title: Arf6 and the 5'phosphatase of synaptojanin 1 regulate autophagy in cone photoreceptors.
abstract: Abnormalities in the ability of cells to properly degrade proteins have been identified in many neurodegenerative diseases. Recent work has implicated synaptojanin 1 (SynJ1) in Alzheimer's disease and Parkinson's disease, although the role of this polyphosphoinositide phosphatase in protein degradation has not been thoroughly described. Here, we dissected in vivo the role of SynJ1 in endolysosomal trafficking in zebrafish cone photoreceptors using a SynJ1-deficient zebrafish mutant, nrc(a14) . We found that loss of SynJ1 leads to specific accumulation of late endosomes and autophagosomes early in photoreceptor development. An analysis of autophagic flux revealed that autophagosomes accumulate because of a defect in maturation. In addition we found an increase in vesicles that are highly enriched for PI(3)P, but negative for an early endosome marker in nrc(a14) cones. A mutational analysis of SynJ1 enzymatic domains found that activity of the 5'phosphatase, but not the Sac1 domain, is required to rescue both aberrant late endosomes and autophagosomes. Finally, modulating activity of the PI(4,5)P2 regulator, Arf6, rescued the disrupted trafficking pathways in nrc(a14) cones. Our study describes a specific role for SynJ1 in autophagosomal and endosomal trafficking and provides evidence that PI(4,5)P2 participates in autophagy in a neuronal cell type.
authors.affiliation: Department of Biochemistry, University of Washington, Seattle, WA, USA.
authors.forename: Ashley A
authors.initials: AA
authors.lastname: George
authors.affiliation: Department of Biochemistry, University of Washington, Seattle, WA, USA.
authors.forename: Sara
authors.initials: S
authors.lastname: Hayden
authors.affiliation: Department of Biochemistry, University of Washington, Seattle, WA, USA.
authors.forename: Gail R
authors.initials: GR
authors.lastname: Stanton
authors.affiliation: Department of Biochemistry, University of Washington, Seattle, WA, USA.
authors.forename: Susan E
authors.initials: SE
authors.lastname: Brockerhoff
mesh_terms: D000089982:ADP-Ribosylation Factor 6; D020727:ADP-Ribosylation Factors; D000818:Animals; D001343:Autophagy; D011992:Endosomes / Q000378:metabolism; D008247:Lysosomes / Q000378:metabolism; D009419:Nerve Tissue Proteins / Q000378:metabolism* / Q000502:physiology; D019269:Phosphatidylinositol 4,5-Diphosphate / Q000378:metabolism; D010744:Phosphoric Monoester Hydrolases / Q000378:metabolism* / Q000502:physiology; D021381:Protein Transport; D017949:Retinal Cone Photoreceptor Cells / Q000378:metabolism* / Q000502:physiology; D015398:Signal Transduction; D015027:Zebrafish / Q000378:metabolism* / Q000502:physiology; D029961:Zebrafish Proteins
chemical_list: D000089982:ADP-Ribosylation Factor 6; D020727:ADP-Ribosylation Factors; D009419:Nerve Tissue Proteins; D019269:Phosphatidylinositol 4,5-Diphosphate; D010744:Phosphoric Monoester Hydrolases; D029961:Zebrafish Proteins; C097702:synaptojanin; C000624134:arf6a protein, zebrafish
keywords: Arf6; autophagy; neuron; phosphoinositides; photoreceptor; synaptojanin 1; zebrafish