Effects of Kv1.2 Intracellular Regions on Activation of Kv2.1 Channels

Scholle, Annette; Zimmer, Thomas; Koopmann, R.; Engeland, Birgit; Pongs, Olaf; Benndorf, Klaus

doi:10.1529/biophysj.104.040550

Cited by 20 publications

(20 citation statements)

References 42 publications

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“…The interaction between N and C termini of several Kv channels, including Shaker, Kv1.2 and Kv2.1, has been suggested before (Schulteis et al, 1996;Ju et al, 2003;Scholle et al, 2004;Long et al, 2005;Kobrinsky et al, 2006). In this study, we have provided evidence that the N/C terminal interaction of Kv3.1 channels is mediated by a direct, Zn 2ϩ -dependent binding between the T1 domain and the ATM region (Figs.…”

Section: Direct Interaction Between the T1 Domain And The Atm Regionsupporting

confidence: 64%

The Axon–Dendrite Targeting of Kv3 (Shaw) Channels Is Determined by a Targeting Motif That Associates with the T1 Domain and Ankyrin G

Xu¹,

Cao²,

Xiao³

et al. 2007

J. Neurosci.

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Kv3 (Shaw) channels regulate rapid spiking, transmitter release and dendritic integration of many central neurons. Crucial to functional diversity are the complex targeting patterns of channel proteins. However, the targeting mechanisms are not known. Here we report that the axon-dendrite targeting of Kv3.1 is controlled by a conditional interaction of a C-terminal axonal targeting motif (ATM) with the N-terminal T1 domain and adaptor protein ankyrin G. In cultured hippocampal neurons, although the two splice variants of Kv3.1, Kv3.1a and Kv3.1b, are differentially targeted to the somatodendritic and axonal membrane, respectively, the lysine-rich ATM is surprisingly common for both splice variants. The ATM not only directly binds to the T1 domain in a Zn 2ϩ -dependent manner, but also associates with the ankyrin-repeat domain of ankyrin G. However, the full-length channel proteins of Kv3.1b display stronger association to ankyrin G than those of Kv3.1a, suggesting that the unique splice domain at Kv3.1b C terminus influences ATM binding to T1 and ankyrin G. Because ankyrin G mainly resides at the axon initial segment, we propose that it may function as a barrier for axon-dendrite targeting of Kv3.1 channels. In support of this idea, disrupting ankyrin G function either by over-expressing a dominant-negative mutant or by siRNA knockdown decreases polarized axon-dendrite targeting of both Kv3.1a and Kv3.1b. We conclude that the conditional ATM masked by the T1 domain in Kv3.1a is exposed by the splice domain in Kv3.1b, and is subsequently recognized by ankyrin G to target Kv3.1b into the axon.

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Section: Direct Interaction Between the T1 Domain And The Atm Regionsupporting

confidence: 64%

The Axon–Dendrite Targeting of Kv3 (Shaw) Channels Is Determined by a Targeting Motif That Associates with the T1 Domain and Ankyrin G

Xu¹,

Cao²,

Xiao³

et al. 2007

J. Neurosci.

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“…The activation gating of a number of ion channels, especially whose gating is influenced by intracellular ligand binding [e.g., cyclic nucleotide gated channels (Gordon et al, 1997;Varnum and Zagotta, 1997;Zheng et al, 2003) and cystic fibrosis transmembrane conductance regulator channels (Naren et al, 1999)], involves N/C interaction. Previous mutational analyses of the effects of N-and C-terminal deletions (VanDongen et al, 1990), point mutations (Ju et al, 2003), and chimeras (Scholle et al, 2004;Mohapatra and Trimmer, 2006) suggested a role for N/C interaction in regulating Kv2.1 voltage-dependent activation, and a direct interaction between Kv2.1 N and C termini has been suggested from in vitro binding studies (Bentley et al, 1999). Voltage-dependent Kv2.1 activation is also profoundly affected by extensive in vivo Kv2.1 C-terminal phosphorylation .…”

Section: Discussionmentioning

confidence: 99%

“…Although they were constructed as nucleotide sequence corresponding to amino acid residues from 411 to 853, the actual start point is at residue M444, the first corresponding 5Ј-ATG sequence in these constructs. Kv2.1-⌬C416-Kv1.2-S4-S5 chimera was generated from the chimera of Kv2.1 with S4 -S5 sequence of Kv1.2 (Scholle et al, 2004).…”

Section: Methodsmentioning

confidence: 99%

“…Previous studies suggested, however, that the cytoplasmic C terminus of Kv2.1 was an important determinant of channel function, by influencing the voltage-dependent gating of Kv2.1 (Ju et al, 2003;Scholle et al, 2004) and determining its polarized expression and clustering (Scannevin et al, 1996;Lim et al, 2000). Voltage-dependent gating and clustering of Kv2.1 are also regulated by phosphorylation (Misonou et al, 2004(Misonou et al, , 2005; Mohapatra and at C-terminal phosphorylation sites .…”

Section: Introductionmentioning

confidence: 99%

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Interdomain Cytoplasmic Interactions Govern the Intracellular Trafficking, Gating, and Modulation of the Kv2.1 Channel

Mohapatra¹,

Siino²,

Trimmer³

2008

J. Neurosci.

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Voltage-gated potassium (Kv) channels comprise four transmembrane ␣ subunits, often associated with cytoplasmic ␤ subunits that impact channel expression and function. Here, we show that cell surface expression, voltage-dependent activation gating, and phosphorylation-dependent modulation of Kv2.1 are regulated by cytoplasmic N/C interaction within the ␣ subunit. Kv2.1 surface expression is greatly reduced by C-terminal truncation. Tailless Kv2.1 channels exhibit altered voltage-dependent gating properties and lack the bulk of the phosphorylation-dependent modulation of channel gating. Remarkably, the soluble C terminus of Kv2.1 associates with tailless channels and rescues their expression, function, and phosphorylation-dependent modulation. Soluble N and C termini of Kv2.1 can also interact directly. We also show that the N/C-terminal interaction in Kv2.1 is governed by a 34 aa motif in the juxtamembrane cytoplasmic C terminus, and a 17 aa motif located in the N terminus at a position equivalent to the ␤ subunit binding site in other Kv channels. Deletion of either motif disrupts N/C-terminal interaction and surface expression, function, and phosphorylationdependent modulation of Kv2.1 channels. These findings provide novel insights into intrinsic mechanisms for the regulation of Kv2.1 trafficking, gating, and phosphorylation-dependent modulation through cytoplasmic N/C-terminal interaction, which resembles ␣/␤ subunit interaction in other Kv channels.

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“…The crystal structure of the T1 domain is known and forms a tetramer below the membrane like a "hanging gondola" (7), while the C-terminal domain surrounds this N-terminal structure (8). There are voltage-dependent interactions between the N terminus and the C terminus that are important determinants of channel activation and modulate the activation time course of K v ␣ channels (6,9).…”

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confidence: 99%

Molecular Rearrangements of the Kv2.1 Potassium Channel Termini Associated with Voltage Gating

Kobrinsky

Stevens

Kazmi

et al. 2006

Journal of Biological Chemistry

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The voltage-gated K v 2.1 channel is composed of four identical subunits folded around the central pore and does not inactivate appreciably during short depolarizing pulses. To study voltageinduced relative molecular rearrangements of the channel, K v 2.1 subunits were genetically fused with enhanced cyan fluorescent protein and/or enhanced yellow fluorescent protein, expressed in COS1 cells, and investigated using fluorescence resonance energy transfer (FRET) microscopy combined with patch clamp. Fusion of fluorophores to either or both termini of the K v 2.1 monomer did not significantly affect the gating properties of the channel. FRET between the N-and C-terminal tags fused to the same or different K v 2.1 monomers decreased upon activation of the channel by depolarization from ؊80 to ؉60 mV, suggesting voltage-gated relative rearrangement between the termini. Because FRET between the K v 2.1 N-or C-terminal tags and the membrane-trapped EYFP N -PH pleckstrin homology domains did not change on depolarization, voltage-gated relative movements between the K v 2.1 termini occurred in a plane parallel to the plasma membrane, within a distance of 1-10 nm. FRET between the N-terminal tags did not change upon depolarization, indicating that the N termini do not rearrange relative to each other, but they could either move cooperatively with the K v 2.1 tetramer or not move at all. No FRET was detected between the C-terminal tags. Assuming their randomized orientation in the symmetrically arranged K v 2.1 subunits, C termini may move outwards in order to produce relative rearrangements between N and C termini upon depolarization.Voltage-activated K ϩ channels are a large and diverse family of homotetrameric membrane proteins that are similar in their ability to select for K ϩ over other ions but show differences in kinetics and voltage dependence of activation and inactivation (1). Each of the K v ␣ subunits is assembled into six transmembrane domains that encode determinants of voltage sensing and ion selectivity. The N and C termini are located in the cytoplasm and support a number of important interactions. The N-terminal tetramerization (T1) domain determines the specificity of assembly of K v ␣ subunits (2-6). The crystal structure of the T1 domain is known and forms a tetramer below the membrane like a "hanging gondola" (7), while the C-terminal domain surrounds this N-terminal structure (8). There are voltage-dependent interactions between the N terminus and the C terminus that are important determinants of channel activation and modulate the activation time course of K v ␣ channels (6, 9).There was remarkable progress in investigation of molecular rearrangements of the membrane-spanning core K v ␣ protein associated with voltage gating of K ϩ channels (10 -12). A recent model (13) provided insight into the folding of the N terminus fragment of K v 1.2 and suggested potentially important association between the gating and C terminus. However, the size and direction of rearrangements that may occur upon gating ...

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Effects of Kv1.2 Intracellular Regions on Activation of Kv2.1 Channels

Cited by 20 publications

References 42 publications

The Axon–Dendrite Targeting of Kv3 (Shaw) Channels Is Determined by a Targeting Motif That Associates with the T1 Domain and Ankyrin G

The Axon–Dendrite Targeting of Kv3 (Shaw) Channels Is Determined by a Targeting Motif That Associates with the T1 Domain and Ankyrin G

Interdomain Cytoplasmic Interactions Govern the Intracellular Trafficking, Gating, and Modulation of the Kv2.1 Channel

Molecular Rearrangements of the Kv2.1 Potassium Channel Termini Associated with Voltage Gating

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