Our lab has several interests related to the mechanisms involved with membrane fusion, synaptic transmission, and synaptic plasticity: 

  1.   Nanomechanics of Ca2+-triggered membrane fusion.  These studies involve the analysis of a number of Ca2+-binding proteins (synaptotagmin, Doc2, Otoferlin, Rabphilin, etc.), as well as a number of other accessory proteins (nSec1, complexin, munc13, etc.) that regulate the core of the fusion apparatus - the SNARE complex - to control fusion reactions. We employ a diverse range of research tools to study membrane fusion including biophysical (electrophysiology, imaging etc.) and time-resolved biochemical (reconstituted fusion, stopped-flow kinetics, SPR, ITC etc.) techniques.  Using these methods we are able to relate the function of individual proteins in in vitro systems with their function(s) in living neurons and in neuronal circuits. 

  1.   How changes in the membrane fusion machinery underlie aspects of synaptic plasticity.  Using electrophysiological approaches and modern microscopy approaches (confocal, TIRF, 2-photon etc.) we are reconstituting and studying simple synaptic circuits to further our understanding of how connectivity impacts synaptic transmission, and to study the phenotypes exhibited by neurons cultured from genetically modified mice.  We also study slice preparations from genetically modified mice to address the role of membrane trafficking proteins in synaptic plasticity, including long term potentiation.

  1.   Structure and function of fusion pores.  The first aqueous connection between the lumen of a secretory vesicle and the extracellular space is called the fusion pore.  The structure of of the pore is the subject of debate, with some evidence that the pore might be composed of the membrane anchors of SNARE proteins while others argue the pore is purely lipidic.  We study the structure and dynamics of fusion pores in neuroendocrine cells using  carbon fiber amperometry and in neurons using optical approaches with single vesicle resolution.   In our view, synaptic vesicle exocytosis often involves a kiss-and-run mechanism in which open fusion pores close without dilating to give rise to full fusion and bilayer merger. 

  1.    Elucidation of the receptors, entry pathways, and the molecular basis for translocation across membranes, of Botulinum (BoNT) and Tetanus neurotoxins (TeNT).  These toxins are the most deadly substances known to humankind, and are also used to treat myriad medical maladies. They are highly specific proteases that target to nerve terminals and cleave SNARE proteins to block exocytosis.  We are in the process of identifying the cell surface receptors, entry pathways, and mechanisms of translocation of these toxins.  We are also using quantum dots to track their movement and putative transcytosis in simple neuronal circuits, and we are building ‘designer’ toxin-receptor pairs to widen the range of cells that these toxins can enter.      

Contact info:                                    

Chapman Lab       

University of Wisconsin

Department of Neuroscience

Wisconsin Institute for Medical Research (WIMR)

1111 Highland Ave, rm 9555

Madison, WI 53705


Research Focus: