Cloning and functional expression of a human gene, hIRK1, encoding the heart inward rectifier K+-channel

Wood, Linda; Tsai, T. D.; Lee, Kai S.; Vögeli, Gabriel

doi:10.1016/0378-1119(95)00244-z

Cited by 14 publications

(7 citation statements)

References 17 publications

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“…From the current/voltage (I/V) relationship, we calculated a conductance of 27.5 pS for individual openings from inside-out experiments performed at equimolar 145 mM concentration of potassium (n ϭ 4) (Gallin & McKinney, 1988;Matsuda & Stanfield, 1989;Kubo et al, 1993). This conductance is very similar to that reported by Raab-Graham et al (1994) (30 pS), Wood et al (1995) (29 pS) and Tang et al (1995) (32 pS) for human heart or brain inward rectifier potassium channel. To further investigate the nature of the ionic pathway, we recorded from a patch of membrane showing the activity of two channels.…”

Section: Electrophysiological Properties Of Ras-grf Transfected Cellssupporting

confidence: 70%

“…This conductance is very similar to that reported by Raab‐Graham et al . (1994) (30 pS), Wood et al . (1995) (29 pS) and Tang et al .…”

Section: Resultsmentioning

confidence: 98%

“…In SO5 cells, we identified, in addition to the I IR current (Arcangeli et al, 1995), a second inward current absent or rarely present in parental cells. The current, for all the biophysical and physiological parameters, including single-channel conductance of 27 pS and the presence of four channel substates, can be associated with the classical inward-rectifying K ϩ current, IRK1 (Matsuda, 1988;Mazzanti & DiFrancesco, 1989;Kubo et al, 1993;Raab-Graham et al, 1994;Tang et al, 1995;Wood et al, 1995). This current, which in neuronal cells sets V rest at hyperpolarized values and controls neuronal excitability (Hille, 1992), could justify the hyperpolarization observed in Ras-GRF-expressing cells.…”

Section: Discussionmentioning

confidence: 99%

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Expression of Ras‐GRF in the SK‐N‐BE neuroblastoma accelerates retinoic‐acid‐induced neuronal differentiation and increases the functional expression of the IRK1 potassium channel

Tonini

Mancinelli

Mazzanti

et al. 1999

Eur J of Neuroscience

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Ras-GRF, a neuron-specific Ras exchange factor of the central nervous system, was transfected in the SK-N-BE neuroblastoma cell line and stable clones were obtained. When exposed to retinoic acid, these clones showed a remarkable enhancement of Ras-GRF expression with a concomitant high increase in the level of active (GTP-bound) Ras already after 24 h of treatment. In the presence of retinoic acid, the transfected cells stopped growing and acquired a differentiated neuronal-like phenotype more rapidly than the parental ones. Cells expressing Ras-GRF also exhibited a more hyperpolarized membrane potential. Moreover, treatment with retinoic acid led to the appearance of an inward rectifying potassium channel with electrophysiological properties similar to IRK1. This current was present in a large number of cells expressing Ras-GRF, while only a small percentage of parental cells exhibited this current. However, Northern analysis with a murine cDNA probe indicated that IRK1 mRNA was induced by retinoic acid at a similar level in both kinds of cells. Brief treatment with a specific inhibitor of the mitogen-activated protein kinase (MAPK) pathway reduced the number of transfected cells showing IRK1 activity. These findings suggest that activation of the Ras pathway accelerates neuronal differentiation of this cell line. In addition, our results suggest that Ras-GRF and/or Ras-pathway may have a modulatory effect on IRK1 channel activity.

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Section: Electrophysiological Properties Of Ras-grf Transfected Cellssupporting

confidence: 70%

“…This conductance is very similar to that reported by Raab‐Graham et al . (1994) (30 pS), Wood et al . (1995) (29 pS) and Tang et al .…”

Section: Resultsmentioning

confidence: 98%

Section: Discussionmentioning

confidence: 99%

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Expression of Ras‐GRF in the SK‐N‐BE neuroblastoma accelerates retinoic‐acid‐induced neuronal differentiation and increases the functional expression of the IRK1 potassium channel

Tonini

Mancinelli

Mazzanti

et al. 1999

Eur J of Neuroscience

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“…Electrophysiological measurements (Fig. 4A) allowed the detection of a Ba 2ϩ -sensitive current, which showed the typical inward rectification properties as already described (13). The kinetics of the whole cell currents exhibited by the human isoform fused to GFP were very similar to those produced by the mouse isoform (compare Figs.…”

Section: Ras-l61 Reduces the Current Density Of Ectopically Expressedmentioning

confidence: 65%

Modulation of the Inward Rectifier Potassium Channel IRK1 by the Ras Signaling Pathway

Giovannardi¹,

Forlani²,

Bossi

et al. 2002

Journal of Biological Chemistry

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In this study, we investigated the role of Ras and the mitogen-activated protein kinase (MAPK) pathway in the modulation of the inward rectifier potassium channel IRK1. We show that although expression of IRK1 in HEK 293 cells leads to the appearance of a potassium current with strong inward rectifying properties, coexpression of the constitutively active form of Ras (Ras-L61) results in a significant reduction of the mean current density without altering the biophysical properties of the channel. The inhibitory effect of Ras-L61 is not due to a decreased expression of IRK1 since Northern analysis indicates that IRK1 mRNA level is not affected by Ras-L61 co-expression. Moreover, the inhibition can be relieved by treatment with the mitogen-activated protein kinase/ERK kinase (MEK) inhibitor PD98059. Confocal microscopy analysis of cells transfected with the fusion construct green fluorescent protein-IRK1 shows that the channel is mainly localized at the plasma membrane. Coexpression of Ras-L61 delocalizes fluorescence to the cytoplasm, whereas treatment with PD98059 partially restores the membrane localization. In conclusion, our data indicate that the Ras-MAPK pathway modulates IRK1 current by affecting the subcellular localization of the channel. This suggests a role for Ras signaling in regulating the intracellular trafficking of this channel.Inwardly rectifying potassium channels play a key role in stabilizing resting membrane potential in both excitable and non-excitable cells. IRK1/Kir 2.1 is a member of this family, showing strong inward rectification properties. It is expressed in a wide variety of tissues and cell types including neurons of the central and peripheral nervous system, glia, muscle, and immune system cells. Phosphorylation of IRK1 protein at both serine/threonine and tyrosine sites modulates its activity. The channel is a substrate of protein kinase A and protein kinase C, and direct activation of these kinases modulates the current (1, 2). In vivo, a reduction of IRK1 conductance has been demonstrated after activation of muscarinic (2) and tyrosine kinase receptors (3). Muscarinic m1 receptors modulate IRK1 probably through protein kinase C, and the small GTPase Rho has been implicated in this effect (4). The activation of nerve growth factor receptors leads to tyrosine phosphorylation of IRK1 and to its endocytosis, although it is not yet clear which kinase is involved (5).In this work, we investigated the role of Ras and of the downstream MAPK 1 pathway on the modulation of IRK1 current. To this purpose and to avoid receptor-mediated effects, we transfected the active form of Ras (Ras-L61) in HEK 293 cells together with the IRK1 channel. We found that activated Ras decreases IRK1 current without modifying the channel properties and that it does so acting through the MAPK kinase pathway. This effect seems to be due to a reduction of channel density at the cell surface, thus suggesting the involvement of the Ras-MAPK pathway in the regulation of IRK1 localization. EXPERIMENTAL PROCEDURESCe...

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“…CsCl was used to suppress hyperpolarization-activated cation current and inwardly rectifying K ? current, which were possibly elicited by membrane hyperpolarization in our voltage protocols [23][24][25]. To preclude the contamination of Cl -currents, Cl -ions inside the pipette solution were also replaced with aspartate (130 mM), as described in ''Materials and Methods'' section.…”

Section: Analysis Of Hyperpolarization-induced Currents In Pituitary mentioning

confidence: 99%

Investigations into the Correlation Properties of Membrane Electroporation-Induced Inward Currents: Prediction of Pore Formation

Yeh

et al. 2011

Cell Biochem Biophys

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Membrane electroporation (MEP) induces a drastic change in membrane conductance and permeability. However, the underlying mechanisms by which MEP-induced currents (I(MEP)) are generated or resealed remain unclear. In this study, we investigated how the fluctuations of I(MEP) might be elicited in different types of cells, including pituitary GH(3) cells, NG108-15 neuronal cells, and RAW 264.7 macrophages. We applied the detrended fluctuation analysis (DFA) to analyze the current signals in response to large hyperpolarizations. The DFA exponents from the current signals at 10 s preceding the start of the initial I(MEP) (I(Pre)) in GH(3) cells exhibited two components (short time lag [α(1)] and long time lag [α(2)]) with a crossover threshold of about 7 ms. The α(1) value was 0.46 ± 0.04 (n = 7), whereas the α(2) value with 0.62 ± 0.05 (n = 7) indicated the presence of long-term correlations of current signals. However, during maximal I(MEP), the slope of double logarithmic plot was linear and estimated to be 0.99 ± 0.02 (n = 8) with no clear crossover. Upon changes in membrane polarization, neither short- nor long-range correlation was altered. Chloroquine (CQ), a lysosomotropic agent, decreased the I(MEP) amplitude with an IC(50) value of 46 μM; however, it had no effects on the scaling exponents of I(Pre) or I(MEP). Although CQ or membrane polarization altered the amplitudes of I(MEP), no changes in correlation properties of this current were detected. The scaling exponents derived from I(Pre) exhibit long-range correlations in these different types of cells, indicating there is a correlated character of the electropore dynamics that may be allowed to predict the MEP process.

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Cloning and functional expression of a human gene, hIRK1, encoding the heart inward rectifier K+-channel

Cited by 14 publications

References 17 publications

Expression of Ras‐GRF in the SK‐N‐BE neuroblastoma accelerates retinoic‐acid‐induced neuronal differentiation and increases the functional expression of the IRK1 potassium channel

Expression of Ras‐GRF in the SK‐N‐BE neuroblastoma accelerates retinoic‐acid‐induced neuronal differentiation and increases the functional expression of the IRK1 potassium channel

Modulation of the Inward Rectifier Potassium Channel IRK1 by the Ras Signaling Pathway

Investigations into the Correlation Properties of Membrane Electroporation-Induced Inward Currents: Prediction of Pore Formation

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