Defective survival of naive CD8+ T lymphocytes in the absence of the beta3 regulatory subunit of voltage-gated calcium channels.

The survival of T lymphocytes requires sustained, Ca(2+) influx-dependent gene expression. The molecular mechanism that governs sustained Ca(2+) influx in naive T lymphocytes is unknown. Here we report an essential role for the beta3 regulatory subunit of voltage-gated calcium (Ca(v)) channels in the maintenance of naive CD8(+) T cells.

Syntaxin 1A is required for normal in utero development.

We have generated a syntaxin 1A knockout mouse by deletion of exons 3 through 6 and a concomitant insertion of a stop codon in exon 2. Heterozygous knockout animals were viable with no apparent phenotype. In contrast, the vast majority of homozygous animals died in utero, with embryos examined at day E15 showing a drastic reduction in body size and development when compared to WT and heterozygous littermates.

Modified Ca(v)1.4 expression in the Cacna1f(nob2) mouse due to alternative splicing of an ETn inserted in exon 2.

The Cacna1f(nob2) mouse is reported to be a naturally occurring null mutation for the Ca(v)1.4 calcium channel gene and the phenotype of this mouse is not identical to that of the targeted gene knockout model. We found two mRNA species in the Cacna1f(nob2) mouse: approximately 90% of the mRNA represents a transcript with an in-frame stop codon within exon 2 of CACNA1F, while approximately 10% of the mRNA represents a transcript in which alternative splicing within the ETn element has removed the stop codon.

The Ca(v)1.4 calcium channel: more than meets the eye.

Ca(v)1.4 channels are the latest calcium channels to be described in the literature. Originally identified in 1997 from the human genome project, several reports have since been published describing mutations in the CACNA1F gene encoding Ca(v)1.

Ca(V)3 T-type calcium channel isoforms differentially distribute to somatic and dendritic compartments in rat central neurons.

Spike output in many neuronal cell types is affected by low-voltage-activated T-type calcium currents arising from the Ca(v)3.1, Ca(v)3.2 and Ca(v)3.

Differential distribution of voltage-gated calcium channels in dopaminergic neurons of the rat retina.

We studied by immunocytochemistry and Western blots the identity and cellular distribution of voltage-gated calcium channels within dopaminergic neurons of the rat retina. The aim was to associate particular calcium channel subtypes with known activities of the neuron (e.g.

Specific T-type calcium channel isoforms are associated with distinct burst phenotypes in deep cerebellar nuclear neurons.

T-type calcium channels are thought to transform neuronal output to a burst mode by generating low voltage-activated (LVA) calcium currents and rebound burst discharge. In this study we assess the expression pattern of the three different T-type channel isoforms (Ca(v)3.1, Ca(v)3.

Functional analysis of Ca3.2 T-type calcium channel mutations linked to childhood absence epilepsy.

Purpose: Childhood absence epilepsy (CAE) is an idiopathic form of seizure disorder that is believed to have a genetic basis.

Methods: We examined the biophysical consequences of seven mutations in the Ca(v)3.2 T-type calcium channel gene linked to CAE.

ORL1 receptor-mediated internalization of N-type calcium channels.

The inhibition of N-type calcium channels by opioid receptor like receptor 1 (ORL1) is a key mechanism for controlling the transmission of nociceptive signals. We recently reported that signaling complexes consisting of ORL1 receptors and N-type channels mediate a tonic inhibition of calcium entry. Here we show that prolonged ( approximately 30 min) exposure of ORL1 receptors to their agonist nociceptin triggers an internalization of these signaling complexes into vesicular compartments.

Cav1.4 encodes a calcium channel with low open probability and unitary conductance.

When transiently expressed in tsA-201 cells, Ca(v)1.4 calcium channels support only modest whole-cell currents with unusually slow voltage-dependent inactivation kinetics. To examine the basis for this unique behavior we used cell-attached patch single-channel recordings using 100 mM external barium as the charge carrier to determine the single-channel properties of Ca(v)1.

Effects of Cav3.2 channel mutations linked to idiopathic generalized epilepsy.

Heron and colleagues (Ann Neurol 2004;55:595-596) identified three missense mutations in the Cav3.2 T-type calcium channel gene (CACNA1H) in patients with idiopathic generalized epilepsy. None of the variants were associated with a specific epilepsy phenotype and were not found in patients with juvenile absence epilepsy or childhood absence epilepsy.

Auxiliary subunit regulation of high-voltage activated calcium channels expressed in mammalian cells.

The effects of auxiliary calcium channel subunits on the expression and functional properties of high-voltage activated (HVA) calcium channels have been studied extensively in the Xenopus oocyte expression system, but are less completely characterized in a mammalian cellular environment. Here, we provide the first systematic analysis of the effects of calcium channel beta and alpha(2)-delta subunits on expression levels and biophysical properties of three different types (Ca(v)1.2, Ca(v)2.

The CACNA1F gene encodes an L-type calcium channel with unique biophysical properties and tissue distribution.

Glutamate release from rod photoreceptors is dependent on a sustained calcium influx through L-type calcium channels. Missense mutations in the CACNA1F gene in patients with incomplete X-linked congenital stationary night blindness implicate the Ca(v)1.4 calcium channel subtype.

Agonist-independent modulation of N-type calcium channels by ORL1 receptors.

We have investigated modulation of voltage-gated calcium channels by nociceptin (ORL1) receptors. In rat DRG neurons and in tsA-201 cells, nociceptin mediated a pronounced inhibition of N-type calcium channels, whereas other calcium channel subtypes were unaffected. In tsA-201 cells, expression of N-type channels with human ORL1 resulted in a voltage-dependent G-protein inhibition of the channel that occurred in the absence of nociceptin, the ORL1 receptor agonist.

Gating effects of mutations in the Cav3.2 T-type calcium channel associated with childhood absence epilepsy.

Childhood absence epilepsy (CAE) is a type of generalized epilepsy observed in 2-10% of epileptic children. In a recent study by Chen et al. (Chen, Y.

Mammalian voltage-gated calcium channels are potently blocked by the pyrethroid insecticide allethrin.

Pyrethroids are commonly used insecticides for both household and agricultural applications. It is generally reported that voltage-gated sodium channels are the primary target for toxicity of these chemicals to humans. The phylogenetic and structural relatedness between sodium channels and voltage-gated calcium (Ca) channels prompted us to examine the effects of the type 1 pyrethroid allethrin on the three major classes of mammalian calcium channels exogenously expressed in human embryonic kidney 293 cells.

Several structural domains contribute to the regulation of N-type calcium channel inactivation by the beta 3 subunit.

Calcium channel beta subunits are essential regulatory elements of the gating properties of high voltage-activated calcium channels. Co-expression with beta(3) subunits typically accelerates inactivation, whereas co-expression with beta(4) subunits results in a slowly inactivating phenotype. Here, we have examined the molecular basis of the differential effect of these two subunits on the inactivation characteristics of Ca(v)2.

Depolarization-induced Ca2+ release in ischemic spinal cord white matter involves L-type Ca2+ channel activation of ryanodine receptors.

The mechanisms of Ca(2+) release from intracellular stores in CNS white matter remain undefined. In rat dorsal columns, electrophysiological recordings showed that in vitro ischemia caused severe injury, which persisted after removal of extracellular Ca(2+); Ca(2+) imaging confirmed that an axoplasmic Ca(2+) rise persisted in Ca(2+)-free perfusate. However, depletion of Ca(2+) stores or reduction of ischemic depolarization (low Na(+), TTX) were protective, but only in Ca(2+)-free bath.

Differential inhibition of T-type calcium channels by neuroleptics.

T-type calcium channels play critical roles in cellular excitability and have been implicated in the pathogenesis of a variety of neurological disorders including epilepsy. Although there have been reports that certain neuroleptics that primarily target D2 dopamine receptors and are used to treat psychoses may also interact with T-type Ca channels, there has been no systematic examination of this phenomenon. In the present paper we provide a detailed analysis of the effects of several widely used neuroleptic agents on a family of exogenously expressed neuronal T-type Ca channels (alpha1G, alpha1H, and alpha1I subtypes).