) Protein Phosphatase 2A (PP2A) is an important regulator of signal transduction pathways, a target of viral oncoproteins, and a potentially useful target for therapeutic drug design. However, PP2A's broad substrate specificity in vitro has hampered attempts to understand its normal regulation and functionally relevant substrates in vivo. We identified a PR55/B regulatory subunit of Protein Phosphatase 2A (SUR-6 PP2A-B) as a positive modulator of Ras signaling in C. elegans, and our genetic data suggest that SUR-6 acts in a common process with KSR and directs PP2A to a specific Ras pathway substrate. Two mutations in SUR-6 PP2A-B preferentially affect Ras-mediated signaling, with minimal effects on other SUR-6- or PP2A-regulated processes. We will use C. elegans vulva development as a genetic model system to elucidate how PP2A-B subunits regulate PP2A catalytic activity and/or substrate specificity, and how PP2A regulates the Ras/Raf/MEK/ERK signaling cascade. To test the absolute requirements for SUR-6 PP2A-B during Ras-mediated vulval induction, we will isolate sur-6 null alleles and use a mosaic analysis strategy to determine their effects on vulval induction. To determine how SUR-6 PP2A-B influences PP2A catalytic activity, we will use RNA-mediated interference, PP2A-C mutations, PP2A-C transgenes and SV4O small t antigen expression to test how altering PP2A catalytic activity influences vulval induction. We will also use RNA-mediated interference to test the requirements for other PP2A-B regulatory subunits that might direct PP2A to alternative Ras pathway substrates, and test which domains of SUR-6 are important for binding to PP2A-A. To test if candidate proteins are likely substrates of PP2A, we will test if specific phospho-acceptor site mutants can bypass the requirement for SUR-6 during vulva induction. Finally, to identify other regulators and targets of PP2A activity during vulval induction, we will conduct a yeast two-hybrid screen for proteins that bind to SUR-6 PP2A-B, and conduct genetic modifier screens for mutations with properties similar to those of sur-6 mutations. Our studies will provide important insights into the normal in vivo regulation of PP2A and its targets, and how PP2A activity might be manipulated for therapeutic effects.

Agency
National Institute of Health (NIH)
Institute
National Cancer Institute (NCI)
Type
Research Project (R01)
Project #
5R01CA087512-04
Application #
6603379
Study Section
Special Emphasis Panel (ZCA1-SRRB-E (M1))
Program Officer
Blair, Donald G
Project Start
2000-07-01
Project End
2005-06-30
Budget Start
2003-07-01
Budget End
2004-06-30
Support Year
4
Fiscal Year
2003
Total Cost
$178,313
Indirect Cost
Name
University of Pennsylvania
Department
Genetics
Type
Schools of Medicine
DUNS #
042250712
City
Philadelphia
State
PA
Country
United States
Zip Code
19104
Sundaram, Meera V (2006) RTK/Ras/MAPK signaling. WormBook :1-19
Sundaram, Meera V (2005) The love-hate relationship between Ras and Notch. Genes Dev 19:1825-39
Vatamaniuk, Olena K; Bucher, Elizabeth A; Sundaram, Meera V et al. (2005) CeHMT-1, a putative phytochelatin transporter, is required for cadmium tolerance in Caenorhabditis elegans. J Biol Chem 280:23684-90
Rocheleau, Christian E; Ronnlund, Agneta; Tuck, Simon et al. (2005) Caenorhabditis elegans CNK-1 promotes Raf activation but is not essential for Ras/Raf signaling. Proc Natl Acad Sci U S A 102:11757-62
Kao, Gautam; Tuck, Simon; Baillie, David et al. (2004) C. elegans SUR-6/PR55 cooperates with LET-92/protein phosphatase 2A and promotes Raf activity independently of inhibitory Akt phosphorylation sites. Development 131:755-65