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.
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 and kinetics of synaptic transmission, and time resolved optical and electrophysiological studies to dissect individual steps in the release pathway and to manipulate the properties of the exocytotic fusion pore.
More recently, we have expanded our efforts to study how changes in membrane trafficking underlie synaptic plasticity and to elucidate the molecular basis for asynchronous synaptic transmission.
Finally, we study the actions of the clostridial neurotoxins, which cause botulism and tetanus poisoning, with emphasis on identifying the pathways of entry, the receptors that mediate entry, and the translocation of the toxins across membranes.
Honors & Awards
- 2012 Kellett Mid-Career Award
- Rose Award, for outstanding thesis in the neurosciences: Jihong Bai (2003), Min Dong (2004), Mike Chicka (2008), Enfu Hui (2009), Sam Kwon (2012)
- 2004 Romnes Award
- 1999 Pew Scholars Award
- 1998 Shaw Scientist Award
Recent Research Breakthroughs
- Liu, H.Bai, H., Xue, R., Takahashi, H., Edwardson, J.M. & Chapman, E.R.. (2014).Linker mutations dissociate the function of synaptotagmin I during evoked and spontaneous release and reveal membrane penetration as a step during excitation-secretion coupling.Nature Neuroscience 17(5): 670-7.PMID: 24657966[PMCID – in process].
- Liu, H., Bai, H. Hui, E., Yang, L., Evans, C.S., Wang, Z. & Chapman, E.R.. (2014).Synaptotagmin 7 functions as a Ca2+-sensor for synaptic vesicle replenishment.eLife(in press).PMCID: PMC3930910.
- Ed Chapman- PI
- Jon Gaffaney- Lab Manager
- Post Docs
- Joel Brittain, Huan Bao, Renhao Xue, Zixuan He, Joe Briguglio
- Grad Students
- Yiwen Gu, Hua Bai, Ewa Bomba, Lindsey Roper, Chantell Evans, David Ruhl
Selected Publications: (Find further publications on PubMed)
- 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. PMCID:PMC3220409
- Hui, E., Johnson, C., Yao, J., Dunning, M. and Chapman, E.R.(2009).Synaptotagmin-mediated bending of the target membrane is a critical step in Ca2+-regulated fusion.Cell 138: 709-721.PMCID: PMC2758036
- *Chai, Q., *Arndt, J.W., *Dong, M., Tepp, W.H., Johnson, E.A., #Chapman, E.R.and #Stevens, R.C.. (2006). Structural basis of receptor recognition by botulinum neurotoxin B.Nature 444: 1096-1100.
*equal contribution #corresponding authors
- Dong, M., Yeh, Y., Tepp, W.H., Dean, C., Johnson, E.A., Janz, R. andChapman, E.R.. (2006).SV2 is the protein receptor for botulinum neurotoxin A.Science312:592-596.
- Tucker, W.T., Weber, T. and Chapman, E.R.. (2004) Reconstitution of Ca2+-triggered membrane fusion by synaptotagmin and SNAREs.Science 304: 435-438.