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0CXA8_HUMAN*   SwissProt (?) | Description Local Annotation Link Reference
General Information
NameGJA8
DescriptionGap junction alpha-8 protein (connexin 50) (cx50) (lens fiber protein mp70).
SpeciesHomo sapiens (NCBI taxonomy ID: 9606)
GO0005922 connexon complex (TAS)
0005887 integral to plasma membrane (TAS)
0015267 channel or pore class transporter activity (TAS)
0006810 transport (TAS)
0007601 visual perception (TAS)

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schematic display of those terms with internal associations, click the node and browse the corresponding GO term
Domain Architecture (Details)
InterPro domains assigned to SynO:
The connexins are a family of integral membrane proteins that oligomerise to form intercellular channels that are clustered at gap junctions. These channels are specialised sites of cell-cell contact that allow the passage of ions.ntracellular metabolites and messenger molecules (with molecular weight less than 1-2 kD) from the cytoplasm of one cell to its opposing neighbours. They are found in almost all vertebrate cell types.nd somewhat similar proteins have been cloned from plant species. Invertebrates utilise a different family of molecules.nnexins.hat share a similar predicted secondary structure to the vertebrate connexins.ut have no sequence identity to them . Vertebrate gap junction channels are thought to participate in diverse biological functions. For instance.n the heart they permit the rapid cell-cell transfer of action potentials.nsuring coordinated contraction of the cardiomyocytes. They are also responsible for neurotransmission at specialised electrical synapses. In non-excitable tissues.uch as the liver.hey may allow metabolic cooperation between cells. In the brain.lial cells are extensively-coupled by gap junctions; this allows waves of intracellular Ca2+ to propagate through nervous tissue.nd may contribute to their ability to spatially-buffer local changes in extracellular K+ concentration .The connexin protein family is encoded by at least 13 genes in rodents.ith many homologues cloned from other species. They show overlapping tissue expression patterns.ost tissues expressing more than one connexin type. Their conductances.ermeability to different molecules.hosphorylation and voltage-dependence of their gating.ave been found to vary. Possible communication diversity is increased further by the fact that gap junctions may be formed by the association of different connexin isoforms from apposing cells. However.n vitro studies have shown that not all possible combinations of connexins produce active channels .Hydropathy analysis predicts that all cloned connexins share a common transmembrane (TM) topology. Each connexin is thought to contain 4 TMdomains.ith two extracellular and three cytoplasmic regions. This modelhas been validated for several of the family members by in vitro biochemicalanalysis. Both N- and C-termini are thought to face the cytoplasm.nd thethird TM domain has an amphipathic character.uggesting that it contributesto the lining of the formed-channel. Amino acid sequence identity betweenthe isoforms is ~50-80%.ith the TM domains being well conserved. Bothextracellular loops contain characteristically conserved cysteine residues.hich likely form intramolecular disulphide bonds. By contrast.he singleputative intracellular loop (between TM domains 2 and 3) and the cytoplasmicC-terminus are highly variable among the family members.Six connexins arethought to associate to form a hemi-channel.r connexon. Two connexons theninteract (likely via the extracellular loops of their connexins) to form thecomplete gap junction channel.Two sets of nomenclature have been used to identify the connexins. Thefirst.nd most commonly used.lassifies the connexin molecules accordingto molecular weight.uch as connexin43 (abbreviated to Cx43).ndicatinga connexin of molecular weight close to 43 kD. However.tudies haverevealed cases where clear functional homologues exist across speciesthat have quite different molecular masses; therefore.n alternativenomenclature was proposed based on evolutionary considerations.hichdivides the family into two major subclasses.lpha and beta.ach with anumber of members . Due to their ubiquity and overlapping tissue distributions.t has proved difficult to elucidate the functions of individual connexin isoforms. To circumvent this problem.articular connexin-encoding genes have been subjected to targeted-disruption in mice.nd the phenotype of the resulting animals investigated. Around half the connexin isoforms have been investigated in this manner . Further insight into the functional roles of connexins has come from the discovery that a number of human diseases are caused by mutations in connexin genes. For instance.utations in Cx32 give rise to a form of inherited peripheral neuropathy called X-linked dominant Charcot-Marie-Tooth disease . Similarly.utations in Cx26 are responsible for both autosomal recessive and dominant forms of nonsyndromic deafness. disorder characterised by hearing loss.ith no apparent effects on other organ systems.
  IPR000500:Connexins
InterPro domains unassigned to SynO:
The connexins are a family of integral membrane proteins that oligomerise to form intercellular channels that are clustered at gap junctions. These channels are specialised sites of cell-cell contact that allow the passage of ions.ntracellular metabolites and messenger molecules (with molecular weight less than 1-2 kD) from the cytoplasm of one cell to its opposing neighbours. They are found in almost all vertebrate cell types.nd somewhat similar proteins have been cloned from plant species. Invertebrates utilise a different family of molecules.nnexins.hat share a similar predicted secondary structure to the vertebrate connexins.ut have no sequence identity to them . Vertebrate gap junction channels are thought to participate in diverse biological functions. For instance.n the heart they permit the rapid cell-cell transfer of action potentials.nsuring coordinated contraction of the cardiomyocytes. They are also responsible for neurotransmission at specialised electrical synapses. In non-excitable tissues.uch as the liver.hey may allow metabolic cooperation between cells. In the brain.lial cells are extensively-coupled by gap junctions; this allows waves of intracellular Ca2+ to propagate through nervous tissue.nd may contribute to their ability to spatially-buffer local changes in extracellular K+ concentration .The connexin protein family is encoded by at least 13 genes in rodents.ith many homologues cloned from other species. They show overlapping tissue expression patterns.ost tissues expressing more than one connexin type. Their conductances.ermeability to different molecules.hosphorylation and voltage-dependence of their gating.ave been found to vary. Possible communication diversity is increased further by the fact that gap junctions may be formed by the association of different connexin isoforms from apposing cells. However.n vitro studies have shown that not all possible combinations of connexins produce active channels .Hydropathy analysis predicts that all cloned connexins share a common transmembrane (TM) topology. Each connexin is thought to contain 4 TMdomains.ith two extracellular and three cytoplasmic regions. This modelhas been validated for several of the family members by in vitro biochemicalanalysis. Both N- and C-termini are thought to face the cytoplasm.nd thethird TM domain has an amphipathic character.uggesting that it contributesto the lining of the formed-channel. Amino acid sequence identity betweenthe isoforms is ~50-80%.ith the TM domains being well conserved. Bothextracellular loops contain characteristically conserved cysteine residues.hich likely form intramolecular disulphide bonds. By contrast.he singleputative intracellular loop (between TM domains 2 and 3) and the cytoplasmicC-terminus are highly variable among the family members.Six connexins arethought to associate to form a hemi-channel.r connexon. Two connexons theninteract (likely via the extracellular loops of their connexins) to form thecomplete gap junction channel.Two sets of nomenclature have been used to identify the connexins. Thefirst.nd most commonly used.lassifies the connexin molecules accordingto molecular weight.uch as connexin43 (abbreviated to Cx43).ndicatinga connexin of molecular weight close to 43 kD. However.tudies haverevealed cases where clear functional homologues exist across speciesthat have quite different molecular masses; therefore.n alternativenomenclature was proposed based on evolutionary considerations.hichdivides the family into two major subclasses.lpha and beta.ach with anumber of members . Due to their ubiquity and overlapping tissue distributions.t has proved difficult to elucidate the functions of individual connexin isoforms. To circumvent this problem.articular connexin-encoding genes have been subjected to targeted-disruption in mice.nd the phenotype of the resulting animals investigated. Around half the connexin isoforms have been investigated in this manner . Further insight into the functional roles of connexins has come from the discovery that a number of human diseases are caused by mutations in connexin genes. For instance.utations in Cx32 give rise to a form of inherited peripheral neuropathy called X-linked dominant Charcot-Marie-Tooth disease . Similarly.utations in Cx26 are responsible for both autosomal recessive and dominant forms of nonsyndromic deafness. disorder characterised by hearing loss.ith no apparent effects on other organ systems.This domain is found in the N-terminal region of these proteins.
  IPR013092:Connexin, N-terminal
The connexins are a family of integral membrane proteins that oligomerise to form intercellular channels that are clustered at gap junctions. These channels are specialised sites of cell-cell contact that allow the passage of ions.ntracellular metabolites and messenger molecules (with molecular weight less than 1-2 kD) from the cytoplasm of one cell to its opposing neighbours. They are found in almost all vertebrate cell types.nd somewhat similar proteins have been cloned from plant species. Invertebrates utilise a different family of molecules.nnexins.hat share a similar predicted secondary structure to the vertebrate connexins.ut have no sequence identity to them . Vertebrate gap junction channels are thought to participate in diverse biological functions. For instance.n the heart they permit the rapid cell-cell transfer of action potentials.nsuring coordinated contraction of the cardiomyocytes. They are also responsible for neurotransmission at specialised electrical synapses. In non-excitable tissues.uch as the liver.hey may allow metabolic cooperation between cells. In the brain.lial cells are extensively-coupled by gap junctions; this allows waves of intracellular Ca2+ to propagate through nervous tissue.nd may contribute to their ability to spatially-buffer local changes in extracellular K+ concentration .The connexin protein family is encoded by at least 13 genes in rodents.ith many homologues cloned from other species. They show overlapping tissue expression patterns.ost tissues expressing more than one connexin type. Their conductances.ermeability to different molecules.hosphorylation and voltage-dependence of their gating.ave been found to vary. Possible communication diversity is increased further by the fact that gap junctions may be formed by the association of different connexin isoforms from apposing cells. However.n vitro studies have shown that not all possible combinations of connexins produce active channels .Hydropathy analysis predicts that all cloned connexins share a common transmembrane (TM) topology. Each connexin is thought to contain 4 TMdomains.ith two extracellular and three cytoplasmic regions. This modelhas been validated for several of the family members by in vitro biochemicalanalysis. Both N- and C-termini are thought to face the cytoplasm.nd thethird TM domain has an amphipathic character.uggesting that it contributesto the lining of the formed-channel. Amino acid sequence identity betweenthe isoforms is ~50-80%.ith the TM domains being well conserved. Bothextracellular loops contain characteristically conserved cysteine residues.hich likely form intramolecular disulphide bonds. By contrast.he singleputative intracellular loop (between TM domains 2 and 3) and the cytoplasmicC-terminus are highly variable among the family members.Six connexins arethought to associate to form a hemi-channel.r connexon. Two connexons theninteract (likely via the extracellular loops of their connexins) to form thecomplete gap junction channel.Gap junction alpha-8 protein (also called connexin50.x50.r lens fibreprotein MP70) is a connexin of ~431 amino acid residues. The chicken isoformis shorter (399 residues) and is hence known as Cx45.6. Cx50 and Cx46 arethe two gap junction proteins normally found in lens fibre cells of the eye.Evidence from both genetically-engineered mice.nd from the identificationof mutations in the human Cx50-encoding gene.ighlight the importance ofthis connexin in maintaining lens transparency. Deletion of mice Cx50produces a viable phenotype.ut these animals start to develop cataracts(of the zonular pulverant type) at about one week old. They also haveabnormally small eyes and lenses. Similarly.utations in the human geneencoding Cx50 have been associated with the occurrence of congenitalcataracts. Affected individuals develop cataracts (with zonular pulverentopacities).nd analysis shows they have a single point mutation in the Cx50coding region.esulting in a non-conservative substitution in the secondputative TM domain of a serine residue for a proline.This domain is found in the C-terminal region of these proteins.
  IPR013125:Gap junction alpha-8 protein (Cx50), C-terminal
The connexins are a family of integral membrane proteins that oligomerise to form intercellular channels that are clustered at gap junctions. These channels are specialised sites of cell-cell contact that allow the passage of ions.ntracellular metabolites and messenger molecules (with molecular weight less than 1-2 kD) from the cytoplasm of one cell to its opposing neighbours. They are found in almost all vertebrate cell types.nd somewhat similar proteins have been cloned from plant species. Invertebrates utilise a different family of molecules.nnexins.hat share a similar predicted secondary structure to the vertebrate connexins.ut have no sequence identity to them . Vertebrate gap junction channels are thought to participate in diverse biological functions. For instance.n the heart they permit the rapid cell-cell transfer of action potentials.nsuring coordinated contraction of the cardiomyocytes. They are also responsible for neurotransmission at specialised electrical synapses. In non-excitable tissues.uch as the liver.hey may allow metabolic cooperation between cells. In the brain.lial cells are extensively-coupled by gap junctions; this allows waves of intracellular Ca2+ to propagate through nervous tissue.nd may contribute to their ability to spatially-buffer local changes in extracellular K+ concentration .The connexin protein family is encoded by at least 13 genes in rodents.ith many homologues cloned from other species. They show overlapping tissue expression patterns.ost tissues expressing more than one connexin type. Their conductances.ermeability to different molecules.hosphorylation and voltage-dependence of their gating.ave been found to vary. Possible communication diversity is increased further by the fact that gap junctions may be formed by the association of different connexin isoforms from apposing cells. However.n vitro studies have shown that not all possible combinations of connexins produce active channels .Hydropathy analysis predicts that all cloned connexins share a common transmembrane (TM) topology. Each connexin is thought to contain 4 TMdomains.ith two extracellular and three cytoplasmic regions. This modelhas been validated for several of the family members by in vitro biochemicalanalysis. Both N- and C-termini are thought to face the cytoplasm.nd thethird TM domain has an amphipathic character.uggesting that it contributesto the lining of the formed-channel. Amino acid sequence identity betweenthe isoforms is ~50-80%.ith the TM domains being well conserved. Bothextracellular loops contain characteristically conserved cysteine residues.hich likely form intramolecular disulphide bonds. By contrast.he singleputative intracellular loop (between TM domains 2 and 3) and the cytoplasmicC-terminus are highly variable among the family members.Six connexins arethought to associate to form a hemi-channel.r connexon. Two connexons theninteract (likely via the extracellular loops of their connexins) to form thecomplete gap junction channel.Two sets of nomenclature have been used to identify the connexins. Thefirst.nd most commonly used.lassifies the connexin molecules accordingto molecular weight.uch as connexin43 (abbreviated to Cx43).ndicatinga connexin of molecular weight close to 43 kD. However.tudies haverevealed cases where clear functional homologues exist across speciesthat have quite different molecular masses; therefore.n alternativenomenclature was proposed based on evolutionary considerations.hichdivides the family into two major subclasses.lpha and beta.ach with anumber of members . Due to their ubiquity and overlapping tissue distributions.t has proved difficult to elucidate the functions of individual connexin isoforms. To circumvent this problem.articular connexin-encoding genes have been subjected to targeted-disruption in mice.nd the phenotype of the resulting animals investigated. Around half the connexin isoforms have been investigated in this manner . Further insight into the functional roles of connexins has come from the discovery that a number of human diseases are caused by mutations in connexin genes. For instance.utations in Cx32 give rise to a form of inherited peripheral neuropathy called X-linked dominant Charcot-Marie-Tooth disease . Similarly.utations in Cx26 are responsible for both autosomal recessive and dominant forms of nonsyndromic deafness. disorder characterised by hearing loss.ith no apparent effects on other organ systems.Gap junction alpha-8 protein (also called connexin50.x50.r lens fibreprotein MP70) is a connexin of ~431 amino acid residues. The chicken isoformis shorter (399 residues) and is hence known as Cx45.6. Cx50 and Cx46 arethe two gap junction proteins normally found in lens fibre cells of the eye.Evidence from both genetically-engineered mice.nd from the identificationof mutations in the human Cx50-encoding gene.ighlight the importance ofthis connexin in maintaining lens transparency. Deletion of mice Cx50produces a viable phenotype.ut these animals start to develop cataracts(of the zonular pulverant type) at about one week old. They also haveabnormally small eyes and lenses. Similarly.utations in the human geneencoding Cx50 have been associated with the occurrence of congenitalcataracts. Affected individuals develop cataracts (with zonular pulverentopacities).nd analysis shows they have a single point mutation in the Cx50coding region.esulting in a non-conservative substitution in the secondputative TM domain of a serine residue for a proline.
  IPR002266:Gap junction alpha-8 protein (Cx50)
IPR013092:Connexin 
Evalue:-160.309799194336 
Location:2-226IPR013125:Connexin50 
Evalue:-51.4948501586914 
Location:259-325IPR002266:CONNEXINA8 
Evalue:0 
Location:413-424
SequencesProtein: CXA8_HUMAN (432 aa)
mRNA: NM_005267
Local Annotation
Synapse Ontology
supporting cells of the nervous system. Glial cells in the brain and spinal cord far outnumber nerve cells. They not only provide physical support, but also respond to injury, regulate the chemical composition surrounding cells, participate in the blood-brain and blood-spinal-cord barriers, form the myelin insulation of nervous pathways, help guide neuronal migration during development, and exchange metabolites with neurons. They may also produce substances that help and hinder regeneration in the spinal cord. The major types of glial cells in the CNS are astrocytes, oligodendrocytes, and microglia.
sdb:0008 Glia  (Evidence:domains)
A neuromuscular junction is the junction of the axon terminal of a motoneuron with the motor end plate, the highly-excitable region of muscle fiber plasma membrane responsible for initiation of action potentials across the muscle's surface.
sdb:0024 neuromuscular junction  (Evidence:domains)
KO assignmentK07617
  Level 3 annotation:
    gap junction protein, alpha 8
  Level 2 annotation:
    Membrane and intracellular structural molecules
Loci Structure (Details)Loci index, Chromosomal location, Length, Possible relational loci clusterExon1: 18 residues, 145841559-145841611Exon2: 442 residues, 145846695-145848017Exon3: 2 residues, -Jump to CXA8_HUMAN  
Tune and view alternative isoforms
Loci Cluster (Details)Loci: 3829 145695516-145712066 ~-17K 2401(GJA5)(-)Loci: 2546 145841559-145848017 ~-6K 2402(GJA8)(+)Loci: 3828 145585791-145609238 ~-23K 2398(ACP6)(-)Link out to UCSC