Physical Interaction of Jab1 with Human Serotonin 6 G-protein-coupled Receptor and Their Possible Roles in Cell Survival

Abstract

The 5-HT 6 receptor (5-HT 6 R) is one of the most recently cloned serotonin receptors, and it plays important roles in Alzheimer disease, depression, and learning and memory disorders. However, unlike the other serotonin receptors, the cellular mechanisms of 5-HT 6 R are poorly elucidated relative to its significance in human brain diseases. Here, using a yeast two-hybrid assay, we found that the human 5-HT 6 R interacts with Jun activation domain-binding protein-1 (Jab1). We also confirmed a physical interaction between 5-HT 6 R and Jab1 using glutathione S-transferase pulldown, fluorescence resonance energy transfer, co-immunoprecipitation, and immunocyto(histo)-chemistry assays. The manipulation of Jab1 expression using Jab1 small interference RNA decreased 5-HT 6 R-mediated activity and cell membrane expression of 5-HT 6 R, whereas overexpression of Jab1 produced no significant effect. In addition, we demonstrated that the activation of 5-HT 6 R induced the translocation of Jab1 into the nucleus and increased c-Jun phosphorylation and the interaction between Jab1 and c-Jun. Furthermore, we found that 5-HT 6 R and Jab1 were up-regulated in middle cerebral artery occlusion-induced focal cerebral ischemic rats and in cultured cells exposed to hypoxic insults, suggesting possible protective roles for 5-HT 6 R and Jab1. These findings suggest that Jab1 provides a novel signal transduction pathway for 5-HT 6 R and may play an important role in 5-HT 6 Rmediated behavior changes in the brain.Neurotransmitters and neurohormones regulate diverse and myriad brain functions ranging from rapid modulation of ligand-gated ion channels to long term modulation such as gene expression, behavior, and mood changes. Serotonin (5-HT) 2 is known to be one of the key neurotransmitters related to mood changes. The serotonergic system has also been implicated in the neurobiological control of learning and memory. Therefore, it emerges as a key player in affective, cognitive, complex sensory, and motor functions (1). 5-HT mediates its diverse physiological responses through seven distinct receptor families: the 5-HT 1 , 5-HT 2 , 5-HT 3 , 5-HT 4 , 5-HT 5 , 5-HT 6 , and 5-HT 7 receptors. With the exception of the 5-HT 3 receptor, all of these receptors are members of the G-protein-coupled receptor (GPCR) superfamily (2). Among the 5-HT receptors, the 5-HT 6 receptor (5-HT 6 R) is coupled to a stimulatory G␣ (G␣ S ) protein. This receptor increases cAMP formation and then activates cAMP-dependent protein kinase (3). 5-HT 6 R is abundantly distributed in the brain, especially in the limbic region (4), and it has a high affinity for antipsychotic compounds and tricyclic antidepressants (5). These preliminary reports imply that 5-HT 6 R has a significant role in the control of mood and emotion in the central nervous system. To date, most findings suggest that 5-HT 6 R plays crucial roles in neurological disorders, including Alzheimer disease, depression, and learning and memory disorders (6 -9). Selective antagonists of 5-HT 6 R improved me...

SNX14 is a bifunctional negative regulator for neuronal 5-HT6 receptor signaling

“…In addition, the C-terminus and iL3 of 5-HT 6 R selectively interact with the N-terminus and C-terminus of Jab1, respectively. Interestingly, hypoxia increases the expression level of 5-HT 6 R and Jab1, indicating that 5-HT 6 R and the Jab1 complex and its downstream signaling pathway protect the cells against hypoxia (Yun et al, 2010). A recent study has further shown that direct recruitment of CDK5 and p35 (also known as CDK5R1) to the C-terminus of 5-HT 6 R leads to the phosphorylation of this region and promotes neurite outgrowth by activating Cdc42 (Duhr et al, 2014).…”

“…Besides Gas, 5-HT 6 R is known to interact with various proteins such as Fyn tyrosine kinase (Yun et al, 2007), Jun activation domain-binding protein-1 (Jab1, also known as COPS5) (Yun et al, 2010), mammalian target of rapamycin (mTOR) (Meffre et al, 2012), microtubule-associated protein 1B light chain (MAP1B-LC) (Kim et al, 2014) and cyclin-dependent kinase 5 (Cdk5) (Duhr et al, 2014). The C-terminus of 5-HT 6 R interacts with the Fyn and activation of 5-HT 6 R stimulates (B-D) HEK293T cells were co-transfected with HA-5-HT6R or HA-b2AR and EGFP-C1 or EGFP-RGSPX.…”

COPS5 (Jab1) Protein Increases β Site Processing of Amyloid Precursor Protein and Amyloid β Peptide Generation by Stabilizing RanBP9 Protein Levels

“…Although a substantial amount of COPS5 is expressed in the neurons and the brain, the role of COPS5 in the brain is completely unknown. Although most studies on COPS5 reported so far were on non-neuronal cells, a recent study found physical interaction between human serotonin receptor 6 (5-HT 6 R), a G protein-coupled receptor, and COPS5 (33). In this study, siRNA-mediated down-regulation of COPS5 decreased the activity of 5-HT 6 R by reducing its protein expression, suggesting that COPS5 is necessary to maintain the activity and expression of endogenous 5-HT 6 R. In another recent study, COPS5 was detected within the huntingtin aggregates (34).…”

Physical interaction between neurofibromin and serotonin 5-HT 6 receptor promotes receptor constitutive activity

“…In addition to its coupling to G proteins, the 5-HT 6 receptor interacts with the Src family tyrosine kinase Fyn (9), the Jun activation domain-binding protein 1 (10), and the microtubule-associated protein Map1b (11). The 5-HT 6 receptor also recruits the mammalian Target of Rapamycin (mTOR) Complex 1, and receptor-operated activation of mTOR signaling in prefrontal cortex (PFC) mediates its deleterious influence on cognition (12).…”