title: The Contribution of Melanoregulin to Microtubule-Associated Protein 1 Light Chain 3 (LC3) Associated Phagocytosis in Retinal Pigment Epithelium.
abstract: A main requisite in the phagocytosis of ingested material is a coordinated series of maturation steps which lead to the degradation of ingested cargo. Photoreceptor outer segment (POS) renewal involves phagocytosis of the distal disk membranes by the retinal pigment epithelium (RPE). Previously, we identified melanoregulin (MREG) as an intracellular cargo-sorting protein required for the degradation of POS disks. Here, we provide evidence that MREG-dependent processing links both autophagic and phagocytic processes in LC3-associated phagocytosis (LAP). Ingested POS phagosomes are associated with endogenous LC3 and MREG. The LC3 association with POSs exhibited properties of LAP; it was independent of rapamycin pretreatment, but dependent on Atg5. Loss of MREG resulted in a decrease in the extent of LC3-POS association. Studies using DQ-BSA suggest that loss of MREG does not compromise the association and fusion of LC3-positive phagosomes with lysosomes. Furthermore, the mechanism of MREG action is likely through a protein complex that includes LC3, as determined by colocalization and immunoprecipitation in both RPE cells and macrophages. We posit that MREG participates in coordinating the association of phagosomes with LC3 for content degradation with the loss of MREG leading to phagosome accumulation.
authors.affiliation: Department of Biochemistry, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA.
authors.forename: Laura S
authors.initials: LS
authors.lastname: Frost
authors.affiliation: UCLA School of Medicine, Jules Stein Eye Institute, Los Angeles, CA, 90095, USA.
authors.forename: Vanda S
authors.initials: VS
authors.lastname: Lopes
authors.affiliation: Department of Biochemistry, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA.
authors.forename: Alvina
authors.initials: A
authors.lastname: Bragin
authors.affiliation: Department of Biochemistry, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA.
authors.forename: Juan
authors.initials: J
authors.lastname: Reyes-Reveles
authors.affiliation: Department of Biochemistry, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA.
authors.forename: Jennifer
authors.initials: J
authors.lastname: Brancato
authors.affiliation: Department of Biochemistry, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA.
authors.forename: Art
authors.initials: A
authors.lastname: Cohen
authors.affiliation: Department of Anatomy and Cell Biology, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA.
authors.forename: Claire H
authors.initials: CH
authors.lastname: Mitchell
authors.affiliation: UCLA School of Medicine, Jules Stein Eye Institute, Los Angeles, CA, 90095, USA.
authors.forename: David S
authors.initials: DS
authors.lastname: Williams
authors.affiliation: Department of Biochemistry, School of Dental Medicine, University of Pennsylvania, Philadelphia, PA, 19104, USA. battagli@upenn.edu.
authors.forename: Kathleen
authors.initials: K
authors.lastname: Boesze-Battaglia
mesh_terms: D033942:Adaptor Proteins, Vesicular Transport; D000818:Animals; D001343:Autophagy / Q000187:drug effects / Q000502:physiology; D000071187:Autophagy-Related Protein 5; D002352:Carrier Proteins / Q000235:genetics / Q000502:physiology*; D002417:Cattle; D002940:Circadian Rhythm; D005136:Eye Proteins / Q000502:physiology*; D006801:Humans; D047908:Intracellular Signaling Peptides and Proteins; D008264:Macrophages / Q000502:physiology; D051379:Mice; D008810:Mice, Inbred C57BL; D008817:Mice, Mutant Strains; D008869:Microtubule-Associated Proteins / Q000502:physiology*; D046912:Multiprotein Complexes; D010587:Phagocytosis / Q000187:drug effects / Q000502:physiology; D010588:Phagosomes / Q000378:metabolism*; D021381:Protein Transport; D059748:Proteolysis; D055214:Retinal Photoreceptor Cell Outer Segment / Q000502:physiology; D055213:Retinal Pigment Epithelium / Q000166:cytology / Q000196:embryology / Q000502:physiology*; D020123:Sirolimus / Q000494:pharmacology
chemical_list: C502778:ATG5 protein, human; D033942:Adaptor Proteins, Vesicular Transport; D000071187:Autophagy-Related Protein 5; D002352:Carrier Proteins; D005136:Eye Proteins; D047908:Intracellular Signaling Peptides and Proteins; C477012:MAP1LC3A protein, human; C000609551:MREG protein, human; D008869:Microtubule-Associated Proteins; D046912:Multiprotein Complexes; C518334:melanoregulin protein, mouse; D020123:Sirolimus
keywords: Autophagy; Melanoregulin; Microtubule-associated protein 1 light chain 3; Phagocytosis; Retinal pigment epithelium