The antidepressant drug fluoxetine is widely used for the treatment of a broad range of psychiatric disorders. Its mechanism of action is thought to involve cellular adaptations that are induced with a slow time course after initiation of treatment. To gain insight into the signaling pathways underlying such changes, the expression levels of proteins in a microsomal sub-fraction enriched in intracellular membranes from the rat forebrain was analyzed after two weeks of treatment with fluoxetine. Proteins were separated by two-dimensional gel electrophoresis, and the differentially regulated protein spots were identified by mass spectrometry. Protein network analysis suggested that most of the identified proteins could potentially be regulated by the insulin family of proteins. Among them, Fructose-bisphosphate aldolase C (AldoC), a glycolytic/gluconeogenic enzyme primarily expressed in forebrain astrocytes, was up-regulated 7.6-fold. An immunohistochemical analysis of the dorsal hippocampus revealed a robust decrease (43±2%) in the co-localization of AldoC and the astrocyte marker GFAP and a diffuse staining pattern, compatible with AldoC secretion into the extracellular space. Consistently, AldoC, contained in an exosome-like fraction in astrocyte conditioned medium, increased significantly in the cerebrospinal fluid. Our findings strongly favor a non-canonic signaling role for AldoC in cellular adaptations induced by repetitive fluoxetine treatment.
Bibliographical noteFunding Information:
We are grateful to Soledad Sandoval for technical assistance. This work was supported by Conicyt (Postdoctoral Fondecyt Project 3100057 to MS), Deutsche Forschungsgemeinschaft (SM38/8-1 to UW and KHS), the Federal State of Saxony-Anhalt and the “European Regional Development Fund” (ERDF 2007–2013) (EDG, KHS), Conicyt and BMBF (CHL 06/027 to UW and KHS) and the Initiative for Research and Innovation of the Leibniz Association (EDG). RHM and MS thank the International Society for Neurochemistry and the Committee for Aid and Education in Neurochemistry (CAEN) for financial support.
- Mass spectrometry
- Signaling networks
- Sub-cellular fractionation