title: Niemann-Pick type C2 deficiency impairs autophagy-lysosomal activity, mitochondrial function, and TLR signaling in adipocytes.
abstract: In this study, we investigated the role and mechanism of Niemann-Pick type C (NPC)2 in regulating lysosomal activity, mitophagy, and mitochondrial function in adipocytes. We found that knocking down NPC2 impaired lysosomal activity, as evidenced by the reduced mature cathepsin B, the increased accumulation of light chain 3 (LC3) and p62, and the decreased autophagic flux. In NPC2-knockdown (kd) adipocytes, the starvation-induced conversion of LC3-I to LC3-II was abolished. More interestingly, the majority of NPC2 was found in the mitochondrial fraction, and NPC2 deficiency led to impaired autophagic flux and decreased induction of LC3-II in the mitochondrial fraction during mitochondrial stress. Moreover, cellular respiration profiling revealed that NPC2-kd adipocytes had significantly decreased basal/maximal respiration and mitochondrial gene expression compared with scrambled cells, suggesting mitochondrial dysfunction. Additionally, we found that the mitochondrial recruitment of LC3-II induced by lipopolysaccharide (LPS), but not TNFα, was blunted in NPC2-kd adipocytes. Most intriguingly, NPC2-kd selectively diminished LPS-induced NFκB and ERK1/2 phosphorylation and the expression of pro-inflammatory genes, indicating that toll-like receptor signaling activation is impaired in the absence of NPC2. Our results suggest that NPC2 is in a mitochondrially associated autophagosome and plays an important role in regulating mitophagy, mitochondrial quality control, and mitochondrial function.
authors.affiliation: Department of Food Science and Nutrition, University of Minnesota-Twin Cities, St. Paul, MN.
authors.forename: Hong
authors.initials: H
authors.lastname: Guo
authors.affiliation: Department of Food Science and Nutrition, University of Minnesota-Twin Cities, St. Paul, MN.
authors.forename: Ming
authors.initials: M
authors.lastname: Zhao
authors.affiliation: Department of Food Science and Nutrition, University of Minnesota-Twin Cities, St. Paul, MN.
authors.forename: Xiaoxue
authors.initials: X
authors.lastname: Qiu
authors.affiliation: Department of Food Science and Nutrition, University of Minnesota-Twin Cities, St. Paul, MN.
authors.forename: Jessica A
authors.initials: JA
authors.lastname: Deis
authors.affiliation: Key Laboratory of Metabolism and Molecular Medicine and Department of Biochemistry and Molecular Biology, Fudan University Shanghai Medical College, Shanghai, China.
authors.forename: Haiyan
authors.initials: H
authors.lastname: Huang
authors.affiliation: Key Laboratory of Metabolism and Molecular Medicine and Department of Biochemistry and Molecular Biology, Fudan University Shanghai Medical College, Shanghai, China.
authors.forename: Qi-Qun
authors.initials: QQ
authors.lastname: Tang
authors.affiliation: Department of Food Science and Nutrition, University of Minnesota-Twin Cities, St. Paul, MN xlchen@umn.edu.
authors.forename: Xiaoli
authors.initials: X
authors.lastname: Chen
mesh_terms: D017667:Adipocytes / Q000187:drug effects / Q000378:metabolism*; D001343:Autophagy / Q000235:genetics*; D002352:Carrier Proteins / Q000235:genetics*; D002401:Cathepsin B / Q000235:genetics; D002460:Cell Line; D006023:Glycoproteins / Q000172:deficiency / Q000235:genetics*; D006801:Humans; D008070:Lipopolysaccharides / Q000008:administration & dosage; D008247:Lysosomes / Q000378:metabolism; D020935:MAP Kinase Signaling System / Q000235:genetics; D008869:Microtubule-Associated Proteins / Q000235:genetics; D008928:Mitochondria / Q000235:genetics / Q000378:metabolism; D016328:NF-kappa B / Q000235:genetics; D052556:Niemann-Pick Disease, Type C / Q000235:genetics* / Q000378:metabolism / Q000473:pathology; D016601:RNA-Binding Proteins / Q000235:genetics; D015398:Signal Transduction / Q000187:drug effects; D051193:Toll-Like Receptors / Q000235:genetics* / Q000378:metabolism; D014409:Tumor Necrosis Factor-alpha / Q000008:administration & dosage; D033921:Vesicular Transport Proteins
chemical_list: D002352:Carrier Proteins; D006023:Glycoproteins; D008070:Lipopolysaccharides; C477012:MAP1LC3A protein, human; D008869:Microtubule-Associated Proteins; D016328:NF-kappa B; C104585:NPC2 protein, human; C118585:P62 protein, human; D016601:RNA-Binding Proteins; D051193:Toll-Like Receptors; D014409:Tumor Necrosis Factor-alpha; D033921:Vesicular Transport Proteins; D002401:Cathepsin B
keywords: Niemann-Pick disease; inflammation; mitochondria; obesity • lysosome; toll-like receptor