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GABAa Receptor Regulates the Dopamine D2 Receptor-mediated ERK Activation in Hippocampal Neuronal Cells

초록/요약

Dopamine D2 receptor(D2R) plays an important role in regulation of numerous dopaminergic functions including locomotor activity, hormone secretion, addiction, and cognition. D2R Knock out mice(D2R-/-) show impairment in locomotor activity and the level of glutamic acid decarboxylase (GAD) was strongly increased in the cortex and the striatum, displaying also altered GABAergic neurotransmission involving GABAA receptor in these mice. To investigate the interaction between D2R and GABAA receptor, I conducted co-immunoprecipitation and I found that GABAA receptor α1 subunit could bind to D2R. I also investigated how GABAA receptor can regulate the D2R-mediated extracellular signal-regulated kinase(ERK) activation in hippocampal neuronal cells where D2R and GABAA receptor co-express in brain. I observed that muscimol, GABAA receptor agonist, suppressed the D2R agonist-induced-ERK phosphorylation in hippocampal neuronal cells. ERK phosphorylation is important for spine development. I investigated the effect of D2R-mediated ERK activation for development of spine density and whether GABAA receptor could regulate this effect. Spine density increased by D2R activation and this effect was inhibited by MAPK inhibitor, D2R antagonist, and GABAA receptor agonist in hippocampal neuronal cells.

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초록/요약

도파민은 운동, 호르몬 분비, 중독, 인식 등 많은 도파민성 기능에 관여한다. D2R Knock out mice(D2R-/-)는 운동능력감소와 함께 cortex와 striatum 부위에서 glutamic acid decarboxylase(GAD)의 증가가 관찰되었고, GABA성 신경전달 또한 야생형과 비교했을 때 다르다는 것이 관찰되었다. D2R과 GABAA receptor간의 상호작용을 규명하기 위해 Co-Immunoprecipitation 실험을 실시한 결과, GABAA receptor α1 subunit이 D2R과 결합할 수 있다는 것을 확인했다. 또한, GABAA receptor가 D2R과 GABAA receptor를 함께 발현하는 hippocampal neuronal cell에서 D2R 매개 extracellular signal-regulated kinase(ERK)를 어떻게 조절하는지도 살펴보았다. GABAA receptor의 agonist인 muscimol을 처리하였을 때, D2R 매개 ERK의 인산화가 저해되는 것을 확인하였다. ERK의 인산화는 spine 발달에 중요하기 때문에, D2R 매개 ERK의 인산화가 spine 발달에 미치는 영향과, GABAA receptor가 관여하는지에 대해서도 알아보았다. 그 결과, hippocampal neuronal cell의 spine 발달은 D2R의 활성화에 의해서 증가하였고, MAPK inhibitor, D2R antagonist, GABAA receptor agonist에 의해서는 그 증가효과가 저해됨을 확인할 수 있었다.

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목차

CONTENTS

List of Figures ……………………………………………… i
Abstract ………………………………………………… ii

Introduction ……………………………………………… 1

Material and Methods …………………………………… 4
1. Animal preparation and neuronal cell culture
2. Immunoprecipitation and western blotting
3. Immunofluorscense staining
4. Western blot analysis of p-ERK
5. Immunocytochemistry
6. YFP transfection and pharmacological treatments
7. Imaging and analysis of dendritic spine morphology
8. Statistical analysis







Results …………………………………………………… 10
1. Interaction between dopamine D2 receptor and GABAA receptor α1 subunit.
2. Co-expressed dopamine D2 receptor and GABAA receptor in hippocampal neuronal cells.
3. Regulation of D2R-mediated ERK signaling by GABAA receptor activation in hippocampal neuronal cells.
4. Development of spine density by D2R-mediated ERK activation with GABAA receptor activation.
5. Effect of GABAA receptor agonist in D2R-mediated ERK signaling and dopaminergic neuron development in mesencephalic neuronal cells.

Discussion ………………………………………………… 22

References ………………………………………………… 25

Abstract in Korean ……………………………………… 30

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