Novel mechanisms of modulating GPCR function may result in improved therapeutics for treating many diseases including schizophrenia and depression. Studies performed during the previous funding cycle of this grant revealed two unexpected effects of drugs on h5-HT6 and h5-HT7 receptor activity. 1. Two groups of inverse agonists have been discovered: """"""""high affinity/high potency"""""""" inverse agonists with potencies that are predicted from their affinities for the receptor, and """"""""high affinity/low potency"""""""" inverse agonists with potencies that are far lower than predicted from their binding affinities for the receptor. 2.The second unexpected result is that risperidone (a widely prescribed antipsychotic drug), 9-OH-risperidone (the active metabolite of risperidone), and methiothepin produce a rapid and potent inactivation of the native h5-HT7 receptor (inactivating antagonists). Therefore, this proposal involves two specific aims: 1) determine the mechanism of action of high potency vs. low potency inverse agonists at CAM h5-HT6 and 5-HT7 receptors;and 2) determine the mechanism(s) of action that results in risperidone's rapid and potent inactivation of the native h5-HT7 receptor.
Specific aim """"""""1 will be approached in three ways: a) detailed pharmacological analysis of the actions of inverse agonists at the CAM h5-HT6 and h5-HT7 receptors to determine if an allosteric mechanism may be involved;b) monitor the effects of inverse agonists on CAM h5-HT6 and h5- HT7 receptor internalization and beta-arrestin translocation;c) monitor the effects of inverse agonists on CAM h5-HT6 and h5-HT7 receptor associated MARK activity.
Specific aim 2 will be approached in three ways: a) determine if inactivating antagonists interact irreversibly with the native h-5HT7 receptor in intact cell preparations;b) monitor the effects of inactivating antagonists on native h5-HT7 receptor internalization and beta-arrestin translocation, and c) monitor the effects of inactivating antagonist treatment on MARK activity in cells expressing native h5-HT7 receptors. The results from these studies may reveal novel mechanisms for modulating the functional state of h5-HT6 and h5-HT7 receptors, which may be applicable to many other GPCR. Dysfunctions of these modulating mechanisms may underly the psychopathology of various mental diseases. These studies may lead to the development of novel therapeutics for brain dysfunctions, including schizophrenia and depression.
|Teitler, Milt; Herrick-Davis, Katharine (2014) Determining the oligomer number of native GPCR using florescence correlation spectroscopy and drug-induced inactivation-reactivation. Curr Pharm Biotechnol 15:927-37|
|Teitler, Milt; Klein, Michael T (2012) A new approach for studying GPCR dimers: drug-induced inactivation and reactivation to reveal GPCR dimer function in vitro, in primary culture, and in vivo. Pharmacol Ther 133:205-17|
|Klein, Mt; Teitler, M (2012) Distribution of 5-ht(1E) receptors in the mammalian brain and cerebral vasculature: an immunohistochemical and pharmacological study. Br J Pharmacol 166:1290-302|
|Klein, M T; Teitler, M (2011) Antagonist interaction with the human 5-HT(7) receptor mediates the rapid and potent inhibition of non-G-protein-stimulated adenylate cyclase activity: a novel GPCR effect. Br J Pharmacol 162:1843-54|
|Klein, Michael T; Dukat, Malgorzata; Glennon, Richard A et al. (2011) Toward selective drug development for the human 5-hydroxytryptamine 1E receptor: a comparison of 5-hydroxytryptamine 1E and 1F receptor structure-affinity relationships. J Pharmacol Exp Ther 337:860-7|
|Smith, Carol; Toohey, Nicole; Knight, Jessica A et al. (2011) Risperidone-induced inactivation and clozapine-induced reactivation of rat cortical astrocyte 5-hydroxytryptamineÃ½Ã½Ã½ receptors: evidence for in situ G protein-coupled receptor homodimer protomer cross-talk. Mol Pharmacol 79:318-25|
|Teitler, Milt; Toohey, Nicole; Knight, Jessica A et al. (2010) Clozapine and other competitive antagonists reactivate risperidone-inactivated h5-HT7 receptors: radioligand binding and functional evidence for GPCR homodimer protomer interactions. Psychopharmacology (Berl) 212:687-97|
|Toohey, Nicole; Klein, Michael T; Knight, Jessica et al. (2009) Human 5-HT7 receptor-induced inactivation of forskolin-stimulated adenylate cyclase by risperidone, 9-OH-risperidone and other ""inactivating antagonists"". Mol Pharmacol 76:552-9|
|Knight, Jessica A; Smith, Carol; Toohey, Nicole et al. (2009) Pharmacological analysis of the novel, rapid, and potent inactivation of the human 5-Hydroxytryptamine7 receptor by risperidone, 9-OH-Risperidone, and other inactivating antagonists. Mol Pharmacol 75:374-80|
|Klein, Michael T; Teitler, Milt (2009) Guinea pig hippocampal 5-HT(1E) receptors: a tool for selective drug development. J Neurochem 109:268-74|
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