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dc.contributor.authorChen, Humanmian
dc.date.accessioned2020-11-01T19:22:32Z
dc.date.available2020-11-01T19:22:32Z
dc.date.issued2000-11
dc.identifier.urien
dc.identifier.urihttp://hdl.handle.net/10675.2/623633
dc.description.abstractPresynaptic inhibition of elicited neurotransmitter release mediated by G protein-coupled receptors (GPCRs) can develop and decay in a few seconds. This time course is too rapid to be accounted for by the intrinsic G TPase ·activity of Ga subunits alone. Here we test the hypothesis that endogenous regulators of G protein §.ignaling (RGS proteins), which are GTPase activating proteins (GAPs) for Ga, are required for rapid, brief presynaptic inhib'ition. Endogenous G protein a subunits were uncoupled from. GPCRs by treating hippocampal microisland cultures with pertussis toxin (PTX). Adenovirusmediated expression of mutant PTX-insensitive (PTX-i) Gai1_3 or Gao subunits rescued adenosine-induced presynaptic inhibition in neurons. Expression of double mutant Gaii or Ga0 subunits that were both PTX-insensitive and unable to bind RGS proteins (PTX/RGS-i) also rescued presynaptic inhibition. Presynaptic inhibition mediated by PTX/RGS-i subunits decayed. much more slowly after agonist removal than that mediated by PTX -i subunits or native G proteins. The onset of presynaptic inhibition mediated by PTX/RGS-i Gao was also slower than that mediated by PTX-i Ga0 • In contrast, the onset of presynaptic inhibition· mediated by PTX/RGS-i Gai1 was similar to that mediated by PTX-i Gail. These results suggest that endogenous RGS proteins are present in presynaptic terminals and essential for fast recovery of presynaptic inhibition. The effect of endogenous RGS proteins on the onset of. presynaptic inhibition appears . dependent on the particular Ga- subunits involved. We also performed experiments to test· whether the functions of RGS proteins are sensitive to upregulation. Over-expression ~f RGS8 in neurons without pretreatment of PTX not only accelerated the time course of the onset but also increased· the steady state level of presynaptic inhibition. Overexpression of RGS4 also enhanced the steady state. These results suggest that RGS8 and probably RGS4 as well can be transported to presynaptic terminals and upregulate the activation of Guo protein signaling. Interestingly, overexpression of these RGS proteins failed to accelerate the recovery of presynaptic inhibition, although it is well established that both RGS8 and E.GS4 are strong GAPs for Gai/o· This result suggests GAP activity for Gau0 in presynaptic terminals is physiologically "saturated" by endogenous RGS proteins.en_US
dc.language.isoen_USen_US
dc.publisherAugusta Universityen_US
dc.rightsCopyright protected. Unauthorized reproduction or use beyond the exceptions granted by the Fair Use clause of U.S. Copyright law may violate federal law.en_US
dc.subjectpresynaptic inhibitionen_US
dc.subjectRGS proteinsen_US
dc.subjectG proteinsen_US
dc.titleRegulators of G protein signaling (RGS proteins) regulate presynaptic inhibition at rat hippocampal synapsesen_US
dc.typeDissertationen_US
dc.contributor.departmentMedical College of Georgiaen_US
dc.description.advisorLambert, Nevin A.
dc.description.degreeDoctor of Philosophyen_US
dc.description.committeeN/A, N/A
dc.embargoen
refterms.dateFOA2020-11-01T19:22:32Z


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