scholarly journals Calcium-dependent inactivation of calcium channels in cochlear hair cells of the chicken

2007 ◽  
Vol 583 (3) ◽  
pp. 909-922 ◽  
Author(s):  
Seunghwan Lee ◽  
Olga Briklin ◽  
Hakim Hiel ◽  
Paul Fuchs
Keyword(s):  
Calcium Channels ◽  
Hair Cells ◽  
Cochlear Hair Cells ◽  
Calcium Dependent ◽  
Dependent Inactivation

Calcium- and Calmodulin-Dependent Inactivation of Calcium Channels in Inner Hair Cells of the Rat Cochlea

2008 ◽  
Vol 99 (5) ◽  
pp. 2183-2193 ◽  
Author(s):  
Lisa Grant ◽  
Paul Fuchs
Keyword(s):  
Calcium Channels ◽  
Hair Cells ◽  
Calcium Currents ◽  
Resting Potential ◽  
Resting Membrane Potential ◽  
Inner Hair Cells ◽  
Voltage Gated ◽  
Voltage Gated Calcium Channels ◽  
Dependent Inactivation ◽  
Calcium Buffering

Modulation of voltage-gated calcium channels was studied in inner hair cells (IHCs) in an ex vivo preparation of the apical turn of the rat organ of Corti. Whole cell voltage clamp in the presence of potassium channel blockers showed inward calcium currents with millisecond activation and deactivation kinetics. When temperature was raised from 22 to 37°C, the calcium currents of immature IHCs [<12 days postnatal (P12)] increased threefold in amplitude, and developed more pronounced inactivation. This was determined to be calcium-dependent inactivation (CDI) on the basis of its reliance on external calcium (substitution with barium), sensitivity to internal calcium-buffering, and voltage dependence (reflecting the calcium driving force). After the onset of hearing at P12, IHC calcium current amplitude and the extent of inactivation were greatly reduced. Although smaller than in prehearing IHCs, CDI remained significant in the mature IHC near the resting membrane potential. CDI in mature IHCs was enhanced by application of the endoplasmic calcium pump blocker, benzo-hydroquinone. Conversely, CDI in immature IHCs was reduced by calmodulin inhibitors. Thus voltage-gated calcium channels in mammalian IHCs are subject to a calmodulin-mediated process of CDI. The extent of CDI depends on the balance of calcium buffering mechanisms and may be regulated by calmodulin-specific processes. CDI provides a means for the rate of spontaneous transmitter release to be adjusted to variations in hair cell resting potential and steady state calcium influx.

Calcium-dependent inactivation of neuronal calcium channels

2002 ◽  
Vol 3 (11) ◽  
pp. 873-883 ◽  
Author(s):  
Thomas Budde ◽  
Sven Meuth ◽  
Hans-Christian Pape
Keyword(s):  
Calcium Channels ◽  
Calcium Dependent ◽  
Dependent Inactivation ◽  
Neuronal Calcium Channels

scholarly journals Calcium-dependent inactivation of the dihydropyridine-sensitive calcium channels in GH3 cells.

1988 ◽  
Vol 92 (4) ◽  
pp. 531-548 ◽  
Author(s):  
D Kalman ◽  
P H O'Lague ◽  
C Erxleben ◽  
D L Armstrong
Keyword(s):  
Calcium Channels ◽  
Calcium Current ◽  
State Level ◽  
Gh3 Cells ◽  
Free Calcium ◽  
Pipette Solution ◽  
Calcium Dependent ◽  
Dependent Inactivation ◽  
Exogenous Calcium ◽  
Free Membrane

The inactivation of calcium channels in mammalian pituitary tumor cells (GH3) was studied with patch electrodes under voltage clamp in cell-free membrane patches and in dialyzed cells. The calcium current elicited by depolarization from a holding potential of -40 mV passed predominantly through one class of channels previously shown to be modulated by dihydropyridines and cAMP-dependent phosphorylation (Armstrong and Eckert, 1987). When exogenous calcium buffers were omitted from the pipette solution, the macroscopic calcium current through those channels inactivated with a half time of approximately 10 ms to a steady state level 40-75% smaller than the peak. Inactivation was also measured as the reduction in peak current during a test pulse that closely followed a prepulse. Inactivation was largely reduced or eliminated by (a) buffering free calcium in the pipette solution to less than 10(-8) M; (b) replacing extracellular calcium with barium; (c) increasing the prepulse voltage from +10 to +60 mV; or (d) increasing the intracellular concentration of cAMP, either 'directly' with dibutyryl-cAMP or indirectly by activating adenylate cyclase with forskolin or vasoactive intestinal peptide. Thus, inactivation of the dihydropyridine-sensitive calcium channels in GH3 cells only occurs when membrane depolarization leads to calcium ion entry and intracellular accumulation.

scholarly journals Localized Calcineurin in Calcium- Dependent Inactivation of L-type Calcium Channels

2010 ◽  
Vol 98 (3) ◽  
pp. 692a
Author(s):  
William A. Sather ◽  
Seth F. Oliveria ◽  
Mark L. Dell'Acqua
Keyword(s):  
Calcium Channels ◽  
Calcium Dependent ◽  
Dependent Inactivation

scholarly journals Switching off calcium-dependent inactivation in L-type calcium channels by an autoinhibitory domain

2006 ◽  
Vol 103 (42) ◽  
pp. 15657-15662 ◽  
Author(s):  
C. Wahl-Schott ◽  
L. Baumann ◽  
H. Cuny ◽  
C. Eckert ◽  
K. Griessmeier ◽  
...  
Keyword(s):  
Calcium Channels ◽  
Autoinhibitory Domain ◽  
Calcium Dependent ◽  
Dependent Inactivation

scholarly journals Cy3-RgIA-5727 Labels and Inhibits α9-Containing nAChRs of Cochlear Hair Cells

2021 ◽  
Vol 15 ◽  
Author(s):  
Fernando Fisher ◽  
Yuanyuan Zhang ◽  
Philippe F. Y. Vincent ◽  
Joanna Gajewiak ◽  
Thomas J. Gordon ◽  
...  
Keyword(s):  
Hair Cell ◽  
Nicotinic Acetylcholine Receptors ◽  
Hair Cells ◽  
Acetylcholine Receptors ◽  
Tight Binding ◽  
Cholinergic Neurons ◽  
Outer Hair Cells ◽  
Cyanine Dye ◽  
Cochlear Hair Cells ◽  
Calcium Dependent

Efferent cholinergic neurons inhibit sensory hair cells of the vertebrate inner ear through the combined action of calcium-permeable α9α10-containing nicotinic acetylcholine receptors (nAChRs) and associated calcium-dependent potassium channels. The venom of cone snails is a rich repository of bioactive peptides, many with channel blocking activities. The conopeptide analog, RgIA-5474, is a specific and potent antagonist of α9α10-containing nAChRs. We added an alkyl functional group to the N-terminus of the RgIA-5474, to enable click chemistry addition of the fluorescent cyanine dye, Cy3. The resulting peptide, Cy3-RgIA-5727, potently blocked mouse α9α10 nAChRs expressed in Xenopus oocytes (IC50 23 pM), with 290-fold less activity on α7 nAChRs and 40,000-fold less activity on all other tested nAChR subtypes. The tight binding of Cy3-RgIA-5727 provided robust visualization of hair cell nAChRs juxtaposed to cholinergic efferent terminals in excised, unfixed cochlear tissue from mice. Presumptive postsynaptic sites on outer hair cells (OHCs) were labeled, but absent from inner hair cells (IHCs) and from OHCs in cochlear tissue from α9-null mice and in cochlear tissue pre-incubated with non-Cy3-conjugated RgIA-5474. In cochlear tissue from younger (postnatal day 10) mice, Cy3-RgIA-5727 also labeled IHCs, corresponding to transient efferent innervation at that age. Cy3 puncta in Kölliker’s organ remained in the α9-null tissue. Pre-exposure with non-Cy3-conjugated RgIA-5474 or bovine serum albumin reduced this non-specific labeling to variable extents in different preparations. Cy3-RgIA-5727 and RgIA-5474 blocked the native hair cell nAChRs, within the constraints of application to the excised cochlear tissue. Cy3-RgIA-5727 or RgIA-5474 block of efferent synaptic currents in young IHCs was not relieved after 50 min washing, so effectively irreversible.

scholarly journals Ser1928 is Required for Regulation of Calcium-Dependent Inactivation of CaV1.2 L-Type Calcium Channels by AKAP79-Anchored PKA and Calcineurin

2012 ◽  
Vol 102 (3) ◽  
pp. 128a
Author(s):  
Dong-ho Youn ◽  
Seth F. Oliveria ◽  
Mark L. Dell'Acqua ◽  
William A. Sather
Keyword(s):  
Calcium Channels ◽  
Calcium Dependent ◽  
Dependent Inactivation
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