title: The putative bZIP transcription factor BzpN slows proliferation and functions in the regulation of cell density by autocrine signals in Dictyostelium.
abstract: The secreted proteins AprA and CfaD function as autocrine signals that inhibit cell proliferation in Dictyostelium discoideum, thereby regulating cell numbers by a negative feedback mechanism. We report here that the putative basic leucine zipper transcription factor BzpN plays a role in the inhibition of proliferation by AprA and CfaD. Cells lacking BzpN proliferate more rapidly than wild-type cells but do not reach a higher stationary density. Recombinant AprA inhibits wild-type cell proliferation but does not inhibit the proliferation of cells lacking BzpN. Recombinant CfaD also inhibits wild-type cell proliferation, but promotes the proliferation of cells lacking BzpN. Overexpression of BzpN results in a reduced cell density at stationary phase, and this phenotype requires AprA, CfaD, and the kinase QkgA. Conditioned media from high-density cells stops the proliferation of wild-type but not bzpN(-) cells and induces a nuclear localization of a BzpN-GFP fusion protein, though this localization does not require AprA or CfaD. Together, the data suggest that BzpN is necessary for some but not all of the effects of AprA and CfaD, and that BzpN may function downstream of AprA and CfaD in a signal transduction pathway that inhibits proliferation.
authors.affiliation: Department of Biochemistry and Cell Biology, Rice University, Houston, Texas, United States of America.
authors.forename: Jonathan E
authors.initials: JE
authors.lastname: Phillips
authors.forename: Eryong
authors.initials: E
authors.lastname: Huang
authors.forename: Gad
authors.initials: G
authors.lastname: Shaulsky
authors.forename: Richard H
authors.initials: RH
authors.lastname: Gomer
mesh_terms: D019898:Autocrine Communication / Q000187:drug effects; D050976:Basic-Leucine Zipper Transcription Factors / Q000378:metabolism*; D002452:Cell Count; D002467:Cell Nucleus / Q000187:drug effects / Q000378:metabolism; D049109:Cell Proliferation / Q000187:drug effects; D002470:Cell Survival / Q000187:drug effects; D002478:Cells, Cultured; D017077:Culture Media, Conditioned / Q000494:pharmacology; D004023:Dictyostelium / Q000166:cytology* / Q000187:drug effects / Q000378:metabolism*; D049452:Green Fluorescent Proteins / Q000378:metabolism; D021381:Protein Transport / Q000187:drug effects; D015800:Protozoan Proteins / Q000378:metabolism; D011993:Recombinant Fusion Proteins / Q000378:metabolism; D015398:Signal Transduction / Q000187:drug effects; D033761:Spores, Protozoan / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D013997:Time Factors
chemical_list: D050976:Basic-Leucine Zipper Transcription Factors; D017077:Culture Media, Conditioned; D015800:Protozoan Proteins; D011993:Recombinant Fusion Proteins; D049452:Green Fluorescent Proteins