Effects of the putative antidepressant psilocin on the lipid‐raft proteome and lipid‐raft signaling

Abstract

Serotonergic hallucinogens psilocybin, and its active metabolite psilocin, have shown promise as rapid‐acting antidepressants. The FDA granted breakthrough therapy designation for psilocybin's use as an antidepressant in 2019, and phase II clinical trials are currently ongoing. Psilocybin is converted to psilocin following oral administration, and this metabolite is the primary active compound found in the central nervous system. As such, it is critically important to understand the cellular and molecular processes contributing to psilocin's antidepressant action, as well as the similarities and differences between the cellular effects of psilocin and those of more traditional antidepressants. Both traditional and rapid‐acting antidepressants cause translocation of Gαs from lipid‐rafts to non‐raft membranes. The sequelae of this translocation event include increased overall Gαs activity, leading to increased cellular cAMP. Antidepressants also accumulate in lipid‐raft membranes, even in cellular models lacking the presumed binding target for these drugs. The lipid‐raft binding target(s) are currently unknown, and the processes which contribute to Gαs translocation have not been fully elucidated. In this study we utilize a proteomic approach in a cellular model to investigate psilocin's effects on both the lipid‐raft and non‐raft proteome. We expect that additional proteins besides Gαs exhibit raft to non‐raft translocation following antidepressant treatment. Proteins exhibiting this translocation pattern may represent as‐of‐yet unrecognized contributors to antidepressant efficacy, or may serve as antidepressant biomarkers. We also measure signaling downstream of Gαs and Gαq in intact cells, as well as purified lipid‐raft membranes, using modified cAMP (AlphaScreen, cADDis) and inositol monophosphate (IP‐One) detection assays. We hypothesize that both psilocin and desipramine attenuate lipid‐raft Gαs (but notGαq) downstream signaling due to the loss of Gαs fromthese membranes. Membranes treated with psilocin or the tricyclic antidepressant desipramine are compared in order to identify candidate proteins that may be generally affected following antidepressant treatment. Both drugs cause raft to non‐raft translocation of hundreds of proteins. Several of these translocated proteins are common to both drug treatments, and we expect to identify novel contributors to the antidepressant response from this subset of proteins. In particular, observed effects on specific integrins, G‐proteins, and cholesterol biosynthesis pathways will be followed up with more in‐depth analyses in future studies. We also show that antidepressant treatments reduce lipid‐raft Gαs signaling, while simultaneously increasing whole cell Gαs signaling. This effect can persist for over 24 hr after drug withdrawal. These results represent one of the first direct measurements of lipid‐raft signaling following antidepressant treatment, and may provide a more complete understanding of both antidepressant action, and the molecular mechanisms by which ha...