The long-term goal of this proposal is to understand the molecular, cellular and physiological mechanisms of signal termination mediated by the novel phosphatase PHLPP (PH domain Leucine- rich repeat Protein Phosphatase;pronounced 'flip') that we discovered. PHLPP terminates signaling by two oncogenic kinases, Akt and protein kinase C, by specifically dephosphorylating a key regulatory residue, the hydrophobic motif, which we originally identified on protein kinase C. PHLPP is frequently deleted in diverse human cancers and its deletion in mice promotes prostate tumors. Thus, the central hypothesis driving this proposal is that PHLPP terminates growth signaling pathways and that deregulation leads to pathophysiological states, notably cancer.
Three Aims are proposed: 1. Molecular Mechanisms of PHLPP. The goals are to identify small molecule inhibitors or activators of PHLPP to use as tools in cellular studies in Aims 2 and 3. In addition, we will test the hypothesis that cancer-associated mutations in PHLPP are inactivating and thus confer a survival advantage to tumor cells. 2. Cellular Mechanisms of PHLPP. The goal of this section is to understand the mechanisms that control the function of PHLPP in cells. First, we will use innovative live cell imaging technologies to test the hypothesis that spatial coordination on the PDZ scaffold NHERF increases the ability of PHLPP to control the amplitude and duration of Akt signaling. Second, we will address the mechanism by which PHLPP suppresses the levels of growth factor receptors in cells. 3. PHLPP in pathophysiology.
This Aim addresses the role of PHLPP in cancer. Specifically, we will test that hypothesis that deregulation of PHLPP by the E3 ligase 2-TrCP contributes to glioblastoma. In addition, we will address the roles of PHLPP1 and PHLPP2 in prostate cancer using a mouse model and in breast cell growth using a 3D culture model.

Public Health Relevance

This research is relevant to public health because it addresses the basic molecular mechanisms of cancer. Specifically, our lab discovered a new tumor suppressor that is frequently deleted in cancer and is poised as a novel and important therapeutic target. We would like to understand how to target this tumor suppressor in disease.

National Institute of Health (NIH)
National Institute of General Medical Sciences (NIGMS)
Research Project (R01)
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Molecular and Integrative Signal Transduction Study Section (MIST)
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Chin, Jean
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University of California San Diego
Schools of Medicine
La Jolla
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Grzechnik, Agnieszka T; Newton, Alexandra C (2016) PHLPPing through history: a decade in the life of PHLPP phosphatases. Biochem Soc Trans 44:1675-1682
Bradley, Elizabeth W; Carpio, Lomeli R; Newton, Alexandra C et al. (2015) Deletion of the PH-domain and Leucine-rich Repeat Protein Phosphatase 1 (Phlpp1) Increases Fibroblast Growth Factor (Fgf) 18 Expression and Promotes Chondrocyte Proliferation. J Biol Chem 290:16272-80
Sierecki, Emma; Newton, Alexandra C (2014) Biochemical characterization of the phosphatase domain of the tumor suppressor PH domain leucine-rich repeat protein phosphatase. Biochemistry 53:3971-81
Wang, Pingping; Zhou, Zhihong; Hu, Anchang et al. (2014) Both decreased and increased SRPK1 levels promote cancer by interfering with PHLPP-mediated dephosphorylation of Akt. Mol Cell 54:378-91
Newton, Alexandra C; Trotman, Lloyd C (2014) Turning off AKT: PHLPP as a drug target. Annu Rev Pharmacol Toxicol 54:537-58
Reyes, Gloria; Niederst, Matt; Cohen-Katsenelson, Ksenya et al. (2014) Pleckstrin homology domain leucine-rich repeat protein phosphatases set the amplitude of receptor tyrosine kinase output. Proc Natl Acad Sci U S A 111:E3957-65
O'Neill, Audrey K; Niederst, Matthew J; Newton, Alexandra C (2013) Suppression of survival signalling pathways by the phosphatase PHLPP. FEBS J 280:572-83
O'Hayre, M; Niederst, M; Fecteau, J F et al. (2012) Mechanisms and consequences of the loss of PHLPP1 phosphatase in chronic lymphocytic leukemia (CLL). Leukemia 26:1689-92
Warfel, Noel A; Newton, Alexandra C (2012) Pleckstrin homology domain leucine-rich repeat protein phosphatase (PHLPP): a new player in cell signaling. J Biol Chem 287:3610-6
Patterson, Scott J; Han, Jonathan M; Garcia, Rosa et al. (2011) Cutting edge: PHLPP regulates the development, function, and molecular signaling pathways of regulatory T cells. J Immunol 186:5533-7

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