Channelpedia

cacnb2

Description: calcium channel, voltage-dependent, beta 2 subunit
Gene: Cacnb2     Synonyms: cacnb2, CACNLB2, CAVB2, Cavbeta2

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Introduction

CACNB2 (also known as MYSB; CAVB2; CACNLB2; FLJ23743) encodes a subunit of a voltage-dependent calcium channel protein which is a member of the voltage-gated calcium channel superfamily. The gene product was originally identified as an antigen target in Lambert-Eaton myasthenic syndrome which is an autoimmune disorder. Mutations in this gene are associated with Brugada symdrome. Alternatively spliced variants have been identified for this gene.

http://www.ncbi.nlm.nih.gov/gene/783


Experimental data


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Gene

Five distinct b2 subunits, varying only in the proximal amino terminus, have been cloned from different species including rat (Perez-Reyes et al., 1992 [1267]), rabbit (Hullin et al., 1992 [1275]), human (Rosenfeld et al., 1993 [1276]), and mouse (Massa et al., 1995 [1277]). Until (2003), however, no more than three of the b2 forms have been identified in any one species (Qin et al., 1998 [1274]), rendering it ambiguous whether they represent bona fide splice variants of the b2 gene. (From Takahashi [235])

RGD ID Chromosome Position Species
67385 17 88832905-89078870 Rat
732577 2 14525933-14908560 Mouse
732576 10 18429606-18830688 Human

Cacnb2 : calcium channel, voltage-dependent, beta 2 subunit


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Transcript

Acc No Sequence Length Source
NM_053851 n/A n/A NCBI
NM_023116 n/A n/A NCBI
NM_201596 n/A n/A NCBI
NM_201593 n/A n/A NCBI
NM_201597 n/A n/A NCBI
NM_201571 n/A n/A NCBI
NM_201572 n/A n/A NCBI
NM_000724 n/A n/A NCBI
NM_201590 n/A n/A NCBI
NM_201570 n/A n/A NCBI
NM_001167945 n/A n/A NCBI

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Ontology

Accession Name Definition Evidence
GO:0005891 voltage-gated calcium channel complex A protein complex that forms a transmembrane channel through which calcium ions may pass in response to changes in membrane potential. IMP
GO:0042383 sarcolemma The outer membrane of a muscle cell, consisting of the plasma membrane, a covering basement membrane (about 100 nm thick and sometimes common to more than one fiber), and the associated loose network of collagen fibers. IEA

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Interaction


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Protein


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Structure


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Distribution


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Expression

cacnb2 is the dominant b subunit expressed in heart (Perez-Reyes et al., 1992 [1267]; Pichler et al., 1997 [1269]; Haase et al., 2000 [1270]) and retina (Ball et al., 2002 [1271]), but is also an important component of HVA Ca21 channels expressed in brain (Ludwig et al., 1997 [474]; Pichler et al., 1997 [1269]), smooth muscle (Reimer et al., 2000 [1272]), and pancreas (Iwashima et al., 2001 [1273]). (List from Takahashi [235])


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Functional

Auxiliary b subunits are potent determinants of Ca2+ channel behavior. Qualitatively, all four b-subunit isoforms act similarly to markedly increase surface membrane expression of co-expressed alpha1-subunits (Chien et al., 1995 [1261]; Brice et al., 1997 [1262]; Gao et al., 1999 [1263]; Yamaguchi et al., 2000 [1264]), dramatically enhance Ca2+ current amplitude over that obtained with alpha1 alone (Singer et al., 1991 [1265]; Jones et al., 1998 [1266]), and produce hyperpolarizing shifts in the voltage-dependence of channel activation (Singer et al., 1991 [1265]; Perez-Reyes et al., 1992 [1267]; De Waard et al., 1994 [1268]).

Sequence analysis of the human genome permitted cloning of five Ca2+-channel b2 splice variants (b2a–b2e) that differed only in their proximal amino-termini. The functional consequences of such b2-subunit diversity were explored in recombinant L-type channels reconstituted in HEK 293 cells. b2a and b2e targeted autonomously to the plasma membrane, whereas b2b–b2d localized to the cytosol when expressed in HEK 293 cells. The pattern of modulation of L-type channel voltage-dependent inactivation gating correlated with the subcellular localization of the component b2 variant—membrane- bound b2a and b2e subunits conferred slow(er) channel inactivation kinetics and displayed a smaller fraction of channels recovering from inactivation with fast kinetics, compared to b2b–b2d channels. (Takahashi [235])


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Kinetics


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Model


References

Biel M. et al. The roles of the subunits in the function of the calcium channel.
Science, 1991 Sep 27 , 253 (1553-7).

Jones LP. et al. Mechanism of auxiliary subunit modulation of neuronal alpha1E calcium channels.
J. Gen. Physiol., 1998 Aug , 112 (125-43).

Castellano A. et al. Cloning and expression of a cardiac/brain beta subunit of the L-type calcium channel.
J. Biol. Chem., 1992 Jan 25 , 267 (1792-7).

De Waard M. et al. Subunit regulation of the neuronal alpha 1A Ca2+ channel expressed in Xenopus oocytes.
J. Physiol. (Lond.), 1995 Jun 15 , 485 ( Pt 3) (619-34).

Reimer D. et al. Beta subunit heterogeneity in neuronal L-type Ca2+ channels.
J. Biol. Chem., 1997 May 23 , 272 (13877-82).

Shin HS. et al. Role of the beta(2) subunit of voltage-dependent calcium channels in the retinal outer plexiform layer.
Invest. Ophthalmol. Vis. Sci., 2002 May , 43 (1595-603).

Reimer D. et al. beta subunit heterogeneity of L-type Ca(2+) channels in smooth muscle tissues.
FEBS Lett., 2000 Feb 4 , 467 (65-9).

Stefani E. et al. Unique regulatory properties of the type 2a Ca2+ channel beta subunit caused by palmitoylation.
Proc. Natl. Acad. Sci. U.S.A., 1998 Apr 14 , 95 (4690-5).

Rosenfeld MR. et al. Cloning and characterization of a Lambert-Eaton myasthenic syndrome antigen.
Ann. Neurol., 1993 Jan , 33 (113-20).


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