Expression Of Voltage-dependent Ca2 Research Articles

Distinct Gene Expression Patterns of Calcium Channels and Related Signaling Pathways Discovered in Lymphomas.

Cell surface calcium (Ca2+) channels permit Ca2+ ion influx, with Ca2+ taking part in cellular functions such as proliferation, survival, and activation. The expression of voltage-dependent Ca2+ (CaV) channels may modulate the growth of hematologic cancers. Profile analysis of Ca2+ channels, with a focus on the Ca2+ release-activated Ca2+ (CRAC) and L-type CaV channels, was performed on RNA sequencing data from lymphoma cell lines and samples derived from patients with diffuse large B cell lymphoma (DLBCL). CaV1.2 expression was found to be elevated in classical Hodgkin lymphoma (CHL) cell lines when compared to other B cell lymphoma cell lines. In contrast, CHL exhibited reduced expression of ORAI2 and STIM2. In our differential expression analysis comparing activated B cell-like DLBCL (ABC-DLBCL) and germinal centre B cell-like DLBCL (GCB-DLBCL) patient samples, ABC-DLBCL revealed stronger expression of CaV1.3, whereas CaV1.1, CaV1.2, and CaV1.4 showed greater expression levels in GCB-DLBCL. Interestingly, no differences in ORAI/STIM expression were noted in the patient samples. As Ca2+ is known to bind to calmodulin, leading to calcineurin activation and the passage of nuclear factor of activated T cells (NFAT) to the cell nucleus, pathways for calcineurin, calmodulin, NFAT, and Ca2+ signaling were also analyzed by gene set enrichment analysis. The NFAT and Ca2+ signaling pathways were found to be upregulated in the CHL cell lines relative to other B cell lymphoma cell lines. Furthermore, the calmodulin and Ca2+ signaling pathways were shown to be downregulated in the ABC-DLBCL patient samples. The findings of this study suggest that L-type CaV channels and Ca2+-related pathways could serve as differentiating components for biologic therapies in targeted lymphoma treatments.

Calcium Channel Subunit α2δ4 Is Regulated by Early Growth Response 1 and Facilitates Epileptogenesis.

Transient brain insults, including status epilepticus (SE), can trigger a period of epileptogenesis during which functional and structural reorganization of neuronal networks occurs resulting in the onset of focal epileptic seizures. In recent years, mechanisms that regulate the dynamic transcription of individual genes during epileptogenesis and thereby contribute to the development of a hyperexcitable neuronal network have been elucidated. Our own results have shown early growth response 1 (Egr1) to transiently increase expression of the T-type voltage-dependent Ca2+ channel (VDCC) subunit CaV3.2, a key proepileptogenic protein. However, epileptogenesis involves complex and dynamic transcriptomic alterations; and so far, our understanding of the transcriptional control mechanism of gene regulatory networks that act in the same processes is limited. Here, we have analyzed whether Egr1 acts as a key transcriptional regulator for genes contributing to the development of hyperexcitability during epileptogenesis. We found Egr1 to drive the expression of the VDCC subunit α2δ4, which was augmented early and persistently after pilocarpine-induced SE. Furthermore, we show that increasing levels of α2δ4 in the CA1 region of the hippocampus elevate seizure susceptibility of mice by slightly decreasing local network activity. Interestingly, we also detected increased expression levels of Egr1 and α2δ4 in human hippocampal biopsies obtained from epilepsy surgery. In conclusion, Egr1 controls the abundance of the VDCC subunits CaV3.2 and α2δ4, which act synergistically in epileptogenesis, and thereby contributes to a seizure-induced "transcriptional Ca2+ channelopathy."SIGNIFICANCE STATEMENT The onset of focal recurrent seizures often occurs after an epileptogenic process induced by transient insults to the brain. Recently, transcriptional control mechanisms for individual genes involved in converting neurons hyperexcitable have been identified, including early growth response 1 (Egr1), which activates transcription of the T-type Ca2+ channel subunit CaV3.2. Here, we find Egr1 to regulate also the expression of the voltage-dependent Ca2+ channel subunit α2δ4, which was augmented after pilocarpine- and kainic acid-induced status epilepticus. In addition, we observed that α2δ4 affected spontaneous network activity and the susceptibility for seizure induction. Furthermore, we detected corresponding dynamics in human biopsies from epilepsy patients. In conclusion, Egr1 orchestrates a seizure-induced "transcriptional Ca2+ channelopathy" consisting of CaV3.2 and α2δ4, which act synergistically in epileptogenesis.

Involvement of the calcium channel β3 subunit in olfactory signal transduction

Despite the expression of voltage-dependent Ca2+ channels in nasal turbinate epithelium, their role in odorant chemosensation has remained obscure. Therefore, we investigated olfactory neurotransduction in β3-deficient mice. RT-PCR and Western blots confirmed the expression of various types of Ca2+ channels in the nasal turbinate. Electrophysiological evaluations revealed that β3-null mice had a 60% reduction in the high-voltage-dependent Ca2+ currents in olfactory receptor neurons due to reduced N- and L-type channel currents. The β3-null mice showed increased olfactory neuronal activity to triethylamine, and this effect was mimicked by the perfusion of the specific N-type Ca2+ channel inhibitor ω-conotoxin GVIA in the electro-olfactogram. Diluted male urine odors induced higher Fos immunoreactivity in the main olfactory bulbs of β3-deficient mice, indicating enhanced signal transduction of odor information in these mice. Our data indicate the involvement of voltage-dependent Ca2+ channels and importance of the β3 subunit in olfactory signal transduction.

Parathyroid cells express dihydropyridine-sensitive cation currents and L-type calcium channel subunits.

Parathyroid cells express Ca2+ -conducting currents that are activated by raising the extracellular Ca2+ concentration ([Ca2+]o). We investigated the sensitivity of these currents to dihydropyridines, the expression of voltage-dependent Ca(2+) channel (VDCC) subunits, and the effects of dihydropyridines on the intracellular free [Ca2+] ([Ca2+]i) and secretion in these cells. Dihydropyridine channel antagonists dose dependently suppressed Ca2+ -conducting currents, and agonists partially reversed the inhibitory effects of the antagonists in these cells. From a bovine parathyroid cDNA library, we isolated cDNA fragments encoding parts of an alpha(1S)- and a beta(3)-subunit of L-type Ca(2+) channels. The alpha(1S)-subunit cDNA from the parathyroid represents an alternatively spliced variant lacking exon 29 of the corresponding gene. Northern blot analysis and immunocytochemistry confirmed the presence of transcripts and proteins for alpha(1)- and beta(3)-subunits in the parathyroid gland. The addition of dihydropyridines had no significant effects on high [Ca2+]o-induced changes in [Ca2+]i and parathyroid hormone (PTH) release. Thus our studies indicate that parathyroid cells express alternatively spliced L-type Ca2+ channel subunits, which do not modulate acute intracellular Ca2+ responses or changes in PTH release.

Altered gene expression of voltage-dependent Ca2+ channels in mouse spinal cord and dorsal root ganglion after chronic inflammation

Altered gene expression of voltage-dependent Ca2+ channels in mouse spinal cord and dorsal root ganglion after chronic inflammation

Expression and Subunit Interaction of Voltage-Dependent Ca2+Channels in PC12 Cells

Nerve growth factor (NGF)-induced differentiation in PC12 cells is accompanied by changes in the expression of voltage-dependent Ca2+ channels. Ca2+ channels are multimeric complexes composed of at least three subunits (alpha1, beta, and alpha2delta) and are involved in neuronal migration, gene expression, and neurotransmitter release. Although attempts have been undertaken to elucidate NGF regulation of Ca2+ channel expression, the changes in subunit composition of these channels during differentiation still remain uncertain. In the present study, patch-clamp recordings show that in addition to the previously documented L-type and N-type Ca2+ currents, undifferentiated PC12 cells also express an omega-agatoxin-IVA-sensitive (P/Q-type) component. In addition, the corresponding mRNA encoding the pore-forming alpha1 subunits for these channels (C, B, and A, respectively) was detected. Likewise, mRNA for three distinct auxiliary beta subunits (1, 2, 3) were also found, beta3 protein being dominantly expressed. Immunoprecipitation experiments show that the N-type Ca2+ channel is associated with either a beta2 or beta3 subunit and that NGF increases the channel expression without affecting its beta subunit association. These results (1) indicate that the diversity of Ca2+ currents in PC12 cells arise from the expression of three distinct alpha1 and three different beta subunit genes; (2) support a model for heterogenous beta subunit association of the N-type Ca2+ channel in a single cell type; and (3) suggest that the regulation of the N-type Ca2+ channel during NGF-mediated differentiation involves an increase in the number of functional channels with no apparent changes in subunit composition.