Expression of low-voltage activated Ca2+ channels from rat brain neurones in Xenopus oocytes

Dzhura, Igor; Kostyuk, P. G.; Lyubanova, O. P.; Naidenov, V. G.; Shuba, Yaroslav

doi:10.1097/00001756-199410000-00030

Cited by 10 publications

(3 citation statements)

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“…It has been argued that the time course of inactivation seen with transiently expressed ␣ 1E channels is slow compared with that of native T-type channels. When RNA fractions presumably encoding for T-type channels from thalamic neurons are injected into Xenopus oocytes, however, the resulting waveform is also slowed compared with the channels in their native environment (Dzhura et al, 1994), suggesting that gating kinetics may in some instances be a poor diagnostic for identifying native counterparts to cloned Ca channels. The rat brain ␣ 1E channel shows two pronounced differences compared with the residual R-type current .…”

Section: Discussion ␣ 1e Permeation Properties Resemble Those Of Lowtmentioning

confidence: 99%

The α_1ECalcium Channel Exhibits Permeation Properties Similar to Low-Voltage-Activated Calcium Channels

et al. 1996

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The physiological and pharmacological properties of the ␣ 1E calcium (Ca) channel subtype do not exactly match any of the established categories described for native neuronal Ca currents. Many of the key diagnostic features used to assign cloned Ca channels to their native counterparts, however, are dependent on a number of factors, including cellular environment, ␤ subunit coexpression, and modulation by second messengers and G-proteins. Here, by examining the intrinsic pore characteristics of a family of transiently expressed neuronal Ca channels, we demonstrate that the permeation properties of ␣ 1E closely resemble those described for a subset of lowthreshold Ca channels. The ␣ 1A (P-/Q-type), ␣ 1B (N-type), and ␣ 1C (L-type) high-threshold Ca channels all exhibit larger whole-cell currents with barium (Ba) as the charge carrier as compared with Ca or strontium (Sr). In contrast, macroscopic ␣ 1E currents are largest in Sr, followed by Ca and then Ba. The unique permeation properties of ␣ 1E are maintained at the single-channel level, are independent of the nature of the expression system, and are not affected by coexpression of ␣ 2 and ␤ subunits. Overall, the permeation characteristics of ␣ 1E are distinct from those described for R-type currents and share some similarities with native low-threshold Ca channels.

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Section: Discussion ␣ 1e Permeation Properties Resemble Those Of Lowtmentioning

confidence: 99%

The α_1ECalcium Channel Exhibits Permeation Properties Similar to Low-Voltage-Activated Calcium Channels

et al. 1996

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“…Although it has been reported that facilitation is a property of cloned Ca v α1 subunits (Kleppisch et al, 1994), another report has suggested that it does not occur in the absence of coexpressed Ca v β subunits (Bourinet et al, 1994), despite the fact that β subunits mimic to some extent the process of facilitation (Dolphin, 1996;Herlitze et al, 2001). Facilitation of L-type channels, as originally observed in native tissues is likely to involve multiple processes, including Ca 2+ entry and phosphorylation (Dzhura et al, 1994;Sculptoreanu et al, 1993a).…”

Section: Effect Of β Subunits On Facilitation Of Calcium Channelsmentioning

confidence: 94%

Subunits of Voltage-Gated Calcium Channels

Dolphin

2003

J Bioenerg Biomembr

384

376

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Calcium channel beta subunits have marked effects on the trafficking and on several of the biophysical properties of all high voltage activated calcium channels. In this article I shall review information on the different genes, on the structure of the beta subunits, and on their differential expression and post-translational modification. Their role in trafficking and assembly of the calcium channel heteromultimer will be described, and I will then review their effects on voltage-dependent and kinetic properties, stressing the differences between palmitoylated beta2a and the other beta subunits. Evidence for effects on calcium channel pharmacology will also be examined. I shall discuss the hypothesis that beta subunits can bind reversibly to calcium channels, and examine their role in the G protein modulation of calcium channels. Finally, I shall describe the consequences of knock-out of different beta subunit genes, and describe evidence for the involvement of beta subunits in disease.

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“…In our experiments, it was possible to express LVA Ca channels in an artificial system --Xenopus oocytes by injecting into them total poly-A-mRNA from the brain structures normally expressing these channels. Typical LVA currents appeared in oocytes after such injections indicating the presence of corresponding individual mRNAs [11 ]. These results are promising for future investigations of the structure of LVA Ca channels.…”

Section: -29"i71~712904105-019151800mentioning

confidence: 61%

Basic mechanisms responsible for calcium signalling in neuronal cells

Kostyuk

1997

Neurophysiology

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Calcium ions are the most universal intracellular me~engers transmitting signals from the plasmalemma of excitable cells to the intracellular structures and triggering or modulating in this way moot cellular functions. The molecular mechanisms responsible for injection of Ca ions into the cytoplasm during cellular activity and for producing transient elevations of their cytoplasmic free level (calcium "transientS," or "signals") have been a subject of extensive investigation in numerous laboratories during last three decades. In a short review it is impossible to summarize the results obtained; two extensive publications on this subject have appeared already from our laboratory [1,2]. Therefore, here the main attention will be paid to the most recent data from our laboratory concerning different aspects of the mechanisms forming calcium signals in neuronal cells. PLASMALEMMAL CALCIUM CHANNELSThe main source of Ca 2 § influx into a cell are the voltage-operated Ca channels (VOCC), which are subdivided into two main categories: high-and low-voltageactivated channels (HVA and LVA, respectively). The structural and functional characteristics of HVA Ca channels have been studied most extensively; they were separated into several distinct subtypes (L, N, P, Q, and R), and their principal at-subunits were isolated, sequenced, and cloned. Now the main interest shifts towards the search for effective and specific antagonists to these channels, their precise location and functional role in the neuronal structures, and physiological mechanisms of their modulation. In this respect, besides direct investigations on mammalian neurons both in I Bogomolets Institute of Physiology, National Academy of Sciences of Ukraine, Kiev, Ukraine. 191vitro and in situ (in brain slices), substantial progress can be achieved in hybrid ceil lines of a neuronal origin (which can express practically the whole spectrum of Ca channels) as well as on large identified invertebrate neurons. Thus, recent experiments on neuroblastoma/glioma cells (NG 108-15), which overexpress phosphatase-2B (calcineurin), have demonstrated the efficiency of permanent up-and down-regulation of Nand L-type Ca channels by a phosphorylating--dephosphorylatmg enzymatic mechanism; close co-localization of calcineurin and HVA Ca channels has been suggested [3]. Such co-localization has been in fact directly demonstrated on dorsal root ganglion (DRG) neurons [4]. On the other hand, investigations on identified snail neurons allowed us to demonstrate a negative feedback effect of elevation of [Ca2+l~ on this modulatory system: smaller elevations depressed channel phosphorylation by Ca2 § activation of phosphodiestherase (K a .-~ 0.04 /~M), while higher elevations directly dephosphorylated them through

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Expression of low-voltage activated Ca2+ channels from rat brain neurones in Xenopus oocytes

Cited by 10 publications

References 0 publications

The α_1ECalcium Channel Exhibits Permeation Properties Similar to Low-Voltage-Activated Calcium Channels

The α_1ECalcium Channel Exhibits Permeation Properties Similar to Low-Voltage-Activated Calcium Channels

Subunits of Voltage-Gated Calcium Channels

Basic mechanisms responsible for calcium signalling in neuronal cells

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Expression of low-voltage activated Ca2+ channels from rat brain neurones in Xenopus oocytes

Cited by 10 publications

References 0 publications

The α1ECalcium Channel Exhibits Permeation Properties Similar to Low-Voltage-Activated Calcium Channels

The α1ECalcium Channel Exhibits Permeation Properties Similar to Low-Voltage-Activated Calcium Channels

Subunits of Voltage-Gated Calcium Channels

Basic mechanisms responsible for calcium signalling in neuronal cells

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The α_1ECalcium Channel Exhibits Permeation Properties Similar to Low-Voltage-Activated Calcium Channels

The α_1ECalcium Channel Exhibits Permeation Properties Similar to Low-Voltage-Activated Calcium Channels