Identification of cofilin and LIM-domain-containing protein kinase 1 as novel interaction partners of 14-3-3zeta

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Abstract
Proteins of the 14-3-3 family have been implicated in various physiological processes, and are thought to function as adaptors in various signal transduction pathways. In addition, 14-3-3 proteins may contribute to the reorganization of the actin cytoskeleton by interacting with as yet unidentified actin-binding proteins. Here we show that the 14-3-3ζ isoform interacts with both the actin-depolymerizing factor cofilin and its regulatory kinase, LIM (Lin-11/Isl-1/Mec-3)-domain-containing protein kinase 1 (LIMK1). In both yeast two-hybrid assays and glutathione S-transferase pull-down experiments, these proteins bound efficiently to 14-3-3ζ. Deletion analysis revealed consensus 14-3-3 binding sites on both cofilin and LIMK1. Furthermore, the C-terminal region of 14-3-3ζ inhibited the binding of cofilin to actin in co-sedimentation experiments. Upon co-transfection into COS-7 cells, 14-3-3ζ-specific immunoreactivity was redistributed into characteristic LIMK1-induced actin aggregations. Our data are consistent with 14-3-3-protein-induced changes to the actin cytoskeleton resulting from interactions with cofilin and/or LIMK1.