Molecular genetic characterization of the Drosophila synaptotagmin family

Proper functioning of the nervous system requires fast, spatially-restricted neuron- neuron communication at synapses. Classic physiology studies have demonstrated the importance of calcium in regulating synaptic communication; however the molecular events underlying basic synaptic transmission and plasticity have only recently become the subject of intense investigation in neuroscience. The synaptotagmin family of vesicle proteins has been implicated in calcium- dependent neurotransmitter release, although Synaptotagmin 1 (Syt 1) is the only isoform demonstrated to control synaptic vesicle fusion. We have characterized the six remaining synaptotagmin isoforms encoded in the Drosophila genome, including homologs of mammalian Synaptotagmins 4, 7, 12 and 14. Using immunolocalization and in situ hybridization experiments (Chapter 2), we demonstrate that each isoform has a unique subcellular localization and expression pattern, suggesting only Synaptotagmin 1 functions in synaptic vesicle exocytosis. Consistent with their distinct localizations, overexpression of Synaptotagmin 4 (Syt 4) or Synaptotagmin 7 (Syt 7) cannot functionally substitute for the loss of Syt 1 in synaptic transmission and loss-of-function mutations in Syts 4 and 7 do not have defects in neurotransmitter release (Chapter 4). Rather, Syt 4 and Syt 7 likely function in novel regulated-exocytosis pathways within neurons, distinct from synaptic vesicle cycling. The unique ability of Syt 1, but not other Syt isoforms, to localize to synaptic vesicles prompted us to determine the domains within Syt 1 responsible for its trafficking to synaptic vesicles (Chapter 3). We find the trafficking of Syt 1 is complex, likely requiring several sorting signals present at the N-terminus and in the C2 domains.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Biology.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2005

Author dc:creator

• Adolfsen William W. (William Wallis)

Advisor dc:contributor.advisor

• J. Troy Littleton.

• Biology.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/31189

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/31189