Organelle relationships in cultured 3T3-L1 preadipocytes.

Novikoff, Alex B.; Novikoff, Phyllis M.; Rosen, Ora M.; Rubin, Charles S.

doi:10.1083/jcb.87.1.180

Cited by 319 publications

(217 citation statements)

References 71 publications

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“…These observations are consistent with a true in vivo relationship between the lipid droplet surface and ER. This has previously been suggested by electron microscopic data showing proximity of some ER cisternae with the lipid droplet surface (23) and by reports that lipid droplets may arise from the ER (24 -26) and of the presence of other ER proteins on the lipid droplet surface (26,27). Given that TGH, a microsomal protein, accounts for most non-HSL intracellular lipase activity in WAT at neutral pH in vitro, the possibility that ER may be directly involved in adipocyte lipolysis merits further study.…”

Section: Discussionmentioning

confidence: 73%

Carboxylesterase 3 (EC 3.1.1.1) Is a Major Adipocyte Lipase

Soni

Lehner

Metalnikov³

et al. 2004

Journal of Biological Chemistry

136

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Hydrolysis of triglycerides is central to energy homeostasis in white adipose tissue (WAT). Hormone-sensitive lipase (HSL) was previously felt to mediate all lipolysis in WAT. Surprisingly, HSL-deficient mice show active HSL-independent lipolysis, suggesting that other lipase(s) also mediate triglyceride hydrolysis. To clarify this, we used functional proteomics to detect non-HSL lipase(s) in mouse WAT. After cell fractionation of intraabdominal WAT, most non-HSL neutral lipase activity is localized in the 100,000 ؋ g infranatant and fat cake fractions. By oleic acid-linked agarose chromatography of infranatant followed by elution in a 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulfonic acid gradient, we identified two peaks of esterase activity using p-nitrophenyl butyrate as a substrate. One of the peaks contained most of the lipase activity. In the corresponding fractions, gel permeation chromatography and SDS-PAGE, followed by tandem mass spectrometric analysis of excised Coomassie Blue-stained peptides, revealed carboxylesterase 3 (triacylglycerol hydrolase (TGH); EC 3.1.1.1). TGH is also the principle lipase of WAT fat cake extracts. Partially purified WAT TGH had lipase activity as well as lesser but detectable neutral cholesteryl ester hydrolase activity. Western blotting of subcellular fractions of WAT and confocal microscopy of fibroblasts following in vitro adipocytic differentiation are consistent with a distribution of TGH to endoplasmic reticulum, cytosol, and the lipid droplet. TGH is responsible for a major part of non-HSL lipase activity in WAT in vitro and may mediate some or all HSL-independent lipolysis in adipocytes.

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Section: Discussionmentioning

confidence: 73%

Carboxylesterase 3 (EC 3.1.1.1) Is a Major Adipocyte Lipase

Soni

Lehner

Metalnikov³

et al. 2004

Journal of Biological Chemistry

136

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“…The cross-sectional area of fat tissue was used to measure the size of adipocytes utilizing ImageJ software (NIH). For Oil Red O staining, fresh liver tissue was immersed and frozen in optimal cutting temperature compound, followed by sectioning and staining with Oil Red O and Harris hematoxylin (49). For energy expenditure measurement, mice were individually housed in metabolic chambers (Lab Master; TSE Systems).…”

Section: Methodsmentioning

confidence: 99%

Ablation of XP-V gene causes adipose tissue senescence and metabolic abnormalities

Chen

Harris

Hatahet

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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Obesity and the metabolic syndrome have evolved to be major health issues throughout the world. Whether loss of genome integrity contributes to this epidemic is an open question. DNA polymerase η (pol η), encoded by the xeroderma pigmentosum (XP-V) gene, plays an essential role in preventing cutaneous cancer caused by UV radiation-induced DNA damage. Herein, we demonstrate that pol η deficiency in mice (pol η −/− ) causes obesity with visceral fat accumulation, hepatic steatosis, hyperleptinemia, hyperinsulinemia, and glucose intolerance. In comparison to WT mice, adipose tissue from pol η −/− mice exhibits increased DNA damage and a greater DNA damage response, indicated by upregulation and/or phosphorylation of ataxia telangiectasia mutated (ATM), phosphorylated H 2 AX (γH 2 AX), and poly[ADP-ribose] polymerase 1 (PARP-1). Concomitantly, increased cellular senescence in the adipose tissue from pol η −/− mice was observed and measured by up-regulation of senescence markers, including p53, p16 Ink4a , p21, senescence-associated (SA) β-gal activity, and SA secretion of proinflammatory cytokines interleukin 6 (IL-6) and tumor necrosis factor α (TNF-α) as early as 4 wk of age. Treatment of pol η −/− mice with a p53 inhibitor, pifithrin-α, reduced adipocyte senescence and attenuated the metabolic abnormalities. Furthermore, elevation of adipocyte DNA damage with a high-fat diet or sodium arsenite exacerbated adipocyte senescence and metabolic abnormalities in pol η −/− mice. In contrast, reduction of adipose DNA damage with N-acetylcysteine or metformin ameliorated cellular senescence and metabolic abnormalities. These studies indicate that elevated DNA damage is a root cause of adipocyte senescence, which plays a determining role in the development of obesity and insulin resistance.T he human genome is constantly challenged by exogenous and endogenous DNA damaging agents. To ensure genome integrity, human cells have faithful DNA replication machinery and DNA repair systems that are coordinated by DNA damage response networks. In response to different extents or types of DNA lesions, the DNA damage response activates appropriate cellular responses, including transient or permanent (senescence) cell cycle arrest, or apoptosis, to minimize the detrimental effects of DNA lesions (1). Reduction or deficiency in DNA repair/replication enzyme activity is well documented to increase vulnerability for the development of cancer, neurodegenerative diseases, and aging (2). In addition, defective DNA repair enzymes are associated with the metabolic symptom; for example, DNA glycosylase (Neil1)-and OGG1-deficient mice are obese (3-5), and nucleotide excision repair protein ERCC1-XPF deficiency causes lipodystrophy (6). Furthermore, DNA damage response protein ataxia telangiectasia mutated (ATM) suppresses JNK activity through p53 signaling and mediates an antioxidant action that has been suggested to be relevant to the metabolic syndrome (7). Nucleotide excision repair XP-A protein may affect metabolism by altering mitochondrial...

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“…First, LDs are often very closely associated with other organelles ( Fig. 3A; Novikoff et al 1980;Stemberger et al 1984;Blanchette-Mackie et al 1995), thus proteins found in isolated LDs may be derived from adhering structures, especially when they are found in both LDs and other fractions. Second, the exposure of lipid esters to an aqueous environment by mechanical disruption may cause artificial adherence of unrelated proteins by hydrophobic interaction .…”

Section: The Lipid Droplet Proteomementioning

confidence: 99%

Not Just Fat: The Structure and Function of the Lipid Droplet

Fujimoto

Parton²

2011

Cold Spring Harbor Perspectives in Biology

388

322

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Lipid droplets (LDs) are independent organelles that are composed of a lipid ester core and a surface phospholipid monolayer. Recent studies have revealed many new proteins, functions, and phenomena associated with LDs. In addition, a number of diseases related to LDs are beginning to be understood at the molecular level. It is now clear that LDs are not an inert store of excess lipids but are dynamically engaged in various cellular functions, some of which are not directly related to lipid metabolism. Compared to conventional membrane organelles, there are still many uncertainties concerning the molecular architecture of LDs and how each function is placed in a structural context. Recent findings and remaining questions are discussed.

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Organelle relationships in cultured 3T3-L1 preadipocytes.

Cited by 319 publications

References 71 publications

Carboxylesterase 3 (EC 3.1.1.1) Is a Major Adipocyte Lipase

Carboxylesterase 3 (EC 3.1.1.1) Is a Major Adipocyte Lipase

Ablation of XP-V gene causes adipose tissue senescence and metabolic abnormalities

Not Just Fat: The Structure and Function of the Lipid Droplet

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