title: The monomeric clathrin assembly protein, AP180, regulates contractile vacuole size in Dictyostelium discoideum.
abstract: AP180, one of many assembly proteins and adaptors for clathrin, stimulates the assembly of clathrin lattices on membranes, but its unique contribution to clathrin function remains elusive. In this study we identified the Dictyostelium discoideum ortholog of the adaptor protein AP180 and characterized a mutant strain carrying a deletion in this gene. Imaging GFP-labeled AP180 showed that it localized to punctae at the plasma membrane, the contractile vacuole, and the cytoplasm and associated with clathrin. AP180 null cells did not display defects characteristic of clathrin mutants and continued to localize clathrin punctae on their plasma membrane and within the cytoplasm. However, like clathrin mutants, AP180 mutants, were osmosensitive. When immersed in water, AP180 null cells formed abnormally large contractile vacuoles. Furthermore, the cycle of expansion and contraction for contractile vacuoles in AP80 null cells was twice as long as that of wild-type cells. Taken together, our results suggest that AP180 plays a unique role as a regulator of contractile vacuole morphology and activity in Dictyostelium.
authors.affiliation: Department of Molecular Cell and Developmental Biology, Institute for Cellular and Molecular Biology, University of Texas at Austin, Austin, TX 78712, USA.
authors.forename: Irene
authors.initials: I
authors.lastname: Stavrou
authors.forename: Theresa J
authors.initials: TJ
authors.lastname: O'Halloran
mesh_terms: D033942:Adaptor Proteins, Vesicular Transport / Q000378:metabolism; D020816:Amino Acid Motifs; D000818:Animals; D002462:Cell Membrane / Q000378:metabolism; D048749:Cytokinesis; D004023:Dictyostelium / Q000166:cytology / Q000254:growth & development / Q000378:metabolism*; D004705:Endocytosis / Q000502:physiology; D034041:Monomeric Clathrin Assembly Proteins / Q000737:chemistry / Q000172:deficiency / Q000378:metabolism*; D050505:Mutant Proteins / Q000378:metabolism; D009154:Mutation / Q000235:genetics; D009995:Osmosis; D021381:Protein Transport; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D013997:Time Factors; D014617:Vacuoles / Q000378:metabolism*
chemical_list: D033942:Adaptor Proteins, Vesicular Transport; D034041:Monomeric Clathrin Assembly Proteins; D050505:Mutant Proteins; D011993:Recombinant Fusion Proteins; C439023:clathrin assembly protein AP180