Description: calcium channel, voltage-dependent, T type, alpha 1I subunit
Gene: Cacna1i     Synonyms: cacna1i, cav3.3, ca3.3, Ca(v)3.3

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CACNA1I (also known as Cav3.3; KIAA1120) encodes Cav3.3, a T type LVA calcium channel found in neurons which is also know as a1I. Voltage-dependent calcium channels control the rapid entry of Ca(2+) into a variety of cell types and are therefore involved in both electrical and cellular signaling. T-type channels, such as CACNA1I, are activated by small membrane depolarizations and can generate burst firing and pacemaker activity



RGD ID Chromosome Position Species
68944 7 118582279-118681537 Rat
1621299 15 80117668-80228722 Mouse
68996 22 39966758-40085740 Human

Cacna1i : calcium channel, voltage-dependent, T type, alpha 1I subunit



Acc No Sequence Length Source
NM_020084 n/A n/A NCBI
NM_001044308 n/A n/A NCBI
NM_021096 n/A n/A NCBI
NM_001003406 n/A n/A NCBI



Accession Name Definition Evidence
GO:0000786 nucleosome A complex comprised of DNA wound around a multisubunit core and associated proteins, which forms the primary packing unit of DNA into higher order structures. IEA
GO:0005634 nucleus A membrane-bounded organelle of eukaryotic cells in which chromosomes are housed and replicated. In most cells, the nucleus contains all of the cell's chromosomes except the organellar chromosomes, and is the site of RNA synthesis and processing. In some species, or in specialized cell types, RNA metabolism or DNA replication may be absent. 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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CaV 3.2 current (IC50 , 0.8 μM) is significantly more sensitive to Zn2 + than are CaV 3.1 and CaV 3.3 currents (IC50 , 80 μM and ∼160 μM, respectively). This inhibition of CaV 3 currents is associated with a shift to more negative membrane potentials of both steady-state inactivation for CaV 3.1, CaV 3.2 and CaV 3.3 and steady-state activation for CaV 3.1 and CaV 3.3 currents. We also document changes in kinetics, especially a significant slowing of the inactivation kinetics for CaV 3.1 and CaV 3.3, but not for CaV 3.2 currents. (Traboulsie [103])

Phorbol-12-myristate-13-acetate (PMA)

PMA augmented the current amplitudes of the three T-type channel isoforms (Cav3.1, Cav3.2, Cav3.3), but the fold stimulations and time courses differed. (Park [112])







T-type Ca2+ currents are central determinants of neuronal excitability that are present in the somatodendritic compartment of many types of neurones (Carbone & Lux, 1984 [1238]; Talley et al. 1999 [1242]).





Genetic and pharmacological inhibition of T-type Ca2+ currents has demonstrated the importance of these currents in various sensory systems, ranging from pain perception and hyperalgesia (Kim et al. 2003 [1243]; Ikeda et al. 2003 [1244]), mechanoreceptor function (Shin et al. 2003 [1245]) and to olfaction (Kawai & Miyachi, 2001 [1246]).

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T-type channels are distinguished from high voltage-activated (HVA)1 Ca2+ channels by their unique biophysical properties, including low voltage activation, fast activation and inactivation kinetics that produce a criss-crossing pattern between successive traces of a current-voltage (IV) protocol, slow deactivation kinetics, and tiny single channel conductance (Perez-Reyes [528], Armstrong [1237], Carbone [1238], Randall [340]).

Expression studies found that Cav3.3 channels generate currents with much slower activation and inactivation kinetics than Cav3.1 and Cav3.2 channels, which show the more typical transient kinetics described for native T-type channels (Perez-Reyes [528], Perez-Reyes [1239], Cribbs [1240], Lee [1241]).

Cav3.1 and Cav3.2 channels are activating and inactivating much faster than Cav3.3 channels. (Park [113])

The kinetics of T-type channels resemble those of Na+ channels, albeit on a slower time scale, suggesting that they may also inactivate by a ball-and-chain mechanism. However, preliminary evidence indicates that T-type channels inactivate by similar processes as HVA Ca2+ channels.Multiple structural elements contribute to the slow kinetics of Cav3.3 channels. (Park [113])



Model Cav3.3 (ID=42)       Edit

CellType CHO
Age 0 Days
Reversal 30.0 mV
Ion Ca +
Ligand ion
Reference [103] Achraf Traboulsie et. al; J. Physiol. (Lond.) 2007 Jan 1
mpower 1.0
m Inf 1/(1+exp((v- -45.454426)/-5.073015))
m Tau 3.394938 +( 54.187616 / (1 + exp((v - -40.040397)/4.110392)))
hpower 1.0
h Inf 1 /(1+exp((v-(-74.031965))/8.416382))
h Tau 109.701136 + (0.003816 * exp(-v/4.781719))

MOD - xml - channelML



Traboulsie A et al. Subunit-specific modulation of T-type calcium channels by zinc.
J. Physiol. (Lond.), 2007 Jan 1 , 578 (159-71).


Park JY et al. Multiple structural elements contribute to the slow kinetics of the Cav3.3 T-type channel.
J. Biol. Chem., 2004 May 21 , 279 (21707-13).


Cataldi M et al. Zn(2+) slows down Ca(V)3.3 gating kinetics: implications for thalamocortical activity.
J. Neurophysiol., 2007 Oct , 98 (2274-84).


Perez-Reyes E Molecular physiology of low-voltage-activated t-type calcium channels.
Physiol. Rev., 2003 Jan , 83 (117-61).

Armstrong CM et al. Two distinct populations of calcium channels in a clonal line of pituitary cells.
Science, 1985 Jan 4 , 227 (65-7).


Randall AD et al. Contrasting biophysical and pharmacological properties of T-type and R-type calcium channels.
Neuropharmacology, 1997 Jul , 36 (879-93).

Perez-Reyes E et al. Molecular characterization of a neuronal low-voltage-activated T-type calcium channel.
Nature, 1998 Feb 26 , 391 (896-900).



Contributors: Rajnish Ranjan, Michael Schartner

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