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J Cell Sci. 2008 Aug 1;121(Pt 15):2473-80. doi: 10.1242/jcs.026682. Epub 2008 Jul 8.

The secreted Dictyostelium protein CfaD is a chalone.

Author information

1
Department of Biochemistry and Cell Biology, MS-140, Rice University, Houston, TX 77005-1892, USA.

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.

PMID:
18611962
PMCID:
PMC2716657
DOI:
10.1242/jcs.026682
[Indexed for MEDLINE]
Free PMC Article

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