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Intracellular ATP does not inhibit Slo2.1 K+ channels.
Garg, Priyanka; Sanguinetti, Michael C.
Afiliação
  • Garg P; Nora Eccles Harrison Cardiovascular Research & Training Institute, University of Utah, Salt Lake City, Utah, USA Department of Pharmaceutics and Pharmaceutical Chemistry, University of Utah, Salt Lake City, Utah, USA.
  • Sanguinetti MC; Nora Eccles Harrison Cardiovascular Research & Training Institute, University of Utah, Salt Lake City, Utah, USA Department of Pharmaceutics and Pharmaceutical Chemistry, University of Utah, Salt Lake City, Utah, USA Department of Internal Medicine, Division of Cardiovascular Medicine, University of Utah, Salt Lake City, Utah, USA.
Physiol Rep ; 2(9)2014 Sep 01.
Article em En | MEDLINE | ID: mdl-25214519
ABSTRACT
Under normal physiological conditions, the open probability of Slo2.1 K(+) channels is low. Elevation of cytosolic [Na(+)] and [Cl(-)] caused by ischemia or rapid electrical pacing of cells increases the open probability of Slo2.1 channels and the resulting outward current can stabilize the resting state of cells. Initial characterization of heterologously expressed human Slo2.1 indicated that these channels were inhibited by physiological levels of intracellular ATP. However, a subsequent study found that intracellular ATP had no effect on Slo2.1 channels. Here, we re-examine the effects of intracellular ATP on cloned human Slo2.1 channels heterologously expressed in Xenopus oocytes. Our studies provide both direct and indirect evidence that changes in intracellular [ATP] have no effect on Slo2.1 channels. First, we directly examined the effects of intracellular ATP on Slo2.1 channel activity in excised inside-out macropatches from Xenopus oocytes. Application of 5 mmol/L ATP to the intracellular solution did not inhibit Slo2.1 currents activated by niflumic acid. Second, we lowered the [ATP]i in whole oocytes using the metabolic inhibitor NaN3. Depletion of [ATP]i in oocytes by 3 mmol/L NaN3 rapidly activated heterologously expressed KATP channels, but did not increase wild-type Slo2.1 channel currents activated by niflumic acid or currents conducted by constitutively active mutant (E275D) Slo2.1 channels. Third, mutation of a conserved residue in the ATP binding consensus site in the C-terminal domain of the channel did not enhance the magnitude of Slo2.1 current as expected if binding to this site inhibited channel function. We conclude that Slo2.1 channels are not inhibited by intracellular ATP.
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Texto completo: 1 Coleções: 01-internacional Base de dados: MEDLINE Idioma: En Revista: Physiol Rep Ano de publicação: 2014 Tipo de documento: Article País de afiliação: Estados Unidos

Texto completo: 1 Coleções: 01-internacional Base de dados: MEDLINE Idioma: En Revista: Physiol Rep Ano de publicação: 2014 Tipo de documento: Article País de afiliação: Estados Unidos