GPR56/ADGRG1 induces biased Rho-ROCK-MLC and JAK-STAT3 signaling to promote amoeboid-like morphology and IL-6 upregulation in melanoma cells

Background: GPR56/ADGRG1 is an adhesion G protein-coupled receptor involved in cell-matrix interactions and metastasis of human melanoma cells. Previously, we demonstrated that GPR56 activation in melanoma cells triggers Gα_12/13-RhoA signaling, leading to increased IL-6 production and enhanced cell migration. Yet little is known of the downstream signaling effectors and their specific roles in regulating melanoma cellular phenotypes. Results: In this study, we show that GPR56 activation induces Rho-ROCK-MLC and JAK-STAT3 signaling, which temporally and differentially drive amoeboid-like morphology and IL-6 upregulation. Interestingly, GPR56-induced JAK-STAT3 activation is partially regulated by Rho-ROCK-MLC signaling but not vice versa. Moreover, receptor auto-proteolysis modulates the magnitude of GPR56-mediated signaling, and its unique intracellular regions contribute to the selective regulation of unique signaling pathways and associated cellular phenotypes. Conclusion: Our findings reveal complex GPR56-mediated biased signaling through the Rho-ROCK-MLC and JAK-STAT3 pathways, highlighting these networks as potential therapeutic targets for modulating distinct tumorigenic phenotypes in human melanoma cells.