Long chain coenzyme A esters activate the pore-forming subunit (Kir6.2) of the ATP-regulated potassium channel

Robert Bränström, Ingo B. Leibiger, Barbara Leibiger, Barbara E. Corkey, Per Olof Berggren, Olof Larsson

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Abstract

The ATP-dependent potassium (K(ATP)) channel in the pancreatic β-cell is a complex of two proteins, the pore-forming Kir6.2 and the sulfonylurea receptor type 1 (SUR1). Both subunits are required for functional K(ATP) channels because expression of Kir6.2 alone does not result in measurable currents. However, truncation of the last 26 or 36 amino acids of the C terminus of Kir6.2 enables functional expression of the pore-forming protein in the absence of SUR1. Thus, by using the truncated form of Kir6.2, expressed in the absence and presence of SUR1, it has been shown that the site at which ATP mediates channel inhibition is likely to be situated on Kir6.2. We have now examined the effects of long chain acyl-CoA (LC-CoA) esters on the C-terminally truncated mouse Kir6.2Δ365-390 (Kir6.2ΔC26) in inside-out patches isolated from Xenopus laevis oocytes. LC-CoA esters, saturated (C14:0, C16:0) and unsaturated (C18:1), increased Kir6.2ΔC26 currents, whereas short and medium chain CoA esters (C3:0, C8:0, C12:0) were unable to affect channel activity. The LC-CoA esters were also able to counteract the blocking effect of ATP on Kir6.2ΔC26. The stimulatory effect of the esters could be explained by the induction of a prolonged open state of Kir6.2ΔC26. In the presence of the esters, channel open time was increased approximately 3-fold, which is identical to what was obtained in the native mouse K(ATP) channel. Coexpression of SUR1 together with Kir6.2ΔC26 did not further increase the ability of LC-CoA esters to stimulate channel activity. We conclude that Kir6.2 is the primary target for LC-CoA esters to activate the K(ATP) channel and that the esters are likely to induce a conformational change by a direct interference with the pore- forming subunit, leading to openings of long duration.

Original languageEnglish
Pages (from-to)31395-31400
Number of pages6
JournalJournal of Biological Chemistry
Volume273
Issue number47
DOIs
StatePublished - Nov 20 1998
Externally publishedYes

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Potassium Channels
Coenzyme A
Esters
Acyl Coenzyme A
Adenosine Triphosphate
Sulfonylurea Receptors
Porins
Xenopus laevis
Oocytes
Potassium
Amino Acids

ASJC Scopus subject areas

  • Biochemistry

Cite this

Bränström, R., Leibiger, I. B., Leibiger, B., Corkey, B. E., Berggren, P. O., & Larsson, O. (1998). Long chain coenzyme A esters activate the pore-forming subunit (Kir6.2) of the ATP-regulated potassium channel. Journal of Biological Chemistry, 273(47), 31395-31400. https://doi.org/10.1074/jbc.273.47.31395

Long chain coenzyme A esters activate the pore-forming subunit (Kir6.2) of the ATP-regulated potassium channel. / Bränström, Robert; Leibiger, Ingo B.; Leibiger, Barbara; Corkey, Barbara E.; Berggren, Per Olof; Larsson, Olof.

In: Journal of Biological Chemistry, Vol. 273, No. 47, 20.11.1998, p. 31395-31400.

Research output: Contribution to journalArticle

Bränström, R, Leibiger, IB, Leibiger, B, Corkey, BE, Berggren, PO & Larsson, O 1998, 'Long chain coenzyme A esters activate the pore-forming subunit (Kir6.2) of the ATP-regulated potassium channel', Journal of Biological Chemistry, vol. 273, no. 47, pp. 31395-31400. https://doi.org/10.1074/jbc.273.47.31395
Bränström, Robert ; Leibiger, Ingo B. ; Leibiger, Barbara ; Corkey, Barbara E. ; Berggren, Per Olof ; Larsson, Olof. / Long chain coenzyme A esters activate the pore-forming subunit (Kir6.2) of the ATP-regulated potassium channel. In: Journal of Biological Chemistry. 1998 ; Vol. 273, No. 47. pp. 31395-31400.
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abstract = "The ATP-dependent potassium (K(ATP)) channel in the pancreatic β-cell is a complex of two proteins, the pore-forming Kir6.2 and the sulfonylurea receptor type 1 (SUR1). Both subunits are required for functional K(ATP) channels because expression of Kir6.2 alone does not result in measurable currents. However, truncation of the last 26 or 36 amino acids of the C terminus of Kir6.2 enables functional expression of the pore-forming protein in the absence of SUR1. Thus, by using the truncated form of Kir6.2, expressed in the absence and presence of SUR1, it has been shown that the site at which ATP mediates channel inhibition is likely to be situated on Kir6.2. We have now examined the effects of long chain acyl-CoA (LC-CoA) esters on the C-terminally truncated mouse Kir6.2Δ365-390 (Kir6.2ΔC26) in inside-out patches isolated from Xenopus laevis oocytes. LC-CoA esters, saturated (C14:0, C16:0) and unsaturated (C18:1), increased Kir6.2ΔC26 currents, whereas short and medium chain CoA esters (C3:0, C8:0, C12:0) were unable to affect channel activity. The LC-CoA esters were also able to counteract the blocking effect of ATP on Kir6.2ΔC26. The stimulatory effect of the esters could be explained by the induction of a prolonged open state of Kir6.2ΔC26. In the presence of the esters, channel open time was increased approximately 3-fold, which is identical to what was obtained in the native mouse K(ATP) channel. Coexpression of SUR1 together with Kir6.2ΔC26 did not further increase the ability of LC-CoA esters to stimulate channel activity. We conclude that Kir6.2 is the primary target for LC-CoA esters to activate the K(ATP) channel and that the esters are likely to induce a conformational change by a direct interference with the pore- forming subunit, leading to openings of long duration.",
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AU - Berggren, Per Olof

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