Dataset Information

Conopeptide Vt3.1 preferentially inhibits BK potassium channels containing ?4 subunits via electrostatic interactions.

ABSTRACT: BK channel ? subunits (?1-?4) modulate the function of channels formed by slo1 subunits to produce tissue-specific phenotypes. The molecular mechanism of how the homologous ? subunits differentially alter BK channel functions and the role of different BK channel functions in various physiologic processes remain unclear. By studying channels expressed in Xenopus laevis oocytes, we show a novel disulfide-cross-linked dimer conopeptide, Vt3.1 that preferentially inhibits BK channels containing the ?4 subunit, which is most abundantly expressed in brain and important for neuronal functions. Vt3.1 inhibits the currents by a maximum of 71%, shifts the G-V relation by 45 mV approximately half-saturation concentrations, and alters both open and closed time of single channel activities, indicating that the toxin alters voltage dependence of the channel. Vt3.1 contains basic residues and inhibits voltage-dependent activation by electrostatic interactions with acidic residues in the extracellular loops of the slo1 and ?4 subunits. These results suggest a large interaction surface between the slo1 subunit of BK channels and the ?4 subunit, providing structural insight into the molecular interactions between slo1 and ?4 subunits. The results also suggest that Vt3.1 is an excellent tool for studying ? subunit modulation of BK channels and for understanding the physiological roles of BK channels in neurophysiology.

SUBMITTER: Li M

PROVIDER: S-EPMC3931035 | biostudies-literature | 2014 Feb

REPOSITORIES: biostudies-literature

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Conopeptide Vt3.1 preferentially inhibits BK potassium channels containing β4 subunits via electrostatic interactions.

Li Min M Chang Shan S Yang Longjin L Shi Jingyi J McFarland Kelli K Yang Xiao X Moller Alyssa A Wang Chunguang C Zou Xiaoqin X Chi Chengwu C Cui Jianmin J

The Journal of biological chemistry 20140107 8

BK channel β subunits (β1-β4) modulate the function of channels formed by slo1 subunits to produce tissue-specific phenotypes. The molecular mechanism of how the homologous β subunits differentially alter BK channel functions and the role of different BK channel functions in various physiologic processes remain unclear. By studying channels expressed in Xenopus laevis oocytes, we show a novel disulfide-cross-linked dimer conopeptide, Vt3.1 that preferentially inhibits BK channels containing the ...[more]

PMID: 24398688

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Project description:Voltage/Ca²?(i)-gated, large conductance K+ (BK) channels result from tetrameric association of ? (slo1) subunits. In most tissues, BK protein complexes include regulatory ? subunits that contain two transmembrane domains (TM1, TM2), an extracellular loop, and two short intracellular termini. Four BK ? types have been identified, each presenting a rather selective tissue-specific expression profile. Thus, BK ? modifies current phenotype to suit physiology in a tissue-specific manner. The smooth muscle-abundant BK ?1 drastically increases the channel's apparent Ca²?(i) sensitivity. The resulting phenotype is critical for BK channel activity to increase in response to Ca2+ levels reached near the channel during depolarization-induced Ca2+ influx and myocyte contraction. The eventual BK channel activation generates outward K+ currents that drive the membrane potential in the negative direction and eventually counteract depolarization-induced Ca2+ influx. The BK ?1 regions responsible for the characteristic phenotype of ?1-containing BK channels remain to be identified. We used patch-clamp electrophysiology on channels resulting from the combination of smooth muscle slo1 (cbv1) subunits with smooth muscle-abundant ?1, neuron-abundant ?4, or chimeras constructed by swapping ?1 and ?4 regions, and determined the contribution of specific ?1 regions to the BK phenotype. At Ca2+ levels found near the channel during myocyte contraction (10 µM), channel complexes that included chimeras having both TMs from ?1 and the remaining regions ("background") from ?4 showed a phenotype (V(half), ?(act), ?(deact)) identical to that of complexes containing wt ?1. This phenotype could not be evoked by complexes that included chimeras combining either ?1 TM1 or ?1 TM2 with a ?4 background. Likewise, ? "halves" (each including ?1 TM1 or ?1 TM2) resulting from interrupting the continuity of the EC loop failed to render the normal phenotype, indicating that physical connection between ?1 TMs via the EC loop is also necessary for proper channel function.

Dataset Information

Conopeptide Vt3.1 preferentially inhibits BK potassium channels containing ?4 subunits via electrostatic interactions.

Publications

Conopeptide Vt3.1 preferentially inhibits BK potassium channels containing β4 subunits via electrostatic interactions.

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