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Xenopus embryonic spinal neurons express potassium channel Kvbeta subunits.

ABSTRACT: Developmental regulation of voltage-dependent delayed rectifier potassium current (I(Kv)) of Xenopus primary spinal neurons regulates the waveform of the action potential. I(Kv) undergoes a tripling in density and acceleration of it activation kinetics during the initial day of its appearance. Another voltage-dependent potassium current, the A current, is acquired during the subsequent day and contributes to further shortening of the impulse duration. To decipher the molecular mechanisms underlying this functional differentiation, we are identifying potassium channel genes expressed in the embryonic amphibian nervous system. Potassium channels consist of pore-forming (alpha) as well as auxiliary (beta) subunits. Here, we report the primary sequence, developmental localization, and functional properties of two Xenopus Kvbeta genes. On the basis of primary sequence, one of these (xKvbeta2) is highly conserved with Kvbeta2 genes identified in other species, whereas the other (xKvbeta4) appears to identify a new member of the Kvbeta family. Both are expressed in developing spinal neurons during the period of impulse maturation but in different neuronal populations. In a heterologous system, coexpression of xKvbeta subunits modulates properties of potassium current that are developmentally regulated in the endogenous I(Kv). Consistent with xKvbeta4's unique primary sequence, the repertoire of functional effects it has on coexpressed Kv1alpha subunits is novel. Taken together, the results implicate auxiliary subunits in regulation of potassium current function and action potential waveforms in subpopulations of embryonic primary spinal neurons.

SUBMITTER: Lazaroff MA

PROVIDER: S-EPMC6784936 | biostudies-literature | 1999 Dec

REPOSITORIES: biostudies-literature

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Xenopus embryonic spinal neurons express potassium channel Kvbeta subunits.

Lazaroff M A MA Hofmann A D AD Ribera A B AB

The Journal of neuroscience : the official journal of the Society for Neuroscience 19991201 24

Developmental regulation of voltage-dependent delayed rectifier potassium current (I(Kv)) of Xenopus primary spinal neurons regulates the waveform of the action potential. I(Kv) undergoes a tripling in density and acceleration of it activation kinetics during the initial day of its appearance. Another voltage-dependent potassium current, the A current, is acquired during the subsequent day and contributes to further shortening of the impulse duration. To decipher the molecular mechanisms underly ...[more]

PMID: 10594054

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Project description:Increased nociceptive neuronal excitability underlies chronic pain conditions. Various ion channels, including sodium, calcium and potassium channels have pivotal roles in the control of neuronal excitability. The members of the family of G protein-gated inwardly rectifying potassium (GIRK) channels, GIRK1-4, have been implicated in modulating excitability. Here, we investigated the expression and distribution of GIRK1 and GIRK2 in normal and injured dorsal root ganglia (DRGs) and spinal cord of rats.We found that ~70% of the DRG neurons expressed GIRK1, while only <10% expressed GIRK2. The neurochemical profiles of GIRK1- and GIRK2-immunoreactive neurons were characterized using the neuronal markers calcitonin gene-related peptide, isolectin-B4 and neurofilament-200, and the calcium-binding proteins calbindin D28k, calretinin, parvalbumin and secretagogin. Both GIRK subunits were expressed in DRG neurons with nociceptive characteristics. However, while GIRK1 was widely expressed in several sensory neuronal subtypes, GIRK2 was detected mainly in a group of small C-fiber neurons. In the spinal dorsal horn, GIRK1- and -2-positive cell bodies and processes were mainly observed in lamina II, but also in superficial and deeper layers. Abundant GIRK1-, but not GIRK2-like immunoreactivity, was found in the ventral horn (laminae VI-X). Fourteen days after axotomy, GIRK1 and GIRK2 were down-regulated in DRG neurons at the mRNA and protein levels. Both after axotomy and rhizotomy there was a reduction of GIRK1- and -2-positive processes in the dorsal horn, suggesting a presynaptic localization of these potassium channels. Furthermore, nerve ligation caused accumulation of both subunits on both sides of the lesion, providing evidence for anterograde and retrograde fast axonal transport.Our data support the hypothesis that reduced GIRK function is associated with increased neuronal excitability and causes sensory disturbances in post-injury conditions, including neuropathic pain.

Dataset Information

Xenopus embryonic spinal neurons express potassium channel Kvbeta subunits.

Publications

Xenopus embryonic spinal neurons express potassium channel Kvbeta subunits.

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