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First published online 11 March 2008
doi: 10.1242/jcs.021113

Journal of Cell Science 121, 1054-1064 (2008)
Published by The Company of Biologists 2008
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Research Article

Dictyostelium MEGAPs: F-BAR domain proteins that regulate motility and membrane tubulation in contractile vacuoles

Robert J. W. Heath1,* and Robert H. Insall1,2

1 School of Biosciences, University of Birmingham, Edgbaston, Birmingham, B15 2TT, UK
2 The Beatson Institute for Cancer Research, Glasgow, G61 1BD, UK

* Author for correspondence (e-mail: rjh451{at}bham.ac.uk)

Accepted 8 January 2008

PCH family proteins are fundamentally important proteins, linking membrane curvature events with cytoskeletal reorganisation. One group, the MEGAPs (also called srGAPs and WRPs) contain RhoGAP domains in addition to the F-BAR domain. We disrupted MEGAP1 and MEGAP2 in Dictyostelium both singly and in combination. We found a strong cytoskeletal phenotype in MEGAP1– cells and a subtle phototaxis defect in MEGAP2– slugs. MEGAP1–/2– cells have an overabundance of filopodia and slug motility and function are affected. The most dramatic changes, however, are on contractile vacuoles. MEGAP1–/2– cells empty their contractile vacuoles less efficiently than normal and consequently have three times the usual number. GFP-tagged MEGAP1 localises to tubules of the contractile vacuole network and when vacuoles start to empty they recruit cytosolic GFP-MEGAP1. Mutants in the Saccharomyces homologues RGD1 and RGD2 also show abnormal vacuoles, implying that this role is conserved. Thus, MEGAP is an important regulator of the contractile vacuole network, and we propose that tubulation of the contractile vacuole by MEGAP1 represents a novel mechanism for driving vacuole emptying.

Key words: Contractile vacuole, F-BAR, MEGAP, Rgd1, Tubulation


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The trials and tubulations of F-BAR proteins

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