Biophysical studies of neuronal signaling
Our research focuses broadly on the function of nerve terminals, both how their neurotransmitter-filled vesicles fuse with the plasma membrane and how their excitability regulates the entry of Ca2+ to trigger membrane fusion. Our investigations of presynaptic mechanisms often take us into detailed studies at the molecular level, but we also venture in the opposite direction into questions about neural circuitry. To address these questions we employ the electrophysiological methods of patch clamping and amperometry, as well as a variety of forms of microscopy to image voltage and Ca2+.
Studies in PC12 cells, a powerful model system, have been especially productive in providing insight into the basic mechanism of Ca2+-triggered exocytosis. We have adapted the classical ideas of single ion channel mechanisms to the study of the fusion pore. This fusion pore spans both the vesicle and plasma membranes and in many ways behaves like an ion channel. We measure the flux through single fusion pores with amperometry and the conductance of single fusion pores by performing phase-lock measurements with a patch clamp amplifier. Experiments with these methods (in collaboration with Ed Chapman of this department) have indicated which proteins form the fusion pore and which proteins control their opening and expansion.