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First published online November 23, 2005

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Synaptic vesicle proteins kept in reserve

Synaptic vesicle protein 2 (SV2) is an important part of the trafficking machinery that directs secretory vesicles to the plasma membrane in neurons and endocrine cells. Three isoforms exist - SV2A, SV2B and SV2C - and previous studies had suggested that SV2A and SV2B function as pumps in Ca²⁺-triggered exocytosis. Claes Wollheim and co-workers now reveal that SV2 has a rather different role in insulin secretion, casting doubt on this idea (see p. 5647). After showing that all three SV2 isoforms are expressed in insulin-secreting ß-cells, the authors examined their roles by overexpressing or knocking down SV2A/SV2C and monitoring the effects on exocytosis. They find that neither has any effect on depolarization-induced Ca²⁺ responses and rapid insulin secretion. By contrast, the more prolonged insulin release induced by glucose is affected by overexpressing or knocking down SV2. This indicates that the protein does not participate in the Ca²⁺-dependent, final stages of endocytosis. Instead, the authors propose, it may act upstream and recruit secretory granules from the reserve pool to the rapidly releasable pool at the plasma membrane.

Related articles in JCS:

SV2A and SV2C are not vesicular Ca²⁺ transporters but control glucose-evoked granule recruitment

Mariella Iezzi, Sten Theander, Roger Janz, Chantal Loze, and Claes B. Wollheim
JCS 2005 118: 5647-5660. [Abstract] [Full Text]  

This Article Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Related articles in JCS Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Search for Related Content