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Mol. Cell. Biol., May 1996, 1896-1908, Vol 16, No. 5
N Harden, J Lee, HY Loh, YM Ong, I Tan, T Leung, E Manser and L Lim
Changes in cell morphology are essential in the development of a
multicellular organism. The regulation of the cytoskeleton by the Rho
subfamily of small GTP-binding proteins is an important determinant of cell
shape. The Rho subfamily has been shown to participate in a variety of
morphogenetic processes during Drosophila melanogaster development. We
describe here a Drosophila homolog, DPAK, of the serine/threonine kinase
PAK, a protein which is a target of the Rho subfamily proteins Rac and
Cdc42. Rac, Cdc42, and PAK have previously been implicated in signaling by
c-Jun amino-terminal kinases. DPAK bound to activated (GTP-bound)
Drosophila Rac (DRacA) and Drosophila Cdc42. Similarities in the
distributions of DPAK, integrin, and phosphotyrosine suggested an
association of DPAK with focal adhesions and Cdc42- and Rac-induced focal
adhesion-like focal complexes. DPAK was elevated in the leading edge of
epidermal cells, whose morphological changes drive dorsal closure of the
embryo. We have previously shown that the accumulation of cytoskeletal
elements initiating cell shape changes in these cells could be inhibited by
expression of a dominant-negative DRacA transgene. We show that leading-
edge epidermal cells flanking segment borders, which express particularly
large amounts of DPAK, undergo transient losses of cytoskeletal structures
during dorsal closure. We propose that DPAK may be regulating the
cytoskeleton through its association with focal adhesions and focal
complexes and may be participating with DRacA in a c-Jun amino-terminal
kinase signaling pathway recently demonstrated to be required for dorsal
closure.
Copyright © 1996, American Society for Microbiology
A Drosophila homolog of the Rac- and Cdc42-activated serine/threonine kinase PAK is a potential focal adhesion and focal complex protein that colocalizes with dynamic actin structures
Glaxo-IMCB Group, Institute of Molecular and Cell Biology, National University of Singapore.
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