Dissecting the roles of the Drosophila EGF receptor in eye development and MAP kinase activation

A new conditional Egfr allele was used to dissect the roles of the receptor in eye development and to test two published models. EGFR function is necessary for morphogenetic furrow initiation, is not required for establishment of the founder R8 cell in each ommatidium, but is necessary to maintain its differentiated state. EGFR is required subsequently for recruitment of all other neuronal cells. The initial EGFR-dependent MAP kinase activation occurs in the furrow, but the active kinase (dp-ERK) is observed only in the cytoplasm for over 2 hours. Similarly, SEVENLESS-dependent activation results in cytoplasmic appearance of dp-ERK for 6 hours. These results suggest an additional regulated step in this pathway and we discuss models for this.

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Role of the EGFR/Ras/Raf pathway in specification of photoreceptor cells in the Drosophila retina

Development ◽

10.1242/dev.128.7.1183 ◽

2001 ◽

Vol 128 (7) ◽

pp. 1183-1191 ◽

Cited By ~ 3

Author(s):

L. Yang ◽

N.E. Baker

Keyword(s):

Map Kinase ◽

Egf Receptor ◽

Eye Development ◽

Photoreceptor Cells ◽

Cell Types ◽

Cell Specification ◽

Kinase Activation ◽

Cell Spacing ◽

Egfr Activation

The Drosophila EGF receptor is required for differentiation of many cell types during eye development. We have used mosaic analysis with definitive null mutations to analyze the effects of complete absence of EGFR, Ras or Raf proteins during eye development. The Egfr, ras and raf genes are each found to be essential for recruitment of R1-R7 cells. In addition Egfr is autonomously required for MAP kinase activation. EGFR is not essential for R8 cell specification, either alone or redundantly with any other receptor that acts through Ras or Raf, or by activating MAP kinase. As with Egfr, loss of ras or raf perturbs the spacing and arrangement of R8 precursor cells. R8 cell spacing is not affected by loss of argos in posteriorly juxtaposed cells, which rules out a model in which EGFR acts through argos expression to position R8 specification in register between adjacent columns of ommatidia. The R8 spacing role of the EGFR was partially affected by simultaneous deletion of spitz and vein, two ligand genes, but the data suggest that EGFR activation independent of spitz and vein is also involved. The results prove that R8 photoreceptors are specified and positioned by distinct mechanisms from photoreceptors R1-R7.

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Integrins can collaborate with growth factors for phosphorylation of receptor tyrosine kinases and MAP kinase activation: roles of integrin aggregation and occupancy of receptors.

The Journal of Cell Biology ◽

10.1083/jcb.135.6.1633 ◽

1996 ◽

Vol 135 (6) ◽

pp. 1633-1642 ◽

Cited By ~ 536

Author(s):

S Miyamoto ◽

H Teramoto ◽

J S Gutkind ◽

K M Yamada

Keyword(s):

Signal Transduction ◽

Growth Factors ◽

Growth Factor ◽

Map Kinase ◽

Tyrosine Kinases ◽

Map Kinases ◽

Egf Receptor ◽

Growth Factor Receptor ◽

Kinase Activation ◽

Transient Activation

Integrins mediate cell adhesion, migration, and a variety of signal transduction events. These integrin actions can overlap or even synergize with those of growth factors. We examined for mechanisms of collaboration or synergy between integrins and growth factors involving MAP kinases, which regulate many cellular functions. In cooperation with integrins, the growth factors EGF, PDGF-BB, and basic FGF each produced a marked, transient activation of the ERK (extracellular signal-regulated kinase) class of MAP kinase, but only if the integrins were both aggregated and occupied by ligand. Transmembrane accumulation of total tyrosine-phosphorylated proteins, as well as nonsynergistic MAP kinase activation, could be induced by simple integrin aggregation, whereas enhanced transient accumulation of the EGF-receptor substrate eps8 required integrin aggregation and occupancy, as well as EGF treatment. Each type of growth factor receptor was itself induced to aggregate transiently by integrin ligand-coated beads in a process requiring both aggregation and occupancy of integrin receptors, but not the presence of growth factor ligand. Synergism was also observed between integrins and growth factors for triggering tyrosine phosphorylation of EGF, PDGF, and FGF receptors. This collaborative response also required both integrin aggregation and occupancy. These studies identify mechanisms in the signal transduction response to integrins and growth factors that require various combinations of integrin aggregation and ligands for integrin or growth factor receptors, providing opportunities for collaboration between these major regulatory systems.

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Interaction between Drosophila EGF receptor and vnd determines three dorsoventral domains of the neuroectoderm

Development ◽

10.1242/dev.125.18.3625 ◽

1998 ◽

Vol 125 (18) ◽

pp. 3625-3633 ◽

Cited By ~ 5

Author(s):

Y. Yagi ◽

T. Suzuki ◽

S. Hayashi

Keyword(s):

Map Kinase ◽

Receptor Tyrosine Kinase ◽

Egf Receptor ◽

Regulatory Region ◽

Homeobox Gene ◽

Kinase Activation ◽

Intermediate Column ◽

Kinase Signaling Pathway ◽

Map Kinase Signaling Pathway

Neurogenesis in Drosophila melanogaster starts by an ordered appearance of neuroblasts arranged in three columns (medial, intermediate and lateral) in each side of the neuroectoderm. Here we show that, in the intermediate column, the receptor tyrosine kinase DER represses expression of proneural genes, achaete and scute, and is required for the formation of neuroblasts. Most of the early function of DER is likely to be mediated by the Ras-MAP kinase signaling pathway, which is activated in the intermediate column, since a loss of a component of this pathway leads to a phenotype identical to that in DER mutants. MAP-kinase activation was also observed in the medial column where esg and proneural gene expression is unaffected by DER. We found that the homeobox gene vnd is required for the expression of esg and scute in the medial column, and show that vnd acts through the negative regulatory region of the esg enhancer that mediates the DER signal, suggesting the role of vnd is to counteract DER-dependent repression. Thus nested expression of vnd and the DER activator rhomboid is crucial to subdivide the neuroectoderm into the three dorsoventral domains.

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The platelet-derived-growth-factor receptor, not the epidermal-growth-factor receptor, is used by lysophosphatidic acid to activate p42/44 mitogen-activated protein kinase and to induce prostaglandin G/H synthase-2 in mesangial cells

Biochemical Journal ◽

10.1042/bj3450217 ◽

2000 ◽

Vol 345 (2) ◽

pp. 217-224 ◽

Cited By ~ 24

Author(s):

Margarete GOPPELT-STRUEBE ◽

Stefanie FICKEL ◽

Christian O. A. REISER

Keyword(s):

Growth Factor ◽

Map Kinase ◽

Map Kinases ◽

Egf Receptor ◽

Mesangial Cells ◽

Growth Factor Receptor ◽

Pdgf Receptor ◽

Kinase Activation ◽

Mitogen Activated Protein ◽

Epidermal Growth

In renal mesangial cells, activation of protein tyrosine kinase receptors may increase the activity of mitogen-activated protein (MAP) kinases and subsequently induce expression of prostaglandin G/H synthase-2 (PGHS-2, cyclo-oxygenase-2). As examples, platelet-derived growth factor (PDGF) and epidermal growth factor (EGF) were shown to transiently enhance p42/44 MAP kinase activity, which was an essential step in the induction of PGHS-2 mRNA and protein. Inhibitors of receptor kinase activities, tyrphostins AG1296 and AG1478, specifically inhibited the effects of PDGF and EGF respectively. Activation of p42/44 and p38 MAP kinases and PGHS-2 induction were also mediated by lysophosphatidic acid (LPA), which binds to pertussis-toxin-sensitive G-protein-coupled receptors. LPA stimulation was inhibited by AG1296, but not AG1478, indicating involvement of the PDGF receptor kinase in LPA-mediated signalling. This was confirmed by pertussis-toxin-sensitive tyrosine phosphorylation of the PDGF receptor by LPA, whereas no phosphorylation of the EGF receptor was detected. For comparison, 5-hydroxytryptamine (‘serotonin’)-mediated signalling was only partially inhibited by AG1296, and also not affected by AG1478. A strong basal AG1296-sensitive tyrosine phosphorylation of the PDGF receptor and a set of other proteins was observed, which by itself was not sufficient to induce p42/44 MAP kinase activation, but played an essential role not only in LPA- but also in phorbol ester-mediated activation. Taken together, the PDGF receptor, but not the EGF receptor, is involved in LPA-mediated MAP kinase activation and PGHS-2 induction in primary mesangial cells, where both protein kinase receptors are present and functionally active.

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