Strong voltage-dependent inward rectification of inward rectifier K+ channels is caused by intracellular spermine

Fakler, Bernd; Brändle, Uwe; Glowatzki, Elisabeth; Weidemann, Susanne; Zenner, Hans‐Peter; Ruppersberg, J. P.

doi:10.1016/0092-8674(95)90459-x

Cited by 337 publications

(312 citation statements)

References 25 publications

Supporting

Mentioning

300

Contrasting

Unclassified

Order By: Relevance

“…The intracellular polyamines spermine and spermidine are important for the rectification of inward rectifier K ϩ channels (33)(34)(35). To test whether the observed ligand-activated I Ϫ40 mV was due (at least partially) to loss of intracellular polyamines during whole-cell recording, we tested whether the addition of a natural [spermine] i (0.1 mM; ref.…”

Section: Resultsmentioning

confidence: 99%

Activation of heteromeric G protein-gated inward rectifier K ⁺ channels overexpressed by adenovirus gene transfer inhibits the excitability of hippocampal neurons

Ehrengruber

Doupnik

et al. 1997

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

101

View full text Add to dashboard Cite

G protein-gated inward rectifier K ؉ channel subunits 1-4 (GIRK1-4) have been cloned from neuronal and atrial tissue and function as heterotetramers. To examine the inhibition of neuronal excitation by GIRKs, we overexpressed GIRKs in cultured hippocampal neurons from 18 day rat embryos, which normally lack or show low amounts of GIRK protein and currents. Adenoviral recombinants containing the cDNAs for GIRK1, GIRK2, GIRK4, and the serotonin 1A receptor were constructed. Typical GIRK currents could be activated by endogenous GABA B , serotonin 5-HT 1A , and adenosine A1 receptors in neurons coinfected with GIRK1؉2 or GIRK1؉4. Under current clamp, GIRK activation increased the cell membrane conductance by 1-to 2-fold, hyperpolarized the cell by 11-14 mV, and inhibited action potential firing by increasing the threshold current for firing by 2-to 3-fold. These effects were not found in non-and mock-infected neurons, and were similar to the effects of muscarinic stimulation of native GIRK currents in atrial myocytes. Two inhibitory effects of GIRK activation, hyperpolarization and diminution of depolarizing pulses, were simulated from the experimental data. These inhibitory effects are physiologically important in the voltage range between the resting membrane potential and the potential where voltage-gated Na ؉ and K ؉ currents are activated; that is where GIRK currents are outward.

show abstract

Section: Resultsmentioning

confidence: 99%

Activation of heteromeric G protein-gated inward rectifier K ⁺ channels overexpressed by adenovirus gene transfer inhibits the excitability of hippocampal neurons

Ehrengruber

Doupnik

et al. 1997

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

101

View full text Add to dashboard Cite

show abstract

“…Electrophysiology-Kv1.1 channels were heterologously expressed in Xenopus oocytes as described elsewhere (23). Giant patch recordings were made at room temperature (approximately 23°C) 3-7 days after injection of capped Kv1.1-specific cRNA.…”

Section: Methodsmentioning

confidence: 99%

NMR Structure and Functional Characteristics of the Hydrophilic N Terminus of the Potassium Channel β-Subunit Kvβ1.1

Wissmann

Baukrowitz

Kalbacher

et al. 1999

Journal of Biological Chemistry

View full text Add to dashboard Cite

Rapid N-type inactivation of voltage-dependent potassium (Kv) channels controls membrane excitability and signal propagation in central neurons and is mediated by protein domains (inactivation gates) occluding the open channel pore from the cytoplasmic side. Inactivation domains (ID) are donated either by the pore-forming ␣-subunit or certain auxiliary ␤-subunits. Upon coexpression, Kv␤1.1 was found to endow non-inactivating members of the Kv1␣ family with fast inactivation via its unique N terminus. Here we investigated structure and functional properties of the Kv␤1.1 N terminus (amino acids 1-62, ␤N-(1-62)) using NMR spectroscopy and patch clamp recordings. ␤N-(1-62) showed all hallmarks of N-type inactivation: it inactivated non-inactivating Kv1.1 channels when applied to the cytoplasmic side as a synthetic peptide, and its interaction with the ␣-subunit was competed with tetraethylammonium and displayed an affinity in the lower micromolar range. In aequous and physiological salt solution, ␤N-(1-62) showed no well defined three-dimensional structure, it rather existed in a fast equilibrium of multiple weakly structured states. These structural and functional properties of ␤N-(1-62) closely resemble those of the "unstructured" ID from Shaker B, but differ markedly from those of the compactly folded ID of the Kv3.4 ␣-subunit.Fast N-type inactivation of voltage-gated potassium (Kv) 1 channels shapes the action potential, governs the firing rate (spiking), and controls signal propagation in central neurons (1). Biophysically, N-type inactivation has long served as the model for gating transitions in ion channels and is realized by a "ball plug-in" mechanism. In this mechanism a protein domain termed "inactivation gate" or "inactivation ball" binds to its receptor at the inner vestibule of the open channel and thereby occludes the ion pathway (2-5). Such inactivation gates have been localized in the N terminus of various Kv␣ subunits and were shown to be functional entities, i.e. they conferred rapid inactivation to "ball-less" Kv␣ subunits when applied to the cytoplasmic side of the channels as synthetic peptides (5-8). Identical to protein-harbored inactivation domains, the synthetic gates interacted with channels in the open state, blocked the pore with low voltage dependence, and were competed with the channel blocker tetraethylammonium (TEA) (9 -11). Recently, the structures of the inactivation domains (ID) from Kv1.4 and Kv3.4 were determined with NMR spectroscopy. Both IDs were found to exhibit well defined and compact folding in aequous solution (12). In contrast, the ID from Shaker B showed no unique, folded structure (13,14).Besides with Kv␣ subunits owning an N-terminal ID, fast inactivation was observed for a subset of non-inactivating Kv␣1 channels when coexpressed with certain ␤-subunits (15-17). These auxiliary subunits constitute a family of cytoplasmic proteins (subdivided into subfamilies Kv␤1, -2, and -3) that are made up of two distinct regions: a highly conserved core region that shows homolo...

show abstract

“…Site-directed mutagenesis was performed as described (22) and verified by sequencing. For oocyte expression, constructs were subcloned into the pBF expression vector (23). Capped cRNAs were synthesized in vitro using SP6 polymerase (Promega, Heidelberg, Germany) and stored in stock solutions at Ϫ70°C.…”

Section: Mutagenesis Crna Synthesis and Oocytes Injection-murinementioning

confidence: 99%

Phosphatidylinositol 4,5-Bisphosphate (PIP2) Modulation of ATP and pH Sensitivity in Kir Channels

Schulze¹,

Krauter²,

Fritzenschaft

et al. 2003

Journal of Biological Chemistry

View full text Add to dashboard Cite

Phosphatidylinositol polyphosphates (PIPs) are potent modulators of Kir channels. Previous studies have implicated basic residues in the C terminus of Kir6.2 channels as interaction sites for the PIPs. Here we examined the role of the N terminus and identified an arginine (Arg-54) as a major determinant for PIP 2 modulation of ATP sensitivity in K ATP channels. Mutation of Arg-54 to the neutral glutamine (R54Q) and, in particular, to the negatively charged glutamate (R54E) impaired PIP 2 modulation of ATP inhibition, while mutation to lysine (R54K) had no effect. These data suggest that electrostatic interactions between PIP 2 and Arg-54 are an essential step for the modulation of ATP sensitivity. This N-terminal PIP 2 site is highly conserved in Kir channels with the exception of the pH-gated channels Kir1.1, Kir4.1, and Kir5.1 that contain a neutral residue at the corresponding positions. Introduction of an arginine at this position in Kir1.1 channels rendered the N-terminal PIP 2 site functional largely increasing the PIP 2 affinity. Moreover, Kir1.1 channels lose the ability to respond to physiological changes of the intracellular pH. These results explain the need of a silent N-terminal PIP 2 site in pH-gated channels and highlight the N terminus as an important region for PIP 2 modulation of Kir channel gating.Kir channels are a superfamily of eukaryotic channel proteins that are expressed in many tissues and responsible for important physiological processes such as cell excitability, insulin secretion, K ϩ homeostasis, vascular tone, and regulation of the heart rate. Four subunits assemble to a channel. Each subunit contains two transmembrane segments with cytoplasmic N-and C-terminal domains and a connecting loop forming the pore (1). Some members of the Kir channel family are endowed with gating mechanisms such as ATP gating (K ATP channels) (2) and pH gating (Kir1.1 and Kir4.1 channels) (3). These gating mechanisms are central for the diverse functions of Kir channels in physiology and the understanding of the related pathophysiology. Kir1, Kir4, and Kir5 channels, that are predominantly expressed in epithelia, are exquisitely sensitive to changes in intracellular pH in the physiological range (3-5). This pH sensitivity is mediated by the protonation of a lysine in the N terminus (Lys-80 in Kir1.1) that induces closure of the channel's pore by an allosteric mechanism (pH gating) (3, 6). Even small changes in the pH sensitivity can cause severe kidney defects such as the Bartter syndrome (3), highlighting the physiological importance of proper pH gating in Kir1.1 channels. Kir6 channels display a very ubiquitous expression pattern and, in coassembly with the sulfonylurea receptor (SUR), 1 represent the ATP-sensitive K ϩ channels (K ATP channels) (7). Intracellular ATP closes K ATP channels by binding to the Kir6.2 subunits (ATP gating), whereas the SURs act as regulatory subunits endowing the channel with sensitivity to MgADP and pharmacological compounds. The ATP/ADP dependence of K ATP channels couple...

show abstract

Strong voltage-dependent inward rectification of inward rectifier K+ channels is caused by intracellular spermine

Cited by 337 publications

References 25 publications

Activation of heteromeric G protein-gated inward rectifier K ⁺ channels overexpressed by adenovirus gene transfer inhibits the excitability of hippocampal neurons

Activation of heteromeric G protein-gated inward rectifier K ⁺ channels overexpressed by adenovirus gene transfer inhibits the excitability of hippocampal neurons

NMR Structure and Functional Characteristics of the Hydrophilic N Terminus of the Potassium Channel β-Subunit Kvβ1.1

Phosphatidylinositol 4,5-Bisphosphate (PIP2) Modulation of ATP and pH Sensitivity in Kir Channels

Contact Info

Product

Resources

About

Strong voltage-dependent inward rectification of inward rectifier K+ channels is caused by intracellular spermine

Cited by 337 publications

References 25 publications

Activation of heteromeric G protein-gated inward rectifier K + channels overexpressed by adenovirus gene transfer inhibits the excitability of hippocampal neurons

Activation of heteromeric G protein-gated inward rectifier K + channels overexpressed by adenovirus gene transfer inhibits the excitability of hippocampal neurons

NMR Structure and Functional Characteristics of the Hydrophilic N Terminus of the Potassium Channel β-Subunit Kvβ1.1

Phosphatidylinositol 4,5-Bisphosphate (PIP2) Modulation of ATP and pH Sensitivity in Kir Channels

Contact Info

Product

Resources

About

Activation of heteromeric G protein-gated inward rectifier K ⁺ channels overexpressed by adenovirus gene transfer inhibits the excitability of hippocampal neurons

Activation of heteromeric G protein-gated inward rectifier K ⁺ channels overexpressed by adenovirus gene transfer inhibits the excitability of hippocampal neurons