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Pannexin

pannexin 1
Identifiers
Symbol PANX1
Entrez 24145
HUGO 8599
OMIM 608420
RefSeq NM_015368
UniProt Q96RD7
Other data
Locus Chr. 11 q14-q21
pannexin 2
Identifiers
Symbol PANX2
Entrez 56666
HUGO 8600
OMIM 608421
RefSeq NM_052839
UniProt Q96RD6
Other data
Locus Chr. 22 q13
pannexin 3
Identifiers
Symbol PANX3
Entrez 116337
HUGO 20573
OMIM 608422
RefSeq NM_052959
UniProt Q96QZ0
Other data
Locus Chr. 11 q24.2

Pannexins (from Greek 'παν' — all, and from Latin 'nexus' — connection) are a family of vertebrate proteins identified by their homology to the invertebrate innexins. While innexins are responsible for forming gap junctions in invertebrates, the pannexins have been shown to predominantly exist as large transmembrane channels connecting the intracellular and extracellular space, allowing the passage of ions and small molecules between these compartments (such as ATP and sulforhodamine B).

Three pannexins have been described in Chordates: Panx1, Panx2 and Panx3.

Pannexin 1 has been shown to be involved in early stages of innate immunity through an interaction with the P2X7 purinergic receptor. Activation of the pannexin channel through binding of ATP to P2X7 receptor leads to the release of interleukin-1β.

Hypothetical roles of pannexins in the nervous system include participating in sensory processing, synchronization between hippocampus and cortex, hippocampal plasticity, and propagation of calcium waves. Calcium waves are supported by glial cells, which help maintain and modulate neuronal metabolism. According to one of the hypotheses, pannexins also may participate in pathological reactions, including the neural damage after ischemia and subsequent cell death.

Pannexin 1 channels are pathways for release of ATP from cells.

Intercellular gap junctions in vertebrates, including humans, are formed by the connexin family of proteins. Structurally, pannexins and connexins are very similar, consisting of 4 transmembrane domains, 2 extracellular and 1 intracellular loop, along with intracellular N- and C-terminal tails. Despite this shared topology, the protein families do not share enough sequence similarity to confidently infer common ancestry.

Pannexins may be involved in the process of tumor development. Particularly, PANX2 expression levels predict post diagnosis survival for patients with glial tumors.


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