1. Molecular mechanism of cofilin dephosphorylation by ouabain
- Author
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Jaehoon Jung, Moonhee Kim, Kyunglim Lee, Eung Chil Choi, Suenghee Choi, Jae kyung Suh, and Min-Jeong Kim
- Subjects
MAPK/ERK pathway ,Time Factors ,MAP Kinase Signaling System ,Down-Regulation ,macromolecular substances ,Biology ,environment and public health ,Models, Biological ,Ouabain ,Lim kinase ,Cell Line ,Dephosphorylation ,Mice ,medicine ,Animals ,Humans ,Enzyme Inhibitors ,Phosphorylation ,Rho-associated protein kinase ,Dose-Response Relationship, Drug ,Kinase ,Cell Biology ,Cofilin ,Molecular biology ,Cell biology ,Actin Depolymerizing Factors ,NIH 3T3 Cells ,Proto-oncogene tyrosine-protein kinase Src ,medicine.drug - Abstract
We previously reported that phosphorylated cofilin-triosephosphate isomerase (TPI) complex interacts with Na,K-ATPase and enhances the pump activity through the phosphorylation of cofilin via Rho-mediated signaling pathway. In this study, we tested the hypothesis that the dephosphorylation of cofilin may be induced through Na,K-ATPase inhibition by ouabain. The phosphorylation level of cofilin by ouabain which decreases in a time- and dose-dependent manner in various human cell lines, remains unchanged by pretreatment with Src inhibitor, PP2; epidermal growth factor receptor (EGFR) inhibitor, AG1478; Raf-1 kinase (Raf) inhibitor, GW5074; and ERK kinase (MEK) inhibitor, PD98059, and by transfection of Ras dominant negative mutant (RasN17). This suggests that ouabain dephosphorylates cofilin through the Src/EGFR/Ras/Raf/MEK pathway. Ouabain activates Ras/Raf/MEK pathway, but down-regulates Rho kinase (ROCK)/LIM kinase (LIMK)/cofilin pathway, implying that there may be a cross-talk by ouabain between the Ras/Raf/MEK and the ROCK/LIMK/cofilin pathways. Immunofluorescence and flow cytometry suggest that ouabain-induced active form of cofilin may be involved in cytoskeletal reorganization and cell volume regulation. Thus, these findings demonstrate a new molecular mechanism for the dephosphorylation of cofilin through the inhibition of Na,K-ATPase by ouabain.
- Published
- 2006