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dc.contributor.authorOkashah, Najeah
dc.date.accessioned2020-03-04T23:01:48Z
dc.date.available2020-03-04T23:01:48Z
dc.date.issued2020-03
dc.identifier.urihttp://hdl.handle.net/10675.2/623126
dc.description.abstractHundreds of human G protein-coupled receptors (GPCRs) converge on activation of four families of heterotrimeric G proteins. Individual receptors select a subset of G proteins in order to produce appropriate cellular responses. While the precise mechanisms of coupling selectivity are uncertain, the G alpha subunit carboxy (C) terminus is believed to be the primary region recognized by GPCRs. We directly assessed coupling between 14 representative GPCRs and 16 G alpha subunits, including one wild-type G alpha subunit from each of the four families and 12 chimeras with exchanged C termini. We found that Gi-coupled receptors were relatively selective for Gi1 heterotrimers, while Gs-, Gq-, and G12- coupled receptors were more promiscuous and always coupled in some measure to Gi1 heterotrimers. Our tests with G alpha subunit chimeras show that the G alpha subunit core and C terminus both play important roles in selectivity. This suggests that the key G protein determinants of selectivity vary widely, even for different receptors that couple to the same G protein. While promiscuous GPCR-G protein coupling is often observed. These interactions behave as expected with receptor-G protein coupling and activation being almost synonymous. Agonist bound GPCRs activate the G protein heterotrimers they interact with, while ignoring G protein subtypes that they cannot activate. However, we have shown that GPCRs can form unproductive complexes with G12 heterotrimers. Vasopressin 2 receptor (V2R) forms agonist-dependent complexes with G12 heterotrimers. Unlike V2R complexes with cognate Gs heterotrimers, V2R-G12 complexes do not dissociate when GDP or GTP is present. Stimulating V2R with arginine vasopressin (AVP) does not activate signaling responses downstream of G12 activation. Evaluation of several G12-coupled receptors demonstrated that agonist induced GPCR-G12 complexes have a wide range resistance to GDP. Like V2R receptors, formyl peptide 2 receptors (FPR2) and smoothened receptors (SMOR) formed complexes with G12 heterotrimers that were relatively resistant to GDP. Our results indicate that several GPCRs can form agonist-dependent unproductive complexes with G12 heterotrimers that are relatively resistant to GDP. Suggesting that for some GPCRs agonist-dependent association with G12 heterotrimers is weakly coupled to nucleotide exchange
dc.publisherAugusta University
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.
dc.subjectPharmacology
dc.subjectMolecular biology
dc.subjectG protein coupled receptor (GPCR)
dc.subjectG protein selectivity
dc.subjectGα12 subunits
dc.subjectVasopressin 2 receptor (V2R)
dc.subjectTernary complex model
dc.titleSELECTIVITY AND PRODUCTIVITY OF GPCR-G PROTEIN INTERACTIONS
dc.typeDissertationen_US
dc.typeDissertationen
dc.contributor.departmentDepartment of Pharmacology and Toxicology
dc.language.rfc3066en
dc.date.updated2020-03-04T23:01:49Z
dc.description.advisorLambert, Nevin
dc.description.majorPharmacology
dc.description.committeeWu, Guangyu
dc.description.committeeTerry, Alvin
dc.description.committeeCameron, Richard
dc.description.committeeKim, Il-man
dc.description.committeeBlake, David
dc.description.degreeDoctor of Philosophy (PhD)
refterms.dateFOA2021-04-23T12:22:44Z


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