The secreted Dictyostelium protein CfaD is a chalone.
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.
Bakthavatsalam
Deenadayalan
D
Department of Biochemistry and Cell Biology, MS-140, Rice University, Houston, TX 77005-1892, USA.
Brock
Debra A
DA
Nikravan
N Neda
NN
Houston
Kevin D
KD
Hatton
R Diane
RD
Gomer
Richard H
RH
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
D050150:Chalones; D015800:Protozoan Proteins