Disease-associated extracellular loop mutations in the adhesion G protein-coupled receptor G1 (ADGRG1; GPR56) differentially regulate downstream signaling.

Abstract

Mutations to the adhesion G protein-coupled receptor ADGRG1 (G1; also known as GPR56) underlie the neurological disorder bilateral frontoparietal polymicrogyria. Disease-associated mutations in G1 studied to date are believed to induce complete loss of receptor function through disruption of either receptor trafficking or signaling activity. Given that N-terminal truncation of G1 and other adhesion G protein-coupled receptors has been shown to significantly increase the receptors' constitutive signaling, we examined two different bilateral frontoparietal polymicrogyria-inducing extracellular loop mutations (R565W and L640R) in the context of both full-length and N-terminally truncated (ΔNT) G1. Interestingly, we found that these mutations reduced surface expression of full-length G1 but not G1-ΔNT in HEK-293 cells. Moreover, the mutations ablated receptor-mediated activation of serum response factor luciferase, a classic measure of Gα12/13-mediated signaling, but had no effect on G1-mediated signaling to nuclear factor of activated T cells (NFAT) luciferase. Given these differential signaling results, we sought to further elucidate the pathway by which G1 can activate NFAT luciferase. We found no evidence that ΔNT activation of NFAT is dependent on Gαq/11-mediated or β-arrestin-mediated signaling but rather involves liberation of Gβγ subunits and activation of calcium channels. These findings reveal that disease-associated mutations to the extracellular loops of G1 differentially alter receptor trafficking, depending on the presence of the N terminus, and differentially alter signaling to distinct downstream pathways.

• Authors: Ayush Kishore, Randy A Hall
• Journal: The Journal of biological chemistry (J Biol Chem) Vol. 292 Issue 23 Pg. 9711-9720 (06 09 2017) ISSN: 1083-351X [Electronic] United States
• PMID: 28424266 (Publication Type: Journal Article)
• Copyright: © 2017 by The American Society for Biochemistry and Molecular Biology, Inc.

Chemical References

• ADGRG1 protein, human
• ARRB1 protein, human
• GTP-Binding Protein beta Subunits
• GTP-Binding Protein gamma Subunits
• Receptors, G-Protein-Coupled
• beta-Arrestin 1
• GTP-Binding Protein alpha Subunits, G12-G13

Topics

• Amino Acid Substitution
• Cell Line
• GTP-Binding Protein alpha Subunits, G12-G13 (genetics, metabolism)
• GTP-Binding Protein beta Subunits (genetics, metabolism)
• GTP-Binding Protein gamma Subunits (genetics, metabolism)
• Humans
• Malformations of Cortical Development (genetics, metabolism, pathology)
• Mutation, Missense
• Protein Structure, Secondary
• Protein Transport (genetics)
• Receptors, G-Protein-Coupled (genetics, metabolism)
• Signal Transduction
• beta-Arrestin 1 (genetics, metabolism)