Functional analysis of the C2A domain of synaptotagmin 1: Implications for calcium-regulated secretion

David M. Thomas, Lisa A. Elferink

Research output: Contribution to journalArticle

34 Scopus citations

Abstract

Synaptotagmin 1 is proposed to function as a low affinity calcium sensor for calcium-triggered exocytosis from neural and neuroendocrine cells. Because of the calcium-binding properties of the C2A domain of synaptotagmin 1, calcium-dependent interactions through this domain may modulate neurotransmitter release. We addressed this question by using alanine- scanning mutagenesis to generate a series of mutations within the C2A domain of synaptotagmin 1. The effects of these mutations on synaptotagmin 1 C2A function were analyzed for (1) calcium-dependent phospholipid binding, (2) calcium-dependent binding to syntaxin 1A, a plasma membrane protein critical for vesicle docking or fusion, and (3) calcium-regulated secretion after microinjection into neuroendocrine pheochromocytoma (PC12) cells. Our analyses reveal that a polylysine motif at residues 189-192 confers an inhibitory effect on secretion by recombinant synaptotagmin C2A fragments. The synaptotagmin 1 C2A polylysine motif functions independently of calcium- mediated interactions with phospholipids and syntaxin 1A. Furthermore, α- latrotoxin reverses the inhibitory effect of injected recombinant C2A fragments, suggesting that they perturb the cellular calcium-sensing machinery by interfering with synaptotagmin 1 activity in vivo. Our results indicate that novel calcium-independent interactions mediated through the C2A polylysine motif of synaptotagmin 1 function to modulate neurotransmitter release.

Original languageEnglish (US)
Pages (from-to)3511-3520
Number of pages10
JournalJournal of Neuroscience
Volume18
Issue number10
StatePublished - May 15 1998
Externally publishedYes

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Keywords

  • C2A domain
  • Calcium
  • Calcium-regulated exocytosis
  • PC12 cells
  • Phospholipids
  • Synaptotagmin
  • Syntaxin

ASJC Scopus subject areas

  • Neuroscience(all)

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