Direct Interaction and Functional Coupling between Human 5-HT6 Receptor and the Light Chain 1 Subunit of the Microtubule-Associated Protein 1B (MAP1B-LC1)

Soon-Hee Kim,Eun-Mi Hur,Hyewhon Rhim,Sun-Kyoung Im,Dong Hyuk Kim,Kwang Chul Chung,Kang Ho Lee,Per Svenningsson

doi:10.1371/journal.pone.0091402

Abstract

Serotonin (5-HT) receptors of type 6 (5-HT6R) play important roles in mood, psychosis, and eating disorders. Recently, a growing number of studies support the use of 5-HT6R-targeting compounds as promising drug candidates for treating cognitive dysfunction associated with Alzheimer’s disease. However, the mechanistic linkage between 5-HT6R and such functions remains poorly understood. By using yeast two-hybrid, GST pull-down, and co-immunoprecipitation assays, here we show that human 5-HT6R interacts with the light chain 1 (LC1) subunit of MAP1B protein (MAP1B-LC1), a classical microtubule-associated protein highly expressed in the brain. Functionally, we have found that expression of MAP1B-LC1 regulates serotonin signaling in a receptor subtype-specific manner, specifically controlling the activities of 5-HT6R, but not those of 5-HT4R and 5-HT7R. In addition, we have demonstrated that MAP1B-LC1 increases the surface expression of 5-HT6R and decreases its endocytosis, suggesting that MAP1B-LC1 is involved in the desensitization and trafficking of 5-HT6R via a direct interaction. Together, we suggest that signal transduction pathways downstream of 5-HT6R are regulated by MAP1B, which might play a role in 5-HT6R-mediated signaling in the brain.

Highlights

Serotonin (5-hydroxytryptamine, 5-HT) is an important neurotransmitter modulating emotion, cognition, sleep, circadian rhythm, and motor functions [1]
We previously reported that Fyn, a member of the Src family of non-receptor protein-tyrosine kinase, and Jun activation domain-binding protein-1 (Jab1) interact with human 5-HT6R and play significant roles in 5-HT6R-mediated signaling in the central nervous system [8,9]
The light chain 1 (LC1) of microtubule-associated protein 1B (MAP1B) is responsible for 5-HT6R binding We previously demonstrated that the C-terminal (CT) region of human 5-HT6R interacts with Fyn tyrosine kinase and characterized the downstream signaling pathways of 5-HT6R activation regulated by Fyn [8]

Summary

Introduction

Serotonin (5-hydroxytryptamine, 5-HT) is an important neurotransmitter modulating emotion, cognition, sleep, circadian rhythm, and motor functions [1]. As expected from distribution, previous studies suggest that 5-HT6R plays an important role in cognition, mood, psychosis, and eating disorder [3,4,5,6,7]. Molecular mechanisms by which such functions relate to 5-HT6R signaling are poorly elucidated. To understand 5-HT6R signaling, we employed a yeast two-hybrid screening method on a human brain cDNA library with the intracellular domains of human 5HT6R. We previously reported that Fyn, a member of the Src family of non-receptor protein-tyrosine kinase, and Jun activation domain-binding protein-1 (Jab1) interact with human 5-HT6R and play significant roles in 5-HT6R-mediated signaling in the central nervous system [8,9]. We report that microtubule-associated protein 1B (MAP1B) directly binds to human 5-HT6R and functionally modulates its activities

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Results

Conclusion