title: HRES-1/Rab4 promotes the formation of LC3(+) autophagosomes and the accumulation of mitochondria during autophagy.
abstract: HRES-1/Rab4 is a small GTPase that regulates endocytic recycling. It has been colocalized to mitochondria and the mechanistic target of rapamycin (mTOR), a suppressor of autophagy. Since the autophagosomal membrane component microtubule-associated protein light chain 3 (LC3) is derived from mitochondria, we investigated the impact of HRES-1/Rab4 on the formation of LC3(+) autophagosomes, their colocalization with HRES-1/Rab4 and mitochondria, and the retention of mitochondria during autophagy induced by starvation and rapamycin. HRES-1/Rab4 exhibited minimal baseline colocalization with LC3, which was enhanced 22-fold upon starvation or 6-fold upon rapamycin treatment. Colocalization of HRES-1/Rab4 with mitochondria was increased >2-fold by starvation or rapamycin. HRES-1/Rab4 overexpression promoted the colocalization of mitochondria with LC3 upon starvation or rapamycin treatment. A dominant-negative mutant, HRES-1/Rab4(S27N) had reduced colocalization with LC3 and mitochondria upon starvation but not rapamycin treatment. A constitutively active mutant, HRES-1/Rab4(Q72L) showed diminished colocalization with LC3 but promoted the partitioning of mitochondria with LC3 upon starvation or rapamycin treatment. Phosphorylation-resistant mutant HRES-1/Rab4(S204Q) showed diminished colocalization with LC3 but increased partitioning to mitochondria. A newly discovered C-terminally truncated native isoform, HRES-1/Rab4(1-121), showed enhanced localization to LC3 and mitochondria without starvation or rapamycin treatment. HRES-1/Rab4(1-121) increased the formation of LC3(+) autophagosomes in resting cells, while other isoforms promoted autophagosome formation upon starvation. HRES-1/Rab4, HRES-1/Rab4(1-121), HRES-1/Rab4(Q72L) and HRES-1/Rab4(S204Q) promoted the accumulation of mitochondria during starvation. The specificity of HRES-1/Rab4-mediated mitochondrial accumulation is indicated by its abrogation by dominant-negative HRES-1/Rab4(S27N) mutation. The formation of interconnected mitochondrial tubular networks was markedly enhanced by HRES-1/Rab4(Q72L) upon starvation, which may contribute to the retention of mitochondria during autophagy. The present study thus indicates that HRES-1/Rab4 regulates autophagy through promoting the formation of LC3(+) autophagosomes and the preservation of mitochondria.
authors.affiliation: Departments of Medicine, State University of New York, Upstate Medical University, Syracuse, New York, United States of America.
authors.forename: Gergely
authors.initials: G
authors.lastname: Talaber
authors.affiliation: Departments of Medicine, State University of New York, Upstate Medical University, Syracuse, New York, United States of America.
authors.forename: Gabriella
authors.initials: G
authors.lastname: Miklossy
authors.affiliation: Departments of Medicine, State University of New York, Upstate Medical University, Syracuse, New York, United States of America ; Biochemistry and Molecular Biology, State University of New York, Upstate Medical University, Syracuse, New York, United States of America.
authors.forename: Zachary
authors.initials: Z
authors.lastname: Oaks
authors.affiliation: Departments of Medicine, State University of New York, Upstate Medical University, Syracuse, New York, United States of America.
authors.forename: Yuxin
authors.initials: Y
authors.lastname: Liu
authors.affiliation: Cancer Research UK London Research Institute, London, England, United Kingdom.
authors.forename: Sharon A
authors.initials: SA
authors.lastname: Tooze
authors.affiliation: Shemiakin-Ovchinnikov Institute of Bioorganic Chemistry, RAS, Moscow, Russia.
authors.forename: Dmitriy M
authors.initials: DM
authors.lastname: Chudakov
authors.affiliation: Department of Pathology, State University of New York, Upstate Medical University, Syracuse, New York, United States of America.
authors.forename: Katalin
authors.initials: K
authors.lastname: Banki
authors.affiliation: Departments of Medicine, State University of New York, Upstate Medical University, Syracuse, New York, United States of America ; Biochemistry and Molecular Biology, State University of New York, Upstate Medical University, Syracuse, New York, United States of America ; Microbiology and Immunology, State University of New York, Upstate Medical University, Syracuse, New York, United States of America.
authors.forename: Andras
authors.initials: A
authors.lastname: Perl
mesh_terms: D000595:Amino Acid Sequence; D001343:Autophagy / Q000502:physiology*; D002460:Cell Line; D015870:Gene Expression; D017930:Genes, Reporter; D006801:Humans; D007425:Intracellular Membranes / Q000378:metabolism; D018942:Macrolides / Q000494:pharmacology; D008869:Microtubule-Associated Proteins / Q000737:chemistry / Q000235:genetics / Q000378:metabolism*; D008928:Mitochondria / Q000187:drug effects / Q000378:metabolism*; D008969:Molecular Sequence Data; D010588:Phagosomes / Q000378:metabolism*; D011485:Protein Binding; D021381:Protein Transport / Q000187:drug effects; D020695:rab4 GTP-Binding Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: C477012:MAP1LC3A protein, human; D018942:Macrolides; D008869:Microtubule-Associated Proteins; C040929:bafilomycin A1; D020695:rab4 GTP-Binding Proteins