Serotonin 5-HT4 receptor boosts functional maturation of dendritic spines via RhoA-dependent control of F-actin

Abstract

Activity-dependent remodeling of excitatory connections underpins memory formation in the brain. Serotonin receptors are known to contribute to such remodeling, yet the underlying molecular machinery remains poorly understood. Here, we employ high-resolution time-lapse FRET imaging in neuroblastoma cells and neuronal dendrites to establish that activation of serotonin receptor 5-HT 4 (5-HT 4 R) rapidly triggers spatially-restricted RhoA activity and G13-mediated phosphorylation of cofilin, thus locally boosting the filamentous actin fraction. In neuroblastoma cells, this leads to cell rounding and neurite retraction. In hippocampal neurons in situ, 5-HT 4 R-mediated RhoA activation triggers maturation of dendritic spines. This is paralleled by RhoA-dependent, transient alterations in cell excitability, as reflected by increased spontaneous synaptic activity, apparent shunting of evoked synaptic responses, and enhanced long-term potentiation of excitatory transmission. The 5-HT 4 R/G13/RhoA signaling thus emerges as a previously unrecognized molecular pathway underpinning usedependent functional remodeling of excitatory synaptic connections.

Serotonin receptor 4 regulates hippocampal astrocyte morphology and function

“…It has been suggested that 5‐HT 4 R activity might affect overall network excitability (Schill et al, 2020). We investigated whether the manipulation of 5‐HT 4 R signaling in astrocytes affected glutamatergic synaptic transmission.…”

The 5-HT4 receptor interacts with adhesion molecule L1 to modulate morphogenic signaling in neurons

“…The 5-HT 4 R activates the heterotrimeric G 13 protein, resulting in RhoA-dependent neurite retraction and cell rounding under basal conditions and after agonist stimulation (Ponimaskin et al, 2002). Moreover, our recent study provided evidence that the 5-HT 4 R-G 13 -RhoA signaling cascade stimulates phosphorylation of the actin-binding protein cofilin in neuroblastoma N1E-115 cells, as well as in neurons (Schill et al, 2020).…”

“…The 5-HT 4 R is a seven transmembrane domain receptor that exerts its effects through coupling to the heterotrimeric G s protein, which activates adenylyl cyclase, inducing an increase in cAMP levels and subsequent increase in phosphorylation of downstream effectors mediated by ERK (ERK1 and ERK2, also known as MAPK3 and MAPK1) (Bockaert et al, 1990;Heine et al, 2002;Norum et al, 2003). We have also shown that the 5-HT 4 R is coupled to G 13 proteins to activate the small GTPase RhoA, leading to changes in cellular morphology and spine maturation via modulation of cofilin phosphorylation and actin polymerization (Ponimaskin et al, 2002;Schill et al, 2020). Several studies have suggested that the functions of the 5-HT 4 R may be regulated through receptor homooligomerization (Pellissier et al, 2011), or through heterooligomerization with other G-protein-coupled receptors (GPCRs) (Berthouze et al, 2005).…”

“…The formation of primary dendrites and dendrite branching are both promoted by activation of the 5-HT 4 R in developing rat hippocampal neurons in vitro (Kozono et al, 2017). We recently demonstrated that the 5-HT 4 R is involved in functional maturation of dendritic spines (Schill et al, 2020). To elucidate the role of the 5-HT 4 R-L1 complex in spine formation and synaptogenesis, we used primary cultures of hippocampal neurons, which allowed visualization of the morphological changes.…”

Arhgef5 Binds α-Dystrobrevin 1 and Regulates Neuromuscular Junction Integrity

“…Experiments were carried out as described previously with minor modifications (Bijata et al, 2015;Schill et al, 2020). Briefly, for biochemical determination of RhoA/Cdc42 activity TA muscles were homogenized in lysis buffer [25 mM HEPES (pH 7.5), 150 mM NaCl, 1% Nonidet P-40, 10 mM MgCl2, 1 mM ethylenediaminetetraacetic acid (EDTA), and 2% glycerol] and centrifuged at 14000 × g for 10 min at 4 • C. The extracts were incubated with GST-PAK-PBD fusion protein that had been conjugated with glutathione beads (for Cdc42; Cell BioLabs) at 4 • C overnight or an anti-active RhoA monoclonal antibody and protein A/G Agarose beads (for RhoA, Neweast Biosciences) for 1 h at 4 • C and then washed three times with lysis buffer.…”