RNA editing of the 5-HT2C receptor in the central nucleus of the amygdala is involved in resilience behavior

Abstract

Post-traumatic-stress-disorder (PTSD) is a stress-related condition that may develop after exposure to a severe trauma-event. One of the core brain areas that is considered to be a key regulatory region of PTSD is the amygdala. Specifically, the central amygdala (CeA) is involved in emotion processing and associative fear learning memory, two main circuits involved in PTSD. Long term dysregulation of trauma-related emotional processing may be caused by neuroadaptations that affect gene expression. The adenosine-(A) to-inosine (I) RNA editing machinery is a post-transcriptional process that converts a genomic encoded A to I and is critical for normal brain function and development. Such editing has the potential to increase the transcriptome diversity, and disruption of this process has been linked to various central nervous system disorders. Here, we employed a unique animal model to examine the possibility that the RNA editing machinery is involved in PTSD. Detection of RNA editing specifically in the CeA revealed changes in the editing pattern of the 5-HT2C serotonin receptor (5-HT2CR) transcript accompanied by dynamic changes in the expression levels of the ADAR family enzymes (ADAR and ADARb1). Deamination by ADAR and ADARb1 enzymes induces conformational changes in the 5-HT2CR that decrease the G-protein-coupling activity, agonist affinity, and thus serotonin signaling. Significantly, a single intra-CeA administration of a 5-HT2CR pharmacological antagonist produced a robust alleviation of PTSD-like behaviors (that was maintained for three weeks) as well as single systemic treatment. This work may suggest the way to a new avenue in the understanding of PTSD regulation.

Molecular insights into the regulation of constitutive activity by RNA editing of 5HT2C serotonin receptors

“…There is significant evidence that the 5HT 2C receptor and its isoforms are responsible for the expression of various pathological phenotypes, which can be linked to differences in basal activity ( Kawahara et al, 2008 ; Morabito et al, 2010 ; Warhaftig et al, 2021 ). Since the orthosteric site remains unchanged across the isoforms, and our structural findings suggest that the differences in Gαq activation are due to the changes in interactions between the receptor and G protein mediated by ICL2, one could imagine that an isoform-selective allosteric modulator could be designed.…”

“…Altering 5HT 2C RNA editing in vivo leads to diverse neuropathological outcomes reminiscent of Prader-Willi syndrome ( Morabito et al, 2010 ) and profound metabolic alterations ( Kawahara et al, 2008 ; Xie et al, 2021 ). Dysregulated 5HT 2C RNA editing has also been implicated in several neuropsychiatric disorders, including depression, substance abuse, and schizophrenia ( O’Neil and Emeson, 2012 ; Warhaftig et al, 2021 ; Zhu et al, 2012 ). Previous reports have suggested that highly edited isoforms VSV and VNV are found in particularly high levels in rat, mouse, and human brains ( Niswender et al, 1999 ; Zhu et al, 2012 ), while both the unedited (INI) and the less edited INV isoforms have been identified in the choroid plexus ( Niswender et al, 1999 , 2001 ).…”

“…One of the most profound consequences of 5HT 2C RNA editing is the selective modulation of constitutive (a.k.a. basal or ligand independent) GPCR signaling ( Niswender et al, 1999 , 2001 ), which has significant functional and pathological consequences ( Kawahara et al, 2008 ; Morabito et al, 2010 ; O’Neil and Emeson, 2012 ; Rauser et al, 2001 ; Warhaftig et al, 2021 ; Xie et al, 2021 ; Zhu et al, 2012 ). The most common 5HT 2C edited isoforms—VGV and VSV—both exhibit a loss of constitutive activity ( Figure 1B ) and reduced potency for 5HT ( Berg et al, 2005 ; Niswender et al, 1999 , 2001 ; Rauser et al, 2001 ; Zhu et al, 2012 ).…”

Modulation of PARP-1 Activity in a Broad Time Window Attenuates Memorizing Fear

“…For cue and contextual fear conditioning, rats were placed in the fear-conditioning apparatus for 3 min (using predator scent method, previously described in an article by Gal Warhaftig et al [7], and then a 30-s tone (2.8 kHz, 65 dB) was delivered. At the last second of the tone, a 1 s shock (1.5 mA) was applied to the floor grid.…”

“…The amygdala is part of the limbic system and is considered essential in the formation and storage of emotional memories [6,7]. It is hypothesized that in fear conditioning, the basolateral amygdala (BLA) supports the formation of conditioned fear memory and projects to neurons in the central nucleus (CeA) for the expression of conditioned fear responses [8,9].…”