*Sorina Grisaru-Granovsky, Arun Kancharla, Mohammad Jaber,
Miriam Maoz, Rachel Bar-Shavit.
Sharett -Institute of Oncology and *Department of Obstetrics and Gynecology, Shaare-Zedek and Hadassah Hebrew University Medical Centers, Jerusalem, Israel
Although the emerging roles of protease- activated receptors1 and 2 (PAR1 &PAR2) in throphoblast invasion and tumor biology is recognized, the underlying signaling events they employ are poorly addressed. We demonstrate here that as shown for PAR1, pleckstrin-homology (PH) domain association with Etk/Bmx is also an early-event in PAR2 signaling. Priority is rendered to Etk/Bmx and only upon its absence other signal proteins associate. We have identified the minimal PH-domain binding site of PAR2 C-tail. Mutants inserted to this site abrogated this association. The significance of PAR2 PH-domain site is demonstrated by the PAR2 C-tail mutants R352A and H349R, incapable of associating with the PH-domain Etk/Bmx. The physiological significance is demonstrated via the inability to induce tumor growth in vivo and inhibition of placenta extravillous-trophoblast invasion in an organ culture. Quantification of EVT outgrowth cell number at 60 mm depth of invasion as shown by histogram mean values. Cells (not the villous compartment) were counted per high power field and expressed as mean + SEM. C. RT-PCR analyses of PAR1 and PAR2 in the cultured EVTs. GAPDH levels were analyzed as a control. Post hoc evaluation of multiple comparison (ANOVA Tukey HSD) showed a p value of 0.0001 within groups. The mean difference is significant at the 0.05 level. These results underscore the importance PAR1&2 PH-domain in tumor growth and early physiological trophoblast invasion into the uterus.