title: STUB1/CHIP is required for HIF1A degradation by chaperone-mediated autophagy.
abstract: The transcription factor HIF1 is mostly regulated by the oxygen-dependent proteasomal degradation of the labile subunit HIF1A. Recent data showed degradation of HIF1A in the lysosome through chaperone-mediated autophagy (CMA). However the molecular mechanism involved has not been elucidated. This study shows that the KFERQ-like motif, that has been identified in all CMA substrates, is required to mediate the interaction between HIF1A and the chaperone HSPA8. Moreover, mutations in the KFERQ-like motif of HIF1A preclude the interaction with the CMA receptor LAMP2A, thus inhibiting its lysosomal degradation. Importantly, we show for the first time that the ubiquitin ligase STUB1 is required for degradation of HIF1A in the lysosome by CMA. Indeed, mutations in STUB1 that inhibit either the ubiquitin ligase activity or its ability to bind to HSPA8, both prevent degradation of HIF1A by CMA. Moreover, we show that HIF1A binds to and is translocated into intact lysosomes isolated from rat livers. This new pathway for degradation of HIF1A does not depend on the presence of oxygen and is activated in response to nutrient deprivation such that the levels of HIF1A bound to CMA positive lysosomes significantly increase in starved animal livers and the binding of HIF1A to LAMP2A increases in response to serum deprivation. Moreover, excessive degradation of HIF1A by CMA compromises cells' ability to respond to and survive under hypoxia, suggesting that this pathway might be of pathophysiological importance in conditions that combine hypoxia with starvation.
authors.affiliation: Center of Ophthalmology and Vision Sciences; Institute for Biomedical Imaging and Life Science (IBILI); Faculty of Medicine; University of Coimbra; Coimbra, Portugal.
authors.forename: João Vasco
authors.initials: JV
authors.lastname: Ferreira
authors.forename: Hugo
authors.initials: H
authors.lastname: Fôfo
authors.forename: Eloy
authors.initials: E
authors.lastname: Bejarano
authors.forename: Carla Figueira
authors.initials: CF
authors.lastname: Bento
authors.forename: José S
authors.initials: JS
authors.lastname: Ramalho
authors.forename: Henrique
authors.initials: H
authors.lastname: Girão
authors.forename: Paulo
authors.initials: P
authors.lastname: Pereira
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D001343:Autophagy / Q000187:drug effects; D015687:Cell Hypoxia / Q000187:drug effects; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects; D020868:Gene Silencing / Q000187:drug effects; D050883:HSC70 Heat-Shock Proteins / Q000378:metabolism; D006801:Humans; D051795:Hypoxia-Inducible Factor 1, alpha Subunit / Q000737:chemistry / Q000378:metabolism*; D052119:Lysosomal-Associated Membrane Protein 2 / Q000378:metabolism; D008247:Lysosomes / Q000187:drug effects / Q000378:metabolism; D051379:Mice; D008969:Molecular Sequence Data; D010100:Oxygen / Q000494:pharmacology; D061988:Proteasome Inhibitors / Q000494:pharmacology; D011485:Protein Binding / Q000187:drug effects; D055550:Protein Stability / Q000187:drug effects; D021381:Protein Transport / Q000187:drug effects; D059748:Proteolysis / Q000187:drug effects; D051381:Rats; D017208:Rats, Wistar; D044767:Ubiquitin-Protein Ligases / Q000378:metabolism*; D015854:Up-Regulation / Q000187:drug effects
chemical_list: D050883:HSC70 Heat-Shock Proteins; C494371:HSPA8 protein, human; D051795:Hypoxia-Inducible Factor 1, alpha Subunit; D052119:Lysosomal-Associated Membrane Protein 2; D061988:Proteasome Inhibitors; C467728:STUB1 protein, human; D044767:Ubiquitin-Protein Ligases; D010100:Oxygen
keywords: CHIP; CMA; HIF1A; STUB1; autophagy; hypoxia; metabolism; starvation; tumor growth; ubiquitin