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Intracellular Mg(2+) enhances the function of BK-type Ca(2+)-activated K(+) channels.

Shi J, Cui J - J. Gen. Physiol. (2001)

Bottom Line: Intracellular Mg(2+) also modulates BK channels in multiple ways with opposite effects on channel function.We have confirmed this result by studying macroscopic currents of the mslo1 channel.We discovered that Mg(2+) also binds to Ca(2+) sites and competitively inhibits Ca(2+)-dependent activation.

View Article: PubMed Central - PubMed

Affiliation: Cardiac Bioelectricity Research and Training Center, Case Western Reserve University, Cleveland, OH 44106-7207, USA.

ABSTRACT
BK channels modulate neurotransmitter release due to their activation by voltage and Ca(2+). Intracellular Mg(2+) also modulates BK channels in multiple ways with opposite effects on channel function. Previous single-channel studies have shown that Mg(2+) blocks the pore of BK channels in a voltage-dependent manner. We have confirmed this result by studying macroscopic currents of the mslo1 channel. We find that Mg(2+) activates mslo1 BK channels independently of Ca(2+) and voltage by preferentially binding to their open conformation. The mslo3 channel, which lacks Ca(2+) binding sites in the tail, is not activated by Mg(2+). However, coexpression of the mslo1 core and mslo3 tail produces channels with Mg(2+) sensitivity similar to mslo1 channels, indicating that Mg(2+) sites differ from Ca(2+) sites. We discovered that Mg(2+) also binds to Ca(2+) sites and competitively inhibits Ca(2+)-dependent activation. Quantitative computation of these effects reveals that the overall effect of Mg(2+) under physiological conditions is to enhance BK channel function.

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Intracellular Mg(2+) enhances the function of BK-type Ca(2+)-activated K(+) channels.

Shi J, Cui J - J. Gen. Physiol. (2001)

© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2233844&req=5

Bottom Line: Intracellular Mg(2+) also modulates BK channels in multiple ways with opposite effects on channel function.We have confirmed this result by studying macroscopic currents of the mslo1 channel.We discovered that Mg(2+) also binds to Ca(2+) sites and competitively inhibits Ca(2+)-dependent activation.

View Article: PubMed Central - PubMed

Affiliation: Cardiac Bioelectricity Research and Training Center, Case Western Reserve University, Cleveland, OH 44106-7207, USA.

ABSTRACT
BK channels modulate neurotransmitter release due to their activation by voltage and Ca(2+). Intracellular Mg(2+) also modulates BK channels in multiple ways with opposite effects on channel function. Previous single-channel studies have shown that Mg(2+) blocks the pore of BK channels in a voltage-dependent manner. We have confirmed this result by studying macroscopic currents of the mslo1 channel. We find that Mg(2+) activates mslo1 BK channels independently of Ca(2+) and voltage by preferentially binding to their open conformation. The mslo3 channel, which lacks Ca(2+) binding sites in the tail, is not activated by Mg(2+). However, coexpression of the mslo1 core and mslo3 tail produces channels with Mg(2+) sensitivity similar to mslo1 channels, indicating that Mg(2+) sites differ from Ca(2+) sites. We discovered that Mg(2+) also binds to Ca(2+) sites and competitively inhibits Ca(2+)-dependent activation. Quantitative computation of these effects reveals that the overall effect of Mg(2+) under physiological conditions is to enhance BK channel function.

Show MeSH
Related in: MedlinePlus