title: Coexpression of auxiliary Kvβ2 subunits with Kv1.1 channels is required for developmental acquisition of unique firing properties of zebrafish Mauthner cells.
abstract: Each neuron possesses a unique firing property, which is largely attributed to heterogeneity in the composition of voltage-gated ion channel complexes. Zebrafish Mauthner (M) cells, which are bilaterally paired giant reticulospinal neurons (RSNs) in the hindbrain and induce rapid escape behavior, generate only a single spike at the onset of depolarization. This single spiking is in contrast with the repetitive firing of the M cell's morphologically homologous RSNs, MiD2cm and MiD3cm, which are also involved in escapes. However, how the unique firing property of M cells is established and the underlying molecular mechanisms remain unclear. In the present study, we first demonstrated that the single-spiking property of M cells was acquired at 4 days postfertilization (dpf), accompanied by an increase in dendrotoxin I (DTX)-sensitive low-threshold K(+) currents, prior to which the M cell repetitively fires as its homologs. Second, in situ hybridization showed that among DTX-sensitive Kv1 channel α-subunits, zKv1.1a was unexpectedly expressed even in the homologs and the bursting M cells at 2 dpf. In contrast, zKvβ2b, an auxiliary β-subunit of Kv1 channels, was expressed only in the single-spiking M cells. Third, zKv1.1a expressed in Xenopus oocytes functioned as a low-threshold K(+) channel, and its currents were enhanced by coexpression of zKvβ2b subunits. Finally, knockdown of zKvβ2b expression in zebrafish larvae resulted in repetitive firing of M cells at 4 dpf. Taken together, these results suggest that associative expression of Kvβ2 subunits with Kv1.1 channels is crucial for developmental acquisition of the unique firing properties of the M cells among homologous neurons.
authors: Division of Biological Science, Graduate School of Science, Nagoya University, Nagoya, Japan; and.
authors: Takaki
authors: T
authors: Watanabe
authors: Takashi
authors: T
authors: Shimazaki
authors: Aoba
authors: A
authors: Mishiro
authors: Takako
authors: T
authors: Suzuki
authors: Hiromi
authors: H
authors: Hirata
authors: Masashi
authors: M
authors: Tanimoto
authors: Yoichi
authors: Y
authors: Oda
mesh_terms: D000200:Action Potentials; D000818:Animals; D004546:Elapid Venoms / Q000494:pharmacology; D051662:Kv1.1 Potassium Channel / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D009474:Neurons / Q000378:metabolism / Q000502:physiology*; D026902:Potassium Channel Blockers / Q000494:pharmacology; D055503:Protein Multimerization; D021122:Protein Subunits / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism; D012249:Rhombencephalon / Q000166:cytology / Q000254:growth & development / Q000502:physiology; D015027:Zebrafish; D029961:Zebrafish Proteins / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*
chemical_list: D004546:Elapid Venoms; D026902:Potassium Channel Blockers; D021122:Protein Subunits; D029961:Zebrafish Proteins; D051662:Kv1.1 Potassium Channel; C020273:dendrotoxin
keywords: Kv1.1; Kvβ2; Mauthner cell; potassium channel; zebrafish