title: A secreted factor represses cell proliferation in Dictyostelium.
abstract: Many cells appear to secrete factors called chalones that limit their proliferation, but in most cases the factors have not been identified. We found that growing Dictyostelium cells secrete a 60 kDa protein called AprA for autocrine proliferation repressor. AprA has similarity to putative bacterial proteins of unknown function. Compared with wild-type cells, aprA-null cells proliferate faster, while AprA overexpressing cells proliferate slower. Growing wild-type cells secrete a factor that inhibits the proliferation of wild-type and aprA- cells; this activity is not secreted by aprA- cells. AprA purified by immunoprecipitation also slows the proliferation of wild-type and aprA- cells. Compared with wild type, there is a higher percentage of multinucleate cells in the aprA- population, and when starved, aprA- cells form abnormal structures that contain fewer spores. AprA may thus decrease the number of multinucleate cells and increase spore production. Together, the data suggest that AprA functions as part of a Dictyostelium chalone.
authors.affiliation: Howard Hughes Medical Institute and Department of Biochemistry and Cell Biology, MS-140, Rice University, 6100 South Main Street, Houston, TX 77005-1892, USA.
authors.forename: Debra A
authors.initials: DA
authors.lastname: Brock
authors.forename: Richard H
authors.initials: RH
authors.lastname: Gomer
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001685:Biological Factors / Q000378:metabolism* / Q000502:physiology*; D002467:Cell Nucleus / Q000737:chemistry / Q000235:genetics / Q000378:metabolism; D049109:Cell Proliferation; D016207:Cytokines / Q000378:metabolism; D004023:Dictyostelium / Q000737:chemistry / Q000166:cytology* / Q000254:growth & development / Q000378:metabolism*; D018507:Gene Expression Regulation, Developmental; D006801:Humans; D008969:Molecular Sequence Data; D011485:Protein Binding; D015800:Protozoan Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D033761:Spores, Protozoan / Q000254:growth & development / Q000378:metabolism
chemical_list: D001685:Biological Factors; D016207:Cytokines; D015800:Protozoan Proteins