Journal
JOURNAL OF COMPARATIVE NEUROLOGY
Volume 436, Issue 1, Pages 4-16Publisher
WILEY
DOI: 10.1002/cne.1049
Keywords
synaptic vesicles; recycling; exocytosis; electrophysiology; genetics
Categories
Ask authors/readers for more resources
The synaptic vesicle protein, synaptotagmin, has been hypothesized to mediate several functions in neurotransmitter release including calcium sensing, vesicle recycling, and synaptic vesicle docking. These hypotheses are based on evidence from in vitro binding assays, peptide and antibody injection experiments, and genetic knockout studies. Synaptotagmin contains two domains that are homologous to the calcium ion (Ca2+)-binding C-2 domain of protein kinase C. The two C-2 domains of synaptotagmin have broadly differing ligand-binding properties. We have focused on the second C-2 domain (C2B) of synaptotagmin I, in particular, on a series of conserved lysine residues on beta -strand 4 of C2B. This polylysine motif binds clathrin-adapter protein AP-2, neuronal calcium channels, and inositol high polyphosphates. It also mediates Ca2+-dependent oligomerization. To investigate the importance of these lysine residues in synaptic transmission, we have introduced synaptotagmin I (syt) transgenes harboring specific polylysine motif mutations into flies otherwise lacking the synaptotagmin I protein (syt(null)). Electrophysiological analyses of these mutants revealed that evoked transmitter release is decreased by approximate to 36% and that spontaneous release is increased approximately twofold relative to syt(null) flies that express a wild type syt transgene. Synaptotagmin expression in both the mutant and the wild type transgenic lines was equivalent, as measured by semiquantitative Western blot analysis. Thus, the alteration in synaptic transmission was due to the mutation and not to the level of synaptotagmin expression. We conclude that synaptotagmin interactions mediated by the C2B polylysine motif are required to attain full synaptotagmin function in vivo. J. Comp. Neurol. 436:4-16, 2001. (C) 2001 Wiley-Liss, Inc.
Authors
I am an author on this paper
Click your name to claim this paper and add it to your profile.
Reviews
Recommended
No Data Available