Orphan G protein-coupled receptor GPRC5A modulates integrin β1-mediated epithelial cell adhesion

Abstract

G-Protein Coupled Receptor (GPCR), Class C, Group 5, Member A (GPRC5A) has been implicated in several malignancies. The underlying mechanisms, however, remain poorly understood. Using a panel of human cell lines, we demonstrate that CRISPR/Cas9-mediated knockout and RNAi-mediated depletion of GPRC5A impairs cell adhesion to integrin substrates: collagens I and IV, fibronectin, as well as to extracellular matrix proteins derived from the Engelbreth-Holm-Swarm (EHS) mouse sarcoma (Matrigel). Consistent with the phenotype, knock-out of GPRC5A correlated with a reduced integrin β1 (ITGB1) protein expression, impaired phosphorylation of the focal adhesion kinase (FAK), and lower activity of small GTPases RhoA and Rac1. Furthermore, we provide the first evidence for a direct interaction between GPRC5A and a receptor tyrosine kinase EphA2, an upstream regulator of FAK, although its contribution to the observed adhesion phenotype is unclear. Our findings reveal an unprecedented role for GPRC5A in regulation of the ITGB1-mediated cell adhesion and it's downstream signaling, thus indicating a potential novel role for GPRC5A in human epithelial cancers.

Genome Editing Provides New Insights into Receptor-Controlled Signalling Pathways

“…(also designated GPR124) from HEK293 cells to allow detailed study of trafficking of variants of this receptor in an Adgra2-'null' cell background. Potential roles of GPRC5A, another 'orphan' GPCR, but part of the class C or glutamate-like receptor subfamily, have also been studied following CPISPR/Cas9-mediated gene targeting in a number of cell lines [14]. These studies indicated an important role for GPRC5A in cell adhesion, and linked this GPCR to the function of integrins via activation of the RhoA and Rac1 small GTPases.…”

“…Regulation of these pathways has also been posited to suggest a role for GPRC5A in cancer progression [14]. Also in a therapeutic context, although the outcomes were predictable because it is well established to act as a co-receptor that allows infection by strains of the human immunodeficiency virus type 1, CPISPR/Cas9-mediated elimination of the chemokine receptor CXCR4 from cells, including human primary CD4 + T cells, was shown to result in resistance to viral entry [15].…”

Adaptive RSK‐EphA2‐GPRC5A signaling switch triggers chemotherapy resistance in ovarian cancer

“…In adhesion-dependent signaling, EphA2 cooperates with integrins, the transmembrane receptors that link the ECM to cell cytoskeleton (Hamidi & Ivaska, 2018). Moreover, the G-protein coupled receptor Class C, Group 5, Member A (GPRC5A) has been identified as an interactor of EphA2 and b1integrin (Bulanova et al, 2017). While tumor-suppressive and oncogenic functions have been reported for this orphan receptor, possible GPRC5A functions in OC remain unknown (Zhou & Rigoutsos, 2014).…”

GPRC5A facilitates cell proliferation through cell cycle regulation and correlates with bone metastasis in prostate cancer

“…We found that G protein‐coupled receptor class C group 5 member A (GPRC5A) had the highest differential expression among orphan GPCRs in progressive prostate cancer cells. GPRC5A is classified into GPCR class C group 5 member A that can be induced by retinoic acid stimulation and are important for embryonic development, differentiation, tumorigenesis and maintenance of epithelial homeostasis . GPRC5A participates in lung tissue homeostasis, and is expressed in pulmonary epithelial cells .…”

“…GPRC5A is classified into GPCR class C group 5 member A that can be induced by retinoic acid stimulation and are important for embryonic development, differentiation, tumorigenesis and maintenance of epithelial homeostasis. 15,16 GPRC5A participates in lung tissue homeostasis, and is expressed in pulmonary epithelial cells. 16 Several reports showed that GPRC5A expression is increased in pancreatic cancer, colon cancer, breast cancer and myelodysplastic syndrome.…”