Different endocytic functions of AGEF-1 in C. elegans coelomocytes

Background: ADP-ribosylation factors (ARFs) are a family of small GTP-binding proteins that play roles in membrane dynamics and vesicle trafficking. AGEF-1, which is thought to act as a guanine nucleotide exchange factor of class I ARFs, is required for caveolin-1 body formation and receptor-mediated endocytosis in oocytes of Caenorhabditis elegans. This study explores additional roles of AGEF-1 in endocytic transport. Methods: agef-1 expression was knocked down by using RNAi in C. elegans. Markers that allow analysis of endocytic transport in scavenger cells were investigated for studying the effect of AGEF-1 on different steps of membrane transport. Results: Knockdown of AGEF-1 levels results in two apparent trafficking defects in coelomocytes of C. elegans. First, there is a delay in the uptake of solutes from the extracellular medium. Second, there is a dramatic enlargement of the sizes of lysosomes, even though lysosomal acidification is normal and degradation still occurs. Conclusion: Our results suggest that AGEF-1 regulates endosome/lysosome fusion or fission events, in addition to earlier steps in endocytic transport. General sigruficance:AGEF-1 is the first identified GTPase regulator that functions at the lysosome fusion or fission stage of the endocytic pathway. Our study provides insight into lysosome dynamics in C. elegans. (C) 2012 Elsevier B.V. All rights reserved.