The active zone T-bar--a plasticity module?
The synaptic active zone, the site where Ca(2+)-triggered fusion of synaptic vesicles takes place, is commonly associated with protein-rich, electron-dense cytomatrices. The molecular composition and functional role of active zones, especially in the context of vesicular exo- and endocytosis, are under intense investigation. Per se, Drosophila synapses, which display so-called T-bars as electron-dense specializations, should be a highly suitable model system, as they allow for a combination of efficient genetics with ultrastructural and electrophysiological analyses. However, it needed a biochemical approach of the Buchner laboratory to "molecularly" access the T-bar by identification of the CAST/ERC-family member Bruchpilot as the first T-bar-residing protein. Genetic elimination of Bruchpilot revealed that the protein is essential for T-bar formation, calcium channel clustering, and hence proper vesicle fusion and patterned synaptic plasticity. Recently, Bruchpilot was shown to directly shape the T-bar, likely by adopting an elongated conformation. Moreover, first mechanisms that control the availability of Bruchpilot for T-bar assembly were described. This review seeks to summarize the information on T-bar structure, as well as on functional aspects, formulating the hypothesis that T-bars are genuine "plasticity modules."
Wichmann
Carolin
C
NeuroCure Cluster of Excellence, Charité Berlin, Berlin, Germany.
Sigrist
Stephan J
SJ
D000818:Animals; D019521:Body Patterning / Q000502:physiology; D015220:Calcium Channels / Q000378:metabolism / Q000502:physiology; D029721:Drosophila Proteins / Q000502:physiology*; D004331:Drosophila melanogaster / Q000502:physiology* / Q000648:ultrastructure; D009473:Neuronal Plasticity / Q000502:physiology*; D013570:Synaptic Membranes / Q000502:physiology* / Q000648:ultrastructure; D013572:Synaptic Vesicles / Q000502:physiology* / Q000648:ultrastructure
C510146:BRP protein, Drosophila; D015220:Calcium Channels; D029721:Drosophila Proteins