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ABSTRACTThe NF2 product, Merlin, has recently been shown to inhibit p21-activated kinases (Paks), enzymes known to activate cell cycle progression and to induce changes in the actin cytoskeleton. These findings suggest that loss of Pak function might inhibit the abnormal growth and/or movement of cells lacking Merlin. We had proposed two aims: to test if loss of all Pak function affects signaling in NF2-/-cells and to test if Paks are required for tumorigenesis in an NF2 mouse model system. In the third year of this project, we published a manuscript describing the first selective small molecule inhibitor of group A Paks; completed crossing NF2 and Pak1-/-mice into a C3H genetic background; used a retroviral vector to express an enhanced Pak inhibitor (the Pak2 inhibitor domain) in normal and NF2 BBA (dominant negative) mutant mouse fibroblasts, and showed that loss of Pak function impedes NF2-driven cell proliferation and abnormal morphology; and used the same approach in xenograft experiments to show that loss of Pak function reduces NF2-induced tumor formation. With these advances, we have matched and in some cases exceeded our timetable for year three. Chernoff, Jonathan 4
INTRODUCTION:The goal of this project is to determine if group A p21-activated kinases (Paks) are important elements in signaling in neurofibromatosis type II (NF2). Our hypothesis is that inactivation of the NF2 gene disrupts a signaling pathway emanating from the small GTPase Rac and its effector, p21-activated kinase (Pak). We propose that stimulation of the Rac/Pak signaling axis in cells lacking Merlin leads to changes in transcriptional activity and cytoskeletal dynamics, ultimately resulting in enhanced cell proliferation and motility, which are hallmarks of tumorigenesis. If this hypothesis is correct, then inhibition of Pak signaling should disable the growth advantages of cells lacking Merlin. We intend to test this theory using Pak loss-of-function cells and animals.
BODY:We s...