cAMP-mediated signaling regulates a myriad of important biological processes under physiological conditions and disease states, including diabetes, heart failure and cancer. In eukaryotic cells, the effects of cAMP are mediated by two ubiquitously expressed intracellular cAMP receptors, the classic protein kinase A/cAMP-dependent protein kinase (PKA/cAPK) and the recently discovered exchange protein directly activated by cAMP/cAMP-regulated guanine nucleotide exchange factor (Epac/cAMP-GEF). The existence of two ubiquitously expressed cAMP effectors provides a mechanism for a more precise and integrated control of the cAMP signaling pathways in a spatial and temporal manner. However, little is known about the mechanism of Epac activation. The objective of this proposal is to fill the gap in our current knowledge by mapping the conformational changes associated with Epac activation. Specifically, we have planned experiments with the following Specific Aims: 1) To determine the specific residues important for Epac activation by site-directed mutagenesis;2) to delineate the conformational changes associated with cAMP binding and Epac activation and to determine the protein interface between Epac and its downstream effector, Rap1, using enhanced deuterium exchange-mass spectrometry (DXMS) and small-angle X-ray scattering;and 3) to solve the crystal structure of Epac2-cAMP using X-ray crystallography. The long-term goals of our research are to understand the physiological functions and mechanisms of Epac regulation. Accomplishing the proposed research in this application will significantly move the field forward towards these goals. Furthermore, the medical and pharmacological implications of this research program are also far-reaching. A better understanding of cAMP mediated signal transduction could potentially lead to the identification of novel mechanism-based therapeutic strategies specifically targeting the cAMP-signaling components.
Cyclic AMP-mediated signaling regulates a myriad of important biological processes under both physiological conditions and disease states, including diabetes, heart failure and cancer. Components of the cAMP-signaling cascade have been implicated in abnormal cell growth and drug actions and successfully targeted for diagnosis and chemotherapy of cancer and other diseases. A better understanding of cAMP mediated signal transduction could potentially lead to the identification of novel drug targets and the development of new or improved therapeutic agents.
|Almahariq, Muayad; Mei, Fang C; Cheng, Xiaodong (2016) The pleiotropic role of exchange protein directly activated by cAMP 1 (EPAC1) in cancer: implications for therapeutic intervention. Acta Biochim Biophys Sin (Shanghai) 48:75-81|
|Singhmar, Pooja; Huo, XiaoJiao; Eijkelkamp, Niels et al. (2016) Critical role for Epac1 in inflammatory pain controlled by GRK2-mediated phosphorylation of Epac1. Proc Natl Acad Sci U S A 113:3036-41|
|Wang, Hui; Robichaux, William G; Wang, Ziqing et al. (2016) Inhibition of Epac1 suppresses mitochondrial fission and reduces neointima formation induced by vascular injury. Sci Rep 6:36552|
|Banerjee, Upasana; Cheng, Xiaodong (2015) Exchange protein directly activated by cAMP encoded by the mammalian rapgef3 gene: Structure, function and therapeutics. Gene 570:157-67|
|Almahariq, Muayad; Chao, Celia; Mei, Fang C et al. (2015) Pharmacological inhibition and genetic knockdown of exchange protein directly activated by cAMP 1 reduce pancreatic cancer metastasis in vivo. Mol Pharmacol 87:142-9|
|Almahariq, Muayad; Mei, Fang C; Wang, Hui et al. (2015) Exchange protein directly activated by cAMP modulates regulatory T-cell-mediated immunosuppression. Biochem J 465:295-303|
|Zhu, Yingmin; Chen, Haijun; Boulton, Stephen et al. (2015) Biochemical and pharmacological characterizations of ESI-09 based EPAC inhibitors: defining the ESI-09 ""therapeutic window"". Sci Rep 5:9344|
|Ye, Na; Zhu, Yingmin; Chen, Haijun et al. (2015) Structure-Activity Relationship Studies of Substituted 2-(Isoxazol-3-yl)-2-oxo-N'-phenyl-acetohydrazonoyl Cyanide Analogues: Identification of Potent Exchange Proteins Directly Activated by cAMP (EPAC) Antagonists. J Med Chem 58:6033-47|
|Schwede, Frank; Chepurny, Oleg G; Kaufholz, Melanie et al. (2015) Rp-cAMPS Prodrugs Reveal the cAMP Dependence of First-Phase Glucose-Stimulated Insulin Secretion. Mol Endocrinol 29:988-1005|
|Almahariq, Muayad; Mei, Fang C; Cheng, Xiaodong (2014) Cyclic AMP sensor EPAC proteins and energy homeostasis. Trends Endocrinol Metab 25:60-71|
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