Genetic analysis of synaptotagmin-7 function in synaptic vesicle exocytosis
Research output: Contribution to journal › Journal article › Research › peer-review
Synaptotagmin-7 is a candidate Ca(2+) sensor for exocytosis that is at least partly localized to synapses. Similar to synaptotagmin-1, which functions as a Ca(2+) sensor for fast synaptic vesicle (SV) exocytosis, synaptotagmin-7 contains C(2)A and C(2)B domains that exhibit Ca(2+)-dependent phospholipid binding. However, synaptotagmin-7 cannot replace synaptotagmin-1 as a Ca(2+) sensor for fast SV exocytosis, raising questions about the physiological significance of its Ca(2+)-binding properties. Here, we examine how synaptotagmin-7 binds Ca(2+) and test whether this Ca(2+) binding regulates Ca(2+)-triggered SV exocytosis. We show that the synaptotagmin-7 C(2)A domain exhibits a Ca(2+)-binding mode similar to that of the synaptotagmin-1 C(2)A domain, suggesting that the synaptotagmin-1 and -7 C(2) domains generally employ comparable Ca(2+)-binding mechanisms. We then generated mutant mice that lack synaptotagmin-7 or contain point mutations inactivating Ca(2+) binding either to both C(2) domains of synaptotagmin-7 or only to its C(2)B domain. Synaptotagmin-7-mutant mice were viable and fertile. Inactivation of Ca(2+) binding to both C(2) domains caused an approximately 70% reduction in synaptotagmin-7 levels, whereas inactivation of Ca(2+) binding to only the C(2)B domain did not alter synaptotagmin-7 levels. The synaptotagmin-7 deletion did not change fast synchronous release, slow asynchronous release, or short-term synaptic plasticity of release of neurotransmitters. Thus, our results show that Ca(2+) binding to the synaptotagmin-7 C(2) domains is physiologically important for stabilizing synaptotagmin-7, but that Ca(2+) binding by synaptotagmin-7 likely does not regulate SV exocytosis, consistent with a role for synaptotagmin-7 in other forms of Ca(2+)-dependent synaptic exocytosis.
Original language | English |
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Journal | Proceedings of the National Academy of Science of the United States of America |
Volume | 105 |
Issue number | 10 |
Pages (from-to) | 3986-91 |
Number of pages | 5 |
ISSN | 0027-8424 |
DOIs | |
Publication status | Published - 2008 |
Externally published | Yes |
Bibliographical note
Keywords: Action Potentials; Animals; Calcium; Cells, Cultured; Exocytosis; Gene Targeting; Magnetic Resonance Spectroscopy; Mice; Mutation; Neurons; Protein Binding; Protein Structure, Tertiary; Synaptic Transmission; Synaptic Vesicles; Synaptotagmin I; Synaptotagmins
ID: 16835338