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Roles of KChIP1 in the regulation of GABA-mediated transmission and behavioral anxiety.

Xia K, Xiong H, Shin Y, Wang D, Deerinck T, Takahashi H, Ellisman MH, Lipton SA, Tong G, Descalzi G, Zhang D, Zhuo M, Zhang Z - Mol Brain (2010)

Bottom Line: Its physiological function, however, remains largely unknown.We report that KChIP1 is predominantly expressed at GABAergic synapses of a subset of parvalbumin-positive neurons in the brain.Forced expression of KChIP1 in cultured hippocampal neurons increased the frequency of miniature inhibitory postsynaptic currents (mIPSCs), reduced paired pulse facilitation of autaptic IPSCs, and decreases potassium current density.

View Article: PubMed Central - HTML - PubMed

Affiliation: State Key Laboratory of Medical Genetics, Central South University, Changsha, Hunan 410078, China.

ABSTRACT
K+ channel interacting protein 1 (KChIP1) is a neuronal calcium sensor (NCS) protein that interacts with multiple intracellular molecules. Its physiological function, however, remains largely unknown. We report that KChIP1 is predominantly expressed at GABAergic synapses of a subset of parvalbumin-positive neurons in the brain. Forced expression of KChIP1 in cultured hippocampal neurons increased the frequency of miniature inhibitory postsynaptic currents (mIPSCs), reduced paired pulse facilitation of autaptic IPSCs, and decreases potassium current density. Furthermore, genetic ablation of KChIP1 potentiated potassium current density in neurons and caused a robust enhancement of anxiety-like behavior in mice. Our study suggests that KChIP1 is a synaptic protein that regulates behavioral anxiety by modulating inhibitory synaptic transmission, and drugs that act on KChIP1 may help to treat patients with mood disorders including anxiety.

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KChIP1 inhibits potassium currents in cultured hippocampal neurons. a: Co-immunoprecipitation of Kv4.3 and KChIP1-EGFP. HEK293 cell lysates co-expressing Flag-tagged Kv4.3 and KChIP1-EGFP were immunoprecipitated with an anti-Flag antibody (left panel; IP: Kv4.3) or an anti-EGFP antibody (right panel; IP: EGFP) followed by immunoblotting with anti-EGFP (left panel; IB: EGFP) or anti-Flag (right panel; IB: Kv4.3), respectively. b: Potentiation of Kv4.3 current density by Kv4.3-EGFP in Xenopus oocytes. Kv4.3 was co-expressed with either KChIP1-EGFP fusion protein, KChIP1, or EGFP in Xenopus oocytes. KChIP1-EGFP and KChIP1 but not EGFP significantly increased Kv4.3 current density (*P < 0.001). c, d: KChIP1-EGFP modulates inactivation of Kv4.3 in Xenopus oocytes. Kv4.3 was co-expressed with either KChIP1-EGFP fusion protein (black line), KChIP1 (red line), or EGFP (green line) in Xenopus oocytes. Expression of KChIP1-EGFP or KChIP1 enhanced inactivation of Kv4.3 from both the open state (c) and the closed state (d) compared with EGFP alone.
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Figure 5: KChIP1 inhibits potassium currents in cultured hippocampal neurons. a: Co-immunoprecipitation of Kv4.3 and KChIP1-EGFP. HEK293 cell lysates co-expressing Flag-tagged Kv4.3 and KChIP1-EGFP were immunoprecipitated with an anti-Flag antibody (left panel; IP: Kv4.3) or an anti-EGFP antibody (right panel; IP: EGFP) followed by immunoblotting with anti-EGFP (left panel; IB: EGFP) or anti-Flag (right panel; IB: Kv4.3), respectively. b: Potentiation of Kv4.3 current density by Kv4.3-EGFP in Xenopus oocytes. Kv4.3 was co-expressed with either KChIP1-EGFP fusion protein, KChIP1, or EGFP in Xenopus oocytes. KChIP1-EGFP and KChIP1 but not EGFP significantly increased Kv4.3 current density (*P < 0.001). c, d: KChIP1-EGFP modulates inactivation of Kv4.3 in Xenopus oocytes. Kv4.3 was co-expressed with either KChIP1-EGFP fusion protein (black line), KChIP1 (red line), or EGFP (green line) in Xenopus oocytes. Expression of KChIP1-EGFP or KChIP1 enhanced inactivation of Kv4.3 from both the open state (c) and the closed state (d) compared with EGFP alone.

Mentions: KChIP1 was previously demonstrated to potentiate Kv4 (A-type, fast inactivating) potassium channels in Xenopus oocytes [7]. In contrast, our results indicate the opposite effect of KChIP1 on non-inactivating potassium channels in cultured rat neurons. In order to ensure that our findings were not due to the EGFP moiety that was used to tag KChIP1 in our expression vector rather than KChIP1 itself, we compared the properties of KChIP1 and KChIP1-EGFP proteins. KChIP1-EGFP fusion protein co-immunoprecipitated with Kv4.3 in HEK293 cells co-transfected with cDNAs encoding KChIP1-EGFP and Kv4.3 (Fig 5a). We found in Xenopus oocytes that Kv4.3 current density was potentiated by expression of either KChIP1-EGFP fusion protein (to 5.1 ± 1.7 μA/pF, n = 10) or KChIP1 alone (to 4.1 ± 2.0 μA/pF, n = 9). Potentiation could be attributed to a slowing of channel inactivation, as previously demonstrated for KChIP1 (Fig 5c and 5d). No significant difference in the potency of modulation of Kv4.3 channels was found between KChIP1-EGFP fusion protein and KChIP1. These results show that KChIP1-EGFP fusion protein and KChIP1 function similarly. These results are further supported by the recent findings that GFP-tagged KChIP1 functionally stimulates Kv4.2 trafficking in transfected cells [27,37]. Hence, our results demonstrating a difference between the effects of KChIP1 on potassium channel modulation in Xenopus oocytes and in neurons cannot be attributed to differing effects of KChIP1-EGFP and KChIP1.


Roles of KChIP1 in the regulation of GABA-mediated transmission and behavioral anxiety.

Xia K, Xiong H, Shin Y, Wang D, Deerinck T, Takahashi H, Ellisman MH, Lipton SA, Tong G, Descalzi G, Zhang D, Zhuo M, Zhang Z - Mol Brain (2010)

KChIP1 inhibits potassium currents in cultured hippocampal neurons. a: Co-immunoprecipitation of Kv4.3 and KChIP1-EGFP. HEK293 cell lysates co-expressing Flag-tagged Kv4.3 and KChIP1-EGFP were immunoprecipitated with an anti-Flag antibody (left panel; IP: Kv4.3) or an anti-EGFP antibody (right panel; IP: EGFP) followed by immunoblotting with anti-EGFP (left panel; IB: EGFP) or anti-Flag (right panel; IB: Kv4.3), respectively. b: Potentiation of Kv4.3 current density by Kv4.3-EGFP in Xenopus oocytes. Kv4.3 was co-expressed with either KChIP1-EGFP fusion protein, KChIP1, or EGFP in Xenopus oocytes. KChIP1-EGFP and KChIP1 but not EGFP significantly increased Kv4.3 current density (*P < 0.001). c, d: KChIP1-EGFP modulates inactivation of Kv4.3 in Xenopus oocytes. Kv4.3 was co-expressed with either KChIP1-EGFP fusion protein (black line), KChIP1 (red line), or EGFP (green line) in Xenopus oocytes. Expression of KChIP1-EGFP or KChIP1 enhanced inactivation of Kv4.3 from both the open state (c) and the closed state (d) compared with EGFP alone.
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Figure 5: KChIP1 inhibits potassium currents in cultured hippocampal neurons. a: Co-immunoprecipitation of Kv4.3 and KChIP1-EGFP. HEK293 cell lysates co-expressing Flag-tagged Kv4.3 and KChIP1-EGFP were immunoprecipitated with an anti-Flag antibody (left panel; IP: Kv4.3) or an anti-EGFP antibody (right panel; IP: EGFP) followed by immunoblotting with anti-EGFP (left panel; IB: EGFP) or anti-Flag (right panel; IB: Kv4.3), respectively. b: Potentiation of Kv4.3 current density by Kv4.3-EGFP in Xenopus oocytes. Kv4.3 was co-expressed with either KChIP1-EGFP fusion protein, KChIP1, or EGFP in Xenopus oocytes. KChIP1-EGFP and KChIP1 but not EGFP significantly increased Kv4.3 current density (*P < 0.001). c, d: KChIP1-EGFP modulates inactivation of Kv4.3 in Xenopus oocytes. Kv4.3 was co-expressed with either KChIP1-EGFP fusion protein (black line), KChIP1 (red line), or EGFP (green line) in Xenopus oocytes. Expression of KChIP1-EGFP or KChIP1 enhanced inactivation of Kv4.3 from both the open state (c) and the closed state (d) compared with EGFP alone.
Mentions: KChIP1 was previously demonstrated to potentiate Kv4 (A-type, fast inactivating) potassium channels in Xenopus oocytes [7]. In contrast, our results indicate the opposite effect of KChIP1 on non-inactivating potassium channels in cultured rat neurons. In order to ensure that our findings were not due to the EGFP moiety that was used to tag KChIP1 in our expression vector rather than KChIP1 itself, we compared the properties of KChIP1 and KChIP1-EGFP proteins. KChIP1-EGFP fusion protein co-immunoprecipitated with Kv4.3 in HEK293 cells co-transfected with cDNAs encoding KChIP1-EGFP and Kv4.3 (Fig 5a). We found in Xenopus oocytes that Kv4.3 current density was potentiated by expression of either KChIP1-EGFP fusion protein (to 5.1 ± 1.7 μA/pF, n = 10) or KChIP1 alone (to 4.1 ± 2.0 μA/pF, n = 9). Potentiation could be attributed to a slowing of channel inactivation, as previously demonstrated for KChIP1 (Fig 5c and 5d). No significant difference in the potency of modulation of Kv4.3 channels was found between KChIP1-EGFP fusion protein and KChIP1. These results show that KChIP1-EGFP fusion protein and KChIP1 function similarly. These results are further supported by the recent findings that GFP-tagged KChIP1 functionally stimulates Kv4.2 trafficking in transfected cells [27,37]. Hence, our results demonstrating a difference between the effects of KChIP1 on potassium channel modulation in Xenopus oocytes and in neurons cannot be attributed to differing effects of KChIP1-EGFP and KChIP1.

Bottom Line: Its physiological function, however, remains largely unknown.We report that KChIP1 is predominantly expressed at GABAergic synapses of a subset of parvalbumin-positive neurons in the brain.Forced expression of KChIP1 in cultured hippocampal neurons increased the frequency of miniature inhibitory postsynaptic currents (mIPSCs), reduced paired pulse facilitation of autaptic IPSCs, and decreases potassium current density.

View Article: PubMed Central - HTML - PubMed

Affiliation: State Key Laboratory of Medical Genetics, Central South University, Changsha, Hunan 410078, China.

ABSTRACT
K+ channel interacting protein 1 (KChIP1) is a neuronal calcium sensor (NCS) protein that interacts with multiple intracellular molecules. Its physiological function, however, remains largely unknown. We report that KChIP1 is predominantly expressed at GABAergic synapses of a subset of parvalbumin-positive neurons in the brain. Forced expression of KChIP1 in cultured hippocampal neurons increased the frequency of miniature inhibitory postsynaptic currents (mIPSCs), reduced paired pulse facilitation of autaptic IPSCs, and decreases potassium current density. Furthermore, genetic ablation of KChIP1 potentiated potassium current density in neurons and caused a robust enhancement of anxiety-like behavior in mice. Our study suggests that KChIP1 is a synaptic protein that regulates behavioral anxiety by modulating inhibitory synaptic transmission, and drugs that act on KChIP1 may help to treat patients with mood disorders including anxiety.

Show MeSH
Related in: MedlinePlus