Dominant-negative Gα subunits are a mechanism of dysregulated heterotrimeric G protein signaling in human disease

Abstract

Auriculo-Condylar Syndrome (ACS), a rare condition that impairs craniofacial development, is caused by mutations in a G protein-coupled receptor (GPCR) signaling pathway. In mice, disruption of signaling by the endothelin type A receptor (ETAR), which is mediated by the G protein subunit Gαq/11 and subsequently phospholipase C (PLC), impairs neural crest cell differentiation that is required for normal craniofacial development. Some ACS patients have mutations in GNAI3, which encodes Gαi3, but it is unknown whether this G protein has a role within the ETAR pathway. Here, we used a Xenopus model of vertebrate development, in vitro biochemistry, and biosensors of G protein activity in mammalian cells to systematically characterize the phenotype and function of all known ACS-associated Gαi3 mutants. We found that ACS-associated mutations in GNAI3 produce dominant-negative Gαi3 mutant proteins that couple to ETAR but cannot bind and hydrolyze guanosine triphosphate, resulting in the prevention of endothelin-mediated activation of Gαq/11 and PLC. Thus, ACS is caused by functionally dominant-negative mutations in a heterotrimeric G protein subunit.

Regulator of G Protein Signaling Protein 12 (Rgs12) Controls Mouse Osteoblast Differentiation via Calcium Channel/Oscillation and Gαi-ERK Signaling

“…(9,42) Emerging evidence shows that Gai3 mutants with defective GTP binding and lower GTPase activity can block the Gaq-PLC-Ca 2þ signaling pathway by forming an unproductive complex. (50,58) In our work, we also found lower GTPase activity toward Gai after Rgs12 deletion. Yamamura and colleagues (59) reported that Bay K8644 can directly activate CaR, increasing CaR-mediated cytosolic Ca 2þ concentration.…”

“…Activation of CaR, in part through the activation of the classic Gαq‐PLCβ pathway that leads to increased Ca 2+ oscillations, promotes OB proliferation . Emerging evidence shows that Gαi3 mutants with defective GTP binding and lower GTPase activity can block the Gαq‐PLC‐Ca 2+ signaling pathway by forming an unproductive complex . In our work, we also found lower GTPase activity toward Gαi after Rgs12 deletion.…”

The N54-αsMutant Has Decreased Affinity forβγand Suggests a Mechanism for Coupling Heterotrimeric G Protein Nucleotide Exchange with Subunit Dissociation

“…One of the mutations fully characterized was the Ga i3 S47R mutant that, remarkably, is homologous to the N54-a s , albeit an arginine (R) is substituted rather than an asparagine (N). The dominant-negative Ga i3 S47R mutant preferentially binds GDP and sequesters its receptor ET A R from activating G q (Marivin et al, 2016), which is very similar to the way in which N54-a s sequesters the thyroid-stimulating hormone receptor (TSHR) and prevents G q activation (Cleator et al, 2004).…”

“…Just recently, it was discovered that dominant-negative Ga i3 subunits are involved in auriculocondylar syndrome (ACS), a rare condition that impairs craniofacial development. ACS is caused by interference of the endothelin type A receptor (ET A R)/phospholipase Cb (PLCb) pathway that induces genes critical for craniofacial development (Marivin et al, 2016). This conclusion is supported by the finding that knockout of G q or G 11 in mice results in craniofacial features that resemble ACS (Offermanns et al, 1998;Dettlaff-Swiercz et al, 2005).…”

Targeted molecular investigation in patients within the clinical spectrum of Auriculocondylar syndrome

“…Among these individuals, the two families that presented IQME had pathogenic variants in EDN1 [Gordon et al, ]. All the three aforementioned genes have been implicated in the EDN1‐EDNRA pathway (reviewed in [Clouthier et al, ; Marivin et al, ]).…”