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J Biol Chem. 2019 Dec 13;294(50):19246-19254. doi: 10.1074/jbc.RA119.008234. Epub 2019 Oct 18.

GAIN domain-mediated cleavage is required for activation of G protein-coupled receptor 56 (GPR56) by its natural ligands and a small-molecule agonist.

Author information

1
Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research, Weill Institute of Neuroscience, University of California, San Francisco, California 94143.
2
Department of Medicine, Children's Hospital and Harvard Medical School, Boston, Massachusetts 02115.
3
Vollum Institute, Oregon Health and Science University, Portland, Oregon 97239.
4
Department of Pharmaceutical Chemistry and Quantitative Biology Institute, University of California, San Francisco, California 94143.
5
Eli and Edythe Broad Center of Regeneration Medicine and Stem Cell Research, Weill Institute of Neuroscience, University of California, San Francisco, California 94143 xianhua.piao@ucsf.edu.
6
Division of Neonatology, Department of Pediatrics, University of California, San Francisco, California 94158.
7
Newborn Brain Research Institute, University of California, San Francisco, California 94158.

Abstract

Adhesion G protein-coupled receptors (aGPCRs) represent a distinct family of GPCRs that regulate several developmental and physiological processes. Most aGPCRs undergo GPCR autoproteolysis-inducing domain-mediated protein cleavage, which produces a cryptic tethered agonist (termed Stachel (stinger)), and cleavage-dependent and -independent aGPCR signaling mechanisms have been described. aGPCR G1 (ADGRG1 or G protein-coupled receptor 56 (GPR56)) has pleiotropic functions in the development of multiple organ systems, which has broad implications for human diseases. To date, two natural GPR56 ligands, collagen III and tissue transglutaminase (TG2), and one small-molecule agonist, 3-α-acetoxydihydrodeoxygedunin (3-α-DOG), have been identified, in addition to a synthetic peptide, P19, that contains seven amino acids of the native Stachel sequence. However, the mechanisms by which these natural and small-molecule agonists signal through GPR56 remain unknown. Here we engineered a noncleavable receptor variant that retains signaling competence via the P19 peptide. We demonstrate that both natural and small-molecule agonists can activate only cleaved GPR56. Interestingly, TG2 required both receptor cleavage and the presence of a matrix protein, laminin, to activate GPR56, whereas collagen III and 3-α-DOG signaled without any cofactors. On the other hand, both TG2/laminin and collagen III activate the receptor by dissociating the N-terminal fragment from its C-terminal fragment, enabling activation by the Stachel sequence, whereas P19 and 3-α-DOG initiate downstream signaling without disengaging the N-terminal fragment from its C-terminal fragment. These findings deepen our understanding of how GPR56 signals via natural ligands, and a small-molecule agonist may be broadly applicable to other aGPCR family members.

KEYWORDS:

3-α-DOG; ADGRG1/GPR56; G protein–coupled receptor (GPCR); GPCR autoproteolysis-inducing (GAIN) domain; TG2; cell signaling; collagen; development; shedding; tethered agonist

PMID:
31628191
PMCID:
PMC6916468
[Available on 2020-12-13]
DOI:
10.1074/jbc.RA119.008234

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