Crosstalk between Protease-activated Receptor 1 and Platelet-activating Factor Receptor Regulates Melanoma Cell Adhesion Molecule (MCAM/MUC18) Expression and Melanoma Metastasis

Abstract

The cellular and molecular pathways that regulate platelet activation, blood coagulation, and inflammation are emerging as critical players in cancer progression and metastasis. Here, we demonstrate a novel signaling mechanism whereby proteaseactivated receptor 1 (PAR1) mediates expression of melanoma cell adhesion molecule MCAM/MUC18 (MUC18), a critical marker of melanoma metastasis, via activation of platelet-activating factor receptor (PAFR) and cAMP-responsive elementbinding protein (CREB). We found that PAR1 silencing with small hairpin RNA inhibits MUC18 expression in metastatic melanoma cells by inhibiting CREB phosphorylation, activity, and binding to the MUC18 promoter. We further demonstrate that the PAF/PAFR pathway mediates MUC18 expression downstream of PAR1. Indeed, PAR1 silencing down-regulates PAFR expression and PAF production, PAFR silencing blocks MUC18 expression, and re-expression of PAFR in PAR1-silenced cells rescues MUC18 expression. We further demonstrate that the PAR1-PAFR-MUC18 pathway mediates melanoma cell adhesion to microvascular endothelial cells, transendothelial migration, and metastatic retention in the lungs. Rescuing PAFR expression in PAR1-silenced cells fully restores metastatic phenotype of melanoma, indicating that PAFR plays critical role in the molecular mechanism of PAR1 action. Our results link the two pro-inflammatory G-proteincoupled receptors, PAR1 and PAFR, with the metastatic dissemination of melanoma and suggest that PAR1, PAFR, and MUC18 are attractive therapeutic targets for preventing melanoma metastasis.

Increased Expression of Matrix Metalloproteinase-1 in Systemic Vessels of Preeclamptic Women

“…This G protein-coupled receptor plays a major role in orchestrating the interaction between coagulation and inflammation. 54 The PAR-1 is a tethered ligand receptor that is activated by proteolytic cleavage of its extracellular domain. 55 Activating proteases include thrombin, trypsin, factor Xa, factor XIIa/X, 56 and MMP-1.…”

Melanoma-Induced Endothelial Cell Growth Involves Phospholipase A2 and COX2 Upregulation

“…In addition, transcription factors CREB/ATF-1 and ATF-2 are upregulated in these cells. The expression of genes involved in angiogenesis, invasion and apoptosis such as bFGF, IL-8, EGF-R, PAR-1 correlates with higher metastatic potential of human melanoma cells (Melnikova et al, 2009) (Fig. 1).…”

GIV/Girdin is a rheostat that fine-tunes growth factor signals during tumor progression

“…The first complexity concerns the fact that most cellular processes like migration, proliferation, differentiation, apoptosis or survival can be driven by more than one receptor or one class of receptors and most of the time requires synergistic signaling of diverse classes of receptors simultaneously in response to a single trigger. [61][62][63][64][65][66][67][68] For example, both growth factor and GPCRs can trigger cell migration. 69 This phenomenon by which receptors can transactivate each other at the cell-surface is referred to as receptor-crosstalk.…”

“…[61][62][63][64][65][66][67][68] Unrestricted signaling due to recruitment of multiple receptors via cross-talk is felt to be critical in driving many pathological processes, e.g., cancer invasion, 67,70-79 fibrogenesi [80][81][82][83] and inflammation. 62,[84][85][86][87] Thus, it appears that there might be decisive points in the cascade of signaling dominos where via its C-terminal PDZ motif. 44 Similarly, GIPIE/FLJ00354 has been recently reported to regulate the ER stress response by interacting with GPR78 also via its C-terminal domain.…”