Premium
Paks integrate polarity and vesicle transport signaling in ovarian epithelial cancers
Author(s) -
Radu Maria,
Mumber Hannah,
Chernoff Jonathan
Publication year - 2016
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.30.1_supplement.lb90
Subject(s) - pak1 , microbiology and biotechnology , cell polarity , kinase , biology , effector , signal transduction , cell signaling , actin cytoskeleton , vesicular transport protein , vesicle , cell , cytoskeleton , chemistry , biochemistry , membrane
P21 activated kinases (Paks) are effectors for small RhoGTPases and have been widely implicated in regulation of cytoskeleton arrangements and cell architecture. Paks gained a lot of momentum when several members of the family have been shown to be over‐expressed in a variety of cancers, including ovarian, breast, prostate and colon. These discoveries led to augmented efforts to discover new and improved Pak inhibitors to be used in clinic. Recent data shows however that the absence or complete inhibition of Pak2 leads to lethality in adult animals. It is thus imperative that we have a better understanding of Pak regulated pathways and their direct substrates. In an effort to unveil new molecular efforts in Pak signaling, we employed a modified kinase assay in conjuncture with peptide identification by LC/MS. A high percentage of the newly discovered Pak substrates fell in the category of molecules that control cell communication. Cell communication relates to all modes of inter and intra cell messaging, including cytoskeleton arrangement and vesicle transport. Importantly, these are also key elements that when deregulated lead to epithelial cancer initiation and progression. Among the newly identified Pak direct targets that regulate cell communication CDK16 and NSF have been previously shown to regulate each other and together to control polarity and vesicle transport respectively. We found that Pak1 and Pak2 phosphorylate CDK16 at S119 and NSF at S207. Our data has shown that unphosphorylatable CDK16 mutants are unable to bind Pak1 and 2 and that inactive Paks do not bind CDK16. This suggests that functional protein complexes are formed between CDK16 and Pak1 and 2. Furthermore, we found that in an ovarian carcinoma cell line overexpression of an unphosphorylatable CDK16 mutants can induce stress fiber and focal adhesion disassembly (link to deregulated polarity), while a CDK16 mutant that mimics a constitutively phosphorylated state can partially rescue stress fiber disassembly induced by Pak inhibition. These data strengthen our hypothesis that Paks regulate epithelial cancer progression by phosphorylating CDK16 and NSF, proteins that integrate polarity and vesicle trafficking pathways. To confirm this hypothesis we will first investigate the temporal and spatial regulatory events that take place between Pak, CDK16 and NSF and how these events influence polarity and vesicle transport. Secondly, we will investigate how the dis regulation of Pak/CDK16/NSF pathway leads to epithelial cancer initiation and spread. Thirdly, we will consider the possibility of combining Pak and CDK16 inhibition to arrest the growth various epithelial carcinomas. Our results address the possibility to target Pak signaling in Pak overexpressing cancers by inhibiting CDK16, a downstream kinase effector and to override some of the critical effects of current Pak inhibitors. Support or Funding Information NIH T32 Training grant; NCI CA06927 to Fox Chase Cancer Center