Synaptic activity modifies the levels of Dorsal and Cactus at the neuromuscular junction of Drosophila.
The Drosophila Rel transcription factor Dorsal and its inhibitor Cactus participate in a signal transduction pathway involved in several biologic processes, including embryonic pattern formation, immunity, and muscle development. In contrast with embryonic muscle, where Dorsal is reportedly absent, this protein and Cactus accumulates in the neuromuscular junctions in the muscle of both larvae and adults. The phenotype of homozygous dorsal mutant larvae suggested that Dorsal and Cactus maybe necessary for normal function and maintenance of the neuromuscular system. Here we investigate if these proteins can respond to synaptic activity. Using larval body wall preparations and antibodies specific for Dorsal or Cactus we show that the amount of these proteins at the neuromuscular junction is substantially decreased after electrical stimulation of the nerves or incubation in glutamate, the principal transmitter in this type of synapse. The specificity of the response was tested with a glutamate receptor antagonist (argiotoxin 636). Because the effect can be reproduced using a calcium ionophore (ionomycin treatment) as well as blocked by the inhibition of the muscle ryanodine receptor (tetracaine treatment), the involvement of calcium in this process seems likely. We also observed that the inhibition of the calcium dependent protein phosphatase calcineurin prevents the effect of glutamate on the fluorescence for Dorsal and Cactus, suggesting its participation in a signal transduction cascade that may activate Dorsal in the muscle independently of Toll. Our results are consistent with a novel function of the Rel factor Dorsal in a molecular pathway turned on by neural activity and/or contractile activity.
Bolatto
Carmen
C
Departamento de Histología y Embriología, Facultad de Medicina, Universidad de la República, Uruguay.
Chifflet
Silvia
S
Megighian
Aram
A
Cantera
Rafael
R
D000779:Anesthetics, Local / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000494:pharmacology; D015816:Cell Adhesion Molecules, Neuronal / Q000378:metabolism; D002614:Chelating Agents / Q000494:pharmacology; D016572:Cyclosporine / Q000494:pharmacology; D004268:DNA-Binding Proteins / Q000187:drug effects / Q000378:metabolism*; D029721:Drosophila Proteins; D004331:Drosophila melanogaster / Q000378:metabolism*; D004533:Egtazic Acid / Q000494:pharmacology; D004558:Electric Stimulation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D018698:Glutamic Acid / Q000494:pharmacology; D007150:Immunohistochemistry; D007210:Indoleacetic Acids; D015759:Ionomycin / Q000494:pharmacology; D007476:Ionophores / Q000494:pharmacology; D007814:Larva; D018613:Microscopy, Confocal; D009469:Neuromuscular Junction / Q000187:drug effects / Q000196:embryology* / Q000378:metabolism*; D009687:Nuclear Proteins / Q000187:drug effects / Q000378:metabolism*; D010648:Phenylacetates / Q000494:pharmacology; D010750:Phosphoproteins / Q000187:drug effects / Q000378:metabolism*; D011073:Polyamines / Q000494:pharmacology; D013748:Tetracaine / Q000494:pharmacology; D014157:Transcription Factors
D000779:Anesthetics, Local; D015816:Cell Adhesion Molecules, Neuronal; D002614:Chelating Agents; D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D004791:Enzyme Inhibitors; D018691:Excitatory Amino Acid Antagonists; D007210:Indoleacetic Acids; D007476:Ionophores; D009687:Nuclear Proteins; D010648:Phenylacetates; D010750:Phosphoproteins; D011073:Polyamines; D014157:Transcription Factors; C062236:dl protein, Drosophila; C051642:fasciclin II; D013748:Tetracaine; C558368:argiotoxin-636; C077938:cact protein, Drosophila; D018698:Glutamic Acid; D004533:Egtazic Acid; D015759:Ionomycin; D016572:Cyclosporine; D002118:Calcium