Low-density lipoprotein receptor-related protein 6 is a novel coreceptor of protease-activated receptor-2 in the dynamics of cancer-associated β-catenin stabilization

// Jeetendra Kumar Nag 1 , Arun Kancharla 1 , Myriam Maoz 1 , Hagit Turm 1 , Daniel Agranovich 1 , Chhedi Lal Gupta 2 , Beatrice Uziely 1 and Rachel Bar-Shavit 1 1 Sharett Institute of Oncology, Hadassah-Hebrew University Medical Center, Jerusalem 91120, Israel 2 Department of Biosciences, Integral University, Lucknow, Uttar Pradesh 226026, India Correspondence to: Rachel Bar-Shavit, email: Rachelbar@ekmd.huji.ac.il Keywords: protease-activated receptors (PARs), protease, G-protein coupled receptors (GPCRs), cancer, β-catenin stabilization Received: April 14, 2016      Accepted: February 17, 2017      Published: March 16, 2017 ABSTRACT Protease-activated receptor-2 (PAR 2 ) plays a central role in cancer; however, the molecular machinery of PAR 2 -instigated tumors remains to be elucidated. We show that PAR 2 is a potent inducer of β-catenin stabilization, a core process in cancer biology, leading to its transcriptional activity. Novel association of low-density lipoprotein-related protein 6 (LRP6), a known coreceptor of Frizzleds ( Fz ), with PAR 2 takes place following PAR 2 activation. The association between PAR 2 and LRP6 was demonstrated employing co-immunoprecipitation, bioluminescence resonance energy transfer (BRET), and confocal microscopy analysis. The association was further supported by ZDOCK protein-protein server. PAR 2 -LRP6 interaction promotes rapid phosphorylation of LRP6, which results in the recruitment of Axin. Confocal microscopy of PAR 2 -driven mammary gland tumors in vivo , as well as in vitro confirms the association between PAR 2 and LRP6. Indeed, sh RNA silencing of LRP6 potently inhibits PAR 2 -induced β-catenin stabilization, demonstrating its critical role in the induced path. We have previously shown a novel link between protease-activated receptor-1 (PAR 1 ) and β-catenin stabilization, both in a transgenic ( tg ) mouse model with overexpression of human PAR 1 ( hPar1 ) in the mammary glands, and in cancer epithelial cell lines. Unlike in PAR 1 -G α13 axis, both G α12 and G α13 are equally involved in PAR 2 -induced β-catenin stabilization. Disheveled (DVL) is translocated to the cell nucleus through the DVL-PDZ domain. Collectively, our data demonstrate a novel PAR 2 -LRP6-Axin interaction as a key axis of PAR 2 -induced β-catenin stabilization in cancer. This newly described axis enhances our understanding of cancer biology, and opens new avenues for future development of anti-cancer therapies.