Modulation of type A K+ current in Drosophila larval muscle by internal Ca2+; effects of the overexpression of frequenin.
Pflugers Arch
; 427(1-2): 71-9, 1994 May.
Article
en En
| MEDLINE
| ID: mdl-8058477
The calcium-dependent modulation of type A K+ current (IA) has been investigated using a two-electrode voltage clamp on larval muscle cells of Drosophila. It was found that the amplitude of IA increases when [Ca2+]o is changed from 0.2 mM to 2 mM. The increase in IA amplitude is not due to overlap with the Ca(2+)-dependent fast K+ current, ICF, since it is observed also in slo1 mutants, which are deficient for this current. This effect is not due to Ca(2+)-dependent shifts in the steady-state activation/inactivation kinetics. The phenomenon is probably due to elevations in internal calcium since it is abolished by Ca2+ channel blockers and promoted by caffeine (5 mM) if added in the absence of external calcium. This calcium effect was dose-dependent since it was not observed in the presence caffeine plus 2 mM calcium in the bath nor for values of [Ca2+]o above 4 mM. The Ca(2+)-dependent modulation of IA is absent in V7, a mutation that causes overexpression of frequenin, a recoverin-like Ca(2+)-binding protein which stimulates guanylyl cyclase [31]. One possible explanation for the loss of IA modulation in the V7 mutation is that the excess of frequenin alters intracellular cGMP-dependent metabolic pathways responsible for the internal calcium homeostasis.
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Colección:
01-internacional
Base de datos:
MEDLINE
Asunto principal:
Potasio
/
Proteínas de Unión al Calcio
/
Calcio
/
Proteínas de Drosophila
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Músculos
/
Proteínas del Tejido Nervioso
Límite:
Animals
Idioma:
En
Revista:
Pflugers Arch
Año:
1994
Tipo del documento:
Article
País de afiliación:
Francia
Pais de publicación:
Alemania