dictyNews
Electronic Edition
Volume 39, number 36
December 20, 2013

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Abstracts
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Calcium dependent regulation of Rab activation and vesicle fusion by an 
intracellular P2X ion channel.

1Katie Parkinson, 1Abigail E. Baines, 1Thomas Keller, 1Nicole Gruenheit, 
2Laricia Bragg, 1,2R. Alan North and 1Christopher R.L. Thompson*

1Faculty of Life Sciences, and 2Faculty of Medical and Human Sciences, 
University of Manchester, Michael Smith Building, Oxford Road, 
Manchester M13 9PT, United Kingdom

Nature Cell Biology, in press


Rab GTPases play key roles in the delivery, docking and fusion of intracellular 
vesicles. However, the mechanism by which spatial and temporal regulation of 
Rab GTPase activity is controlled is poorly understood. Here we describe a 
mechanism by which localized calcium release through a vesicular ion channel 
controls Rab GTPase activity. We show that activation of P2XA, an intracellular 
ion channel localized to the Dictyostelium discoideum contractile vacuole system, 
results in calcium efflux required for downregulation of Rab11a activity and 
efficient vacuole fusion. Vacuole fusion and Rab11a downregulation require the 
activity of CnrF, an EF-hand-containing Rab GAP found in a complex with Rab11a 
and P2XA. CnrF Rab GAP activity for Rab11a is enhanced by the presence of calcium 
and the EF-hand domain. These findings suggest that P2XA activation results in 
vacuolar calcium release, which triggers activation of CnrF Rab GAP activity and 
subsequent downregulation of Rab11a to allow vacuole fusion.

Submitted by Christopher Thompson [christopher.thompson@manchester.ac.uk]
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[End dictyNews, volume 39, number 36]