Mammary gland tissue targeted overexpression of human protease-activated receptor 1 reveals a novel link to beta-catenin stabilization.
Protease-activated receptor 1 (PAR1) is emerging with distinct assignments in tumor biology. We show that tissue targeted overexpression of hPar1 in mice mammary glands results in precocious hyperplasia, characterized by a dense network of ductal side branching and accelerated proliferation. These glands exhibit increased levels of wnt-4 and wnt-7b and a striking beta-catenin stabilization. Nuclear localization of beta-catenin is observed in hPar1 transgenic mouse tissue sections but not in the wild-type, age-matched counterparts. PAR1 induces beta-catenin nuclear localization also in established epithelial tumor cell lines of intact beta-catenin system (transformed on the background of mismatch repair system; RKO cells). We propose hereby that PAR1-mediated beta-catenin stabilization is taking place primarily via the increase of Wnt expression. Enforced expression of a specific Wnt antagonist family member, secreted frizzled receptor protein 5 (SFRP5), efficiently inhibited PAR1-induced beta-catenin stabilization. Likewise, application of either SFRP2 or SFRP5 on epithelial tumor cells completely abrogated PAR1-induced beta-catenin nuclear accumulation. This takes place most likely via inhibition of Wnt signaling at the level of cell surface (forming a neutralizing complex of "Receptors-SFRP-Wnt"). Furthermore, depletion of hPar1 by small interfering RNA (siRNA) vectors markedly inhibited PAR1-induced Wnt-4. The striking stabilization of beta-catenin, inhibited by SFRPs on one hand and Wnt-4 silencing by hPar1 siRNA on the other hand, points to a novel role of hPar1 in Wnt-mediated beta-catenin stabilization. This link between PAR1 and beta-catenin may bear substantial implications both in developmental and tumor progression processes.
Yin
Yong-Jun
YJ
Department of Oncology, Hadassah-Hebrew University Hospital, Jerusalem, Israel.
Katz
Vered
V
Salah
Zaidoun
Z
Maoz
Myriam
M
Cohen
Irit
I
Uziely
Beatrice
B
Turm
Hagit
H
Grisaru-Granovsky
Sorina
S
Suzuki
Hiromu
H
Bar-Shavit
Rachel
R
D048868:Adaptor Proteins, Signal Transducing; D000818:Animals; D005260:Female; D020868:Gene Silencing; D006023:Glycoproteins / Q000096:biosynthesis / Q000235:genetics; D006801:Humans; D006965:Hyperplasia / Q000235:genetics / Q000378:metabolism; D036341:Intercellular Signaling Peptides and Proteins / Q000096:biosynthesis / Q000235:genetics; D008297:Male; D008321:Mammary Glands, Animal / Q000378:metabolism* / Q000473:pathology; D008565:Membrane Proteins / Q000096:biosynthesis / Q000235:genetics; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D011518:Proto-Oncogene Proteins / Q000096:biosynthesis / Q000235:genetics; D034741:RNA, Small Interfering / Q000235:genetics; D044463:Receptor, PAR-1 / Q000096:biosynthesis* / Q000235:genetics; D051153:Wnt Proteins / Q000096:biosynthesis / Q000235:genetics; D060528:Wnt4 Protein; D051176:beta Catenin / Q000378:metabolism*; D010975:Platelet Aggregation Inhibitors; D000094742:Secreted Frizzled-Related Proteins
D048868:Adaptor Proteins, Signal Transducing; D006023:Glycoproteins; D036341:Intercellular Signaling Peptides and Proteins; D008565:Membrane Proteins; D011518:Proto-Oncogene Proteins; D034741:RNA, Small Interfering; D044463:Receptor, PAR-1; D051153:Wnt Proteins; D060528:Wnt4 Protein; D051176:beta Catenin; D010975:Platelet Aggregation Inhibitors; C491628:Sfrp2 protein, mouse; D000094742:Secreted Frizzled-Related Proteins; C487972:Sfrp5 protein, mouse; C555581:WNT4 protein, human; C555582:Wnt4 protein, mouse; C095937:Wnt7b protein, mouse