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Unformatted text preview: Bio 16-11- 2008 Export via exocytosis In nerve cells a specific exocytotic pathway exists . - The Golgi play for the loading of the vesicles an indirect role, since neurotransmitters are frequently low molecular weight molecules and derived from amino acids. - Vesicles transported from the Golgi has to travel a long distance. Therefore these vesicles are stored in the synapse for secretion. - The vesicles run within the synapse through a specific cycle. - Endocytotic vesicles containing resident components of the synaptic vesicle fuse in a localized endosome. After budding of a new secretory vesicle, the transmitter is loaded into the vesicle for the next exocytosis. Export via exocytosis Synaptic vesicles are the best investigated vesicles. The figure shows the model of a synaptic vesicle containing gluatamate as a neurotransmitter. Loading of the vesicle is mediated by the proton gradient of the vesicle induced by the v-type ATPase . 1 The gradient is used by the H+-glutamate antiporter for importing the transmitter glutamate from the synaptic cytosol . The import of the transmitter into the vesicle is therefore not mediated by the golgi apparatus. The model is drawn to scale and shows also the v- SNARE on the surface, necessary for vesicle fusion with the presynaptic membrane....
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