Differential contribution of Kv4-containing channels to A-type, voltage-gated potassium currents in somatic and visceral dorsal root ganglion neurons

Takakazu Yunoki, Koichi Takimoto, Kaori Kita, Yasuhito Funahashi, Ryosuke Takahashi, Hiroko Matsuyoshi, Seiji Naito, Naoki Yoshimura

Research output: Contribution to journalArticle

12 Citations (Scopus)

Abstract

Little is known about electrophysiological differences of A-type transient K+(KA) currents in nociceptive afferent neurons that innervate somatic and visceral tissues. Staining with isolectin B4 (IB4)-FITC classifies L6-S1 dorsal root ganglion (DRG) neurons into three populations with distinct staining intensities: negative to weak, moderate, and intense fluorescence signals. All IB4 intensely stained cells are negative for a fluorescent dye, Fast Blue (FB), injected into the bladder wall, whereas a fraction of somatic neurons labeled by FB, injected to the external urethral dermis, is intensely stained with IB4. In whole-cell, patch-clamp recordings, phrixotoxin 2 (PaTx2), a voltage-gated K+(Kv)4 channel blocker, exhibits voltage-independent inhibition of the KA current in IB4 intensely stained cells but not the one in bladderinnervating cells. The toxin also shows voltage-independent inhibition of heterologously expressed Kv4.1 current, whereas its inhibition of Kv4.2 and Kv4.3 currents is voltage dependent. The swapping of four amino acids at the carboxyl portion of the S3 region between Kv4.1 and Kv4.2 transfers this characteristic. RT-PCRs detected Kv4.1 and the long isoform of Kv4.3 mRNAs without significant Kv4.2 mRNA in L6-S1 DRGs. Kv4.1 and Kv4.3 mRNA levels were higher in laser-captured, IB4-stained neurons than in bladder afferent neurons. These results indicate that PaTx2 acts differently on channels in the Kv4 family and that Kv4.1 and possibly Kv4.3 subunits functionally participate in the formation of KA channels in a subpopulation of somatic C-fiber neurons but not in visceral C-fiber neurons innervating the bladder.

Original languageEnglish
Pages (from-to)2492-2504
Number of pages13
JournalJournal of Neurophysiology
Volume112
Issue number10
DOIs
Publication statusPublished - Nov 15 2014

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Spinal Ganglia
Lectins
Potassium
Neurons
Afferent Neurons
Unmyelinated Nerve Fibers
Urinary Bladder
RNA Isoforms
Negative Staining
Messenger RNA
Nociceptors
Fluorescein-5-isothiocyanate
Diagnosis-Related Groups
Dermis
Fluorescent Dyes
Lasers
Fluorescence
Staining and Labeling
Amino Acids
Polymerase Chain Reaction

All Science Journal Classification (ASJC) codes

  • Neuroscience(all)
  • Physiology

Cite this

Differential contribution of Kv4-containing channels to A-type, voltage-gated potassium currents in somatic and visceral dorsal root ganglion neurons. / Yunoki, Takakazu; Takimoto, Koichi; Kita, Kaori; Funahashi, Yasuhito; Takahashi, Ryosuke; Matsuyoshi, Hiroko; Naito, Seiji; Yoshimura, Naoki.

In: Journal of Neurophysiology, Vol. 112, No. 10, 15.11.2014, p. 2492-2504.

Research output: Contribution to journalArticle

Yunoki, T, Takimoto, K, Kita, K, Funahashi, Y, Takahashi, R, Matsuyoshi, H, Naito, S & Yoshimura, N 2014, 'Differential contribution of Kv4-containing channels to A-type, voltage-gated potassium currents in somatic and visceral dorsal root ganglion neurons', Journal of Neurophysiology, vol. 112, no. 10, pp. 2492-2504. https://doi.org/10.1152/jn.00054.2014
Yunoki, Takakazu ; Takimoto, Koichi ; Kita, Kaori ; Funahashi, Yasuhito ; Takahashi, Ryosuke ; Matsuyoshi, Hiroko ; Naito, Seiji ; Yoshimura, Naoki. / Differential contribution of Kv4-containing channels to A-type, voltage-gated potassium currents in somatic and visceral dorsal root ganglion neurons. In: Journal of Neurophysiology. 2014 ; Vol. 112, No. 10. pp. 2492-2504.
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abstract = "Little is known about electrophysiological differences of A-type transient K+(KA) currents in nociceptive afferent neurons that innervate somatic and visceral tissues. Staining with isolectin B4 (IB4)-FITC classifies L6-S1 dorsal root ganglion (DRG) neurons into three populations with distinct staining intensities: negative to weak, moderate, and intense fluorescence signals. All IB4 intensely stained cells are negative for a fluorescent dye, Fast Blue (FB), injected into the bladder wall, whereas a fraction of somatic neurons labeled by FB, injected to the external urethral dermis, is intensely stained with IB4. In whole-cell, patch-clamp recordings, phrixotoxin 2 (PaTx2), a voltage-gated K+(Kv)4 channel blocker, exhibits voltage-independent inhibition of the KA current in IB4 intensely stained cells but not the one in bladderinnervating cells. The toxin also shows voltage-independent inhibition of heterologously expressed Kv4.1 current, whereas its inhibition of Kv4.2 and Kv4.3 currents is voltage dependent. The swapping of four amino acids at the carboxyl portion of the S3 region between Kv4.1 and Kv4.2 transfers this characteristic. RT-PCRs detected Kv4.1 and the long isoform of Kv4.3 mRNAs without significant Kv4.2 mRNA in L6-S1 DRGs. Kv4.1 and Kv4.3 mRNA levels were higher in laser-captured, IB4-stained neurons than in bladder afferent neurons. These results indicate that PaTx2 acts differently on channels in the Kv4 family and that Kv4.1 and possibly Kv4.3 subunits functionally participate in the formation of KA channels in a subpopulation of somatic C-fiber neurons but not in visceral C-fiber neurons innervating the bladder.",
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AU - Funahashi, Yasuhito

AU - Takahashi, Ryosuke

AU - Matsuyoshi, Hiroko

AU - Naito, Seiji

AU - Yoshimura, Naoki

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