Channelpedia

cacng7

Description: calcium channel, voltage-dependent, gamma subunit 7
Gene: Cacng7     Synonyms: cacng7

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Introduction

The protein encoded by CACNG7 is a type II transmembrane AMPA receptor regulatory protein (TARP). TARPs regulate both trafficking and channel gating of the AMPA receptors. This gene is part of a functionally diverse eight-member protein subfamily of the PMP-22/EMP/MP20 family and is located in a cluster with two family members, a type I TARP and a calcium channel gamma subunit. http://www.ncbi.nlm.nih.gov/gene/59284


Experimental data


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Gene

Phylogenetic analysis suggests that all c subunits evolved from a single ancestral gene through tandem repeat and chromosome duplication (Burgesse [1312], Chu [1311]). Based on sequence homology and chromosomal linkage the c subunits can be divided into three clusters: (c1, c6), (c5, c7), and (c2, c3, c4, c8) (Burgesse [1312], Chu [1311]). See also the phylogenetic tree, fig.2 in Black [478].

c5 and c7 are encoded by five exons in contrast to all other c subunits, which are encoded by four exons (Moss [1336], Chu [1311]). A protein originally identified as mouse c5 (Klugbauer [1328]) is currently named transmembrane protein 37 (Tmem37, NCBI database). Although Tmem37 is also a tetraspanin protein with the GLW motif characteristic of the pfam0082 protein family, its gene consists of only two exons, indicating a divergence from other c subunit genes during evolution. Based on phylogenetic evidence, Chu et al. proposed that Tmem37 should not be considered a member of the calcium channel c family (Chu [1311]). This conclusion is further supported by the observation that Tmem37 does not share the chromosomal linkage to c4 and c1 in human (Burgess [1313]), mouse and rat (Chu [1311]) that is seen for c5 (Table 2 in Chen [1310]).

RGD ID Chromosome Position Species
628807 1 64114233-64140485 Rat
732587 7 3336685-3366537 Mouse
732586 19 54416071-54446268 Human

Cacng7 : calcium channel, voltage-dependent, gamma subunit 7


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Transcript

Acc No Sequence Length Source
NM_080695 n/A n/A NCBI
NM_133189 n/A n/A NCBI
NM_031896 n/A n/A NCBI

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Ontology

Accession Name Definition Evidence
GO:0016021 integral to membrane Penetrating at least one phospholipid bilayer of a membrane. May also refer to the state of being buried in the bilayer with no exposure outside the bilayer. When used to describe a protein, indicates that all or part of the peptide sequence is embedded in the membrane. IEA
GO:0016020 membrane Double layer of lipid molecules that encloses all cells, and, in eukaryotes, many organelles; may be a single or double lipid bilayer; also includes associated proteins. IEA

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Interaction


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Protein


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Structure

The eight calcium channel c subunits share a predicted structure that includes four transmembrane domains with intracellular N- and C- termini (Fig. 1 in Chen [1310]). They are members of a large protein superfamily (pfam00822, a subset of the tetraspanin supergroup) that also includes claudins, proteins that are important components of tight junctions in epithelia. The c subunits share with the claudins a conserved GLW motif of unknown significance in the first extracellular loop. Chen [1310]

The c5 and c7 subunits are highly expressed in brain tissue and lack a C-terminal PDZ-binding motif in comparison to other gamma subunits (Chu [1311], Moss [1336]).

c5, c7: c5, and c7 are palmitoylated at both the N- and C- termini. Additionally, their C-terminal tails contain tyrosine phosphorylation sites. Chen [1310]


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Distribution


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Expression


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Functional

c7 subunit dramatically reduced current density produced by the Cav2.2 subunit in Xenopus oocytes and COS-7 cells (Moss [1336]). However, when expressed in sympathetic neurons c7 failed to affect pre-existing HVA Ca2+ channels. Therefore, confirmation of the physiological influence of c7 on calcium current remains elusive. (Chen [1310])

γ7, which is homologous to γ5, regulates stability of certain mRNAs (Ferron [1342]) and, along with γ2 and γ8, controls trafficking and gating of AMPA receptors (Tomita [1343], Kato [1344]). It thus may be involved in ischemic cardiomyopathy (Gronich [1341]).


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Kinetics


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Model


References

Chen RS et al. Calcium channel gamma subunits: a functionally diverse protein family.
Cell Biochem. Biophys., 2007 , 47 (178-86).

Klugbauer N et al. A family of gamma-like calcium channel subunits.
FEBS Lett., 2000 Mar 24 , 470 (189-97).


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Credits

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