TY - JOUR
T1 - ATP-induced Ca2+ release in cochlear outer hair cells
T2 - Localization of an inositol triphosphate-gated Ca2+ store to the base of the sensory hair bundle
AU - Mammano, Fabio
AU - Frolenkov, Gregory I.
AU - Lagostena, Laura
AU - Belyantseva, Inna A.
AU - Kurc, Mauricio
AU - Dodane, Valerie
AU - Colavita, Alberto
AU - Kachar, Bechara
PY - 1999/8/15
Y1 - 1999/8/15
N2 - We used a high-performance fluorescence imaging system to visualize rapid changes in intracellular free Ca2+ concentration ([Ca2+](l)) 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 [Ca2+](i). After an initial entry of Ca2+ through the apical membrane, a second and larger, inositol triphosphate (InsP3)-gated, [Ca2+](i) surge occurred at the base of the hair bundle. Electron microscopy of this intracellular Ca2+ 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 InsP3 receptors share this location. Consistent with a Ca2+-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 [Ca2+](i) rise did not interfere with the OHC electromotility mechanism. This second messenger signaling mechanism bypasses the Ca2+- clearance power of the stereocilia and transiently elevates [Ca2+](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.
AB - We used a high-performance fluorescence imaging system to visualize rapid changes in intracellular free Ca2+ concentration ([Ca2+](l)) 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 [Ca2+](i). After an initial entry of Ca2+ through the apical membrane, a second and larger, inositol triphosphate (InsP3)-gated, [Ca2+](i) surge occurred at the base of the hair bundle. Electron microscopy of this intracellular Ca2+ 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 InsP3 receptors share this location. Consistent with a Ca2+-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 [Ca2+](i) rise did not interfere with the OHC electromotility mechanism. This second messenger signaling mechanism bypasses the Ca2+- clearance power of the stereocilia and transiently elevates [Ca2+](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.
KW - Calcium imaging
KW - Cochlea
KW - Electromotility
KW - Endoplasmic reticulum
KW - G-proteins
KW - Hensen's body
KW - InsP
KW - Mitochondria
KW - Organ of Corti
KW - Patch-clamp
KW - Purinergic receptors
KW - Sensory transduction
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UR - http://www.scopus.com/inward/citedby.url?scp=0033566874&partnerID=8YFLogxK
U2 - 10.1523/jneurosci.19-16-06918.1999
DO - 10.1523/jneurosci.19-16-06918.1999
M3 - Article
C2 - 10436049
AN - SCOPUS:0033566874
SN - 0270-6474
VL - 19
SP - 6918
EP - 6929
JO - Journal of Neuroscience
JF - Journal of Neuroscience
IS - 16
ER -