title: Calcium destabilises Drosophila cactus protein and dephosphorylates the dorsal transcription factor.
abstract: The Drosophila cactus and dorsal proteins are required for the development of embryonic dorso-ventral polarity and probably also for the innate immune response of the insect. Like their mammalian counterparts (the cytoplasmic anchor protein I kappa B and the rel/NF kappa B transcription factors) cactus and dorsal are regulated at the level of nuclear localisation. We showed previously that increased intra-cellular calcium levels induced by the ionophore ionomycin can activate dorsal/cactus complexes in the Drosophila cell line SL2. In order to study further the activation of dorsal/cactus complexes by calcium, we have prepared a cell line (SLDL) in which dorsal is expressed constitutively. In this paper we show that in SLDL cells ionomycin induces a rapid destruction of cactus and dephosphorylation of dorsal. These results suggest a role for the protein phosphatase calcineurin in calcium mediated activation of dorsal/cactus complexes. They also indicate that in the resting cell constitutive phosphorylation of dorsal is in equilibrium with calcium dependent dephosphorylation.
authors.affiliation: Department of Biochemistry, University of Cambridge, UK.
authors.forename: K
authors.initials: K
authors.lastname: Kubota
authors.forename: N J
authors.initials: NJ
authors.lastname: Gay
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D015153:Blotting, Western; D002118:Calcium / Q000494:pharmacology*; D002460:Cell Line; D017124:Conserved Sequence; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000187:drug effects / Q000378:metabolism*; D029721:Drosophila Proteins; D004331:Drosophila melanogaster / Q000196:embryology; D004625:Embryo, Nonmammalian; D015759:Ionomycin / Q000494:pharmacology; D008969:Molecular Sequence Data; D009687:Nuclear Proteins / Q000187:drug effects / Q000378:metabolism*; D010750:Phosphoproteins / Q000737:chemistry* / Q000187:drug effects / Q000378:metabolism*; D010766:Phosphorylation; D017386:Sequence Homology, Amino Acid; D014157:Transcription Factors / Q000378:metabolism*
chemical_list: D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D009687:Nuclear Proteins; D010750:Phosphoproteins; D014157:Transcription Factors; C062236:dl protein, Drosophila; C077938:cact protein, Drosophila; D015759:Ionomycin; D002118:Calcium