Neuron
Volume 41, Issue 1, 8 January 2004, Pages 85-99
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Article
N-Glycosylation Is Essential for Vesicular Targeting of Synaptotagmin 1

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Abstract

Synaptotagmins 1 and 7 are candidate Ca2+ sensors for exocytosis localized to synaptic vesicles and plasma membranes, respectively. We now show that the N-terminal intraluminal sequence of synaptotagmin 1, when transplanted onto synaptotagmin 7, redirects synaptotagmin 7 from the plasma membrane to secretory vesicles. Conversely, mutation of the N-terminal N-glycosylation site of synaptotagmin 1 redirects synaptotagmin 1 from vesicles to the plasma membrane. In cultured hippocampal neurons, the plasma membrane-localized mutant of synaptotagmin 1 suppressed the readily releasable pool of synaptic vesicles, whereas wild-type synaptotagmin 1 did not. In addition to the intraluminal N-glycosylation site, the cytoplasmic C2 domains of synaptotagmin 1 were required for correct targeting but could be functionally replaced by the C2 domains of synaptotagmin 7. Our data suggest that the intravesicular N-glycosylation site of synaptotagmin 1 collaborates with its cytoplasmic C2 domains in directing synaptotagmin 1 to synaptic vesicles via a novel N-glycosylation-dependent mechanism.

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