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Author Notes:

To whom correspondence should be addressed: Randy Hall, Emory University School of Medicine, Dept. of Pharmacology, 1510 Clifton Road NE, Atlanta, GA 30322. E-mail: rhall3@emory.edu.

Ayush Kishore and Ryan Purcell contributed equally to this work.

A. K., R. H. P., and R. A. H. designed the experiments and wrote the manuscript.

AK performed the experiments focused on ADGRG1 as well as the TGFα shedding assays focused on ADGRB1.

R. H. P. and Z. N. T. performed all other experiments focused on ADGRB1.

A. K., R. H. P., and R. A. H. analyzed the data and created the figures.

We thank Michelle Giddens (Emory University) for helpful comments about this work and Tohru Kozasa (University of Illinois, Chicago), Keqiang Ye (Emory University) and Shigeki Higashiyama (Ehime University) for kindly providing constructs to facilitate these studies.

The authors declare that they have no conflicts of interest with the contents of this article.

The content is solely the responsibility of the authors and does not necessarily represent the official views of the National Institutes of Health.


Research Funding:

This work was supported by Grant R01 NS072394 from the National Institutes of Health (to R. A. H.), NIH Training Grant T32 GM008602 (to A. K.), and NIH Training Grant T32 GM008605 (to R. H. P.).


  • Science & Technology
  • Life Sciences & Biomedicine
  • Biochemistry & Molecular Biology
  • arrestin
  • G protein-coupled receptor (GPCR)
  • proteolysis
  • receptor structure-function
  • signal transduction
  • ubiquitylation (ubiquitination)

Stalk-dependent and Stalk-independent Signaling by the Adhesion G Protein-coupled Receptors GPR56 (ADGRG1) and BAI1 (ADGRB1)


Journal Title:

Journal of Biological Chemistry


Volume 291, Number 7


, Pages 3385-3394

Type of Work:

Article | Final Publisher PDF


The adhesion G protein-coupled receptors (aGPCRs) are a large yet poorly understood family of seven-transmembrane proteins. A defining characteristic of the aGPCR family is the conserved GAIN domain, which has autoproteolytic activity and can cleave the receptors near the first transmembrane domain. Several aGPCRs, including ADGRB1 (BAI1 or B1) and ADGRG1 (GPR56 or G1), have been found to exhibit significantly increased constitutive activity when truncated to mimic GAIN domain cleavage (ΔNT). Recent reports have suggested that the new N-terminal stalk, which is revealed by GAIN domain cleavage, can directly activate aGPCRs as a tethered agonist. We tested this hypothesis in studies on two distinct aGPCRs, B1 and G1, by engineering mutant receptors lacking the entire NT including the stalk (B1- and G1-SL, with "SL" indicating "stalk-less"). These receptors were evaluated in a battery of signaling assays and compared with full-length wild-type and cleavage-mimicking (ΔNT) forms of the two receptors. We found that B1-SL, in multiple assays, exhibited robust signaling activity, suggesting that the membrane-proximal stalk region is not necessary for its activation. For G1, however, the results were mixed, with the SL mutant exhibiting robust activity in several signaling assays (including TGFα shedding, activation of NFAT luciferase, and β-arrestin recruitment) but reduced activity relative to ΔNT in a distinct assay (activation of SRF luciferase). These data support a model in which the activation of certain pathways downstream of aGPCRs is stalk-dependent, whereas signaling to other pathways is stalk-independent.

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© 2016 by The American Society for Biochemistry and Molecular Biology, Inc.

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