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Mol Cell. 1999 Jun;3(6):741-50.

PTP-ER, a novel tyrosine phosphatase, functions downstream of Ras1 to downregulate MAP kinase during Drosophila eye development.

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Howard Hughes Medical Institute, Department of Molecular and Cell Biology, University of California, Berkeley 94720-3200, USA.


Activation of ERK/MAPK is a key event downstream of RAS. The duration, extent, and timing of MAPK activity is integral to signal specificity. Consequently, inactivation of MAPK by phosphatases has emerged as a critical element in the precise control of signal output. We have cloned and characterized a novel cytoplasmic protein tyrosine phosphatase, PTP-ER, which is related to mammalian PCPTP1, LC-PTP/HePTP, and STEP tyrosine phosphatases. PTP-ER mutants produce extra R7 cells and enhance activated Ras1 signaling. Ectopic expression of PTP-ER dramatically inhibits RAS1/MAPK signaling. PTP-ER binds to and inactivates Drosophila ERK/MAPK; however, it is unable to dephosphorylate and downregulate Drosophila MAPKSevenmaker. Resistance to PTP-ER activity partially accounts for the Sevenmaker mutant phenotype.

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