Mechanisms of dominant negative G‐protein α subunits

Abstract

G-protein-coupled receptors (GPCRs) represent the largest class of membrane proteins and are the targets of 25-50% of drugs currently on the market. Dominant negative mutant Galpha subunits of heterotrimeric G-proteins have been extensively utilized to delineate G-protein signaling pathways and represent a promising new tool to study GPCR-dependent signaling in the CNS. There are different regions in various types of Galpha subunits in which mutations can give rise to a dominant negative phenotype. Such a mutant Galpha would compete with wild-type Galpha for binding to other proteins involved in the G-protein cycle and either block or reduce the response caused by wild-type Galpha. To date, there are three different mechanisms described for dominant negative Galpha subunits: sequestration of the Gbetagamma subunits, sequestration of the activated GPCR by the heterotrimeric complex, and sequestration of the activated GPCR by nucleotide-free Galpha. This review focuses on the development of dominant negative Galpha subunits, the different mechanisms used by various mutant Galpha subunits, and potential structural changes underlying the dominant negative effects.

Novel variants in GNAI3 associated with auriculocondylar syndrome strengthen a common dominant negative effect

“…11 Although it was speculated that p.(Gly40Arg) modified the conformation of a portion of the protein that interacts with downstream effectors, resulting in a gain-of-function protein, 5 we suggest rather that all GNAI3 variants may disrupt GDP/GTP binding (directly or indirectly) without disrupting the overall structure of the protein, thereby resulting in dominant negative effects, perhaps via sequestration of GNAI3's cognate beta-gamma G protein subunits or G protein-coupled receptor, as has been shown for other G-alpha proteins. 12 Supporting this idea, the equivalent variant to GNAI3 p.(Asn269Tyr) in the G4 box of HRAS (p.Asn116Tyr) shows a dominant negative effect, inhibiting GTP binding activity and proliferation, and causing induction of apoptosis in human cancer cell lines. 13,14 Similarly, the previously published p.(Ser47Arg) GNAI3 variant is predicted to be a dominant negative, based on the dominant negative action of other G proteins and RAS family members with a variant of the equivalent residue.…”

Ca2+-dependent GTPase, Extra-large G Protein 2 (XLG2), Promotes Activation of DNA-binding Protein Related to Vernalization 1 (RTV1), Leading to Activation of Floral Integrator Genes and Early Flowering in Arabidopsis

“…The G-1 to G-3 domains of G proteins provide critical contacts for the ␣-, ␤-, and ␥-phosphates of the guanine nucleotide and also for the coordination of Mg 2ϩ (50). The G-4 and G-5 domains are important for the binding of the guanine ring (50). XLG2 has the conserved amino acid motifs in the G-1, G-2, and G-4 regions.…”

“…XLG2 has the conserved amino acid motifs in the G-1, G-2, and G-4 regions. XLG2 utilizes Ca 2ϩ but not Mg 2ϩ as a cofactor although it has the well conserved threonine residue in the G-2 region (Table 1), which plays a critical role in coordinating Mg 2ϩ (50). However, XLG proteins do not have the conserved motifs of the G-3 and G-5 regions (21) ( Table 1).…”

Illuminating the activation mechanisms and allosteric properties of metabotropic glutamate receptors

“…7A). To improve the coupling between Gα o and mGlu2, we used the Gα o mutant G203T known to have a low affinity for both GDP and GTP and resulting in a stabilization of the Gα empty state that displays dominant negative properties (39). The coexpression of this G-protein mutant alone (SI Appendix, Fig.…”