Kathleen M. Buckley - US grants

Neurons are highly polarized cells with distinct domains that mediate specialized functions. Incoming signals from other neurons are generally detected at synapses localized to the dendrites and cell body. The outgoing signal is conducted via the axon to the nerve terminal, where the resulting depolarization causes an influx of calcium and the release of neurotransmitter by fusion of synaptic vesicles with the presynaptic plasma membrane. These functional differences are reflected in differences in the distributions of specific proteins and organelles. For example, neurotransmitter receptors must be targeted to postsynaptic membrane specializations at dendrites, while synaptic vesicles and their constituent proteins are concentrated at the nerve terminal. The specific aims of this proposal are designed to determine the mechanism mediating the specific targeting of synaptic vesicle proteins to the nerve terminal and, ultimately, their assembly into synaptic vesicles. Hippocampal neurons grown at low density in tissue culture develop the characteristic polarized morphology of neurons in vivo. Synaptic vesicle proteins are enriched in the axon, while proteins such as the transferrin receptor are localized to the somatodendritic region. We will use this system to investigate the amino acid sequences that are responsible for the targeting of synaptic vesicles to the axon, and ultimately to synaptic vesicles. We will identify the signals responsible for the sorting of the synaptic vesicle protein synaptobrevin to the nerve terminal. We will determine if sorting to the axonal or somatodendritic domain is mediated by different determinants, and how those determinants interact to create a polarized distribution of proteins in the neuron. Finally, we will determine whether sorting determinants are conserved between different types of regulated secretory vesicles. With these results in hand, we will have taken the first step towards understanding the complex mechanism that results in the formation of synaptic vesicles during development and during recycling at the nerve terminal.

DESCRIPTION (Adapted From The Applicant's Abstract): This proposal requests funds to continue and combine two previous longstanding training grants centered in the Department of Neurobiology at Harvard Medical School. Support is requested to offer a broadly based training program for 8 postdoctoral trainees. The training program involves several components: background course work, attendance at two weekly neuroscience seminar series, and supervised research in the laboratory of a program faculty member. In addition, each trainee will meet regularly with a small group of preceptors appointed to monitor his or her progress and offer advice relevant to the trainee's career development. The 34 participating faculty members have appointments in the Department of Neurobiology (24) or in other programs associated with Harvard Medical School, including Children's Hospital, Beth Israel- Deaconess Medical Center, Brigham and Women's Hospital, Dana Farber Cancer Institute, and Massachusetts General Hospital. Their areas of expertise include integrative neuroscience (5), developmental neuroscience (10), molecular and cellular neuroscience (12), and the mechanisms of neural disease (3). The program will be administered by the Principal Investigator, Dr. Kathleen Buckley (Associate Professor of Neurobiology), together with a steering committee composed of 4 members representing different facets of the program.