Calcium Triggered Synaptic Vesicle Exocytosis
| dc.contributor.advisor | Südhof, Thomas C. | en |
| dc.creator | Pang, Zhiping | en |
| dc.date.accessioned | 2010-07-12T18:42:42Z | |
| dc.date.available | 2010-07-12T18:42:42Z | |
| dc.date.issued | 2007-08-08 | |
| dc.description.abstract | Neurotransmitter release is triggered by the action potential induced influx of Ca 2+ into nerve terminals. One of the central questions in neuroscience is how Ca 2+ promotes synaptic vesicles from rest to fusion leading to release of neurotransmitters. In this thesis, I first addressed if synaptogmin-1/SNARE binding is important for synaptic vesicle release. Using two knock-in mouse lines each with single amino-acid substitution, namely D232N and D238N in synaptotagmin-1, combined with electrophysiology, I found evoked release in D232N mutant neuronal cultures is significantly increased, whereas in D238N cultures release is slightly but significantly decreased. Ca 2+ titration curves indicated the apparent Ca 2+-affinity for vesicle release significantly increased in D232N synapses. These data are consistent with biochemical studies that showed that the D232N substitution in synaptotagmin-1 increases Ca 2+-dependent SNARE bindings but leaves phospholipid binding unchanged, whereas the D238N mutant slightly decreased phospholipid binding but leaves SNARE binding insignificantly changed. Second, I addressed if synaptotamgin-2 is another Ca 2+-sensor for synaptic vesicle release. I and my colleagues used two mouse lines: one contains a single amino acid mutation in synaptotagmin-2 (I377N) and one has synaptotagmin-2 ablated from the genome. By using a combination of biophysical, biochemical and functional techniques, we determined that synaptotagmin-2 is a fast synchronous Ca 2+-sensor. Third, in collaboration with Jianyuan Sun, we explored the biophysical properties of the slow Ca 2+-sensor in the Calyx of Held. Using Ca 2+-uncaging combined with electrophysiology, we mapped increasing Ca 2+ concentrations in relation to neurotransmitter release and built a comprehensive mathematical model for the Ca 2+ control of synaptic vesicle fusion. We found compelling evidence for the existence of two Ca 2+- sensors: one (synaptotagmin-2 in the Calyx of Held) is responsible for fast synchronous release, and the other one is responsible for slow delayed synaptic release. Surprisingly, we found the two Ca 2+-sensors have similar apparent Ca 2+ affinities. This study showed clearly that synaptotagmin-2 is a fast Ca 2+-sensor, and gave us a prediction that narrows down the potential candidate for the slow Ca 2+-sensor. | en |
| dc.format.digitalOrigin | born digital | en |
| dc.format.medium | Electronic | en |
| dc.format.mimetype | application/pdf | en |
| dc.identifier.oclc | 664113598 | |
| dc.identifier.uri | https://hdl.handle.net/2152.5/643 | |
| dc.language.iso | en | en |
| dc.subject | Calcium | en |
| dc.subject | Synapses | en |
| dc.subject | Synaptic Transmission | en |
| dc.title | Calcium Triggered Synaptic Vesicle Exocytosis | en |
| dc.type | Thesis | en |
| dc.type.genre | dissertation | en |
| dc.type.material | Text | en |
| thesis.date.available | 2007-08-08 | |
| thesis.degree.department | Graduate School of Biomedical Sciences | en |
| thesis.degree.discipline | Neuroscience | en |
| thesis.degree.grantor | UT Southwestern Medical Center | en |
| thesis.degree.level | Doctoral | en |
| thesis.degree.name | Doctor of Philosophy | en |