Kir6.1: A Possible Subunit of ATP-Sensitive K+Channels in Mitochondria

Suzuki, Masakazu; Kotake, Ken-Ichiro; Fujikura, Keiko; Inagaki, Nobuya; Suzuki, Takeshi; Gonoi, Tohru; Seino, Susumu; Takata, Kuniaki

doi:10.1006/bbrc.1997.7891

Cited by 144 publications

(82 citation statements)

References 27 publications

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“…These observations may not be inconsistent as trafficking of these subunits may differ according to the cellular context. For example, it is possible that Kir 6.1 may be able to form a component of the mitochondrial ATP-sensitive potassium channel in brain, liver, and skeletal muscle (27,28).…”

Section: Discussionmentioning

confidence: 99%

A mechanism for ATP-sensitive potassium channel diversity: Functional coassembly of two pore-forming subunits

Cui¹

2001

Proceedings of the National Academy of Sciences

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ATP-sensitive potassium channels are an octomeric complex of four pore-forming subunits of the Kir 6.0 family and four sulfonylurea receptors. The Kir 6.0 family consists of two known members, Kir 6.1 and Kir 6.2, with distinct functional properties. The tetrameric structure of the pore-forming domain leads to the possibility that mixed heteromultimers may form. In this study, we examine this by using biochemical and electrophysiological techniques after heterologous expression of these subunits in HEK293 cells. After the coexpression of Kir 6.1 and Kir 6.2, Kir 6.1 can be coimmunoprecipitated with isoform-specific Kir 6.2 antisera and vice versa. Coexpression of SUR2B and Kir 6.2 with Kir 6.1 dominant negatives at a 1:1 expression ratio and vice versa led to a potent suppression of current. Kir 6.1, and Kir 6.2 dominant negative mutants were without effect on an inwardly rectifying potassium channel from a different family, Kir 2.1. Single-channel analysis, after coexpression of SUR2B, Kir 6.1, and Kir 6.2, revealed the existence of five distinct populations with differing single-channel current amplitudes. All channel populations were inhibited by glibenclamide. A dimeric Kir 6.1-Kir 6.2 construct expressed with SUR2B had a single-channel conductance intermediate between that of either Kir 6.2 or Kir 6.1 expressed with SUR2B. In conclusion, Kir 6.1 and Kir 6.2 readily coassemble to produce functional channels, and such phenomena may contribute to the diversity of nucleotide-regulated potassium currents seen in native tissues.

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Section: Discussionmentioning

confidence: 99%

A mechanism for ATP-sensitive potassium channel diversity: Functional coassembly of two pore-forming subunits

Cui¹

2001

Proceedings of the National Academy of Sciences

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“…18). In separate experiments using affinity bead-purified ⌬C26͞FLAG protein as substrate, PKC (19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31) appeared more effective in blocking the effects of PKC (data not shown). Also, in inside-out patch recordings, 5 M PKC (19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31) completely inhibited up-regulation of channel activity by PKC ( Fig.…”

Section: Methodsmentioning

confidence: 95%

“…Using either crude membrane homogenates or purified ⌬C26͞ FLAG protein, a reduction in the amount of PKC-catalyzed phosphorylation was always observed when the threonine residue at position 180 was substituted by an alanine or glutamate residue. The inability of PKC peptide inhibitor PKC (19)(20)(21)(22)(23)(24)(25)(26)(27)(28)(29)(30)(31) to completely abolish PKC-mediated phosphorylation probably can be attributed to its effective ''quenching'' by the excess protein in crude tissue homogenates used for the phosphorylation reaction (see ref. 18).…”

Section: Methodsmentioning

confidence: 99%

Molecular basis of protein kinase C-induced activation of ATP-sensitive potassium channels

Light

Bladen

Winkfein

et al. 2000

Proc. Natl. Acad. Sci. U.S.A.

124

108

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Potassium channels that are inhibited by internal ATP (KATP channels) provide a critical link between metabolism and cellular excitability. Protein kinase C (PKC) acts on K ATP channels to regulate diverse cellular processes, including cardioprotection by ischemic preconditioning and pancreatic insulin secretion. PKC action decreases the Hill coefficient of ATP binding to cardiac K ATP channels, thereby increasing their open probability at physiological ATP concentrations. We show that PKC similarly regulates recombinant channels from both the pancreas and heart. Surprisingly, PKC acts via phosphorylation of a specific, conserved threonine residue (T180) in the pore-forming subunit (Kir6.2). Additional PKC consensus sites exist on both Kir and the larger sulfonylurea receptor (SUR) subunits. Nonetheless, T180 controls changes in open probability induced by direct PKC action either in the absence of, or in complex with, the accessory SUR1 (pancreatic) or SUR2A (cardiac) subunits. The high degree of conservation of this site among different K ATP channel isoforms suggests that this pathway may have wide significance for the physiological regulation of KATP channels in various tissues and organelles. P otassium channels that are inhibited by ATP (K ATP channels) consist of a heterooctamer of four sulfonylurea receptor (SURx) and four inwardly rectifying K ϩ channel (Kir6.x) subunits (1-5). The SUR is a member of the ATP-binding cassette (ABC) family of proteins and acts as a regulatory subunit, conferring ADP sensitivity and the distinctive pharmacological characteristics on the K ATP channel complex (1-6). In contrast, the Kir6.x subunit forms the pore of the channel and mediates the defining ATP-dependent inhibition of K ATP channels (6). Protein kinase-catalyzed phosphorylation is an important mechanism by which the activity of ion channels, including the K ATP channel, can be controlled (7-9). For instance, another ABC protein ion channel, the cystic fibrosis transmembrane conductance regulator, is regulated by cAMP-dependent protein kinase-mediated phosphorylation, which, itself, may be permissively regulated by protein kinase C (PKC) (8, 10, 11). In addition, mounting evidence suggests the importance of PKC in activating K ATP channels during both the protective mechanism of ischemic preconditioning (12, 13) and in regulating insulin secretion (14), although the site(s) and mechanism of action of PKC-mediated phosphorylation events have not been described. Therefore, we sought to determine: (i) the functional effects of PKC on the K ATP channel, (ii) whether the action of PKC is mediated via the SUR or Kir6.2 subunit, and (iii) the identity of specific amino acid residue(s) phosphorylated by PKC. Materials and MethodsCell Culture and Transfection. tsA201 cells (an SV40-transformed variant of the HEK293 human embryonic kidney cell line) were maintained in DMEM supplemented with 10 mM glucose͞2 mM L-glutamine͞10% FCS͞0.1% penicillin/streptomycin at 37°C (10% CO 2 ). Cells were plated at 30-40% confluence on 35-...

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“…Suzuki et al [56] reported that a Kir6.1 antibody immunolocalizes to the mitochondria and binds to a 51 kDa protein in mitochondrial membrane preparations. In another study, a dominant negative Kir6.1 adenovirus, in which the pore signature sequence GFG was mutated to AFA, was constructed and infected into adult myocytes [57].…”

Section: Lack Of Molecular Identitymentioning

confidence: 99%

Mitochondrial K channels in cell survival and death

Ardehali¹,

O’Rourke²

2005

Journal of Molecular and Cellular Cardiology

196

151

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Since the discovery of the mitochondrial ATP-sensitive potassium channel (mitoK ATP ) more than 13 years ago, it has been implicated in the processes of ischemic preconditioning (IPC), apoptosis and mitochondrial matrix swelling. Different approaches have been employed to characterize the pharmacological profile of the channel, and these studies strongly suggest that cellular protection well correlates with the opening of mitoK ATP . However, there are many questions regarding mitoK ATP that remain to be answered. These include the very existence of mitoK ATP itself, its degree of importance in the process of IPC, its response to different pharmacological agents, and how its activation leads to the process of IPC and protection against cell death. Recent findings suggest that mitoK ATP may be a complex of multiple mitochondrial proteins, including some which have been suggested to be components of the mitochondrial permeability transition pore. However, the identity of the pore-forming unit of the channel and the details of the interactions between these proteins remain unclear. In this review, we attempt to highlight the recent advances in the physiological role of mitoK ATP and discuss the controversies and unanswered questions.

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Kir6.1: A Possible Subunit of ATP-Sensitive K+Channels in Mitochondria

Cited by 144 publications

References 27 publications

A mechanism for ATP-sensitive potassium channel diversity: Functional coassembly of two pore-forming subunits

A mechanism for ATP-sensitive potassium channel diversity: Functional coassembly of two pore-forming subunits

Molecular basis of protein kinase C-induced activation of ATP-sensitive potassium channels

Mitochondrial K channels in cell survival and death

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