{PDOC51013}
{PS51013; PANNEXIN}
{BEGIN}
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* Pannexin family profile *
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The pannexin family combines invertebrate gap junction proteins (innexins) and
their vertebrate  homologs.  Gap  junctions are composed of membrane proteins,
which form  a  channel  permeable  for  ions  and  small  molecules connecting
cytoplasm of  adjacent cells. Although gap junctions provide similar functions
in all   multicellular   organisms,   until  recently  it  was  believed  that
vertebrates and  invertebrates  use unrelated proteins for this purpose. While
the connexins  family  of  gap  junction  proteins  (see <PDOC00341>) is well-
characterized in vertebrates, no homologs heve been found in invertebrates. In
turn, gap  junction molecules with no sequence homology to connexins have been
identified in insects and nematodes. It has been suggested that these proteins
are specific  invertebrate  gap  junctions,  and they were thus named innexins
(invertebrate analog  of  connexins) [1,2]. As innexins homologs were recently
identified in  other  taxonomic groups including vertebrates, indicating their
ubiquitous distribution  in  the  animal  kingdom,  they were called pannexins
(from the  Latin  pan-all,  throughout,  and  nexus-connection, bond) [3,4,5].
Genomes of  vertebrates  carry probably a conserved set of 3 pannexin paralogs
(PANX1, PANX2  and  PANX3). Invertebrates genome may contain more than a dozen
pannexin (innexin)  genes.  Vinnexins,  viral  homologs of pannexins/innexins,
were identified   in   Polydnaviruses   that   occur   in  obligate  symbiotic
associations with  parasitoid  wasps.  It  was  suggested that virally encoded
vinnexin proteins may function to alter gap junction proteins in infected host
cells, possibly   modifying   cell-cell   communication  during  encapsulation
responses in parasitized insects [6,7].

Structurally pannexins  are  simillar  to  connexins.  Both  types  of protein
consist of  a  cytoplasmic  N-terminal  domain, followed by four transmembrane
segments that  delimit  two  extracellular  and  one cytoplasmic loops; the C-
terminal domain is cytoplasmic. The schematic representation of this structure
is shown below.

                 NH2-***        ***          *********-COOH
                       **     **   **      **
                       **    **     **    **   Cytoplasmic
                    ---**----**-----**----**----------------
                       **    **     **    **   Membrane
                       **    **     **    **
                    ---**----**-----**----**----------------
                       **    **     **    **   Extracellular
                        **  **       **  **
                          **           **

The profile we developed spans the entire pannexin family.

-Sequences known to belong to this class detected by the profile: ALL.
-Other sequence(s) detected in Swiss-Prot: NONE.

-Expert(s) to contact by email:
           Panchin Y.; ypanchin@yahoo.com

-Last update: August 2004 / First entry.

[ 1] Phelan P., Bacon J.P., Davies J.A., Stebbings L.A., Todman M.G.,
     Avery L., Baines R.A., Barnes T.M., Ford C., Hekimi S., Lee R.,
     Shaw J.E., Starich T.A., Curtin K.D., Sun Y.-A., Wyman R.J.
     "Innexins: a family of invertebrate gap-junction proteins."
     Trends Genet. 14:348-349(1998).
     PubMed=9769729
[ 2] Phelan P., Starich T.A.
     "Innexins get into the gap."
     BioEssays 23:388-396(2001).
     PubMed=11340620; DOI=10.1002/bies.1057
[ 3] Panchin Y., Kelmanson I., Matz M., Lukyanov K., Usman N., Lukyanov S.
     "A ubiquitous family of putative gap junction molecules."
     Curr. Biol. 10:R473-R474(2000).
     PubMed=10898987
[ 4] Kelmanson I.V., Shagin D.A., Usman N., Matz M.V., Lukyanov S.A.,
     Panchin Y.V.
     "Altering electrical connections in the nervous system of the pteropod
     mollusc Clione limacina by neuronal injections of gap junction mRNA."
     Eur. J. Neurosci. 16:2475-2476(2002).
     PubMed=12492443
[ 5] Baranova A., Ivanov D., Petrash N., Pestova A., Skoblov M.,
     Kelmanson I., Shagin D., Nazarenko S., Geraymovych E., Litvin O.,
     Tiunova A., Born T.L., Usman N., Staroverov D., Lukyanov S.,
     Panchin Y.
     "The mammalian pannexin family is homologous to the invertebrate
     innexin gap junction proteins."
     Genomics 83:706-716(2004).
     PubMed=15028292; DOI=10.1016/j.ygeno.2003.09.025
[ 6] Turnbull M., Webb B.
     "Perspectives on polydnavirus origins and evolution."
     Adv. Virus. Res. 58:203-254(2002).
     PubMed=12205780
[ 7] Kroemer J.A., Webb B.A.
     "Polydnavirus genes and genomes: emerging gene families and new
     insights into polydnavirus replication."
     Annu. Rev. Entomol. 49:431-456(2004).
     PubMed=14651471; DOI=10.1146/annurev.ento.49.072103.120132

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