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Death takes a holiday

Border cells (arrow) migrate to the wrong spot in DIAP-1 mutants. Montell/Elsevier

At times, the DIAP-1 anti-apoptotic protein is not what it seems. Erika Geisbrecht and Denise Montell (Johns Hopkins School of Medicine, Baltimore, MD) show that, in the fly ovary, this caspase inhibitor is needed for cell migration but not survival.

Montell's group studies border cells in the fly egg chamber, which migrate to help establish the sperm entry site. Rac activity is needed for this; so to identify more players, the group screened for proteins that restore migration when Rac activity is reduced. They found DIAP-1. Although DIAP-1 is essential for cell survival in the embryo, its loss in the ovary caused migration defects but not cell death.

Extra actin or profilin, presumably leading to increased actin polymerization, also compensated for the loss of Rac. DIAP-1 may also promote actin polymerization. To block apoptosis, DIAP-1 inhibits the fly caspase-9 homologue, called Dronc. Dronc is probably the DIAP-1 target in border cell migration as well, as reducing its activity suppressed the loss of Rac. Possible Dronc substrates include Rac and actin, which are cleaved by caspases during apoptosis, or profilin.

The unexpected identification of DIAP-1 as a suppressor emphasizes the importance of random screens. "The whole point is to find something that you can't even imagine would be involved," says Montell. Tumor cells that manage to increase their levels of DIAP-1–like proteins could gain both a survival advantage and the ability to migrate.

Reference:

Geisbrecht, E., and D. Montell. 2004. Cell. 118:111–125.[CrossRef][Medline]

Nicole LeBrasseur

lebrasn{at}rockefeller.edu

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This Article Full Text (PDF, 2428K) PPT slides of all figures Alert me when this article is cited Services Email this article Similar articles in this journal Alert me to new content in the JCB Download to citation manager Citing Articles Citing Articles via CrossRef Citing Articles via Google Scholar Google Scholar Articles by LeBrasseur, N. Search for Related Content PubMed Articles by LeBrasseur, N. Social Bookmarking                            What's this?