cx59 Show summary »

Cx62 Show summary »

Px1 Show summary »

Px2 Show summary »

Px3 Show summary »


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Further reading

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How to cite this family page

Database page citation:

Connexins and Pannexins. Accessed on 28/02/2017. IUPHAR/BPS Guide to PHARMACOLOGY,

Concise Guide to PHARMACOLOGY citation:

Alexander SPH, Kelly E, Marrion N, Peters JA, Benson HE, Faccenda E, Pawson AJ, Sharman JL, Southan C, Davies JA and CGTP Collaborators (2015) The Concise Guide to PHARMACOLOGY 2015/16: Other ion channels. Br J Pharmacol. 172: 5942-5955.