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The human mitochondrial KATP channel is modulated by calcium and nitric oxide: a patch-clamp approach
Authors:Yuliya A Dahlem  Thomas FW Horn  Tohru Gonoi  Detlef Siemen
Institution:a Institute of Medical Neurobiology, Otto-von-Guericke University of Magdeburg, D-39120 Magdeburg, Germany
b Department of Neurology, Otto-von-Guericke University of Magdeburg, D-39120 Magdeburg, Germany
c Research Center for Pathogenic Fungi and Microbial Toxicoses, Chiba University, Chiba 260, Japan
Abstract:ATP-sensitive potassium channels of the inner mitochondrial membrane (mtKATP) are blocked by ATP. They are suggested to be involved in protective mechanisms such as ischemic preconditioning (IPC). Here we identify this channel type for the first time in a human cell line (Jurkat cells). Vesicles of the inner mitochondrial membrane (mitoplasts) were prepared by hypoosmotic shock. Single-channel currents were measured by means of the patch-clamp technique. We identified an outward-rectifying channel with a slope conductance of 15 and 82 pS at negative and positive potentials, respectively. The block by 5-hydroxydecanoic acid and inhibition by ATP characterize this channel as the mtKATP channel. ATP also increased the frequency of events within the burst. This effect was modulated by the Ca2+-bath concentration. We also show that the human mtKATP channel is a direct target for nitric oxide that blocked the channel activity. Although the molecular structure of this channel type is still unknown, its characterization as an outward-rectifying channel and modulation by calcium ions and nitric oxide may help to elucidate its functional significance, which possibly implicates a role in cell survival after IPC.
Keywords:Apoptosis  Oxidative stress  Ischemic preconditioning  Protection  Diazoxide  5-Hydroxydecanoate
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