title: Phosphorylation of Synaptojanin Differentially Regulates Endocytosis of Functionally Distinct Synaptic Vesicle Pools.
abstract: The rapid replenishment of synaptic vesicles through endocytosis is crucial for sustaining synaptic transmission during intense neuronal activity. Synaptojanin (Synj), a phosphoinositide phosphatase, is known to play an important role in vesicle recycling by promoting the uncoating of clathrin following synaptic vesicle uptake. Synj has been shown to be a substrate of the minibrain (Mnb) kinase, a fly homolog of the dual-specificity tyrosine phosphorylation-regulated kinase 1A (DYRK1A); however, the functional impacts of Synj phosphorylation by Mnb are not well understood. Here we identify that Mnb phosphorylates Synj at S1029 in Drosophila We find that phosphorylation of Synj at S1029 enhances Synj phosphatase activity, alters interaction between Synj and endophilin, and promotes efficient endocytosis of the active cycling vesicle pool (also referred to as exo-endo cycling pool) at the expense of reserve pool vesicle endocytosis. Dephosphorylated Synj, on the other hand, is deficient in the endocytosis of the active recycling pool vesicles but maintains reserve pool vesicle endocytosis to restore total vesicle pool size and sustain synaptic transmission. Together, our findings reveal a novel role for Synj in modulating reserve pool vesicle endocytosis and further indicate that dynamic phosphorylation and dephosphorylation of Synj differentially maintain endocytosis of distinct functional synaptic vesicle pools.
  
  
  
  Synaptic vesicle endocytosis sustains communication between neurons during a wide range of neuronal activities by recycling used vesicle membrane and protein components. Here we identify that Synaptojanin, a protein with a known role in synaptic vesicle endocytosis, is phosphorylated at S1029 in vivo by the Minibrain kinase. We further demonstrate that the phosphorylation status of Synaptojanin at S1029 differentially regulates its participation in the recycling of distinct synaptic vesicle pools. Our results reveal a new role for Synaptojanin in maintaining synaptic vesicle pool size and in reserve vesicle endocytosis. As Synaptojanin and Minibrain perturbations are associated with various neurological disorders, such as Parkinson's, autism, and Down syndrome, understanding mechanisms modulating Synaptojanin function provides valuable insights into processes affecting neuronal communication.
authors: Zilkha Neurogenetic Institute.
authors: Junhua
authors: 0000-0001-5817-8870
authors: J
authors: Geng
authors: Zilkha Neurogenetic Institute, Department of Biochemistry and Molecular Biology, and.
authors: Liping
authors: L
authors: Wang
authors: Zilkha Neurogenetic Institute, Neuroscience Graduate Program, University of Southern California, Los Angeles, California 90089.
authors: Joo Yeun
authors: JY
authors: Lee
authors: Zilkha Neurogenetic Institute.
authors: Chun-Kan
authors: 0000-0002-1194-9137
authors: CK
authors: Chen
authors: Zilkha Neurogenetic Institute, Department of Cell and Neurobiology, Keck School of Medicine, University of Southern California, Los Angeles, California 90089, and Neuroscience Graduate Program, University of Southern California, Los Angeles, California 90089 changkt@usc.edu.
authors: Karen T
authors: KT
authors: Chang
mesh_terms: D000217:Acyltransferases / Q000235:genetics / Q000378:metabolism; D000469:Alkaline Phosphatase / Q000494:pharmacology; D000818:Animals; D030801:Animals, Genetically Modified; D016572:Cyclosporine / Q000494:pharmacology; D004330:Drosophila; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism; D004705:Endocytosis / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects / Q000235:genetics; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D047468:Immunoprecipitation; D066298:In Vitro Techniques; D007814:Larva; D013058:Mass Spectrometry; D008636:Mesencephalon / Q000166:cytology / Q000378:metabolism; D018613:Microscopy, Confocal; D016297:Mutagenesis, Site-Directed; D009419:Nerve Tissue Proteins / Q000235:genetics / Q000378:metabolism*; D009469:Neuromuscular Junction / Q000187:drug effects / Q000502:physiology*; D018408:Patch-Clamp Techniques; D018129:Phosphatidylinositol Phosphates / Q000378:metabolism; D010744:Phosphoric Monoester Hydrolases / Q000235:genetics / Q000378:metabolism*; D010766:Phosphorylation / Q000235:genetics; D012694:Serine / Q000378:metabolism; D009435:Synaptic Transmission / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D013572:Synaptic Vesicles / Q000235:genetics / Q000502:physiology*
chemical_list: D029721:Drosophila Proteins; D009419:Nerve Tissue Proteins; D018129:Phosphatidylinositol Phosphates; C113567:phosphatidylinositol 5-phosphate; D049452:Green Fluorescent Proteins; D012694:Serine; D016572:Cyclosporine; D000217:Acyltransferases; C018764:2-acylglycerophosphate acyltransferase; C097702:synaptojanin; D000469:Alkaline Phosphatase; D010744:Phosphoric Monoester Hydrolases
keywords: endocytosis; minibrain; phosphorylation; synaptojanin