Specific Functions of BIG1 and BIG2 in Endomembrane Organization
Open Access
- 25 March 2010
- journal article
- research article
- Published by Public Library of Science (PLoS) in PLOS ONE
- Vol. 5 (3), e9898
- https://doi.org/10.1371/journal.pone.0009898
Abstract
Transport of molecules from one subcellular compartment to another involves the recruitment of cytosolic coat protein complexes to a donor membrane to concentrate cargo, deform the membrane and ultimately to form an independent carrier. Small-GTP-binding proteins of the Arf family are central to many membrane trafficking events. Arfs are activated by guanine nucleotide exchange factors (GEFs) which results in their recruitment to membranes and subsequent engagement with Arf-effectors, many of which are coat proteins. Among the human BFA-sensitive large Arf-GEFs, the function of the two closely related BIG1 and BIG2 is still not clear, and recent studies have raised the question of functional redundancy between the two proteins. Here we have used small-interfering RNA on human cells and a combination of fixed and live-cell imaging to investigate the differential functions of BIG1 and BIG2 in endomembrane organization and function. Importantly, in this direct comparative study, we show discrete functions for BIG1 and BIG2. Our results show that depletion of BIG2 but not of BIG1 induces a tubulation of the recycling endosomal compartment, consistent with a specific role for BIG2 here. In contrast, suppression of BIG1 induces the formation of Golgi mini-stacks still polarized and functional in terms of cargo export. A key finding from our work is that suppression of BIG1 expression results in a fragmentation of the Golgi apparatus. Our data indicate that the human BFA-sensitive large Arf-GEFs have non-redundant functions in cell organization and membrane trafficking. BIG1 is required to maintain the normal morphology of the Golgi; BIG2 is important for endosomal compartment integrity and cannot replace the function of BIG1 in Golgi organization.This publication has 56 references indexed in Scilit:
- Specificity of Cytoplasmic Dynein Subunits in Discrete Membrane-trafficking StepsMolecular Biology of the Cell, 2009
- Golgicide A reveals essential roles for GBF1 in Golgi assembly and functionNature Chemical Biology, 2009
- Redundant Roles of BIG2 and BIG1, Guanine-Nucleotide Exchange Factors for ADP-Ribosylation Factors in Membrane Traffic between thetrans-Golgi Network and EndosomesMolecular Biology of the Cell, 2008
- Distinct Functions for Arf Guanine Nucleotide Exchange Factors at the Golgi Complex: GBF1 and BIGs Are Required for Assembly and Maintenance of the Golgi Stack andtrans-Golgi Network, RespectivelyMolecular Biology of the Cell, 2008
- Regulation of brefeldin A-inhibited guanine nucleotide-exchange protein 1 (BIG1) and BIG2 activity via PKA and protein phosphatase 1γProceedings of the National Academy of Sciences of the United States of America, 2007
- BIG1, a brefeldin A-inhibited guanine nucleotide-exchange protein, is required for correct glycosylation and function of integrin β1Proceedings of the National Academy of Sciences of the United States of America, 2007
- Sec16 Defines Endoplasmic Reticulum Exit Sites and is Required for Secretory Cargo Export in Mammalian CellsTraffic, 2006
- Adaptable adaptors for coated vesiclesTrends in Cell Biology, 2004
- Sar1 promotes vesicle budding from the endoplasmic reticulum but not Golgi compartments.The Journal of cell biology, 1994
- Rapid redistribution of Golgi proteins into the ER in cells treated with brefeldin A: Evidence for membrane cycling from Golgi to ERCell, 1989