Differential association of psychopharmacological compounds with membrane microdomains in relation to the modulation of ligand-gated ion channels
The concept of lipid rafts has attracted considerable interest, because these membrane domains have been implicated in numerous cellular functions such as membrane trafficking and signal transduction processes. We have shown that antidepressants and antipsychotics colocalize with 5-HT3 receptors in raft-like domains and that they inhibit serotonin-evoked cation currents through 5-HT3 receptors in a noncompetitive manner (Eisensamer et al. 2005). However, there is increasing evidence that the raft association of distinct proteins largely depends on the biochemical preparation procedure (Nothdurfter et al. 2007) (Fig. 1). Using a detergent-free protocol, the 5-HT3 receptor is predominantly found in raft-like domains as shown by means of Western blot analysis (Fig. 2).
In contrast to sucrose density gradients, immunocytochemistry revealed only a weak colocalization between the 5-HT3 receptor and raft marker proteins (Fig. 3). Moreover, cholesterol depletion by ß-methylcyclodextrin showed an impairment of lipid raft integrity in immunocytochemistry but did not prevent the effects of DMI on 5-HT3 receptor function (Fig. 4) thereby indicating that the allosteric modulation of 5-HT3 receptors by antidepressants involves also non-raft 5-HT3 receptors. In conclusion, the differential accumulation of psychopharmacological compounds in relation to their colocalization with neurotransmitter subunits within the cell membrane may represent an important determinant for their effects on neuronal excitability, which may play a role for their distinct pharmacological profile both with regard to clinical effects and side effects.
Research groups involved:
RG Rainer Rupprecht: Caroline Nothdurfter, Sascha Tanasic, Eva-Maria Wagner, Barbara Di Benedetto, Julia Kessler
RG Theo Rein: Thomas Kirmeier
RG Matthias Eder: Gerhard Rammes
Gerald Gimpl, Insitute of Biochemistry, Johannes Gutenberg University Mainz
Jeremy Lambert, Neuroscience Institute, Division of Pathology & Neuroscience, Ninewells Hospital & Medical School, Dundee University
Nothdurfter C, Tanasic, S, Rammes G, Rupprecht R (2011) Modulation of ligand gated ion channels as a novel pharmacological principle. Pharmacopsychiatry 44: 527-534
Nothdurfter C, Tanasic, S, di Benedetto B, Rammes G, Wagner EM, Kirmeier T, Ganal V, Kessler JS, Rein T, Holsboer F, Rupprecht R (2010) Impact of lipid raft integrity on 5-HT3 receptor function and its modulation by antidepressants. Neuropsychopharmacology 35: 1510-1519
Nothdurfter C, Rammes G, Rein T, Rupprecht R: (2007) Pitfalls in isolating lipid rafts. Nature Reviews Neuroscience 8: 567
Eisensamer B, Uhr M, Meyr S, Gimpl G, Deiml T, Rammes G, Lambert J, Zieglgänsberger W, Holsboer F, Rupprecht R (2005) Antidepressants and antipsychotic drugs co-localize with serotonin type 3 (5-HT3) receptors in raft-like domains. Journal of Neuroscience 25: 10198-10206