title: The secreted Dictyostelium protein CfaD is a chalone.
abstract: Dictyostelium discoideum cells secrete CfaD, a protein that is similar to cathepsin proteases. Cells that lack cfaD proliferate faster and reach a higher stationary-phase density than wild-type cells, whereas cells that overexpress CfaD proliferate slowly and reach the stationary phase when at a low density. On a per-nucleus basis, CfaD affects proliferation but not growth. The drawback of not having CfaD is a reduced spore viability. Recombinant CfaD has no detectable protease activity but, when added to cells, inhibits the proliferation of wild-type and cfaD(-) cells. The secreted protein AprA also inhibits proliferation. AprA is necessary for the effect of CfaD on proliferation. Molecular-sieve chromatography indicates that in conditioned growth medium, the 60 kDa CfaD is part of a approximately 150 kDa complex, and both chromatography and pull-down assays suggest that CfaD interacts with AprA. These results suggest that two interacting proteins may function together as a chalone signal in a negative feedback loop that slows Dictyostelium cell proliferation.
authors.affiliation: Department of Biochemistry and Cell Biology, MS-140, Rice University, Houston, TX 77005-1892, USA.
authors.forename: Deenadayalan
authors.initials: D
authors.lastname: Bakthavatsalam
authors.forename: Debra A
authors.initials: DA
authors.lastname: Brock
authors.forename: N Neda
authors.initials: NN
authors.lastname: Nikravan
authors.forename: Kevin D
authors.initials: KD
authors.lastname: Houston
authors.forename: R Diane
authors.initials: RD
authors.lastname: Hatton
authors.forename: Richard H
authors.initials: RH
authors.lastname: Gomer
mesh_terms: D000818:Animals; D049109:Cell Proliferation; D002478:Cells, Cultured; D050150:Chalones / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D004023:Dictyostelium / Q000378:metabolism*; D015800:Protozoan Proteins / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D033761:Spores, Protozoan / Q000254:growth & development / Q000378:metabolism
chemical_list: D050150:Chalones; D015800:Protozoan Proteins