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Investigating Mast Cell Secretory Granules; from Biosynthesis to Exocytosis
16:01

Investigating Mast Cell Secretory Granules; from Biosynthesis to Exocytosis

Published on: January 26, 2015

The Rab27 effector Rabphilin, unlike Granuphilin and Noc2, rapidly exchanges between secretory granules and cytosol

Mark T W Handley1, Robert D Burgoyne

  • 1The Physiological Laboratory, School of Biomedical Sciences, University of Liverpool, Crown Street, Liverpool L693BX, UK.

Biochemical and Biophysical Research Communications
|June 25, 2008
PubMed

Rab proteins are GTPases that transit between GTP- and GDP-bound states. In the GTP-bound form they can recruit specific effector to membrane domains. It is possible that the exchange of Rab effectors between membranes and cytosol would be determined by the exchange of the particular Rab partner. We have compared the cycling of three Rab3/27 effectors, Granuphilin, Noc2, and Rabphilin, in PC12 cells using fluorescence recovery after photobleaching of EGFP-tagged proteins. All three effectors become localised to secretory granules. Granuphilin and Noc2 showed little or no exchange between secretory granules and cytosol whereas Rabphilin showed rapid and complete exchange. Both Noc2 and Rabphilin were found to be recruited to granules by Rab27 but the data suggest that Rabphilin did not form stable complexes with Rab27 on secretory granules and so Rab effector cycling between membranes and cytosol can be independent of that of the Rab protein.

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