title: A new environmentally resistant cell type from Dictyostelium.
abstract: This paper describes the serendipitous discovery and first characterization of a new resistant cell type from Dictyostelium, for which the name aspidocyte (from aspis: Greek for shield) is proposed. These cells are induced from amoebae by a range of toxins including heavy metals and antibiotics, and were first detected by their striking resistance to detergent lysis. Aspidocytes are separate, rounded or irregular-shaped cells, which are immotile but remain fully viable; once the toxic stress is removed, they revert to amoeboid cells within an hour. Induction takes a few hours and is completely blocked by the protein synthesis inhibitor cycloheximide. Aspidocytes lack a cell wall and their resistance to detergent lysis is active, requiring continued energy metabolism, and may be assisted by a complete cessation of endocytosis, as measured by uptake of the dye FM1-43. Microarray analysis shows that aspidocytes have a distinct pattern of gene expression, with a number of genes up-regulated that are predicted to be involved in lipid metabolism. Aspidocytes were initially detected in a hypersensitive mutant, in which the AMP deaminase gene is disrupted, suggesting that the inductive pathway involves AMP levels or metabolism. Since aspidocytes can also be induced from wild-type cells and are much more resistant than amoebae to a membrane-disrupting antibiotic, it is possible that they are an adaptation allowing Dictyostelium cells to survive a sudden onslaught of toxins in the wild.
authors.affiliation: MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, UK.
authors.forename: Ioannis
authors.initials: I
authors.lastname: Serafimidis
authors.affiliation: MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, UK.
authors.forename: Gareth
authors.initials: G
authors.lastname: Bloomfield
authors.affiliation: The Wellcome Trust Sanger Institute, Hinxton, Cambridgeshire CB10 1SA, UK.
authors.forename: Jason
authors.initials: J
authors.lastname: Skelton
authors.affiliation: The Wellcome Trust Sanger Institute, Hinxton, Cambridgeshire CB10 1SA, UK.
authors.forename: Al
authors.initials: A
authors.lastname: Ivens
authors.affiliation: MRC Laboratory of Molecular Biology, Hills Road, Cambridge CB2 2QH, UK.
authors.forename: Robert R
authors.initials: RR
authors.lastname: Kay
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology; D002454:Cell Differentiation; D003902:Detergents / Q000494:pharmacology*; D004023:Dictyostelium / Q000166:cytology* / Q000235:genetics / Q000254:growth & development / Q000502:physiology; D004351:Drug Resistance; D004705:Endocytosis; D020869:Gene Expression Profiling; D005786:Gene Expression Regulation; D018869:Heat-Shock Response; D020411:Oligonucleotide Array Sequence Analysis; D015800:Protozoan Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D000900:Anti-Bacterial Agents; D003902:Detergents; D015800:Protozoan Proteins