Functional interactions between the pelle kinase, Toll receptor, and tube suggest a mechanism for activation of dorsal.
A complex signal transduction pathway functions in the early Drosophila embryo to establish dorsal-ventral polarity. Activation of this pathway results in the nuclear transport of the protein dorsal (dl), a member of the rel/NF-kappaB family of transcription factors. Genetic studies have identified three intracellular components whose activity is required for activation of dl: Toll, a transmembrane receptor; pelle (pll), a serine/threonine protein kinase; and tube, a protein of unknown function. Here we examine the activities of these proteins when coexpressed in Drosophila Schneider cells. Coexpression of pll with dl enhanced dl nuclear localization and resulted in a modest increase in transcriptional activity. However, when pll was coexpressed with a specific mutant derivative of Toll (TlNaeI), although not with wild-type Toll, a striking synergistic activation of dl was detected. Unexpectedly, coexpression of pll plus TlNaeI, in the absence of dl, resulted in a similar synergistic activation of a GAL4-tube fusion protein. Based on these and other results, we propose a model in which pll receives a signal from activated Toll and phosphorylates tube, which then participates directly in dl activation.
Norris
J L
JL
Department of Biological Sciences, Columbia University, New York, NY 10027, USA.
Manley
J L
JL
D000818:Animals; D001692:Biological Transport; D002451:Cell Compartmentation; D002467:Cell Nucleus / Q000378:metabolism; D002478:Cells, Cultured; D004268:DNA-Binding Proteins; D004330:Drosophila / Q000196:embryology / Q000378:metabolism*; D029721:Drosophila Proteins; D005656:Fungal Proteins / Q000235:genetics; D017353:Gene Deletion; D018507:Gene Expression Regulation, Developmental; D007301:Insect Hormones / Q000235:genetics / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism; D008957:Models, Genetic; D009687:Nuclear Proteins / Q000378:metabolism*; D010750:Phosphoproteins / Q000378:metabolism*; D017346:Protein Serine-Threonine Kinases / Q000235:genetics / Q000378:metabolism; D011506:Proteins / Q000378:metabolism; D011956:Receptors, Cell Surface / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000378:metabolism; D029701:Saccharomyces cerevisiae Proteins; D015398:Signal Transduction; D051193:Toll-Like Receptors; D014157:Transcription Factors / Q000378:metabolism*; D014158:Transcription, Genetic; D014162:Transfection
D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D005656:Fungal Proteins; C052130:GAL4 protein, S cerevisiae; D007301:Insect Hormones; D008562:Membrane Glycoproteins; D009687:Nuclear Proteins; D010750:Phosphoproteins; D011506:Proteins; D011956:Receptors, Cell Surface; D011994:Recombinant Proteins; D029701:Saccharomyces cerevisiae Proteins; C068721:Tl protein, Drosophila; D051193:Toll-Like Receptors; D014157:Transcription Factors; C062236:dl protein, Drosophila; C084727:tub protein, Drosophila; C079896:pll protein, Drosophila; D017346:Protein Serine-Threonine Kinases