1 Synergistic roles for G-protein γ 3 and γ 7 as revealed in double knockout mice* subtypes in seizure susceptibility William F. Schwindinger 1 , Uyenlinh L. Mirshahi 1 , Kelly A. Baylor 1 , Kathleen M. Sheridan 1 , Anna M. Stauffer 1 , Stephanie Usefof 1 , Mark M. Stecker 1,2 , Tooraj Mirshahi 1 , and Janet D. Robishaw 1 From 1 Weis Center for Research, Geisinger Clinic, Danville, PA; 2 Marshall University Department of Neuroscience, Huntington, WV Running Title: Gng3 -/- Gng7 -/- mice have severe seizure phenotype To whom correspondence should be addressed: Janet D. Robishaw PhD, 100 North Academy Avenue, Danville, PA, USA, 17822; Phone: 570-271-6659; Fax: 570-271-6701; E-mail: jrobishaw@geisinger.edu . Background: Specificity of G-protein function may be determined by a specific αβγ composition. Keywords: seizures, signal transduction, G protein coupled receptor, heterotrimeric G protein Results: Combinatorial disruption of γ 3 and γ 7 Conclusion: This reflects distinct roles for γ produces a severe seizure phenotype not observed with either gene alone. 3 and γ 7 in G i/o - and G olf Significance: The γ subunits direct the assembly of distinct G protein αβγ heterotrimers that specify diverse receptor actions. -signaling pathways that modulate seizure susceptibility. SUMMARY The functions of different G protein αβγ subunit combinations are traditionally ascribed to their various α components. However, the discovery of similarly diverse γ subtypes raises the possibility that they may also contribute to specificity. To test this possibility, we used a gene targeting approach to determine whether the closely related γ 3 and γ 7 subunits can perform functionally interchangeable roles in mice. In contrast to single knockout mice that show normal survival, Gng3 -/- Gng7 -/- double knockout mice display a progressive seizure disorder that dramatically reduces their median lifespan to only 75 days. Biochemical analyses reveal that the severe phenotype is not due to redundant roles for the two γ subunits in the same signaling pathway, but rather is attributed to their unique actions in different signaling pathways. The results suggest that the γ 3 subunit is a component of a G i/o protein that is required for GABA B receptor regulated neuronal excitability, while the γ 7 subunit is a component of a G olf protein that is responsible for A 2A adenosine or D 1 ____________________________________ dopamine receptor induced neuro- protective response. The development of this mouse model offers a novel experimental framework for exploring how signaling pathways integrate to produce normal brain function, and how their combined dysfunction leads to spontaneous seizures and premature death. The results underscore the critical role of the γ subunit in this process. Proper functioning of the central nervous system requires the coordination of several hundred receptors whose actions may be mediated by a similarly large number of distinct G-protein αβγ hetero- trimers. Identifying the specific G-protein http://www.jbc.org/cgi/doi/10.1074/jbc.M111.308395 The latest version is at JBC Papers in Press. Published on December 29, 2011 as Manuscript M111.308395 Copyright 2011 by The American Society for Biochemistry and Molecular Biology, Inc. by guest on August 2, 2016 http://www.jbc.org/ Downloaded from by guest on August 2, 2016 http://www.jbc.org/ Downloaded from by guest on August 2, 2016 http://www.jbc.org/ Downloaded from