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Vol. 9, Issue 11, 3095-3106, November 1998

Identification of Darlin, a Dictyostelium Protein with Armadillo-like Repeats that Binds to Small GTPases and Is Important for the Proper Aggregation of Developing Cells

Kalpa K. Vithalani,^* Carole A. Parent, Eric M. Thorn, Marcus Penn, Denis A. Larochelle, Peter N. Devreotes, and Arturo De Lozanne^§

Department of Cell Biology, Duke University Medical Center, Durham, North Carolina 27710

We purified from Dictyostelium lysates an 88-kDa protein that bound to a subset of small GTPases, including racE, racC, cdc42Hs, and TC4ran, but did not bind to R-ras or rabB. Cloning of the gene encoding this 88-kDa protein revealed that it contained multiple armadillo-like repeats most closely related to the mammalian GTP exchange factor smgGDS. We named this protein darlin (Dictyostelium armadillo-like protein). Disruption of the gene encoding darlin demonstrated that this protein is not essential for cytokinesis, pinocytosis, phagocytosis, or development. However, the ability of darlin null cells to aggregate in response to starvation is severely affected. When starved under liquid medium, the mutant cells were unable to form aggregation centers and streams, possibly because of a defect in cAMP relay signaling. This defect was not due to an inability of the darlin mutants to activate adenylate cyclase in response to G protein stimulation. These results suggest that the darlin protein is involved in a signaling pathway that may modulate the chemotactic response during early development.

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^*   Present address: Department of Molecular Biology, Cleveland Clinic Research Institute, 9500 Euclid Avenue, Cleveland, OH 44195.
   Present address: Department of Biological Chemistry, Johns Hopkins University School of Medicine, 725 North Wolfe Street, Baltimore, MD 21205.
   Present address: Department of Biology, Clark University, 950 Main Street, Worcester, MA 01610.
^§   Corresponding author. E-mail address: a.delozanne{at}cellbio.duke.edu.

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Molecular Biology of the Cell
Vol. 9, 3095-3106, November 1998
Copyright © 1998 by The American Society for Cell Biology

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