Ancient Ubiquitous Protein 1 (AUP1) Localizes to Lipid Droplets and Binds the E2 Ubiquitin Conjugase G2 (Ube2g2) via Its G2 Binding Region

Spandl, Johanna; Lohmann, Daniel; Kuerschner, Lars; Moessinger, Christine; Thiele, Christoph

doi:10.1074/jbc.m110.190785

Cited by 105 publications

(89 citation statements)

References 57 publications

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“…includes proteins involved in protein degradation, such as AUP1 ( 14,17,18,49 ) and UBXDs ( 10,50 ). A hypothesis that lipid droplets may mediate intracellular protein degradation was proposed ( 51 ), and interestingly, several studies support this possibility ( 52,53 ).…”

mentioning

confidence: 77%

The proteomics of lipid droplets: structure, dynamics, and functions of the organelle conserved from bacteria to humans

Yang

Ding

Chen

et al. 2012

Journal of Lipid Research

202

184

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mentioning

confidence: 77%

The proteomics of lipid droplets: structure, dynamics, and functions of the organelle conserved from bacteria to humans

Yang

Ding

Chen

et al. 2012

Journal of Lipid Research

202

184

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“…Indeed, associated with the LD phospholipid monolayer are at least three proteins functionally linked to ERAD: UBXD8 (26), AUP1 (27), and UBE2G2 (27). Their presence might signify the existence of an LD protein degradation complex that contributes to the turnover or remodeling of the droplet proteome.…”

Section: Resultsmentioning

confidence: 99%

Lipid Droplet Formation Is Dispensable for Endoplasmic Reticulum-associated Degradation

Olzmann¹,

Kopito

2011

Journal of Biological Chemistry

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Proteins that fail to fold or assemble in the endoplasmic reticulum (ER) are destroyed by cytoplasmic proteasomes through a process known as ER-associated degradation. Substrates of this pathway are initially sequestered within the ER lumen and must therefore be dislocated across the ER membrane to be degraded. It has been proposed that generation of bicellar structures during lipid droplet formation may provide an "escape hatch" through which misfolded proteins, toxins, and viruses can exit the ER. We have directly tested this hypothesis by exploiting yeast strains defective in lipid droplet formation. Our data demonstrate that lipid droplet formation is dispensable for the dislocation of a plant toxin and the degradation of both soluble and integral membrane glycoproteins.Secreted and transmembrane proteins are co-translationally inserted into the endoplasmic reticulum (ER), 3 where they are folded, modified, and assembled into higher order complexes prior to transport to their final destinations. Proteins failing to reach their native conformation are recognized and delivered to the cytosolic ubiquitin-proteasome system for degradation by a process termed ER-associated degradation (ERAD). How substrates overcome the spatial segregation imposed by the ER membrane and are finally dislocated from the ER into the cytosol is a fundamental question that remains unresolved (1, 2). Polytopic ER-resident membrane proteins including Sec61p (3), Derlins (4, 5), and Hrd1p (6) have been suggested, largely on the basis of their polytopic membrane-spanning topology, their proximity to other membrane-associated components of the ERAD system, and the ability to co-precipitate or be crosslinked to putative dislocation intermediates, to be structural elements of a transmembrane channel that mediates substrate dislocation. However, the structure and composition of such a channel remain obscure, and its existence remains controversial (1, 2, 7). The ability of the ER dislocation apparatus to accommodate large bulky substrates such as glycoproteins with intact N-glycans (8), ligand-stabilized folded proteins (9), as well as toxins (10) and even intact viruses (11), which appear to hijack this pathway to enter the cytosol, disfavors the existence of such a pore. In response to these concerns, Ploegh (7) has proposed a provocative ER exit model in which substrate dislocation is coupled to the formation of lipid droplets (LDs), which are ER-derived organelles required for the storage and mobilization of neutral lipids. Relatively little is known about how LDs form, and Ploegh (7) hypothesized that generation of bicellar structures during LD formation could result in transient pores, or "escape hatches," in the ER membrane, allowing the escape of luminal ERAD substrates and/or the direct extraction of polytopic substrates associated with the LD membrane. This LD-based ER exit model remains untested.Yeast strains lacking the acyltransferases (Dga1p, Lro1p, Are1p, and Are2p) necessary for the synthesis of triacylglycerides and steryl es...

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“…are able to insert into a PL bilayer as well as in a PL monolayer, i.e. to ER or to LDs [23][24][25]. Accordingly, the association of a protein identified by proteomics to LDs must be validated by other methods.…”

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confidence: 98%

Characteristics and functions of lipid droplets and associated proteins in enterocytes

Beilstein

Carrière

Leturque

et al. 2016

Experimental Cell Research

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Cytosolic lipid droplets (LDs) are observed in enterocytes of jejunum during lipid absorption. One important function of the intestine is to secrete chylomicrons, which provide dietary lipids throughout the body, from digested lipids in meals. The current hypothesis is that cytosolic LDs in enterocytes constitute a transient pool of stored lipids that provides lipids during interprandial period while lowering chylomicron production during the post-prandial phase. This smoothens the magnitude of peaks of hypertriglyceridemia. Here, we review the composition and functions of lipids and associated proteins of enterocyte LDs, the known physiological functions of LDs as well as the role of LDs in pathological processes in the context of the intestine.

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Ancient Ubiquitous Protein 1 (AUP1) Localizes to Lipid Droplets and Binds the E2 Ubiquitin Conjugase G2 (Ube2g2) via Its G2 Binding Region

Cited by 105 publications

References 57 publications

The proteomics of lipid droplets: structure, dynamics, and functions of the organelle conserved from bacteria to humans

The proteomics of lipid droplets: structure, dynamics, and functions of the organelle conserved from bacteria to humans

Lipid Droplet Formation Is Dispensable for Endoplasmic Reticulum-associated Degradation

Characteristics and functions of lipid droplets and associated proteins in enterocytes

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