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Forschungsdatenbank PMU-SQQUID

A Shaker homologue encodes an A-type current in Xenopus laevis.
Kerschbaum, HH; Grissmer, S; Engel, E; Richter, K; Lehner, C; Jäger, H;
Brain Res. 2002; 927(1):55-68
Originalarbeiten (Zeitschrift)

PMU-Autor/inn/en

Lehner Christine

Abstract

In Xenopus laevis, several distinct K(+)-channels (xKv1.1, xKv1.2, xKv2,1, xKv2.2, xKv3.1) have been cloned, sequenced, and electrophysiologically characterized. K(+)-channels significantly shape neuronal excitability by setting the membrane potential, and latency and duration of action potentials. We identified a further Shaker homologue, xKv1.4, in X. laevis. The open reading frame encodes a K(+)-channel that shares 72% of its 698 amino acids with the human Shaker homologue, hKv1.4. Northern blot analysis revealed xKv1.4 in the brain, muscle, and spleen but not in the ovary, intestine, heart, liver, kidney, lung, and skin. Whole-cell patch clamp recording from rat basophilic leukaemia (RBL) cells transfected with xKv1.4 revealed a voltage-gated, outward rectifying, transient A-type, K(+) selective current. xKv1.4 was strongly dependent on extracellular K(+). Exposure of cells to K(+) free bath solution almost completely abolished the current, whereas in the presence of high K(+), inactivation in response to a maintained depolarizing step and the frequency-dependent cumulative inactivation decreased. Ion channels encoded by xKv1.4 are sensitive to 4-aminopyridine and quinidine but insensitive to tetraethylammonium and the peptide toxins, charybdotoxin, margatoxin, and dendrotoxin. In conclusion, our results indicate that the biophysical and pharmacological signature of xKv1.4 closely resemble those of the A-current described in Xenopus embryonic neurons and is similar to the human Shaker homologue, hKv1.4.


Useful keywords (using NLM MeSH Indexing)

Animals

Base Sequence

Brain Chemistry/physiology

Cells, Cultured

Female

Gene Expression/physiology

Ion Channel Gating/physiology

Kv1.4 Potassium Channel

Leukemia, Basophilic, Acute

Membrane Potentials/physiology

Molecular Sequence Data

Neurons/cytology

Neurons/physiology*

Patch-Clamp Techniques

Potassium Channels/chemistry

Potassium Channels/genetics*

Potassium Channels/metabolism

Potassium Channels, Voltage-Gated*

Rats

Sequence Homology, Amino Acid

Shaker Superfamily of Potassium Channels

Transfection

Tumor Cells, Cultured

Xenopus Proteins

Xenopus laevis