Characterization of the Functional Domains of a Novel Vertebrate-Specific Presynaptic Protein-Mover

by Asha Kiran Akula
Doctoral thesis
Date of Examination:2015-07-28
Date of issue:2016-04-05
Advisor:Prof. Dr. Thomas Dresbach
Referee:Prof. Dr. Tobias Moser
Referee:Prof. Dr. Nils Brose
Persistent Address: http://dx.doi.org/10.53846/goediss-5597

 

 

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Abstract

English

Synapses are asymmetric intercellular junctions. Targeting of synaptic vesicles to presynaptic sites is one of the most intricate examples of polarized trafficking and selective protein accumulation. Little is known about amino acid sequences or structural determinants mediating presynaptic targeting of synaptic vesicle proteins. Mover / TPRGL / SVAP30 is a 266 amino acid protein associated with synaptic vesicles as a peripheral membrane protein. Structurally nothing is known about Mover except for the presence of a predicted HSac2 domain, phosphorylation sites and a predicted Calmodulin binding site. The regions or amino acid sequences mediating targeting of Mover to presynaptic terminals are unknown. I found that dimerization of Mover allows the targeting of Mover to synaptic vesicles. Sites widely distributed over large parts of Mover mediate both self-interaction and presynaptic targeting of Mover. The HSac2 homology domain of Mover and the part encoded by the alternatively spliced exon 2 are required but not sufficient for targeting. Despite strong homomerization Mover does not heterodimerize with its paralogue TPRG. Mover is a novel binding partner for Ca2+/Calmodulin but this interaction does not mediate the presynaptic targeting of Mover, because a point mutated variant of Mover that still binds to Calmodulin is deficient for dimerization and targeting. Mutations introduced into the predicted phosphorylation sites had no effect on dimerization and targeting of Mover suggesting a function for phosphorylation other than targeting. Over-expression of Mover reduces the pool of recycling vesicles suggesting an inhibitory role in neurotransmitter release. A Mover knockout mouse was generated to explore the role of Mover for presynaptic function, and studies investigating synaptic vesicle recycling in cultures from these mice are underway
Keywords: Presynaptic protein
 
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