Drosophila endosomal proteins hook and deep orange regulate synapse size but not synaptic vesicle recycling

Radhakrishnan Narayanan, Helmut Krämer, Mani Ramaswami

Research output: Contribution to journalArticlepeer-review

26 Scopus citations


To study the function of endosomes at synapses we analyzed the localization and function of two Drosophila endosomal proteins, Hook and Deep orange (Dor), at the larval neuromuscular junction. Hook, a negative regulator of endocytic trafficking, and Dor, a positive regulator of endocytic trafficking, are highly enriched at synapses, especially close to postsynaptic membranes. Mutations in hook (hk) and dor do not affect synaptic vesicle recycling, as assessed by electro-physiological analysis of synaptic transmission and behavioral studies of double mutants with shi(ts) mutations that alter vesicle recycling. However, hk and dor mutations alter the number of presynaptic varicosities (synapse size) in opposing ways. Synapse size is increased in hk11 mutants and is decreased in dor4 mutants. Double mutants for dor and hk show a dor-like phenotype. These effects on synapse size parallel known functions of Hook and Dor in endocytosis and strongly indicate a role for endocytic trafficking in the regulation of synapse size in vivo. Our observations suggest a model in which Hook and Dor function in later stages of endocytosis is essential for regulating synaptic plasma membrane composition but not synaptic vesicle recycling. (C) 2000 John Wiley and Sons, Inc.

Original languageEnglish (US)
Pages (from-to)105-119
Number of pages15
JournalJournal of Neurobiology
Issue number2
StatePublished - Nov 5 2000


  • Cell adhesion
  • Endocytosis
  • Eye color
  • Lysosomes
  • Synaptic plasticity

ASJC Scopus subject areas

  • Neuroscience(all)
  • Cellular and Molecular Neuroscience


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