Ion interaction at the pore of Lc‐type Ca<sup>2+</sup> channel is sufficient to mediate depolarization‐induced exocytosis

Lerner, Immanuel; Trus, Michael; Cohen, Roy; Nussinovitch, Itzhak; Atlas, Daphné

doi:10.1111/j.1471-4159.2006.03709.x

Cited by 42 publications

(70 citation statements)

References 67 publications

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“…Indeed, our present findings showed a larger latency when Ba 2+ substituted for Ca 2+ , consistent with previous findings by Wang et al 35 However, a significant shorter delay was observed also in La 3+ , despite its impermeability and having no effect on either [La 3+ ] i or [Ca 2+ ] I . 11 Furthermore, when either intracellular Ca 2+ or Sr 2+ was elevated by ionophore the kinetics of the fusion pore was virtually identical. The insensitivity of the fusion pore to the type of the cytosolic cation stands in marked contrast to changes in fusion pore kinetics observed by the extracellular ion binding at the channel.…”

Section: Discussionmentioning

confidence: 86%

“…These results further confirm La 3+ exclusion from entry into chromaffin cell, during depolarization consistent with previous studies. 11,22 'Foot' parameters are affected by the charge carrier cations. In chromaffin cells, amperometric spikes recorded during membrane depolarization are often preceded by a pre-spike current event ('foot') corresponding to the open state of the fusion pore.…”

Section: Resultsmentioning

confidence: 99%

“…Further support for this linkage was demonstrated by conferring a prolonged 'releasing state' upon the channel when the non-permeable La 3+ was substituted for Ca 2+ , producing amperometric currents (spikes) and pre-spike currents ('foot'). 11 The differences observed in the 'foot' parameters with La 3+ compared to Ca 2+ , indicate an intimate affiliation between the interaction of the resident ion at the VGCC cavity and the fusion pore configuration. The VGCC was therefore, proposed a likely candidate as a structural constituent of the fusion pore.…”

Section: Introductionmentioning

confidence: 99%

“…The VGCC was therefore, proposed a likely candidate as a structural constituent of the fusion pore. 11 Based on modulation of 'foot' parameters, both synaptotagmin and syntaxin 1A have been suggested to be associated with the fusion pore configuration. [12][13][14][15] To address the 378 Channels 2007; Vol.…”

Section: Introductionmentioning

confidence: 99%

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Cations Residing at the Selectivity Filter of the Voltage-Gated Ca²⁺-Channel Modify Fusion-Pore Kinetics

Marom¹,

Sebag²,

Atlas³

2007

Channels

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Strontium (Sr 2+ ), Barium (Ba 2+ ) and Lanthanum (La 3+ ) can substitute for Ca 2+ in driving synaptic transmission during membrane depolarization. Ion recognition at the polyglutamate motif (EEEE), comprising the channel selectivity-filter, during voltage-driven transitions, controls the kinetics of the voltage-gated calcium channel (VGCC) and its interactions with the synaptic proteins. We tested the effect of different charge carriers on evoked-release, as a means of exploring the involvement of VGCC in the fusion pore configuration. Employing amperometry recordings in single bovine chromaffin cells we show that the size of the fusion pore, designated by the 'foot'-amplitude, was increased when Ba 2+ substituted for Ca 2+ and decreased, with La 3+ . The fusion pore stability, indicated by 'foot'-width, was decreased in La 3+ . Also, the mean open time of the fusion pore (t fp ) was significantly lower in Sr 2+ and La 3+ compared to Ba 2+ and Ca 2+ . These cations when occupying the selectivity filter reduced the spike frequency in the order of Ca 2+ > Sr 2+ > Ba 2+ > La 3+ , which is parallel to the reduction in total catecholamine release. The correlation between ion binding at the selectivity filter and fusion pore properties supports a model in which the Ca 2+ channel regulates secretion through a site at the selectivity filter, upstream to cation entry into the cell.

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Section: Discussionmentioning

confidence: 86%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Cations Residing at the Selectivity Filter of the Voltage-Gated Ca²⁺-Channel Modify Fusion-Pore Kinetics

Marom¹,

Sebag²,

Atlas³

2007

Channels

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“…Third, L-type channels can be up-and down-modulated by secreted products through the activation of -adrenergic autoreceptors (Hernandez-Guijo et al 1999;Cesetti et al 2003) and play a regulatory function in the depolarization-evoked exocytosis in chromaYn cells Nagy et al 2004). Fourth, recent data suggest an additional role for L-type channels, which can act as Ca 2+ sensor proteins in neuroendocrine secretion (Lerner et al 2006). The occupancy of L-type channel pore by an impermeable cation, such as La 3+ , lead to a conformational change that is transmitted to the exocytotic machinery upstream of intracellular Ca 2+ concentration.…”

Section: Discussionmentioning

confidence: 99%

Fast exocytosis mediated by T- and L-type channels in chromaffin cells: distinct voltage-dependence but similar Ca2+-dependence

et al. 2007

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Expression, spatial distribution and speciWc roles of diVerent Ca 2+ channels in stimulus-secretion coupling of chromaYn cells are intriguing issues still open to discussion. Most of the evidence supports a role of high-voltage activated (HVA) Ca 2+ channels (L-, N-, P/Q-and R-types) in the control of exocytosis: some suggesting a preferential coupling of speciWc Ca 2+ channel subunits with the secretory apparatus, others favoring the idea of a contribution to secretion proportional to the expression density and gating properties of Ca 2+ channels. In this work we review recent Wndings and bring new evidence in favor of the hypothesis that also the LVA (low-voltage-activated, T-type) Ca 2+ channels eVectively control fast exocytosis near resting potential in adrenal chromaYn cells of adult rats. Ttype channels recruited after long-term treatments with pCPT-cAMP (or chronic hypoxia) are shown to control exocytosis with the same eYcacy of L-type channels, which are the dominant Ca 2+ channel types expressed in rodent chromaYn cells. A rigorous comparison of T-and L-type channel properties shows that, although operating at diVerent potentials and with diVerent voltage-sensitivity, the two channels possess otherwise similar Ca 2+ -dependence of exocytosis, size and kinetics of depletion of the immediately releasable pool and mobilize vesicles of the same quantal size. Thus, T-and L-type channels are coupled with the same Ca 2+ -eYciency to the secretory apparatus and deplete the same number of vesicles ready for release.The major diVerence of the secretory signals controlled by the two channels appear to be the voltage range of operation, suggesting the idea that stressful conditions (hypoxia and persistent -adrenergic stimulation) can lower the threshold of cell excitability by recruiting new Ca 2+ channels and activate an additional source of catecholamine secretion.

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Reconstitution of Depolarization and Ca2+-Evoked Secretion in Xenopus Oocytes Monitored by Membrane Capacitance

Cohen

Schmitt

Atlas

2008

Methods in Molecular Biology

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The identity of the proteins that constitute the "minimal molecular machinery" required for depolarization-evoked neurotransmitter release at synapses is still not fully disclosed. Using capacitance monitoring combined with heterologous protein expression in Xenopus oocytes, we were able to reconstitute a fast (<.5 s) secretion that was triggered directly by membrane depolarization. The functional assembly of voltage-gated Ca2+ channel (Cav1.2 or Cav2.2) coexpressed with syntaxin 1A, synaptosome-associated protein of 25 kDa (SNAP-25), and synaptotagmin led to the reconstitution of depolarization-evoked secretion. Botulinum C1, botulinum A, and tetanus toxin were used to establish that this minimal set of proteins, named the excitosome complex, was necessary and sufficient for reconstituting depolarization-induced exocytosis. Similar to synaptic transmission, the capacitance changes were sensitive to neurotoxins, modulated by divalent cations (Ca2+, Ba2+, and Sr2+) or channels (Lc or N type; ionotropic glutamate GLUR3), and depended nonlinearly on extracellular divalent cation concentration. Expression of a recombinant intracellular domain of the calcium channel (Lc753-893) abolished evoked release in the reconstituted assay. Also, mutations at the synaptotagmin C2A polylysine motif, a channel interaction site, abolished depolarization-evoked capacitance transients, consistent with release studies in PC12 cells. Because of its improved speed, native trigger, and great experimental versatility, this reconstitution assay provides a novel, promising tool to study synaptic and nonsynaptic exocytosis and examine the role of other proteins implicated in these processes.

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Ion interaction at the pore of Lc‐type Ca²⁺ channel is sufficient to mediate depolarization‐induced exocytosis

Abstract: Abstract

Cited by 42 publications

References 67 publications

Cations Residing at the Selectivity Filter of the Voltage-Gated Ca²⁺-Channel Modify Fusion-Pore Kinetics

Cations Residing at the Selectivity Filter of the Voltage-Gated Ca²⁺-Channel Modify Fusion-Pore Kinetics

Fast exocytosis mediated by T- and L-type channels in chromaffin cells: distinct voltage-dependence but similar Ca2+-dependence

Reconstitution of Depolarization and Ca2+-Evoked Secretion in Xenopus Oocytes Monitored by Membrane Capacitance

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Ion interaction at the pore of Lc‐type Ca2+ channel is sufficient to mediate depolarization‐induced exocytosis

Abstract: Abstract

Cited by 42 publications

References 67 publications

Cations Residing at the Selectivity Filter of the Voltage-Gated Ca2+-Channel Modify Fusion-Pore Kinetics

Cations Residing at the Selectivity Filter of the Voltage-Gated Ca2+-Channel Modify Fusion-Pore Kinetics

Fast exocytosis mediated by T- and L-type channels in chromaffin cells: distinct voltage-dependence but similar Ca2+-dependence

Reconstitution of Depolarization and Ca2+-Evoked Secretion in Xenopus Oocytes Monitored by Membrane Capacitance

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Ion interaction at the pore of Lc‐type Ca²⁺ channel is sufficient to mediate depolarization‐induced exocytosis

Cations Residing at the Selectivity Filter of the Voltage-Gated Ca²⁺-Channel Modify Fusion-Pore Kinetics

Cations Residing at the Selectivity Filter of the Voltage-Gated Ca²⁺-Channel Modify Fusion-Pore Kinetics