title: A splice isoform of DNedd4, DNedd4-long, negatively regulates neuromuscular synaptogenesis and viability in Drosophila.
abstract: BACKGROUND
  Neuromuscular (NM) synaptogenesis is a tightly regulated process. We previously showed that in flies, Drosophila Nedd4 (dNedd4/dNedd4S) is required for proper NM synaptogenesis by promoting endocytosis of commissureless from the muscle surface, a pre-requisite step for muscle innervation. DNedd4 is an E3 ubiquitin ligase comprised of a C2-WW(x3)-Hect domain architecture, which includes several splice isoforms, the most prominent ones are dNedd4-short (dNedd4S) and dNedd4-long (dNedd4Lo).
  
  
  RESULTS
  We show here that while dNedd4S is essential for NM synaptogenesis, the dNedd4Lo isoform inhibits this process and causes lethality. Our results reveal that unlike dNedd4S, dNedd4Lo cannot rescue the lethality of dNedd4 null (DNedd4(T121FS)) flies. Moreover, overexpression of UAS-dNedd4Lo specifically in wildtype muscles leads to NM synaptogenesis defects, impaired locomotion and larval lethality. These negative effects of dNedd4Lo are ameliorated by deletion of two regions (N-terminus and Middle region) unique to this isoform, and by inactivating the catalytic activity of dNedd4Lo, suggesting that these unique regions, as well as catalytic activity, are responsible for the inhibitory effects of dNedd4Lo on synaptogenesis. In accord with these findings, we demonstrate by sqRT-PCR an increase in dNedd4S expression relative to the expression of dNedd4Lo during embryonic stages when synaptogenesis takes place.
  
  
  CONCLUSIONS
  Our studies demonstrate that splice isoforms of the same dNedd4 gene can lead to opposite effects on NM synaptogenesis.
authors: Program in Cell Biology, The Hospital for Sick Children, Toronto, Canada.
authors: Yunan
authors: Y
authors: Zhong
authors: Alina
authors: A
authors: Shtineman-Kotler
authors: Leo
authors: L
authors: Nguyen
authors: Konstantin G
authors: KG
authors: Iliadi
authors: Gabrielle L
authors: GL
authors: Boulianne
authors: Daniela
authors: D
authors: Rotin
mesh_terms: D000818:Animals; D055162:Biocatalysis; D004331:Drosophila melanogaster / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D056827:Endosomal Sorting Complexes Required for Transport / Q000235:genetics / Q000378:metabolism*; D005786:Gene Expression Regulation; D007814:Larva / Q000378:metabolism / Q000502:physiology; D008124:Locomotion; D009132:Muscles / Q000378:metabolism / Q000502:physiology; D009154:Mutation; D000075702:Nedd4 Ubiquitin Protein Ligases; D009469:Neuromuscular Junction / Q000378:metabolism*; D020033:Protein Isoforms / Q000235:genetics / Q000378:metabolism; D051057:Proto-Oncogene Proteins c-akt / Q000378:metabolism; D044767:Ubiquitin-Protein Ligases / Q000235:genetics / Q000378:metabolism*
chemical_list: D056827:Endosomal Sorting Complexes Required for Transport; D020033:Protein Isoforms; D000075702:Nedd4 Ubiquitin Protein Ligases; D044767:Ubiquitin-Protein Ligases; D051057:Proto-Oncogene Proteins c-akt