Kurtoxin, a gating modifier of neuronal high- and low-threshold ca channels.
J Neurosci
; 22(6): 2023-34, 2002 Mar 15.
Article
em En
| MEDLINE
| ID: mdl-11896142
ABSTRACT
Studies of Ca channels expressed in oocytes have identified kurtoxin as a promising tool for functional and structural studies of low-threshold T-type Ca channels. This peptide, isolated from the venomous scorpion Parabuthus transvaalicus, inhibits low-threshold alpha1G and alpha1H Ca channels expressed in oocytes with relatively high potency and high selectivity. Here we report its effects on Ca channel currents, carried by 5 mm Ba(2+) ions, in rat central and peripheral neurons. In thalamic neurons 500 nm kurtoxin inhibited T-type Ca channel currents almost completely (90.2 +/- 2.5% at -85 mV; n = 6). Its selectivity, however, was less than expected because it also reduced the composite high-threshold Ca channel current recorded in these cells (46.1 +/- 6.9% at -30 mV; n = 6). In sympathetic and thalamic neurons, 250-500 nm kurtoxin partially inhibited N-type and L-type Ca channel currents, respectively. It similarly reduced the high-threshold Ca channel current that remains after a blockade of P-type, N-type, and L-type Ca channels in thalamic neurons. In contrast, kurtoxin facilitated steady-state P-type Ba currents in Purkinje neurons (by 34.9 +/- 3.7%; n = 10). In all cases the kurtoxin effect was voltage-dependent and entailed a modification of channel gating. Exposure to kurtoxin slowed current activation kinetics, although its effects on deactivation varied with the channel types. Kurtoxin thus appears as a unique gating-modifier that interacts with different Ca channel types with high affinity. This unusual property and the complex gating modifications it induces may facilitate future studies of gating in voltage-dependent ion channels.
Texto completo:
1
Coleções:
01-internacional
Base de dados:
MEDLINE
Assunto principal:
Venenos de Escorpião
/
Bloqueadores dos Canais de Cálcio
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Canais de Cálcio
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Ativação do Canal Iônico
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Neurônios
/
Neurotoxinas
Tipo de estudo:
Prognostic_studies
Limite:
Animals
Idioma:
En
Ano de publicação:
2002
Tipo de documento:
Article