Lacking ASIC1a in ASIC4-positive amygdala/bed nucleus of the stria terminalis (BNST) neurons reduces anxiety and innate fear in mice.

Background: Anxiety is an innate response in the face of danger. When anxiety is overwhelming or persistent, it could be considered an anxiety disorder. Recent studies have shown that acid-sensing ion channels (ASICs) represent a novel class of promising targets for developing effective therapies for anxiety. Especially, ASIC1a and ASIC4 of the ASIC family are widely expressed in the central nervous system and their gene knockouts result in reducing or enhancing anxiety-like responses in mice respectively. However, how ASIC1a and ASIC4 modulate anxiety-associated responses remains unknown.

Methods: Here we combined chemo-optogenetic, conditional knockout, gene rescue, molecular biology and biochemistry, and electrophysiological approaches to probe the roles of ASIC4 and ASIC4-expressing cells in anxiety-associated responses in mouse models.

Results: Chemo-optogenetically activating ASIC4-positive cells induced fear and anxiety-like responses in mice. Also, mice lacking ASIC4 (Asic4^-/-) in the amygdala or the bed nucleus of the stria terminalis (BNST) exhibited anxiety-associated phenotypes. Conditional knockout of ASIC1a in ASIC4-positive cells reduced anxiety-associated behaviors. In situ hybridization analyses indicated that ASIC4 transcripts were highly co-localized with ASIC1a in the amygdala and BNST. We identified two glycosylation sites of ASIC4, Asn191 and Asn341, that were involved in interacting with ASIC1a and thus could modulate ASIC1a surface protein expression and channel activity. More importantly, viral vector-mediated gene transfer of wild-type ASIC4 but not Asn191 and Asn341 mutants in the amygdala or BNST rescued the anxiogenic phenotypes of Asic4^-/- mice.

Conclusions: Together, these data suggest that ASIC4 plays an important role in fear and anxiety-related behaviors in mice by modulating ASIC1a activity in the amygdala and BNST.