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Physiology and
cell biology of the presynaptic terminal Neurons
communicate with one another by the release of neurotransmitters through exocytosis.
Upon depolarization, presynaptic neurons open voltage-gated channels, which allow
the entry of calcium, which in turn rapidly triggers the fusion of synaptic vesicles
with the plasma membrane. Although all eukaryotic cells secrete molecules, a hallmark
of neurons is the speed and spatial regulation of the secretion process. The main
objective of the research in my laboratory is to understand how presynaptic terminals
are specialized for these tasks. This work involves the study of several aspects
of presynaptic function including vesicle transport, exocytosis and endocytosis.
The primary model system in the laboratory is the retinal bipolar neuron, which
has an unusually large synaptic terminal. These cells belong to a class of neurons
that have specialized structures known as synaptic ribbons. One specific focus
of the laboratory is to understand the role of these structures in synaptic transmission
in sensory neurons of the retina and inner ear. In order to study presynaptic
function my laboratory uses a combination of electrophysiological and optical
approaches. One technique that has proven particularly useful for this purpose
has been evanescent field fluorescence microscopy. Evanescent field fluorescence
microscopy takes advantage of the sub-wavelength sized evanescent field of light
created by light traveling at a supercritical angle, from a high refractive index
coverslip to lower refractive index cell, to selectively illuminate fluorophores
near the cell surface. This method enables us to directly image single 30-nm vesicles
in living retinal neurons, which will improve our ability to study the mechanisms
that control vesicle movement and capture in the synaptic terminal. 
Figure
caption: Three consecutive evanescent field fluorescence
video images from an FM1-43 labeled vesicle fusing with the plasma membrane. Scale
bar is 1 micron. Recent publications:
Merrifield, C.J., Perrais, D. and Zenisek, D. (2005). Coupling between clathrin-coated pit invagination, cortactin recruitment and membrane scission observed in live cells. Cell, 121:593-606
Prescott, E.D. and Zenisek, D. (2005). Recent progress toward understanding the synaptic ribbon. Current Opinion in Neurobiology, 15: 431-436.
Zenisek, D., Horst, N., Merrifield, C.J., Sterling, P. and Matthews, G. (2004). Visualization of synaptic ribbons in the living cell. Journal of Neuroscience. 24: 9752- 9759
An, S.and Zenisek, D. (2004). Regulation of exocytosis in neurons and neuroendocrine cells. Current Opinion in Neurobiology 14: 522-530.
Zenisek, D., Davila, V., Wan, L., and Almers, W. (2003). Imaging
calcium entry sites in two presynaptic cells. Journal of Neuroscience: 23:
2538-2548.
Zenisek,
D., Steyer, J.A., Feldman, M. and Almers, W. (2002). A
membrane marker leaves synaptic vesicles in milliseconds after exocytosis in retinal
bipolar cells. Neuron 35: 185-197.
Zenisek, D. Steyer, J.A.
and Almers, W. (2000). Transport,
capture and exocytosis of single synaptic vesicles at active zones. Nature.
406:849-854
david.zenisek@cmp.yale.edu
Phone:
(203) 785-6474
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