title: Anterograde Activin signaling regulates postsynaptic membrane potential and GluRIIA/B abundance at the Drosophila neuromuscular junction.
abstract: Members of the TGF-β superfamily play numerous roles in nervous system development and function. In Drosophila, retrograde BMP signaling at the neuromuscular junction (NMJ) is required presynaptically for proper synapse growth and neurotransmitter release. In this study, we analyzed whether the Activin branch of the TGF-β superfamily also contributes to NMJ development and function. We find that elimination of the Activin/TGF-β type I receptor babo, or its downstream signal transducer smox, does not affect presynaptic NMJ growth or evoked excitatory junctional potentials (EJPs), but instead results in a number of postsynaptic defects including depolarized membrane potential, small size and frequency of miniature excitatory junction potentials (mEJPs), and decreased synaptic densities of the glutamate receptors GluRIIA and B. The majority of the defective smox synaptic phenotypes were rescued by muscle-specific expression of a smox transgene. Furthermore, a mutation in actβ, an Activin-like ligand that is strongly expressed in motor neurons, phenocopies babo and smox loss-of-function alleles. Our results demonstrate that anterograde Activin/TGF-β signaling at the Drosophila NMJ is crucial for achieving normal abundance and localization of several important postsynaptic signaling molecules and for regulating postsynaptic membrane physiology. Together with the well-established presynaptic role of the retrograde BMP signaling, our findings indicate that the two branches of the TGF-β superfamily are differentially deployed on each side of the Drosophila NMJ synapse to regulate distinct aspects of its development and function.
authors.affiliation: Department of Genetics, Cell Biology and Development, University of Minnesota, Minneapolis, Minnesota, United States of America.
authors.forename: Myung-Jun
authors.initials: MJ
authors.lastname: Kim
authors.affiliation: Department of Genetics, Cell Biology and Development, University of Minnesota, Minneapolis, Minnesota, United States of America.
authors.forename: Michael B
authors.initials: MB
authors.lastname: O'Connor
mesh_terms: D028341:Activins / Q000235:genetics / Q000378:metabolism*; D000818:Animals; D004268:DNA-Binding Proteins / Q000378:metabolism; D029721:Drosophila Proteins / Q000172:deficiency / Q000235:genetics / Q000378:metabolism; D004331:Drosophila melanogaster / Q000166:cytology* / Q000378:metabolism; D008024:Ligands; D009154:Mutation; D009469:Neuromuscular Junction / Q000166:cytology* / Q000378:metabolism*; D021381:Protein Transport; D017470:Receptors, Glutamate / Q000378:metabolism*; D015398:Signal Transduction; D051896:Smad Proteins, Receptor-Regulated / Q000172:deficiency / Q000235:genetics; D055366:Synaptic Potentials; D014157:Transcription Factors / Q000378:metabolism; D016212:Transforming Growth Factor beta / Q000378:metabolism; D025521:Tumor Suppressor Proteins / Q000378:metabolism
chemical_list: D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D008024:Ligands; C112506:MAD protein, Drosophila; D017470:Receptors, Glutamate; D051896:Smad Proteins, Receptor-Regulated; C115826:Smox protein, Drosophila; D014157:Transcription Factors; D016212:Transforming Growth Factor beta; D025521:Tumor Suppressor Proteins; D028341:Activins; C070350:dlg1 protein, Drosophila