RNA splicing and editing modulation of 5-HT2C receptor function: relevance to anxiety and aggression in VGV mice

Abstract

Changes in serotonin(2C) receptor (5-HTR2c) editing, splicing and density were found in conditions such as depression and suicide, but mechanisms explaining the changes in 5-HTR2c function are unknown. Thus, mice expressing only the fully edited VGV isoform of 5-HTR2c, in which clinically relevant behavioral changes are associated with alterations in splicing and receptor density, were studied. VGV mice displayed enhanced anxiety-like behavior in response to a preferential 5-HTR2c agonist in the social interaction test. Nearly half of interactions between pairs of VGV congeners consisted of fighting behaviors, whereas no fighting occurred in wild-type (WT) mice. VGV mice also exhibited a striking increase in freezing behaviors in reaction to an innately aversive ultrasonic stimulus. This behavioral phenotype occurred in conjunction with decreased brain 5-HT turnover during stress. These functional data were put in relation with the 5-HTR2c mRNA splicing process generating a truncated protein (5-HTR2c-Tr) in addition to the full-length receptor (5-HTR2c-Fl). 5-HTR2c-Tr mRNA was less abundant in many brain regions of VGV mice, which concomitantly had more 5-HTR2c than WT mice. Fluorescence resonance energy transfer and bioluminescence resonance energy transfer studies in transfected living HEK293T cells showed that 5-HTR2c-Tr interacts with 5-HTR2c-Fl. The 5-HTR2c-Tr was localized in the endoplasmic reticulum where it retained 5-HTR2c-Fl, preventing the latter to reach the plasma membrane. Consequently, 5-HTR2c-Tr decreased (3)H-mesulergine binding to 5-HTR2c-Fl at the plasma membrane in a concentration-dependent manner and more strongly with edited 5-HTR2c-Fl. These results suggest that 5-HTR2c pre-mRNA editing and splicing are entwined processes determining increased 5-HTR2c levels in pathological conditions through a deficit in 5-HTR2c-Tr.

Serotonergic modulation of suicidal behaviour: integrating preclinical data with clinical practice and psychotherapy

“…For instance, an increased density of prefrontal cortex 5-Ht 2C R mRnA (Pandey et al 2006) and differences in pre-mRnA editing of these receptors between control subjects and suicidal victims have been found (Gurevich et al 2002;Dracheva et al 2008). Consistently, full edited 5-Ht 2C R receptor mice displayed enhanced anxiety-like behaviour in response to the preferential 5-Ht 2C agonist, m-chlorophenylpiperazine (mCPP; Di Giovanni et al 2000), in the social interaction test and increase in freezing behaviours in reaction to an innately aversive ultrasonic stimulus (Martin et al 2013). these authors suggested that enhanced 5-Ht 2C receptor editing through interference from alternative splicing would lead to a deficit of truncated receptors that normally exert a dominant negative effect on the addressing of the full-length 5-Ht 2C receptor protein to the membrane (Martin et al 2013).…”

“…Consistently, full edited 5-Ht 2C R receptor mice displayed enhanced anxiety-like behaviour in response to the preferential 5-Ht 2C agonist, m-chlorophenylpiperazine (mCPP; Di Giovanni et al 2000), in the social interaction test and increase in freezing behaviours in reaction to an innately aversive ultrasonic stimulus (Martin et al 2013). these authors suggested that enhanced 5-Ht 2C receptor editing through interference from alternative splicing would lead to a deficit of truncated receptors that normally exert a dominant negative effect on the addressing of the full-length 5-Ht 2C receptor protein to the membrane (Martin et al 2013). Moreover, it is known that the pharmacological stimulation of 5-Ht 2C receptors reduces aggressive responses and enhances the display of submissive behaviour (Rosenzweig-Lipson et al 2007;Dekeyne et al 2012;Harvey et al 2012).…”

Serotonin 2C Receptor as a Superhero: Diversities and Talents in the RNA Universe for Editing, Variant, Small RNA and Other Expected Functional RNAs

“…Because food intake is higher in the VGV type, this change is thought to be caused by energy increases due to hyperfunction in the sympathetic system. It has also been suggested that decreased short variant generation, which is described later, is also related to the increase in 5-HT2C density (27). In the case of 5-HT2C-knockout mice, the mice become bulimic and obese (28).…”

“…Although it is expected that responsiveness attenuates in the VGV type from the above-mentioned molecular knowledge, the 5-HT2C-related responses for the agonist actually increase in the VGV animal model. Increased anxiety (26,27) and decreased fat (24) are observed. Because food intake is higher in the VGV type, this change is thought to be caused by energy increases due to hyperfunction in the sympathetic system.…”

“…Only a few reports mentioned the expression difference by neuronal differentiation in cloned neuronal cells (37) and the expression changes during the cultivation period in primary cultured neuronal cells (38). Recently, this short variant protein was shown to combine with the full-length 5-HT2C protein to form a hetero-dimer (27). In other words, the idea that the short variant controls the function of the 5-HT2C is emerging.…”