Post-translational modification of
G-protein coupled receptors (GPCRs) plays a central role in tissue hemostasis and
cancer. The molecular mechanism of post-translational regulation of
protease-activated receptors (PARs), a subgroup of GPCRs is yet understudied. Here we show that the cell-surface transmembrane
E3 ubiquitin ligase ring finger 43 (RNF43) is a negative feedback regulator of PAR2 , impacting PAR2 -induced signaling and
colon cancer growth. RNF43 co-associates with PAR2 , promoting its membrane elimination and degradation as shown by reduced cell surface biotinylated PAR2 levels and polyubiquitination. PAR2 degradation is rescued by R-spondin2 in the presence of
leucine-rich repeat-containing
G-protein-coupled receptor5 (LGR5). In fact, PAR2 acts jointly with LGR5, as recapitulated by increased β-
catenin levels, transcriptional activity, phospho-LRP6, and anchorage-independent colony growth in
agar. Animal models of the chemically induced AOM/DSS
colon cancer of wt versus Par2/f2rl1 KO mice as also the 'spleen-liver'
colon cancer metastasis, allocated a central role for PAR2 in
colon cancer growth and development. RNF43 is abundantly expressed in the Par2/f2rl1 KO-treated AOM/DSS colon tissues while its level is very low to nearly null in
colon cancer adenocarcinomas of the wt mice. The same result is obtained in the 'spleen-liver' model of spleen-inoculated cells, metastasized to the liver. High RNF43 expression is observed in the liver upon
shRNA -Par2 silencing. "Limited-dilution-assay" performed in mice in-vivo, assigned PAR2 as a member of the cancer stem cell niche compartment. Collectively, we elucidate an original regulation of PAR2 oncogene, a member of cancer stem cells, by RNF43
ubiquitin ligase. It impacts β-
catenin signaling and
colon cancer growth.