title: LegC3, an effector protein from Legionella pneumophila, inhibits homotypic yeast vacuole fusion in vivo and in vitro.
abstract: During infection, the intracellular pathogenic bacterium Legionella pneumophila causes an extensive remodeling of host membrane trafficking pathways, both in the construction of a replication-competent vacuole comprised of ER-derived vesicles and plasma membrane components, and in the inhibition of normal phagosome:endosome/lysosome fusion pathways. Here, we identify the LegC3 secreted effector protein from L. pneumophila as able to inhibit a SNARE- and Rab GTPase-dependent membrane fusion pathway in vitro, the homotypic fusion of yeast vacuoles (lysosomes). This vacuole fusion inhibition appeared to be specific, as similar secreted coiled-coiled domain containing proteins from L. pneumophila, LegC7/YlfA and LegC2/YlfB, did not inhibit vacuole fusion. The LegC3-mediated fusion inhibition was reversible by a yeast cytosolic extract, as well as by a purified soluble SNARE, Vam7p. LegC3 blocked the formation of trans-SNARE complexes during vacuole fusion, although we did not detect a direct interaction of LegC3 with the vacuolar SNARE protein complexes required for fusion. Additionally, LegC3 was incapable of inhibiting a defined synthetic model of vacuolar SNARE-driven membrane fusion, further suggesting that LegC3 does not directly inhibit the activity of vacuolar SNAREs, HOPS complex, or Sec17p/18p during membrane fusion. LegC3 is likely utilized by Legionella to modulate eukaryotic membrane fusion events during pathogenesis.
authors: Department of Microbiology University of Georgia, Athens, GA, USA.
authors: Terry L
authors: TL
authors: Bennett
authors: Shannon M
authors: SM
authors: Kraft
authors: Barbara J
authors: BJ
authors: Reaves
authors: Joji
authors: J
authors: Mima
authors: Kevin M
authors: KM
authors: O'Brien
authors: Vincent J
authors: VJ
authors: Starai
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D015870:Gene Expression; D016952:Legionella pneumophila / Q000235:genetics / Q000378:metabolism*; D008247:Lysosomes / Q000378:metabolism; D008561:Membrane Fusion / Q000502:physiology*; D009154:Mutation; D011485:Protein Binding; D054730:Protein Interaction Domains and Motifs; D050600:SNARE Proteins / Q000378:metabolism; D012441:Saccharomyces cerevisiae / Q000235:genetics / Q000378:metabolism*; D014617:Vacuoles / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D050600:SNARE Proteins