Functional Analysis of the Rat I Sodium Channel in<i>Xenopus</i>Oocytes

Smith, Raymond D.; Goldin, Alan L.

doi:10.1523/jneurosci.18-03-00811.1998

Cited by 118 publications

(108 citation statements)

References 40 publications

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“…There were no significant differences in either the V 1/2 or the slope values between mutant and wild-type channels (Table 2) under either condition. In addition, the presence of the ␤1 subunit did not significantly alter the voltage dependence of activation, consistent with previously published data (Smith and Goldin, 1998).…”

Section: The D1866y Mutation Does Not Alter the Voltage Dependence Ofsupporting

confidence: 92%

“…To determine the effects of the D1866Y mutation on the functional properties of the sodium channel, the mutation was introduced into the previously described orthologous full-length rat Na v 1.1 cDNA clone (Smith and Goldin, 1998;Spampanato et al, 2003). The biophysical properties of the mutant channels were characterized using the Xenopus oocyte expression system, for the following reasons.…”

Section: The D1866y Mutation Does Not Alter the Voltage Dependence Ofmentioning

confidence: 99%

“…For these experiments, the channels were expressed in the absence and presence of the ␤1 subunit. The ␤2 subunit was not included because its presence did not significantly affect any properties of the wild-type channel (Smith and Goldin, 1998). The fast-gated properties of the mutant channels were compared with those of the wild-type Na v 1.1 channels using the cut-open oocyte voltage clamp.…”

Section: The D1866y Mutation Does Not Alter the Voltage Dependence Ofmentioning

confidence: 99%

See 2 more Smart Citations

A Novel Epilepsy Mutation in the Sodium ChannelSCN1AIdentifies a Cytoplasmic Domain for β Subunit Interaction

Spampanato¹,

Kearney²,

Haan³

et al. 2004

J. Neurosci.

150

142

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A mutation in the sodium channel SCN1A was identified in a small Italian family with dominantly inherited generalized epilepsy with febrile seizures plus (GEFSϩ). The mutation, D1866Y, alters an evolutionarily conserved aspartate residue in the C-terminal cytoplasmic domain of the sodium channel ␣ subunit. The mutation decreased modulation of the ␣ subunit by ␤1, which normally causes a negative shift in the voltage dependence of inactivation in oocytes. There was less of a shift with the mutant channel, resulting in a 10 mV difference between the wild-type and mutant channels in the presence of ␤1. This shift increased the magnitude of the window current, which resulted in more persistent current during a voltage ramp. Computational analysis suggests that neurons expressing the mutant channels will fire an action potential with a shorter onset delay in response to a threshold current injection, and that they will fire multiple action potentials with a shorter interspike interval at a higher input stimulus. These results suggest a causal relationship between a positive shift in the voltage dependence of sodium channel inactivation and spontaneous seizure activity. Direct interaction between the cytoplasmic C-terminal domain of the wild-type ␣ subunit with the ␤1 or ␤3 subunit was first demonstrated by yeast two-hybrid analysis. The SCN1A peptide K1846-R1886 is sufficient for ␤ subunit interaction. Coimmunoprecipitation from transfected mammalian cells confirmed the interaction between the C-terminal domains of the ␣ and ␤1 subunits. The D1866Y mutation weakens this interaction, demonstrating a novel molecular mechanism leading to seizure susceptibility.

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Section: The D1866y Mutation Does Not Alter the Voltage Dependence Ofsupporting

confidence: 92%

Section: The D1866y Mutation Does Not Alter the Voltage Dependence Ofmentioning

confidence: 99%

Section: The D1866y Mutation Does Not Alter the Voltage Dependence Ofmentioning

confidence: 99%

See 1 more Smart Citation

A Novel Epilepsy Mutation in the Sodium ChannelSCN1AIdentifies a Cytoplasmic Domain for β Subunit Interaction

Spampanato¹,

Kearney²,

Haan³

et al. 2004

J. Neurosci.

150

142

View full text Add to dashboard Cite

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“…Only Na v 1.4 gating was unaffected by ␤ 1 . The data agree in general with previously published work, with most studies indicating that ␤ 1 induces a hyperpolarizing shift in the gating of various ␣ subunits (4,24,(45)(46)(47)(48).…”

Section: ␤ 1 Sialic Acids Modulate Nasupporting

confidence: 92%

The Sialic Acid Component of the β1 Subunit Modulates Voltage-gated Sodium Channel Function

Johnson

Montpetit

Stocker

et al. 2004

Journal of Biological Chemistry

103

101

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Voltage-gated sodium channels (Na v ) are responsible for initiation and propagation of nerve, skeletal muscle, and cardiac action potentials. Na v are composed of a pore-forming ␣ subunit and often one to several modulating ␤ subunits. Previous work showed that terminal sialic acid residues attached to ␣ subunits affect channel gating. Here we show that the fully sialylated ␤ 1 subunit induces a uniform, hyperpolarizing shift in steady state and kinetic gating of the cardiac and two neuronal ␣ subunit isoforms. Under conditions of reduced sialylation, the ␤ 1 -induced gating effect was eliminated. Consistent with this, mutation of ␤ 1 N-glycosylation sites abolished all effects of ␤ 1 on channel gating. Data also suggest an interaction between the cis effect of ␣ sialic acids and the trans effect of ␤ 1 sialic acids on channel gating. Thus, ␤ 1 sialic acids had no effect on the gating of the heavily glycosylated skeletal muscle ␣ subunit. However, when glycosylation of the skeletal muscle ␣ subunit was reduced through chimeragenesis such that ␣ sialic acids did not impact gating, ␤ 1 sialic acids caused a significant hyperpolarizing shift in channel gating. Together, the data indicate that ␤ 1 N-linked sialic acids can modulate Na v gating through an apparent saturating electrostatic mechanism. A model is proposed in which a spectrum of differentially sialylated Na v can directly modulate channel gating, thereby impacting cardiac, skeletal muscle, and neuronal excitability.

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“…Previously cloned Na channels, expressed within the nervous system, include ␣I, -II, -III (42-44), and Na6 (45); of these, ␣I, -II, and -III now have been characterized in heterologous expression systems (46)(47)(48) and are known to be TTX-S. NaG, originally thought to be glial-specific (49), also FIG.…”

Section: Discussionmentioning

confidence: 99%

NaN, a novel voltage-gated Na channel, is expressed preferentially in peripheral sensory neurons and down-regulated after axotomy

Dib‐Hajj

Tyrrell

Black

et al. 1998

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

465

306

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Although physiological and pharmacological evidence suggests the presence of multiple tetrodotoxinresistant (TTX-R) Na channels in neurons of peripheral nervous system ganglia, only one, SNS͞PN3, has been identified in these cells to date. We have identified and sequenced a novel Na channel ␣-subunit (NaN), predicted to be TTX-R and voltage-gated, that is expressed preferentially in sensory neurons within dorsal root ganglia (DRG) and trigeminal ganglia. The predicted amino acid sequence of NaN can be aligned with the predicted structure of known Na channel ␣-subunits; all relevant landmark sequences, including positively charged S4 and pore-lining SS1-SS2 segments, and the inactivation tripeptide IFM, are present at predicted positions. However, NaN exhibits only 42-53% similarity to other mammalian Na channels, including SNS͞PN3, indicating that it is a novel channel, and suggesting that it may represent a third subfamily of Na channels. NaN transcript levels are reduced significantly 7 days post axotomy in DRG neurons, consistent with previous findings of a reduction in TTX-R Na currents. The preferential expression of NaN in DRG and trigeminal ganglia and the reduction of NaN mRNA levels in DRG after axonal injury suggest that NaN, together with SNS͞PN3, may produce TTX-R currents in peripheral sensory neurons and may inf luence the generation of electrical activity in these cells.Voltage-gated Na channels in rat brain are composed of three subunits: the pore-forming ␣-subunit (260 kDa), which is sufficient to generate Na current flow across the membrane, and two auxiliary subunits, ␤1 (36 kDa) and ␤2 (33 kDa), which can modulate the properties of the ␣-subunit (1, 2). Nine distinct ␣-subunits have been identified in the rat (ref. 3 and references therein, refs. 4-6), and homologues have been cloned from various mammalian species, including humans (3). Specific ␣-subunits are expressed in a tissue-and developmentally specific manner (7). Aberrant expression patterns or mutations of voltage-gated sodium channel ␣-subunits underlie a number of human and animal disorders (1, 8-11).Multiple voltage-gated Na currents, some tetrodotoxinsensitive (TTX-S) and others TTX-resistant (TTX-R) (12-15), have been observed in dorsal root ganglia (DRG) neurons, which express multiple Na channel ␣-subunit mRNAs (16). The complex Na current profile in DRG neurons influences their excitability (13,(17)(18)(19) and may contribute to ectopic or spontaneous firing in these cells after injury to their axons (8,20,21).Excitability and Na current density are altered in neurons after axonal injury (22)(23)(24)(25). After axotomy, rat DRG neurons display dramatic changes in their TTX-R and TTX-S Na currents and in their Na channel mRNA profile; these changes include an attenuation of TTX-R and enhancement of TTX-S Na currents (21, 26), down-regulation of SNS͞PN3 transcripts and up-regulation of ␣III transcripts (20), and moderate elevation in the levels of ␣I and ␣II mRNAs (27). Inflammatory modulators also up-regulate TTX-R c...

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Functional Analysis of the Rat I Sodium Channel inXenopusOocytes

Cited by 118 publications

References 40 publications

A Novel Epilepsy Mutation in the Sodium ChannelSCN1AIdentifies a Cytoplasmic Domain for β Subunit Interaction

A Novel Epilepsy Mutation in the Sodium ChannelSCN1AIdentifies a Cytoplasmic Domain for β Subunit Interaction

The Sialic Acid Component of the β1 Subunit Modulates Voltage-gated Sodium Channel Function

NaN, a novel voltage-gated Na channel, is expressed preferentially in peripheral sensory neurons and down-regulated after axotomy

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