Orphan G-Protein Coupled Receptor GPRC5B Is Critical for Lymphatic Development

• Published in: International journal of molecular sciences 2022-05, Vol.23 (10), p.5712
• Main Authors: Xu, Wenjing, Nelson-Maney, Nathan P, Bálint, László, Kwon, Hyouk-Bum, Davis, Reema B, Dy, Danielle C M, Dunleavey, James M, St Croix, Brad, Caron, Kathleen M
• Format: Article
• Language: English
• Subjects: Animals; cardiac lymphatics; Cell proliferation; Cells, Cultured; Compression therapy; Danio rerio; Edema; Embryos; Endothelial cells; Endothelial Cells - metabolism; G protein-coupled receptors; Gene expression; Genetic engineering; Genomes; GPRC5B; Hemorrhage; Hydrops fetalis; Ligands; Localization; lymphangiogenesis; lymphatic; Lymphatic system; Lymphedema; Mice; mRNA; orphan G protein-coupled receptors; Orphan receptors; Proteins; Receptor mechanisms; Receptors, G-Protein-Coupled - metabolism; Signal Transduction; Thoracic duct; Veins & arteries; Weaning; Zebrafish; Zebrafish - genetics; Zebrafish - metabolism
• ISSN: 1422-0067; 1661-6596; 1422-0067
• DOI: 10.3390/ijms23105712

Numerous studies have focused on the molecular signaling pathways that govern the development and growth of lymphatics in the hopes of elucidating promising druggable targets. G protein-coupled receptors (GPCRs) are currently the largest family of membrane receptors targeted by FDA-approved drugs, but there remain many unexplored receptors, including orphan GPCRs with no known biological ligand or physiological function. Thus, we sought to illuminate the cadre of GPCRs expressed at high levels in lymphatic endothelial cells and identified four orphan receptors: GPRC5B, AGDRF5/GPR116, FZD8 and GPR61. Compared to blood endothelial cells, GPRC5B is the most abundant GPCR expressed in cultured human lymphatic endothelial cells (LECs), and in situ RNAscope shows high mRNA levels in lymphatics of mice. Using genetic engineering approaches in both zebrafish and mice, we characterized the function of GPRC5B in lymphatic development. Morphant zebrafish exhibited failure of thoracic duct formation, and mice suffered from embryonic hydrops fetalis and hemorrhage associated with subcutaneous edema and blood-filled lymphatic vessels. Compared to littermate controls, embryos exhibited attenuated developmental lymphangiogenesis. During the postnatal period, ~30% of mice were growth-restricted or died prior to weaning, with associated attenuation of postnatal cardiac lymphatic growth. In cultured human primary LECs, expression of GPRC5B is required to maintain cell proliferation and viability. Collectively, we identify a novel role for the lymphatic-enriched orphan GPRC5B receptor in lymphangiogenesis of fish, mice and human cells. Elucidating the roles of orphan GPCRs in lymphatics provides new avenues for discovery of druggable targets to treat lymphatic-related conditions such as lymphedema and cancer.