[Abstract Title]. - Society for Neuroscience

Poster
236. Neurotransmitter Release: Docking and Fusion
Time: Sunday, November 16, 2008, 1:00 pm - 5:00 pm
Program#/Poster#: 236.12/D12
Topic: B.06.a. Docking and fusion
Support: 1211/07 to U.A
EUSynapse project, contract No. 019055 to AJG
Title: DOC2B acts as a calcium switch and enhances vesicle fusion
Authors: *R. FRIEDRICH 1 , A. J. GROFFEN 2 , E. CONNELL 3 , J. R. T. VAN WEERING 2 , O.
GUTMAN 1 , Y. I. HENIS 1 , B. DAVLETOV 3 , U. ASHERY 1 ;
1 Tel Aviv Univ., Tel Aviv, Israel; 2 Dept. of Functional Genomics, Ctr. for Neurogenomics and
Cognition Research, Vrije Univ. (VU) and VU Med. Ctr., Amsterdam, Netherlands; 3 Neurobio.
Division, Med. Res. Council-Laboratory of Mol. Biol., Cambridge, Cambridge, United Kingdom
Abstract: Calcium-dependent exocytosis is regulated by a vast number of proteins. DOC2B is a
synaptic protein that translocates to the plasma membrane (PM) upon small elevations in
intracellular calcium concentration. The aim of this study is to investigate the role of DOC2B in
calcium-triggered exocytosis and its interactions with other proteins of the exocytotic machinery.
Using biochemical and biophysical measurements, we demonstrate that the C2A domain of
DOC2B interacts directly with the PM in a calcium-dependent manner. Using a combination of
electrophysiological, morphological and total internal reflection fluorescent measurements, we
found that DOC2B acts as a priming factor and increases the number of fusion-competent
vesicles. Comparing secretion during repeated stimulation between wild-type DOC2B and a
mutated DOC2B that is constantly at the PM, showed that DOC2B enhances catecholamine
secretion also during repeated stimulation and that DOC2B has to translocate to the PM to exert
its facilitating effect, suggesting that its activity is dependent on calcium. The hypothesis that
DOC2B exerts its effect at the PM was supported by the finding that DOC2B affects the fusion
kinetics of single vesicles and interacts with the PM SNAREs. We conclude that DOC2B is a
calcium-dependent priming factor and its activity at the PM enables efficient expansion of the
fusion pore, leading to increased catecholamine release. The interaction of DOC2B with Munc18
and/or Munc13 might be important for DOC2B's ability of to increase the exocytotic burst.
Disclosures: R. Friedrich , None; A.J. Groffen, None; E. Connell, None; J.R.T. van Weering,
None; O. Gutman, None; Y.I. Henis, None; B. Davletov, None; U. Ashery, None.