title: Suppression of MAPK/JNK-MTORC1 signaling leads to premature loss of organelles and nuclei by autophagy during terminal differentiation of lens fiber cells.
abstract: Although autophagic pathways are essential to developmental processes, many questions still remain regarding the initiation signals that regulate autophagy in the context of differentiation. To address these questions we studied the ocular lens, as the programmed elimination of nuclei and organelles occurs in a precisely regulated spatiotemporal manner to form the organelle-free zone (OFZ), a characteristic essential for vision acuity. Here, we report our discovery that inactivation of MAPK/JNK induces autophagy for formation of the OFZ through its regulation of MTORC1, where MAPK/JNK signaling is required for both MTOR activation and RPTOR/RAPTOR phosphorylation. Autophagy pathway proteins including ULK1, BECN1/Beclin 1, and MAP1LC3B2/LC3B-II were upregulated in the presence of inhibitors to either MAPK/JNK or MTOR, inducing autophagic loss of organelles to form the OFZ. These results reveal that MAPK/JNK is a positive regulator of MTORC1 signaling and its developmentally regulated inactivation provides an inducing signal for the coordinated autophagic removal of nuclei and organelles required for lens function.
authors.affiliation: Department of Pathology, Anatomy and Cell Biology; Thomas Jefferson University; Philadelphia, PA USA.
authors.forename: Subhasree
authors.initials: S
authors.lastname: Basu
authors.affiliation: Department of Pathology, Anatomy and Cell Biology; Thomas Jefferson University; Philadelphia, PA USA.
authors.forename: Suren
authors.initials: S
authors.lastname: Rajakaruna
authors.affiliation: Department of Neuroscience; Farber Institute for Neuroscience; Thomas Jefferson University; Philadelphia, PA USA.
authors.forename: Beverly
authors.initials: B
authors.lastname: Reyes
authors.affiliation: Department of Neuroscience; Farber Institute for Neuroscience; Thomas Jefferson University; Philadelphia, PA USA.
authors.forename: Elisabeth
authors.initials: E
authors.lastname: Van Bockstaele
authors.affiliation: Department of Pathology, Anatomy and Cell Biology; Thomas Jefferson University; Philadelphia, PA USA.
authors.forename: A Sue
authors.initials: AS
authors.lastname: Menko
mesh_terms: D000818:Animals; D001343:Autophagy; D030161:Avian Proteins / Q000378:metabolism; D002454:Cell Differentiation; D002467:Cell Nucleus / Q000378:metabolism* / Q000648:ultrastructure; D002642:Chick Embryo; D022162:Cytoplasmic Vesicles / Q000378:metabolism / Q000648:ultrastructure; D004721:Endoplasmic Reticulum / Q000378:metabolism / Q000648:ultrastructure; D006056:Golgi Apparatus / Q000378:metabolism / Q000648:ultrastructure; D048031:JNK Mitogen-Activated Protein Kinases / Q000378:metabolism*; D007908:Lens, Crystalline / Q000196:embryology / Q000473:pathology* / Q000648:ultrastructure; D020935:MAP Kinase Signaling System; D000076222:Mechanistic Target of Rapamycin Complex 1; D008954:Models, Biological; D046912:Multiprotein Complexes / Q000378:metabolism*; D058570:TOR Serine-Threonine Kinases / Q000378:metabolism*; D013997:Time Factors
chemical_list: D030161:Avian Proteins; D046912:Multiprotein Complexes; D000076222:Mechanistic Target of Rapamycin Complex 1; D058570:TOR Serine-Threonine Kinases; D048031:JNK Mitogen-Activated Protein Kinases
keywords: MAPK/JNK (mitogen-activated protein kinase/c-Jun N-terminal kinase); RAPTOR; autophagy; cell development; cell maturation; lens; mechanistic target of rapamycin; organelle-free zone formation; organelles; signal transduction