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First published online September 26, 2003

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Synaptotagmin IX – receptor recycler

The synaptotagmins are a highly conserved family of proteins represented in all tissues. Synaptotagmins expressed in neurons appear to function as Ca²⁺ sensors in synaptic vesicle trafficking. But what are the roles of these proteins in non-neuronal cells? Ronit Sagi-Eisenberg and co-workers have approached this question by studying synaptotagmin IX in rat basophilic leukaemia (RBL) cells (see p. 4307). Combining immunofluorescence analyses with subcellular fractionation, they observe that synaptotagmin IX resides in the pericentriolar endocytic recycling compartment (ERC) – a compartment involved in both recycling of plasma membrane receptors and trafficking between early endosomes and the trans Golgi network. They also find that synaptotagmin IX colocalizes with tubulin at the microtubule-organizing centre. Furthermore, they demonstrate that it coimmunoprecipitates with tubulin from intact cells and that chimeric proteins containing the synaptotagmin IX C2A/C2B domain pull down tubulin from cell lysates. The authors go on to show that antisense synaptotagmin IX RNA slows recycling of transferrin from the ERC to the plasma membrane. They therefore propose that the protein functions as link between vesicles recycling from the ERC to the surface and the microtubule tracks on which they travel.

Related articles in JCS:

Synaptotagmin IX, a possible linker between the perinuclear endocytic recycling compartment and the microtubules

Yael Haberman, Elena Grimberg, Mitsunori Fukuda, and Ronit Sagi-Eisenberg
JCS 2003 116: 4307-4318. [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