Elevated expression of the adhesion GPCR ADGRL4/ELTD1 promotes endothelial sprouting angiogenesis without activating canonical GPCR signalling

Journal article

ADGRL4/ELTD1 is an orphan adhesion GPCR (aGPCR) expressed in endothelial cells that regulates tumour angiogenesis. The majority of aGPCRs are orphan receptors. The Stachel Hypothesis proposes a mechanism for aGPCR activation, in which aGPCRs contain a tethered agonist (termed Stachel) C-terminal to the GPCR-proteolytic site (GPS) cleavage point which, when exposed, initiates canonical GPCR signalling. This has been shown in a growing number of aGPCRs. We tested this hypothesis on ADGRL4/ELTD1 by designing full length (FL) and C-terminal fragment (CTF) ADGRL4/ELTD1 constructs, and a range of potential Stachel peptides. Constructs were transfected into HEK293T cells and HTRF FRET, luciferase-reporter and Alphascreen GPCR signalling assays were performed. A stable ADGRL4/ELTD1 overexpressing HUVEC line was additionally generated and angiogenesis assays, signalling assays and transcriptional profiling were performed. ADGRL4/ELTD1 has the lowest GC content in the aGPCR family and codon optimisation significantly increased its expression. FL and CTF ADGRL4/ELTD1 constructs, as well as Stachel peptides, did not activate canonical GPCR signalling. Furthermore, stable overexpression of ADGRL4/ELTD1 in HUVECs induced sprouting angiogenesis, lowered in vitro anastomoses, and decreased proliferation, without activating canonical GPCR signalling or MAPK/ERK, PI3K/AKT, JNK, JAK/HIF-1α, beta catenin or STAT3 pathways. Overexpression upregulated ANTXR1, SLC39A6, HBB, CHRNA, ELMOD1, JAG1 and downregulated DLL4, KIT, CCL15, CYP26B1. ADGRL4/ELTD1 specifically regulates the endothelial tip-cell phenotype through yet undefined signalling pathways.

Authors: Favara, DM; Liebscher, I; Jazayeri, A; Nambiar, M; Sheldon, H

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Nature Research
• Journal: Scientific Reports
• Volume: 11
• Issue: 1
• Pages: 8870-8870
• Article number: 8870
• Publication date: 2021-04-23
• DOI: 10.1038/s41598-021-85408-x
• EISSN: 2045-2322
• ISSN: 2045-2322
• Language: English
• Keywords: Chemistry; Biology; G protein-coupled receptor; Sprouting angiogenesis; Cell adhesion; Adhesion; Cancer research; Neovascularization; Signal transduction; Non canonical; Angiogenesis; Cell biology; Signalling