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Molecular and Cellular Biology, June 1999, p. 4379-4389, Vol. 19, No. 6
Departments of
Pediatrics,1 Medicine,2
and Cell Biology,3 Washington University
School of Medicine, St. Louis, Missouri 63110
Received 25 August 1998/Returned for modification 22 October
1998/Accepted 8 February 1999
LIM domain-containing proteins contribute to cell fate
determination, the regulation of cell proliferation and
differentiation, and remodeling of the cell cytoskeleton. These
proteins can be found in the cell nucleus, cytoplasm, or both. Whether
and how cytoplasmic LIM proteins contribute to the cellular response to extracellular stimuli is an area of active investigation. We have identified and characterized a new LIM protein, Ajuba. Although predominantly a cytosolic protein, in contrast to other like proteins, it did not localize to sites of cellular adhesion to extracellular matrix or interact with the actin cytoskeleton. Removal of the pre-LIM
domain of Ajuba, including a putative nuclear export signal, led to an
accumulation of the LIM domains in the cell nucleus. The pre-LIM domain
contains two putative proline-rich SH3 recognition motifs. Ajuba
specifically associated with Grb2 in vitro and in vivo. The interaction
between these proteins was mediated by either SH3 domain of Grb2 and
the N-terminal proline-rich pre-LIM domain of Ajuba. In fibroblasts
expressing Ajuba mitogen-activated protein kinase activity persisted
despite serum starvation and upon serum stimulation generated levels
fivefold higher than that seen in control cells. Finally, when Ajuba
was expressed in fully developed Xenopus oocytes, it
promoted meiotic maturation in a Grb2- and Ras-dependent manner.
0270-7306/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
Ajuba, a Novel LIM Protein, Interacts with Grb2,
Augments Mitogen-Activated Protein Kinase Activity in Fibroblasts,
and Promotes Meiotic Maturation of Xenopus Oocytes in a
Grb2- and Ras-Dependent Manner

*
Corresponding author. Mailing address: Division of
Hematology, Washington University School of Medicine, Campus Box 8125, 660 South Euclid Ave., St. Louis, MO 63110. Phone: (314) 362-8834. Fax:
(314) 362-8826. E-mail: longmorg{at}medicine.wustl.edu.
Present address: Department of Pediatrics, University of
Pittsburgh, Pittsburgh, PA 15213-2583.
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