Schober D.A.,Discovery Neuroscience Research |
Gill M.B.,Discovery Neuroscience Research |
Yu H.,Discovery Neuroscience Research |
Gernert D.L.,Discovery Chemistry Research |
And 5 more authors.
Journal of Biological Chemistry | Year: 2011
AMPA receptors mediate fast excitatory transmission in the brain. Neuronal AMPA receptors comprise GluA pore-forming principal subunits and can associate with multiple modulatory components, including transmembraneAMPAreceptor regulatory proteins (TARPs) and CNIHs (cornichons). AMPA receptor potentiators and non-competitive antagonists represent potential targets for a variety of neuropsychiatric disorders. Previous studies showed that theAMPAreceptor antagonist GYKI-53655 displaces binding of a potentiator from brain receptors but not from recombinant GluA subunits. Here, we asked whether AMPA receptor modulatory subunits might resolve this discrepancy. We find that the cerebellar TARP, stargazin (γ-2), enhances the binding affinity of the AMPA receptor potentiator [ 3H]-LY450295 and confers sensitivity to displacement by non-competitive antagonists. In cerebellar membranes from stargazer mice, [ 3H]-LY450295 binding is reduced and relatively resistant to displacement by non-competitive antagonists. Coexpression of AMPA receptors with CNIH-2, which is expressed in the hippocampus and at low levels in the cerebellar Purkinje neurons, confers partial sensitivity of [ 3H]-LY450295 potentiator binding to displacement by non-competitive antagonists. Autoradiography of [ 3H]-LY450295 binding to stargazer and γ-8-deficient mouse brain sections, demonstrates that TARPs regulate the pharmacology of allosteric AMPA potentiators and antagonists in the cerebellum and hippocampus, respectively. These studies demonstrate that accessory proteins define AMPA receptor pharmacology by functionally linking allosteric AMPA receptor potentiator and antagonist sites. © 2011 by The American Society for Biochemistry and Molecular Biology.
Shen S.,National University of Ireland |
Gehlert D.R.,Eli Lilly and Company |
Collier D.A.,Discovery Neuroscience Research
Neuropeptides | Year: 2013
Pituitary adenylate cyclase-activating polypeptide (PACAP) and vasoactive intestinal peptide (VIP) act through three class B G-protein coupled receptors, PAC1, VPAC1 and VPAC2, initiating multiple signaling pathways. In addition to natural peptides ligands, a number of synthetic peptides and a small molecular antagonist have been generated. Genetically modified animals have been produced for the neuropeptides and receptors. Neuroanatomical, electrophysiological, behavioral and pharmacological characterization of the mutants and transgenic mice uncovered diverse roles of PACAP-PAC1-VAPC2 signaling in peripheral tissues and in the central nervous system. Human genetic studies suggest that the PACAP-PAC1-VPAC2 signaling can be associated with psychiatric illness via mechanisms of not only loss-of-function, but also gain-of-function. For example, a duplication of chromosome 7q36.3 (encoding the VPAC2 receptor) was shown to be associated with schizophrenia, and high levels of PACAP-PAC1 signaling are associated with posttraumatic stress disorder. Whereas knockout animals are appropriate to address loss-of-function of human genetics, transgenic mice overexpressing human transgenes in native environment using artificial chromosomes are particularly valuable and essential to address the consequences of gain-of-function. This review focuses on role of PACAP and PAC1 receptor in brain development, behavior of animals and potential implication in human neurodevelopmental disorders. It also encourages keeping an open mind that alterations of VIP/PACAP signaling may associate with psychiatric illness without overt neuroanatomic changes, and that tuning of VIP/PACAP signaling may represent a novel avenue for the treatment of the psychiatric illness. © 2013 Elsevier Ltd.