Isolation and characterization of a Drosophila homologue of mitogen-activated protein kinase phosphatase-3 which has a high substrate specificity towards extracellular-signal-regulated kinase

Abstract

A partial C-terminal cDNA sequence of a novel Drosophila mitogen-activated protein kinase phosphatase (MKP), designated DMKP-3, was identified from an epitope expressed sequence tag database, and the missing N-terminal cDNA fragment was cloned from a Drosophila cDNA library. DMKP-3 is a protein of 411 amino acids, with a calculated molecular mass of 45.8kDa; the deduced amino acid sequence is most similar to that of mammalian MKP-3. Recombinant DMKP-3 produced in Escherichia coli retained intrinsic tyrosine phosphatase activity. In addition, DMKP-3 specifically inhibited extracellular-signal-regulated kinase (ERK) activity, but was without a significant affect on c-Jun N-terminal kinase (JNK) and p38 activities, when it was overexpressed in Schneider cells. DMKP-3 interacted specifically with Drosophila ERK (DERK) via its N-terminal domain. In addition, DMKP-3 specifically inhibited Elk-1-dependent trans-reporter gene expression in mammalian CV1 cells, and dephosphorylated activated mammalian ERK in vitro. DMKP-3 is uniquely localized in the cytoplasm within Schneider cells, and gene expression is tightly regulated during development. Thus DMKP-3 is a Drosophila homologue of mammalian MKP-3, and may play important roles in the regulation of various developmental processes.

TheDrosophiladual-specificity ERK phosphatase DMKP3 cooperates with the ERK tyrosine phosphatase PTP-ER

“…This hypothesis is supported by data from Chu et al (Chu et al, 1996) who showed that the mammalian Sevenmaker homologue ERK2 D319N is inactivated by DSPs in COS-7 cells at high, but not in NIH3T3 cells at lower expression. The genetic interactions are consistent with a function of DMKP3 between Raf and Rl SEM and strongly support the interpretation that ERK is the main target of DMKP3 (Kim et al, 2002).…”

“…In a recent study Kim et al (Kim et al, 2002) have shown that the Drosophila dual specificity phosphatase DMKP3 dephosphorylates ERK, but not JNK or p38 MAP kinases in vitro. Here we provide in vivo evidence in Drosophila that DMKP3 is a phosphatase specific for ERK.…”

“…(1) DMKP3 dephosphorylates ERK but not JNK in vitro (Kim et al, 2002). (2) showing both Dmkp3 -(pink in the bar diagram) and Dmkp3 + photoreceptors (red) at any position.…”

Egfr is essential for maintaining epithelial integrity during tracheal remodelling inDrosophila

“…The MAPK pathway plays a role in the maintenance of tracheal branch integrity, but not through the nuclear effector Pnt Mkp3 has been shown to act as a specific negative regulator of the ERK-type MAPK (Kim et al, 2002;Rintelen et al, 2003). ERK is a central element of the Ras/MAPK pathway whose activity is regulated by phosphorylation (Roux and Blenis, 2004).…”

La signalisation RTK/RAS/ERK élargie

“…PTP-ER est ellemême phosphorylée et inactivée par ERK, décrivant ainsi une boucle de rétroaction. Par ailleurs, MKP3, une phosphatase à double spécificité (sérine/thréo-nine et tyrosine) agissant aussi sur ERK, a été mise en évidence par homologie de séquence chez la mouche et le nématode [45,46]. Une étude chez la drosophile a montré que PTP-ER et MKP3 peuvent agir indépen-damment l'une de l'autre, ou de manière concertée selon le contexte cellulaire [47].…”