Cells are able to process an enormous amount of information about their environment and their internal status via highly regulated signaling pathways. Small molecule second messengers (for example cAMP, Ca2+, and nitric oxide) are an important component of signal transduction cascades. These second messengers are diffusible signaling molecules, which can be rapidly generated or released to then regulate the activity of particular effector proteins. Our lab focuses on two classes of metabolic second messengers, namely the diphosphoinositol polyphosphates (PP-IPs) and inorganic polyphosphates (polyP), because these molecules harness a recurring theme in signaling: phosphate groups.
A recently discovered group of eukaryotic second messengers are the highly phosphorylated inositides. Among the many derivatives of the inositol phosphate messengers is a subgroup that possesses high energy diphosphate groups. This intriguing class of diphosphoinositol polyphosphates (PP-IPs) has been linked to several cellular functions such as telomere maintenance, vesicular trafficking, and protein phosphorylation. Moreover, it has been demonstrated that the PP-IPs are intimately involved in insulin secretion, glucose uptake, and the metabolic state of cancer cells.
Inorganic polyphosphate (polyP) is a linear polymer in which tens to hundreds of phosphate residues are linked by phosphoanhydride bonds. The biological functions of polyP have mainly been investigated in microorganisms, although evidence is accumulating that polyP carries many important functions in mammalian systems. These functions include blood coagulation, osteoblast calcification, and breast cancer cell proliferation.
To date many of the signaling functions of PP-IPs and polyP have remained elusive, because these metabolites are difficult to study with standard cell biology techniques. Their chemical tractability, however, provides the unique opportunity to investigate their functions with chemical tools. With these probes we hope to be able to answer the following questions: Which proteins interact physically with PP-IPs? Which proteins are phosphorylated by PP-IPs? What are the metal-binding properties of PP-IPs? How are PP-IPs linked to cellular energy homeostasis? Which proteins are involved in polyP biosynthesis? Which proteins interact physically with polyP? How does polyP interact with specific metal cations? Can we use polyP for the bioremediation of toxic metals?
Investigating these problems requires an interdisciplinary approach that combines synthetic organic and inorganic chemistry with biochemical analyses and molecular and cellular biology techniques. Initial efforts will focus on understanding the molecular signaling mechanisms by employing chemical reagents. These reagents are then to be evaluated in the relevant cell models, in combination with different genetic perturbations. This will allow us to place the second messengers into their cellular context. Ultimately, this research will highlight new drug targets and can thus be exploited for the design of novel therapeutics.
Selected Recent Publications
- D. Fiedler, H. Braberg, M. Mehta, G. Chechik, G. Cagney, P. Mukherjee, A. C. Silva, M. Shales, S. R. Collins S. van Wageningen, P. Kemmeren, F. C. P. Holstege, J. S. Weissman, M. Christopher-Keogh, D. Koller, K. M. Shokat, N. J. Krogan. “Functional Organization of the S. cerevisiae Phosphorylation Network.” Cell 2009, 136, 952-963.
- T. Okuzumi, D. Fiedler, C. Zhang, D. C. Gray, B. Aizenstein, R. Hoffman, K. M. Shokat. “Inhibitor Hijacking of Akt Activation.” Nat. Chem. Bio. 2009, 5, 484-493.
- A. V. Davis, D. Fiedler, M. Ziegler, A. Terpin, K. N. Raymond. “The Resolution of Chiral M4L6 Tetrahedral Hosts.” J. Am. Chem. Soc. 2007, 129, 15354-15363.
- D. Fiedler, H. Van Halbeek, R. G. Bergman, K. N. Raymond. “Supramolecular Catalysis of Unimolecular Rearrangements: Substrate Scope and Mechanistic Insights.” J. Am. Chem. Soc. 2006, 128, 10240-10252.
- D. Fiedler, R. G. Bergman, K. N. Raymond. “Stabilization of Reactive Organometallic Intermediates inside a Self-Assembled Nanoscale Host.” Angew. Chem. Int. Ed. 2006, 45, 745-748.
- D. Fiedler, R. G. Bergman, K. N. Raymond. “Supramolecular Catalysis of a Unimolecular Transformation: Aza-Cope Rearrangement within a Self-Assembled Host.” Angew. Chem. Int. Ed. 2004, 43, 6748-6751.
- D. Fiedler, D. H. Leung, R. G. Bergman, K. N. Raymond. “Enantioselective Guest Binding and Dynamic Resolution of Cationic Ruthenium Complexes by a Chiral Metal-Ligand Assembly.” J. Am. Chem. Soc. 2004, 44, 1000-1002.