cAMP Biosensors with Restricted Subcellular Localization Reveal Persistent Signaling Changes Following Antidepressant Withdrawal

Abstract

Many patients experience a constellation of side effects following termination of antidepressant therapy. Collectively these effects are known as the antidepressant discontinuation syndrome. All currently prescribed antidepressant medications can cause this syndrome, regardless of primary mechanism of action. This suggests that some shared mechanism, independent of these drugs’ known binding targets, may contribute to the discontinuation syndrome. Lipid rafts are membrane microdomains with distinct signaling characteristics and protein expression compared to other membrane regions. Previous work has shown that chronic, but not acute, treatment with traditional antidepressants induces translocation of Gs out of lipid raft microdomains. In contrast, rapid acting antidepressants such as ketamine cause Gs translocation following acute exposure. This promotes Gs signaling in general, likely due to increased coupling to downstream effectors such as adenylyl cyclase. Using a lipid raft restricted cAMP biosensor we show that perturbations of Gs signaling persist for over 24 hr after antidepressant withdrawal in an in vitro model system. These signaling changes are variable between different subcellular microdomains, and between different cell types. In general, signaling changes in lipid rafts are more persistent than changes observed in non‐raft membrane regions, or in the cytoplasm. Effects are compared between c6 glioma, SK‐N‐SH neuronal, and HEK‐293 kidney derived cell lines. We also show that changes in lipid raft cAMP signaling are reflected by persistent reductions in lipid raft Gs expression following drug withdrawal. Protein expression is quantified following membrane isolation and sequential detergent extraction to separate lipid raft from non‐raft membranes. The observed antidepressant effects occur in model systems lacking the primary target for these drugs (e.g. SERT and escitalopram), and as such may represent a novel mechanism by which antidepressants regulate cellular activity. Understanding these residual antidepressant effects may aid in the development of novel antidepressants without an associated discontinuation syndrome, and in the discovery of new strategies to mitigate these persistent effects following drug withdrawal. Support or Funding Information Supported by: VA Merit BX001149, NIH T32 MH067631 and NIH R01 AT009169