CUX1 Transcription Factor Is a Downstream Effector of the Proteinase- activated Receptor 2 (PAR2)

Proteinase-activated receptors (PARs) are G-protein-coupled receptors that have been linked to an array of cellular processes, including inflammation, migration, and proliferation. Although signal transduction downstream of PARs has been actively investigated, little is known about the mechanisms that lead to changes in transcriptional programs. Here we show that the CUX1 homeodomain protein is a downstream effector of PAR(2). Treatment of epithelial and fibroblastic cells with trypsin or the PAR(2)-activating peptide (PAR(2)-AP) caused a rapid increase in CUX1 DNA binding activity. The stimulation of CUX1 was specific to PAR(2) because no effect was observed with thrombin or the PAR(1)-AP. Using a panel of recombinant CUX1 proteins, the regulation was found to involve the cut repeat 3 (CR3) and the cut homeodomain, two DNA binding domains that are present in all CUX1 isoforms. Expression analysis in cux1(-/-) mouse embryo fibroblasts led to the identification of three genes that are regulated downstream of both PAR(2) and CUX1 as follows: interleukin-1 alpha, matrix metalloproteinase-10, and cyclo-oxygenase-2. p110CUX1 was able to activate each of these genes, both in reporter assays and following the infection of cells. Moreover, the treatment of Hs578T breast tumor cells with trypsin led to a rapid recruitment of p110 CUX1 to the promoter of these genes and to a concomitant increase in their mRNA steady-state levels. Altogether, these results suggest a model whereby activation of PAR(2) triggers a signaling cascade that culminates with the stimulation of p110 CUX1 DNA binding and the transcriptional activation of target genes.