ATP-Induced Ca(2+) release in cochlear outer hair cells: localization of an inositol triphosphate-gated Ca(2+) store to the base of the sensory hair bundle.
J Neurosci
; 19(16): 6918-29, 1999 Aug 15.
Article
en En
| MEDLINE
| ID: mdl-10436049
ABSTRACT
We used a high-performance fluorescence imaging system to visualize rapid changes in intracellular free Ca(2+) concentration ([Ca(2+)](i)) evoked by focal applications of extracellular ATP to the hair bundle of outer hair cells (OHCs) the sensory-motor receptors of the cochlea. Simultaneous recordings of the whole-cell current and Calcium Green-1 fluorescence showed a two-component increase in [Ca(2+)](i). After an initial entry of Ca(2+) through the apical membrane, a second and larger, inositol triphosphate (InsP(3))-gated, [Ca(2+)](i) surge occurred at the base of the hair bundle. Electron microscopy of this intracellular Ca(2+) release site showed that it coincides with the localization of a unique system of endoplasmic reticulum (ER) membranes and mitochondria known as Hensen's body. Using confocal immunofluorescence microscopy, we showed that InsP(3) receptors share this location. Consistent with a Ca(2+)-mobilizing second messenger system linked to ATP-P2 receptors, we also determined that an isoform of G-proteins is present in the stereocilia. Voltage-driven cell shape changes and nonlinear capacitance were monitored before and after ATP application, showing that the ATP-evoked [Ca(2+)](i) rise did not interfere with the OHC electromotility mechanism. This second messenger signaling mechanism bypasses the Ca(2+)-clearance power of the stereocilia and transiently elevates [Ca(2+)](i) at the base of the hair bundle, where it can potentially modulate the action of unconventional myosin isozymes involved in maintaining the hair bundle integrity and potentially influence mechanotransduction.
Texto completo:
1
Banco de datos:
MEDLINE
Asunto principal:
Inositol 1,4,5-Trifosfato
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Activación del Canal Iónico
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Adenosina Trifosfato
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Calcio
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Células Ciliadas Auditivas Externas
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Mecanorreceptores
Límite:
Animals
Idioma:
En
Revista:
J Neurosci
Año:
1999
Tipo del documento:
Article
País de afiliación:
Italia