Restoration of Physiological Expression of 5-HT₆ Receptor into the Primary Cilia of Null Mutant Neurons Lengthens Both Primary Cilia and Dendrites

Abstract

receptors increases the likelihood for receptors to localize outside of the primary cilium and have been associated with changes in cilia morphology and dendritic outgrowth. In the present study, we explore the role of 5-HT6R rescue on neuronal morphology in primary neuronal cultures from 5-HT6R-KO mice, while maintaining a more physiological level of expression, wherein the receptor localizes to cilia in 80-90% of neurons (similar to endogenous 5-HT6R localization). We found that rescue of 5-HT6R expression is sufficient to increase cilia length and dendritic outgrowth, but primarily in neurons in which the receptor is located exclusively in the primary cilia. Additionally, we found that expression of 5-HT6R mutants, deficient in agonist-stimulated cAMP or without the predicted Fyn kinase binding domain, maintain constitutive activity for stimulating cAMP and still increased the length of cilia, while the proposed Fyn kinase domain was required for stimulating dendritic outgrowth. These findings highlight the complexity of 5-HT6R function and localization, particularly when using exogenous overexpression, and provide greater understanding and potential mechanisms for 5-HT6R drug therapies.

Loss of Bardet-Biedl syndrome proteins causes synaptic aberrations in principal neurons

“…Further studies are needed to unveil the exact molecular mechanisms of how cilia and ciliary BBS proteins might be involved in the control of receptor trafficking and microtubule organisation in the dendrites and to establish the exact function of synaptic BBS proteins. Potential cilia-dendritic cross talk has recently been discussed [44], suggesting that restoration of 5-hydroxytryptamine, 5HT (5-HT 6 ) receptor into the primary cilia of null mutant neurons lengthens both primary cilia and dendrites.…”

Synchronizing Protein Traffic to the Primary Cilium

“…To demonstrate the feasibility of monitoring transport into the primary cilium in live cells, we co-transfected cells with pCMV-CAD4-SSTR3-GFP and p5HT6-tdTomato as a ciliary marker (Berbari et al, 2008 ; Lesiak et al, 2018 ). As it can be seen in Figure 5 and in Supplementary Movie 1 , this enabled to image the gradual accumulation of SSTR3-GFP at the primary cilium by spinning disc confocal microscopy.…”

2-Phenyl-1H-pyrrole-3-carboxamide as a New Scaffold for Developing 5-HT6 Receptor Inverse Agonists with Cognition-Enhancing Activity

“…Further lines of evidence demonstrated the expression of the 5-HT 6 R in the primary cilium, highlighting the involvement of the 5-HT 6 R in neuronal morphology. 14 , 15 The cognitive-enhancing properties result from the blockade of 5-HT 6 Rs located on GABAergic neurons and promotion of corticolimbic release of acetylcholine and glutamate. 16 …”