A temperature-sensitive MEK mutation demonstrates the conservation of the signaling pathways activated by receptor tyrosine kinases.
MEK, a dual specificity threonine/tyrosine kinase, has been postulated to be a convergent point for signaling from receptor protein tyrosine kinases (RTKs) and G-protein-coupled receptors. In contrast to yeast and mammalian cells where several MEKs have been isolated, only one Drosophila MEK (D-Mek) has been characterized to date. Previous studies have shown that D-Mek acts in the Torso RTK signaling pathway. To demonstrate that D-Mek also operates downstream of other RTKs, we generated a temperature-sensitive allele of D-mek (D-mekts) by site-directed mutagenesis based on the amino acid change of a yeast cdc2ts mutation. Using D-mekts, we show that in addition to its role in Torso signaling, D-Mek operates in the Sevenless and in the Drosophila epidermal growth factor RTK pathways. Because loss-of-function mutations in D-mek and the upstream receptors give rise to similar phenotypes, it suggests that D-mek is the only MEK activated by Drosophila RTKs. In addition, we demonstrate that different RTK pathways respond differently to alteration in D-Mek activity.
Howard Hughes Medical Institute, Department of Genetics, Harvard Medical School, Boston, Massachusetts 02115.
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Hsu
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Perrimon
D000483:Alleles; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D017124:Conserved Sequence; D017931:DNA Primers / Q000235:genetics; D004330:Drosophila / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D005260:Female; D018507:Gene Expression Regulation, Developmental; D015971:Gene Expression Regulation, Enzymologic; D017344:Genes, Insect; D048369:MAP Kinase Kinase 1; D008297:Male; D020929:Mitogen-Activated Protein Kinase Kinases; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D017346:Protein Serine-Threonine Kinases / Q000235:genetics* / Q000378:metabolism; D011505:Protein-Tyrosine Kinases / Q000235:genetics* / Q000378:metabolism; D020794:Receptor Protein-Tyrosine Kinases / Q000378:metabolism*; D015398:Signal Transduction / Q000235:genetics; D013045:Species Specificity; D013696:Temperature
D017931:DNA Primers; D011505:Protein-Tyrosine Kinases; D020794:Receptor Protein-Tyrosine Kinases; D017346:Protein Serine-Threonine Kinases; D048369:MAP Kinase Kinase 1; D020929:Mitogen-Activated Protein Kinase Kinases