University of Wisconsin–Madison

Ed Chapman

Professor, Investigator- Howard Hughes Medical Institute, Ph.D., University of Washington

chapman@wisc.edu

(608) 263-1762

RESEARCH INTERESTS - Molecular mechanisms that underlie neuronal exocytosis

Ed Chapman

Visit the Chapman Lab

Our research is focused on understanding the structure, function and dynamics of the exocytotic membrane “fusion machine” that mediates the release of neurotransmitters from neurons. These studies have begun to reveal insights into how the release machinery is regulated and thereby contributes to neuronal plasticity. Neuronal exocytosis is triggered by Ca2+ and occurs via the abrupt opening of a pre-assembled fusion pore. Subsequent dilation of the pore results in the complete fusion of the vesicle membrane with the plasma membrane.

We are currently identifying and reconstituting the sequential protein-protein and protein-lipid interactions that underlie excitation-secretion coupling. To delineate this pathway, we have primarily focused on the Ca2+-binding synaptic-vesicle protein, synaptotagmin, which appears to function as the Ca2+-sensor that regulates release.

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Neuron | Click to enlarge

Our work is also focused on components of the “SNARE-complex”, which is thought to form the core of the fusion apparatus. The rapid kinetics of exocytosis (<1 ms) indicate that only a handful of molecular rearrangements occur to couple Ca2+-synaptotagmin to the opening of the fusion pore. We are using a combination of biochemical, biophysical, imaging, spectroscopic and genetic approaches to delineate the interactions/conformational changes that occur during this window of time.

Current experiments include the reconstitution of Ca2+-triggered membrane fusion in vitro, visualization of protein rearrangements and vesicle dynamics inside living cells, genetic manipulations to modulate the efficiency of synaptic transmission, time resolved electrophysiological studies to dissect individual steps in the release pathway and to manipulate the properties of the exocytotic fusion pore, and imaging approaches to monitor ‘sub-quantal’ exocytosis.

"movie" GIF - 2Click on figure at left to play movie (2 MB movie)

Other major interests are focused on the mechanism by which clostridial neurotoxins bind to and enter presynaptic nerve terminals, the selective sorting of proteins in neurons, and membrane*protein interactions.

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Selected Publications

  • Yao, J, Gaffaney, J.D., Kwon, S.E. and Chapman, E.R.. (2011). Doc2 is a Ca2+-sensor required for asynchronous neurotransmitter release. Cell 147(3):666-77. PMID: 22036572 [PMCID – in process]
  • Yao, J., Kwon, S.E., Gaffaney, J.D., Dunning, F.M., and Chapman, E.R.. (2011). Uncoupling the roles of synaptotagmin I as a dual Ca2+ sensor during endocytosis and exocytosis of synaptic vesicles. Nature Neuroscience 5(2): 243-9. PMID: 22197832 [PMCID – in process]
  • Kwon SE and Chapman ER (2011) Synaptophysin Regulates the Kinetics of Synaptic Vesicle Endocytosis in Central Neurons Neuron 70, Supplemental information
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  • Hui E, Gaffaney JD, Wang Z, Johnson CP, Evans CS, Chapman ER (2011) Mechanism and function of synaptotagmin-mediated membrane apposition. Nat Struct Mol Biol. 2011 Jun 5. [Epub ahead of print] PMID: 21642967
  • Sun, S., Suresh, S., Liu, H., Tepp, W.H., Johnson, E.A., Edwardson, J.M., Chapman, E.R.. (2011). Probing the assembly of a botulinum neurotoxin translocation channel. Cell Host & Microbe 10(3):237-47. PMID: 21925111 [PMCID – in process]
  • Wang, Z., Liu, H., Gu, Y. and Chapman, E.R… (2011). Reconstituted synaptotagmin I mediates vesicle docking, priming, and fusion. J. Cell Biol. 195(7):1159-70. PMID: 22184197 [PMCID – in process]
  • Yeh, F., Zhu, Y., Tepp, W.H., Johnson, E.A., Bertics, P.J., Chapman, E.R.. (2011). Retargeting clostridial neurotoxins to macrophages reduces TNFa release. Biochemistry 50(48):10419-21. PMCID PMC3226321.
  • Wu, Y., Ma, L., Cheley, S., Bayley, H., Cui, Q. and Chapman, E.R.. (2011). Permeation of styryl dyes through nanometer-scale pores in membranes. Biochemistry 50(35): 7493-502. PMID: 21815625 [PMCID – in process]
  • Wang D, Zhang Z, Dong M, Sun S, Chapman ER, Jackson MB (2011) Syntaxin requirement for Ca2+-triggered exocytosis in neurons and endocrine cells demonstrated with an engineered neurotoxin Biochemistry. 2011 Apr 12;50(14):2711-3. Epub 2011 Mar 18. PMID: 21401123
  • Paddock, B.E., Wang, Z., Biela, L.M., Chen, K., Getzy, M.D., Striegel, A., Richmond, J.E., Chapman, E.R., Featherstone, D.E. and Reist, N.E.. (2011) Membrane penetration by synaptotagmin is required for coupling calcium binding to vesicle fusion in vivo. J. Neurosci. 31(6): 2248-57. PMID: 21307261 [PubMed – in process]
  • Mayers, J.R., Olendrowitz, C., Schuh, A.L., Chapman, E.R., Eimer, S. and Audhya, A.. Multiple roles for Hrs and STAM in multivesicular endosome dynamics. (2011). J. Biol. Chem. 86(11):9636-45. PMID: 21193406 [PMCID – in process]
  • Zhang, Z., Wu, Y., Wang, Z., Dunning, F.M., Rehfuss, J., Ramanan, D., Chapman, E.R., and Jackson, M.B.. (2011). Release mode of large and small dense-core vesicles specified by different synaptotagmin isoforms in PC12 cells. Mol. Biol. Cell 22(13): 2324-36. PMCID: PMC3128534