Selective nuclear transport of the Drosophila morphogen dorsal can be established by a signaling pathway involving the transmembrane protein Toll and protein kinase A.
Establishment of dorsal-ventral polarity in the early Drosophila embryo requires a concentration gradient of the maternal morphogen dorsal (dl). This concentration gradient is established by selective nuclear transport of dl so that dl protein is present only in ventral nuclei. The activity of 11 genes is required for dl nuclear localization. One of these genes, Toll, encodes a transmembrane protein that appears to play the most direct role in regulating dl localization. We have examined the effects of Toll on dl in cotransfected Schneider cells to gain insight into the nature of the interaction between these proteins. We have found that Toll can enhance the nuclear localization of dl and, independently, the ability of dl to activate transcription once in the nucleus. We present evidence that the signaling pathway from Toll to dl involves protein kinase A (PKA) and that nuclear transport and activation of dl results from phosphorylation of dl by PKA. We discuss the significance of these results with respect both to Drosophila embryogenesis and to the regulation of the mammalian transcription factor NF-kappa B.
Norris
J L
JL
Department of Biological Sciences, Columbia University, New York, New York 10027.
Manley
J L
JL
D000818:Animals; D001483:Base Sequence; D001692:Biological Transport; D002460:Cell Line; D002467:Cell Nucleus / Q000378:metabolism; D004330:Drosophila / Q000378:metabolism*; D029721:Drosophila Proteins; D007301:Insect Hormones / Q000235:genetics / Q000378:metabolism*; D008562:Membrane Glycoproteins / Q000235:genetics / Q000378:metabolism*; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D009687:Nuclear Proteins / Q000378:metabolism*; D010750:Phosphoproteins; D010766:Phosphorylation; D010957:Plasmids / Q000235:genetics; D011494:Protein Kinases / Q000235:genetics / Q000378:metabolism*; D011956:Receptors, Cell Surface / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology; D051193:Toll-Like Receptors; D014157:Transcription Factors; D014158:Transcription, Genetic / Q000502:physiology; D014162:Transfection / Q000235:genetics
D029721:Drosophila Proteins; D007301:Insect Hormones; D008562:Membrane Glycoproteins; D009687:Nuclear Proteins; D010750:Phosphoproteins; D011956:Receptors, Cell Surface; C068721:Tl protein, Drosophila; D051193:Toll-Like Receptors; D014157:Transcription Factors; C062236:dl protein, Drosophila; D011494:Protein Kinases