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TRPC3 and TRPC6 are essential for normal mechanotransduction in subsets of sensory neurons and cochlear hair cells.

Quick K, Zhao J, Eijkelkamp N, Linley JE, Rugiero F, Cox JJ, Raouf R, Gringhuis M, Sexton JE, Abramowitz J, Taylor R, Forge A, Ashmore J, Kirkwood N, Kros CJ, Richardson GP, Freichel M, Flockerzi V, Birnbaumer L, Wood JN - Open Biol (2012)

Bottom Line: Deletion of both TRPC3 and TRPC6 caused deficits in light touch and silenced half of small-diameter sensory neurons expressing mechanically activated RA currents.Basal, but not apical, cochlear outer hair cells lost more than 75 per cent of their responses to mechanical stimulation.FM1-43-sensitive mechanically gated currents were induced when TRPC3 and TRPC6 were co-expressed in sensory neuron cell lines.

View Article: PubMed Central - PubMed

Affiliation: Molecular Nociception Group, Wolfson Institute for Biomedical Research, University College London, London WC1E 6BT, UK.

ABSTRACT
Transient receptor potential (TRP) channels TRPC3 and TRPC6 are expressed in both sensory neurons and cochlear hair cells. Deletion of TRPC3 or TRPC6 in mice caused no behavioural phenotype, although loss of TRPC3 caused a shift of rapidly adapting (RA) mechanosensitive currents to intermediate-adapting currents in dorsal root ganglion sensory neurons. Deletion of both TRPC3 and TRPC6 caused deficits in light touch and silenced half of small-diameter sensory neurons expressing mechanically activated RA currents. Double TRPC3/TRPC6 knock-out mice also showed hearing impairment, vestibular deficits and defective auditory brain stem responses to high-frequency sounds. Basal, but not apical, cochlear outer hair cells lost more than 75 per cent of their responses to mechanical stimulation. FM1-43-sensitive mechanically gated currents were induced when TRPC3 and TRPC6 were co-expressed in sensory neuron cell lines. TRPC3 and TRPC6 are thus required for the normal function of cells involved in touch and hearing, and are potential components of mechanotransducing complexes.

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Mechano-electrical transduction in WT and TRPC3/TRPC6 DKO OHCs. (a–c) MET currents in response to 45 Hz sinusoidal force stimuli from a fluid jet in WT and TRPC3/TRPC6 OHCs. The holding potential was −84 mV and the membrane potential was stepped in 20 mV increments from −164 mV to +96 mV. Driver voltage (DV, amplitude 40 V) waveform to the fluid jet is shown above the current traces. Positive DV moves the hair bundles in the excitatory direction towards the kinocilium. Recordings in a–c are averages from two stimulus presentations each. (a) WT OHC, mid-basal coil P2 + 1. Cm 5.6 pF; Rs 0.80 MΩ. (b) TRPC3/TRPC6 DKO OHC, basal end of apical coil P2 + 2. Cm 7.4 pF; Rs 0.63 MΩ. (c) TRPC3/TRPC6 DKO OHC, mid-basal coil P2 + 2. Cm 6.9 pF; Rs 0.74 MΩ. (d) Current-voltage curves averaged from 4 WT OHCs from the basal coil (black squares), 5 apical-coil TRPC3/TRPC6 DKO OHCs (blue circles) and 8 basal-coil TRPC3/TRPC6 DKO OHCs (red circles).
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RSOB120068F7: Mechano-electrical transduction in WT and TRPC3/TRPC6 DKO OHCs. (a–c) MET currents in response to 45 Hz sinusoidal force stimuli from a fluid jet in WT and TRPC3/TRPC6 OHCs. The holding potential was −84 mV and the membrane potential was stepped in 20 mV increments from −164 mV to +96 mV. Driver voltage (DV, amplitude 40 V) waveform to the fluid jet is shown above the current traces. Positive DV moves the hair bundles in the excitatory direction towards the kinocilium. Recordings in a–c are averages from two stimulus presentations each. (a) WT OHC, mid-basal coil P2 + 1. Cm 5.6 pF; Rs 0.80 MΩ. (b) TRPC3/TRPC6 DKO OHC, basal end of apical coil P2 + 2. Cm 7.4 pF; Rs 0.63 MΩ. (c) TRPC3/TRPC6 DKO OHC, mid-basal coil P2 + 2. Cm 6.9 pF; Rs 0.74 MΩ. (d) Current-voltage curves averaged from 4 WT OHCs from the basal coil (black squares), 5 apical-coil TRPC3/TRPC6 DKO OHCs (blue circles) and 8 basal-coil TRPC3/TRPC6 DKO OHCs (red circles).

Mentions: Mechano-electrical transduction (MET) currents were recorded from outer hair cells (OHCs) in organotypic cochlear cultures [31] using sinusoidal force stimuli. MET currents in TRPC3/TRPC6 DKO OHCs from the basal end of the apical coil were similar in all aspects to those of WT controls from the basal coil (figure 7). In both groups, large MET currents were elicited at all potentials during the positive phase of the stimulus waveform (figure 7a,b,d). For example, at −104 mV, the size of the MET currents in the WT controls was −357 ± 47 pA (n = 4) in the OHCs and −290 ± 46 pA (n = 5) in the TRPC3/TRPC6 DKO OHCs situated in the apical coil (p > 0.05). A fraction of the MET channels was open at rest, i.e. in the absence of any stimulus, and could be seen to close in the inhibitory phase of the stimulus waveform. This fraction increased upon depolarization to positive membrane potentials, indicative of a degree of external Ca-dependent adaptation of the MET currents at hyperpolarized potentials [32]. TRPC3/TRPC6 DKO OHCs from the basal coil (figure 7c,d) had 75–80% smaller MET currents at −104 mV of −73 ± 34 pA (n = 8), significantly different from both other groups (p < 0.01). The MET currents became progressively smaller further towards the basal end of the basal coil for the TRPC3/TRPC6 DKO mutant OHCs, in contrast to the WT controls, in which this trend was not observed. Some resting MET current was nevertheless present in these OHCs (figure 7c). MET currents in all three groups reversed near 0 mV, as expected for non-selective cation channels.Figure 7.


TRPC3 and TRPC6 are essential for normal mechanotransduction in subsets of sensory neurons and cochlear hair cells.

Quick K, Zhao J, Eijkelkamp N, Linley JE, Rugiero F, Cox JJ, Raouf R, Gringhuis M, Sexton JE, Abramowitz J, Taylor R, Forge A, Ashmore J, Kirkwood N, Kros CJ, Richardson GP, Freichel M, Flockerzi V, Birnbaumer L, Wood JN - Open Biol (2012)

Mechano-electrical transduction in WT and TRPC3/TRPC6 DKO OHCs. (a–c) MET currents in response to 45 Hz sinusoidal force stimuli from a fluid jet in WT and TRPC3/TRPC6 OHCs. The holding potential was −84 mV and the membrane potential was stepped in 20 mV increments from −164 mV to +96 mV. Driver voltage (DV, amplitude 40 V) waveform to the fluid jet is shown above the current traces. Positive DV moves the hair bundles in the excitatory direction towards the kinocilium. Recordings in a–c are averages from two stimulus presentations each. (a) WT OHC, mid-basal coil P2 + 1. Cm 5.6 pF; Rs 0.80 MΩ. (b) TRPC3/TRPC6 DKO OHC, basal end of apical coil P2 + 2. Cm 7.4 pF; Rs 0.63 MΩ. (c) TRPC3/TRPC6 DKO OHC, mid-basal coil P2 + 2. Cm 6.9 pF; Rs 0.74 MΩ. (d) Current-voltage curves averaged from 4 WT OHCs from the basal coil (black squares), 5 apical-coil TRPC3/TRPC6 DKO OHCs (blue circles) and 8 basal-coil TRPC3/TRPC6 DKO OHCs (red circles).
© Copyright Policy - open-access
Related In: Results  -  Collection

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Show All Figures
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RSOB120068F7: Mechano-electrical transduction in WT and TRPC3/TRPC6 DKO OHCs. (a–c) MET currents in response to 45 Hz sinusoidal force stimuli from a fluid jet in WT and TRPC3/TRPC6 OHCs. The holding potential was −84 mV and the membrane potential was stepped in 20 mV increments from −164 mV to +96 mV. Driver voltage (DV, amplitude 40 V) waveform to the fluid jet is shown above the current traces. Positive DV moves the hair bundles in the excitatory direction towards the kinocilium. Recordings in a–c are averages from two stimulus presentations each. (a) WT OHC, mid-basal coil P2 + 1. Cm 5.6 pF; Rs 0.80 MΩ. (b) TRPC3/TRPC6 DKO OHC, basal end of apical coil P2 + 2. Cm 7.4 pF; Rs 0.63 MΩ. (c) TRPC3/TRPC6 DKO OHC, mid-basal coil P2 + 2. Cm 6.9 pF; Rs 0.74 MΩ. (d) Current-voltage curves averaged from 4 WT OHCs from the basal coil (black squares), 5 apical-coil TRPC3/TRPC6 DKO OHCs (blue circles) and 8 basal-coil TRPC3/TRPC6 DKO OHCs (red circles).
Mentions: Mechano-electrical transduction (MET) currents were recorded from outer hair cells (OHCs) in organotypic cochlear cultures [31] using sinusoidal force stimuli. MET currents in TRPC3/TRPC6 DKO OHCs from the basal end of the apical coil were similar in all aspects to those of WT controls from the basal coil (figure 7). In both groups, large MET currents were elicited at all potentials during the positive phase of the stimulus waveform (figure 7a,b,d). For example, at −104 mV, the size of the MET currents in the WT controls was −357 ± 47 pA (n = 4) in the OHCs and −290 ± 46 pA (n = 5) in the TRPC3/TRPC6 DKO OHCs situated in the apical coil (p > 0.05). A fraction of the MET channels was open at rest, i.e. in the absence of any stimulus, and could be seen to close in the inhibitory phase of the stimulus waveform. This fraction increased upon depolarization to positive membrane potentials, indicative of a degree of external Ca-dependent adaptation of the MET currents at hyperpolarized potentials [32]. TRPC3/TRPC6 DKO OHCs from the basal coil (figure 7c,d) had 75–80% smaller MET currents at −104 mV of −73 ± 34 pA (n = 8), significantly different from both other groups (p < 0.01). The MET currents became progressively smaller further towards the basal end of the basal coil for the TRPC3/TRPC6 DKO mutant OHCs, in contrast to the WT controls, in which this trend was not observed. Some resting MET current was nevertheless present in these OHCs (figure 7c). MET currents in all three groups reversed near 0 mV, as expected for non-selective cation channels.Figure 7.

Bottom Line: Deletion of both TRPC3 and TRPC6 caused deficits in light touch and silenced half of small-diameter sensory neurons expressing mechanically activated RA currents.Basal, but not apical, cochlear outer hair cells lost more than 75 per cent of their responses to mechanical stimulation.FM1-43-sensitive mechanically gated currents were induced when TRPC3 and TRPC6 were co-expressed in sensory neuron cell lines.

View Article: PubMed Central - PubMed

Affiliation: Molecular Nociception Group, Wolfson Institute for Biomedical Research, University College London, London WC1E 6BT, UK.

ABSTRACT
Transient receptor potential (TRP) channels TRPC3 and TRPC6 are expressed in both sensory neurons and cochlear hair cells. Deletion of TRPC3 or TRPC6 in mice caused no behavioural phenotype, although loss of TRPC3 caused a shift of rapidly adapting (RA) mechanosensitive currents to intermediate-adapting currents in dorsal root ganglion sensory neurons. Deletion of both TRPC3 and TRPC6 caused deficits in light touch and silenced half of small-diameter sensory neurons expressing mechanically activated RA currents. Double TRPC3/TRPC6 knock-out mice also showed hearing impairment, vestibular deficits and defective auditory brain stem responses to high-frequency sounds. Basal, but not apical, cochlear outer hair cells lost more than 75 per cent of their responses to mechanical stimulation. FM1-43-sensitive mechanically gated currents were induced when TRPC3 and TRPC6 were co-expressed in sensory neuron cell lines. TRPC3 and TRPC6 are thus required for the normal function of cells involved in touch and hearing, and are potential components of mechanotransducing complexes.

Show MeSH
Related in: MedlinePlus