Collagen VI Is a Gi-Biased Ligand of the Adhesion GPCR GPR126/ADGRG6.

GPR126/ADGRG6, a member of the adhesion G-protein-coupled receptor family, balances cell differentiation and proliferation through fine-tuning of intracellular cAMP levels, which is achieved through coupling to Gs and Gi proteins. While GPR126-mediated cAMP increase has been proven to be essential for differentiation of Schwann cells, adipocytes and osteoblasts, Gi-signaling of the receptor was found to propagate breast cancer cell proliferation. Extracellular ligands or mechanical forces can modulate GPR126 activity but require an intact encrypted agonist sequence, coined the .

The role of ADGRE5/CD97 in human retinal pigment epithelial cell growth and survival.

Cell surface molecules of retinal pigment epithelial (RPE) cells participate in the pathogenesis of retinal diseases. In an attempt to identify cell surface proteins that play a role in RPE cell-cell interactions, we have considered studying the expression, regulation, and signaling of ADGRE5/CD97, an adhesion G protein-coupled receptor family member, based on its known adhesive function in other cell types such as leukocytes. We showed that RPE cells express three isoforms of CD97 and identified inflammation-related cytokines as important mediators regulating CD97 expression.

Activation of Adhesion G Protein-coupled Receptors: AGONIST SPECIFICITY OF STACHEL SEQUENCE-DERIVED PEPTIDES.

Members of the adhesion G protein-coupled receptor (aGPCR) family carry an agonistic sequence within their large ectodomains. Peptides derived from this region, called the sequence, can activate the respective receptor. As the conserved core region of the sequence is highly similar between aGPCRs, the agonist specificity of sequence-derived peptides was tested between family members using cell culture-based second messenger assays.

A tethered agonist within the ectodomain activates the adhesion G protein-coupled receptors GPR126 and GPR133.

Adhesion G protein-coupled receptors (aGPCRs) comprise the second largest yet least studied class of the GPCR superfamily. aGPCRs are involved in many developmental processes and immune and synaptic functions, but the mode of their signal transduction is unclear. Here, we show that a short peptide sequence (termed the Stachel sequence) within the ectodomain of two aGPCRs (GPR126 and GPR133) functions as a tethered agonist.