Electrophysiological Analysis of the Synaptic Vesicle Priming Process
von Dennis Bernd Nestvogel
Datum der mündl. Prüfung:2017-05-18
Betreuer:Prof. Dr. Nils Brose
Gutachter:Prof. Dr. Erwin Neher
Gutachter:Prof. Dr. Thomas Dresbach
EnglischChemical synaptic transmission is the most prominent communication channel employed by neural circuits. It is initiated by the action potential triggered fusion of transmitter-filled synaptic vesicles with the presynaptic plasma membrane. Proteins of the CAPS and Munc13 families are required to prime synaptic vesicles for fusion before these can release their contents into the synaptic cleft. In the present study, I dissected the functional interplay of both protein families during the priming process and furthermore tested the significance of two recently described presynaptic proteins in the modulation of the Munc13- and CAPS dependent priming reaction. The data presented here indicate that CAPSs and Munc13s differentially prime SVs at low versus high levels of presynaptic activity in a lipid-dependent manner. Specifically, CAPSs engage in a lipid-sensitive priming step at low intraterminal Ca2+ concentrations, while Munc13-lipid interactions predominate at high Ca2+ levels. This step, in turn, likely precedes the partial assembly of fusogenic SNARE complexes, which is catalyzed by the MUN domain of Munc13s. The two recently described presynaptic proteins, mSYD1A and Mover, did not modulate the priming reactions as assessed in the autaptic hippocampal culture system. In addition, I studied the relevance of the priming process in the etiology of bipolar disorder, which involved a detailed structure function analysis of disease associated CADPS1 mutations in cultured hippocampal neurons and the generation of a knock-in mouse carrying one such mutation. Two out of eight mutations led to altered forms of short-term synaptic plasticity in cultured neurons, which may indicate that perturbations of the priming process contribute to the etiology of bipolar disorder. Lastly, I established an experimental system for the future study of the significance of the priming process for short-term synaptic plasticity phenomena in the context of visual information processing in-vivo.
Keywords: Synapse; Synaptic Vesicle Priming; Transmitter Release