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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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Electrophysiological characterization of sensory neurons of TRPC3/TRPC6 DKO mice. (a) Exemplar whole-cell voltage clamp trace from a large-diameter (narrow action potential) mouse DRG neuron in response to a 7.8 μm membrane deformation (holding potential −70 mV). All large-diameter neurons responded with a rapidly adapting current (black line, WT; red line, TRPC3/TRPC6 DKO). (b) The stimulus response curve of mechanically evoked peak currents in large-diameter WT (n = 12, black squares) and TRPC3/TRPC6 DKO (n = 12, red circles) mouse DRG neurons with action potential widths less than 1 ms voltage clamped at −70 mV. (c) The magnitude of currents evoked by a 7.8 μm stimulus in small-diameter DRG neurons with action potential width more than 1 ms (holding potential −70 mV) (black bars, WT; red bars, TRPC3/TRPC6 DKO). (d) Small-diameter DRG neurons had mechanically activated currents which could be classified based on their adaptation kinetics to a static mechanical stimulus: rapidly adapting (RA), intermediately adapting (IA), slowly adapting (SA). The proportion of small-diameter mouse DRG neurons expressing each current type from WT and TRPC3/TRPC6 DKO mice is shown. A significant reduction in the number of neurons displaying RA currents and an increase in number of non-responsive neurons was observed in TRPC3/TRPC6 DKO mice (χ2-test, p < 0.05) (red, no response; black, RA; dark grey, IA; light grey, SA).
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RSOB120068F4: Electrophysiological characterization of sensory neurons of TRPC3/TRPC6 DKO mice. (a) Exemplar whole-cell voltage clamp trace from a large-diameter (narrow action potential) mouse DRG neuron in response to a 7.8 μm membrane deformation (holding potential −70 mV). All large-diameter neurons responded with a rapidly adapting current (black line, WT; red line, TRPC3/TRPC6 DKO). (b) The stimulus response curve of mechanically evoked peak currents in large-diameter WT (n = 12, black squares) and TRPC3/TRPC6 DKO (n = 12, red circles) mouse DRG neurons with action potential widths less than 1 ms voltage clamped at −70 mV. (c) The magnitude of currents evoked by a 7.8 μm stimulus in small-diameter DRG neurons with action potential width more than 1 ms (holding potential −70 mV) (black bars, WT; red bars, TRPC3/TRPC6 DKO). (d) Small-diameter DRG neurons had mechanically activated currents which could be classified based on their adaptation kinetics to a static mechanical stimulus: rapidly adapting (RA), intermediately adapting (IA), slowly adapting (SA). The proportion of small-diameter mouse DRG neurons expressing each current type from WT and TRPC3/TRPC6 DKO mice is shown. A significant reduction in the number of neurons displaying RA currents and an increase in number of non-responsive neurons was observed in TRPC3/TRPC6 DKO mice (χ2-test, p < 0.05) (red, no response; black, RA; dark grey, IA; light grey, SA).

Mentions: We next examined the mechanosensitive properties of DRG neurons from TRPC3/TRPC6 DKO mice. Mechanical stimulation of large-diameter neurons (greater than 30 μm) with narrow action potentials (width of action potential is less than 1 ms) in WT and TRPC3/TRPC6 DKO mice evoked low-threshold RA mechanical currents in all cells (figure 4a). These inward currents in response to increasing mechanical stimuli were identical with respect to mechanical threshold of activation (WT = 3.6 ± 0.6 µm, TRPC3/TRPC6 DKO = 3.0 ± 0.4 µm, p > 0.05, n = 12), kinetics of current activation/inactivation and current magnitude in both WT and TRPC3/TRPC6 DKO mice (figure 4a,b).Figure 4.


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)

Electrophysiological characterization of sensory neurons of TRPC3/TRPC6 DKO mice. (a) Exemplar whole-cell voltage clamp trace from a large-diameter (narrow action potential) mouse DRG neuron in response to a 7.8 μm membrane deformation (holding potential −70 mV). All large-diameter neurons responded with a rapidly adapting current (black line, WT; red line, TRPC3/TRPC6 DKO). (b) The stimulus response curve of mechanically evoked peak currents in large-diameter WT (n = 12, black squares) and TRPC3/TRPC6 DKO (n = 12, red circles) mouse DRG neurons with action potential widths less than 1 ms voltage clamped at −70 mV. (c) The magnitude of currents evoked by a 7.8 μm stimulus in small-diameter DRG neurons with action potential width more than 1 ms (holding potential −70 mV) (black bars, WT; red bars, TRPC3/TRPC6 DKO). (d) Small-diameter DRG neurons had mechanically activated currents which could be classified based on their adaptation kinetics to a static mechanical stimulus: rapidly adapting (RA), intermediately adapting (IA), slowly adapting (SA). The proportion of small-diameter mouse DRG neurons expressing each current type from WT and TRPC3/TRPC6 DKO mice is shown. A significant reduction in the number of neurons displaying RA currents and an increase in number of non-responsive neurons was observed in TRPC3/TRPC6 DKO mice (χ2-test, p < 0.05) (red, no response; black, RA; dark grey, IA; light grey, SA).
© Copyright Policy - open-access
Related In: Results  -  Collection

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RSOB120068F4: Electrophysiological characterization of sensory neurons of TRPC3/TRPC6 DKO mice. (a) Exemplar whole-cell voltage clamp trace from a large-diameter (narrow action potential) mouse DRG neuron in response to a 7.8 μm membrane deformation (holding potential −70 mV). All large-diameter neurons responded with a rapidly adapting current (black line, WT; red line, TRPC3/TRPC6 DKO). (b) The stimulus response curve of mechanically evoked peak currents in large-diameter WT (n = 12, black squares) and TRPC3/TRPC6 DKO (n = 12, red circles) mouse DRG neurons with action potential widths less than 1 ms voltage clamped at −70 mV. (c) The magnitude of currents evoked by a 7.8 μm stimulus in small-diameter DRG neurons with action potential width more than 1 ms (holding potential −70 mV) (black bars, WT; red bars, TRPC3/TRPC6 DKO). (d) Small-diameter DRG neurons had mechanically activated currents which could be classified based on their adaptation kinetics to a static mechanical stimulus: rapidly adapting (RA), intermediately adapting (IA), slowly adapting (SA). The proportion of small-diameter mouse DRG neurons expressing each current type from WT and TRPC3/TRPC6 DKO mice is shown. A significant reduction in the number of neurons displaying RA currents and an increase in number of non-responsive neurons was observed in TRPC3/TRPC6 DKO mice (χ2-test, p < 0.05) (red, no response; black, RA; dark grey, IA; light grey, SA).
Mentions: We next examined the mechanosensitive properties of DRG neurons from TRPC3/TRPC6 DKO mice. Mechanical stimulation of large-diameter neurons (greater than 30 μm) with narrow action potentials (width of action potential is less than 1 ms) in WT and TRPC3/TRPC6 DKO mice evoked low-threshold RA mechanical currents in all cells (figure 4a). These inward currents in response to increasing mechanical stimuli were identical with respect to mechanical threshold of activation (WT = 3.6 ± 0.6 µm, TRPC3/TRPC6 DKO = 3.0 ± 0.4 µm, p > 0.05, n = 12), kinetics of current activation/inactivation and current magnitude in both WT and TRPC3/TRPC6 DKO mice (figure 4a,b).Figure 4.

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