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MBC in Press, published online ahead of print August 15, 2007
Mol. Biol. Cell 10.1091/mbc.E06-07-0659

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Submitted on August 1, 2006
Revised on July 17, 2007
Accepted on August 3, 2007

Nuclear Localization of the ERK MAP Kinase Mediated by Drosophila {alpha}PS2{beta}PS Integrin and Importin-7

Brian P. James,*{dagger} Thomas A. Bunch,* Srinivasan Krishnamoorthy,{ddagger}{sect} Lizabeth A. Perkins,{ddagger} and Danny L. Brower*

*Department of Molecular and Cellular Biology, Center for Insect Science, and Department of Biochemistry and Molecular Biophysics, Arizona Cancer Center, Tucson, AZ 85724; {ddagger}Pediatric Surgical Research Laboratories, Department of Surgery, Massachusetts General Hospital, Harvard Medical School, Boston, MA 02115

Monitoring Editor: Jean Schwarzbauer

The control of gene expression by the MAP kinase ERK requires its translocation into the nucleus. In Drosophila S2 cells nuclear accumulation of diphospho-ERK (dpERK) is greatly reduced by interfering dsRNA against DIM-7 (Drosophila importin-7) or by the expression of integrin mutants, either during active cell spreading or following stimulation by insulin. In both cases, total ERK phosphorylation (on westerns) is not significantly affected, and ERK accumulates in a perinuclear ring. Tyrosine phosphorylation of DIM-7 is reduced in cells expressing integrin mutants, indicating a mechanistic link between these components. DIM-7 and integrins localize to the same actin-containing peripheral regions in spreading cells, but DIM-7 is not concentrated in paxillin-positive focal contacts or stable focal adhesions. The Corkscrew (SHP-2) tyrosine phosphatase binds DIM-7, and Corkscrew is required for the cortical localization of DIM-7. These data suggest a model in which ERK phosphorylation must be spatially coupled to integrin-mediated DIM-7 activation in order to make a complex that can be imported efficiently. Moreover, dpERK nuclear import can be restored in DIM-7 deficient cells by Xenopus Importin-7, demonstrating that ERK import is an evolutionarily conserved function of this protein.

Present addresses: {dagger}M.D. Anderson Cancer Center, 1515 Holcombe Blvd., Houston, TX 77030; {sect}Department of Genetics, Drosophila RNAi Screening Center, Harvard Medical School, 77 Avenue Louis Pasteur, Boston, MA 02115.

Address correspondence to: Danny L. Brower (dbrower{at}email.arizona.edu)






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