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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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Disruption of mouse KChIP1 gene potentiates potassium currents in cultured Purkinje neurons. a: Lack of KChIP1 mRNA in KChIP1-/- mouse brain tissue. KChIP1a and KChIP1b mRNAs in wild-type (WT) and KChIP1-/- (KO) mouse brain were analyzed by RT-PCR. The brain tissues examined include cerebellum (Ce), hippocampus (Hipp), cortex (Cx) and thalamus (Tha). Expression of GAPDH was monitored as a positive control. b: Primary cultures of Purkinje cells from KChIP1-/- mouse cerebella. A phase contrast image (left panel) and an immunofluorescence image of Purkinje cells stained by with anti-calbindin antibody (right panel) are illustrated. c, d: Potentiation of potassium currents in KChIP1-/- Purkinje cells. Representative recordings from wild-type (WT) and KChIP1-/- (KO) Purkinje cells (c). Potassium current density in WT was significantly smaller than that seen in KO neurons (d, *P < 0.05). Whole-cell potassium currents were evoked by a voltage step to -15 mV from a holding potential of -75 mV. Steady-state amplitudes were normalized to cell capacitance.
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Figure 6: Disruption of mouse KChIP1 gene potentiates potassium currents in cultured Purkinje neurons. a: Lack of KChIP1 mRNA in KChIP1-/- mouse brain tissue. KChIP1a and KChIP1b mRNAs in wild-type (WT) and KChIP1-/- (KO) mouse brain were analyzed by RT-PCR. The brain tissues examined include cerebellum (Ce), hippocampus (Hipp), cortex (Cx) and thalamus (Tha). Expression of GAPDH was monitored as a positive control. b: Primary cultures of Purkinje cells from KChIP1-/- mouse cerebella. A phase contrast image (left panel) and an immunofluorescence image of Purkinje cells stained by with anti-calbindin antibody (right panel) are illustrated. c, d: Potentiation of potassium currents in KChIP1-/- Purkinje cells. Representative recordings from wild-type (WT) and KChIP1-/- (KO) Purkinje cells (c). Potassium current density in WT was significantly smaller than that seen in KO neurons (d, *P < 0.05). Whole-cell potassium currents were evoked by a voltage step to -15 mV from a holding potential of -75 mV. Steady-state amplitudes were normalized to cell capacitance.

Mentions: To further investigate KChIP1 function in vivo, we generated mice with a genetic disruption of the KChIP1 gene. Expression of KChIP1a and KChIP1b, two reported KChIP1 splice variants [7,38], are ablated in the brains of these knockout (KO) mice (Fig. 4a). Since Purkinje neurons represent neurons that express high levels of KChIP1 and are morphologically identifiable in culture, we compared potassium currents in cultured Purkinje neurons generated from KChIP1 wild-type (WT) mice and KChIP1 KO mice. Cultured mouse Purkinje cells were morphologically identified under microscopy and immuno-verified with anti-calbindin antibody staining after electrophysiological recording (Fig. 6b). Potassium currents were normalized to neuronal membrane capacitance. We found that potassium current density in KChIP1 KO Purkinje cells was significantly larger (11.3 ± 0.95 pA/pF, n = 13) than in WT Purkinje neurons (8.8 ± 0.60 pA/pF, n = 13; P < 0.05) (Fig. 6c and 6d). Thus, ablation of KChIP1a and KChIP1b resulted in increased potassium current density in Purkinje cell neurons. These findings are consistent with those in neurons overexpressing KChIP1-EGFP and provide further evidence that KChIP1 inhibits neuronal potassium channels in vivo.


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)

Disruption of mouse KChIP1 gene potentiates potassium currents in cultured Purkinje neurons. a: Lack of KChIP1 mRNA in KChIP1-/- mouse brain tissue. KChIP1a and KChIP1b mRNAs in wild-type (WT) and KChIP1-/- (KO) mouse brain were analyzed by RT-PCR. The brain tissues examined include cerebellum (Ce), hippocampus (Hipp), cortex (Cx) and thalamus (Tha). Expression of GAPDH was monitored as a positive control. b: Primary cultures of Purkinje cells from KChIP1-/- mouse cerebella. A phase contrast image (left panel) and an immunofluorescence image of Purkinje cells stained by with anti-calbindin antibody (right panel) are illustrated. c, d: Potentiation of potassium currents in KChIP1-/- Purkinje cells. Representative recordings from wild-type (WT) and KChIP1-/- (KO) Purkinje cells (c). Potassium current density in WT was significantly smaller than that seen in KO neurons (d, *P < 0.05). Whole-cell potassium currents were evoked by a voltage step to -15 mV from a holding potential of -75 mV. Steady-state amplitudes were normalized to cell capacitance.
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Figure 6: Disruption of mouse KChIP1 gene potentiates potassium currents in cultured Purkinje neurons. a: Lack of KChIP1 mRNA in KChIP1-/- mouse brain tissue. KChIP1a and KChIP1b mRNAs in wild-type (WT) and KChIP1-/- (KO) mouse brain were analyzed by RT-PCR. The brain tissues examined include cerebellum (Ce), hippocampus (Hipp), cortex (Cx) and thalamus (Tha). Expression of GAPDH was monitored as a positive control. b: Primary cultures of Purkinje cells from KChIP1-/- mouse cerebella. A phase contrast image (left panel) and an immunofluorescence image of Purkinje cells stained by with anti-calbindin antibody (right panel) are illustrated. c, d: Potentiation of potassium currents in KChIP1-/- Purkinje cells. Representative recordings from wild-type (WT) and KChIP1-/- (KO) Purkinje cells (c). Potassium current density in WT was significantly smaller than that seen in KO neurons (d, *P < 0.05). Whole-cell potassium currents were evoked by a voltage step to -15 mV from a holding potential of -75 mV. Steady-state amplitudes were normalized to cell capacitance.
Mentions: To further investigate KChIP1 function in vivo, we generated mice with a genetic disruption of the KChIP1 gene. Expression of KChIP1a and KChIP1b, two reported KChIP1 splice variants [7,38], are ablated in the brains of these knockout (KO) mice (Fig. 4a). Since Purkinje neurons represent neurons that express high levels of KChIP1 and are morphologically identifiable in culture, we compared potassium currents in cultured Purkinje neurons generated from KChIP1 wild-type (WT) mice and KChIP1 KO mice. Cultured mouse Purkinje cells were morphologically identified under microscopy and immuno-verified with anti-calbindin antibody staining after electrophysiological recording (Fig. 6b). Potassium currents were normalized to neuronal membrane capacitance. We found that potassium current density in KChIP1 KO Purkinje cells was significantly larger (11.3 ± 0.95 pA/pF, n = 13) than in WT Purkinje neurons (8.8 ± 0.60 pA/pF, n = 13; P < 0.05) (Fig. 6c and 6d). Thus, ablation of KChIP1a and KChIP1b resulted in increased potassium current density in Purkinje cell neurons. These findings are consistent with those in neurons overexpressing KChIP1-EGFP and provide further evidence that KChIP1 inhibits neuronal potassium channels in vivo.

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