Yeast Vps55p, a Functional Homolog of Human Obesity Receptor Gene-related Protein, Is Involved in Late Endosome to Vacuole Trafficking

Belgareh‐Touzé, Naïma; Avaro, Sandrine; Rouillé, Yves; Hoflack, Bernard; Haguenauer‐Tsapis, Rosine

doi:10.1091/mbc.01-12-0597

Cited by 43 publications

(46 citation statements)

References 77 publications

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“…In contrast, vps68 cells showed an accumulation of Ste3-GFP in endosomal compartments adjacent to the vacuole that also labeled with the endocytic dye FM4-64 ( Figure 5A and Figure S1B). The delayed turnover and endosomal retention of vps55 and vps68 mutants is consistent with previous results showing that vps55 mutants are defective in a postendocytic step in down-regulation of the uracil transporter Fur4p (Belgareh-Touze et al, 2002).…”

Section: Vps68 Mutants Accumulate Endocytic and Biosyntheticsupporting

confidence: 92%

“…VPS68 was originally identified in a screen of the yeast deletion collection for mutants defective in CPY sorting (Bonangelino et al, 2002) and was localized to the vacuolar membrane in a genome-wide study of GFP fusion proteins (Huh et al, 2003). In contrast, Vps55p was reported to act at the late endosome and colocalize with the endosomal marker Snf7p (Belgareh-Touze et al, 2002;Huh et al, 2003). By double-label immunofluorescence microscopy of cells coexpressing two differently tagged forms of Vps68p and Vps55p, we found these proteins colocalized at the vacuolar limiting membrane and adjacent punctate structures that contain Vps21p but are devoid of the late Golgi marker Sec7p, indicating they are endosomes (Figure 3, A-D).…”

Section: Discovery Of the New Endosomal-sorting Complex Vps55/68mentioning

confidence: 99%

“…Both SMP1 (small membrane protein 1) and c21orf4 encode predicted homologues of Vps68p, whereas OB-RGRP and LEPROTL1 are homologous to Vps55p (Bailleul et al, 1997). OBRGRP has previously been shown to complement the CPY-trafficking defects of a vps55 mutant when expressed in yeast, indicating functional conservation (Belgareh-Touze et al, 2002). The presence of two sets of Vps55p-and Vps68p-related proteins raises the interesting possibility that they may form distinct, functionally divergent complexes in higher cells.…”

Section: The Vps55/68 Complex Is Required For Two Transport Steps Outmentioning

confidence: 99%

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Global Analysis of Yeast Endosomal Transport Identifies the Vps55/68 Sorting Complex

Schluter

Lam

Brumm

et al. 2008

MBoC

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Endosomal transport is critical for cellular processes ranging from receptor down-regulation and retroviral budding to the immune response. A full understanding of endosome sorting requires a comprehensive picture of the multiprotein complexes that orchestrate vesicle formation and fusion. Here, we use unsupervised, large-scale phenotypic analysis and a novel computational approach for the global identification of endosomal transport factors. This technique effectively identifies components of known and novel protein assemblies. We report the characterization of a previously undescribed endosome sorting complex that contains two well-conserved proteins with four predicted membrane-spanning domains. Vps55p and Vps68p form a complex that acts with or downstream of ESCRT function to regulate endosomal trafficking. Loss of Vps68p disrupts recycling to the TGN as well as onward trafficking to the vacuole without preventing the formation of lumenal vesicles within the MVB. Our results suggest the Vps55/68 complex mediates a novel, conserved step in the endosomal maturation process. INTRODUCTIONEndosomal protein sorting is a highly conserved cellular process that is required for receptor down-regulation, viral replication, and development (Katzmann et al., 2002;Morita and Sundquist, 2004). Much progress has been made in recent years in identifying distinct multiprotein complexes that regulate the fusion of primary endocytic vesicles, the maturation of an early endosome into a multivesicular body (MVB), and the recycling of proteins and lipids to other organelles (Gruenberg and Stenmark, 2004;Bonifacino and Rojas, 2006). The ESCRT-I, -II, and -III complexes (endosomal-sorting complex required for transport), which act in sequence to regulate the formation of internal vesicles at the MVB, play a central role in endosome biogenesis (Katzmann et al., 2002;Hurley and Emr, 2006). Other transport complexes regulate the targeting and fusion of endosomes or endosome-derived vesicles with other organelles (Bowers and Stevens, 2005;Bonifacino and Rojas, 2006).Many components of the endosomal-sorting machinery were first identified in yeast genetic screens for mutants that are defective in protein transport to the yeast vacuole, which requires functional endosomal sorting and recycling (Bowers and Stevens, 2005). Most of these components have a conserved role in endosome biogenesis in higher cells. Mammalian homologues have been identified for most if not all yeast ESCRT subunits (von Schwedler et al., 2003;Hurley and Emr, 2006), and at least some of the machinery that regulates recycling from the MVB is also well conserved. For example, the five-subunit retromer complex that mediates endosome-to-trans-Golgi network (TGN) transport in yeast is associated with tubular regions of the endosome in mammalian cells and mediates retrograde transport (Arighi et al., 2004;Seaman, 2004). In the past 20 years, classical genetic screens have identified more than 50 vacuole protein-sorting (VPS) genes (Bowers and Stevens, 2005). Surprisingly, ...

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Section: Vps68 Mutants Accumulate Endocytic and Biosyntheticsupporting

confidence: 92%

Section: Discovery Of the New Endosomal-sorting Complex Vps55/68mentioning

confidence: 99%

Section: The Vps55/68 Complex Is Required For Two Transport Steps Outmentioning

confidence: 99%

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Global Analysis of Yeast Endosomal Transport Identifies the Vps55/68 Sorting Complex

Schluter

Lam

Brumm

et al. 2008

MBoC

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“…Endospanin-1 is a small protein of 131 residues and is the type member of a new family of proteins conserved from yeast to humans. A first clue to the function of endospanin family members at the cellular level was provided by a study that identified the yeast endospanin-1 homologue Vps55p as a protein involved in the transport of proteins to the vacuole (13). Disruption of the VPS55 gene led to a phenotype of abnormal secretion of the vacuolar carboxypeptidase Y and of blocking of a late step of the endocytic pathway, which indicated that Vps55p functions as a regulator of membrane traffic between endosomes and the vacuole, the yeast degradative organelle equivalent of the mammalian lysosome.…”

mentioning

confidence: 99%

Endospanins Regulate a Postinternalization Step of the Leptin Receptor Endocytic Pathway

Séron

Couturier

Belouzard

et al. 2011

Journal of Biological Chemistry

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Endospanin-1 is a negative regulator of the cell surface expression of leptin receptor (OB-R), and endospanin-2 is a homologue of unknown function. We investigated the mechanism for endospanin-1 action in regulating OB-R cell surface expression. Here we show that endospanin-1 and -2 are small integral membrane proteins that localize in endosomes and the trans-Golgi network. Antibody uptake experiments showed that both endospanins are transported to the plasma membrane and then internalized into early endosomes but do not recycle back to the trans-Golgi network. Overexpression of endospanin-1 or endospanin-2 led to a decrease of OB-R cell surface expression, whereas shRNA-mediated depletion of each protein increased OB-R cell surface expression. This increased cell surface expression was not observed with OB-Ra mutants defective in endocytosis or with transferrin and EGF receptors. Endospanin-1 or endospanin-2 depletion did not change the internalization rate of OB-Ra but slowed down its lysosomal degradation. Thus, both endospanins are regulators of postinternalization membrane traffic of the endocytic pathway of OB-R.Leptin and the leptin receptor are key proteins in pathways regulating energy balance and body weight in both humans and rodents (1-3). The leptin receptor is a single membrane-spanning protein of the class I cytokine receptor family. The leptin receptor gene is transcribed in a number of different messenger RNAs by alternative promoter usage and mRNA splicing (4). Most of these transcripts are splice variants that encode receptor isoforms with different cytoplasmic tails, which are referred to as OB-Ra, OB-Rc, OB-Rd (short isoforms), and OB-Rb (long isoform). The long splice variant OB-Rb mediates the majority of the effects of leptin, mainly via the JAK-STAT signaling pathway (1, 5, 6). The exact function of the short isoforms is still unclear. Short and long isoforms follow very similar intracellular membrane trafficking pathways (7-9).Recently, we identified a negative regulator of leptin receptor function (10). This protein, originally named leptin receptor gene-related protein, or OB-RGRP, is encoded by a transcript expressed from the leptin receptor gene (11). The OB-RGRP mRNA shares two exons that are untranslated in leptin receptor transcripts and contains two additional exons that are absent in leptin receptor transcripts. This transcript is named LEPROT (leptin receptor overlapping transcript). This overlapping gene structure is conserved in humans and rodents (11,12). We named this protein endospanin-1, due to its topology and intracellular localization. We have shown that endospanin-1 down-regulates leptin signaling by lowering the expression of the receptor at the cell surface and thus the sensitivity of the cell to leptin. Furthermore, the physiological relevance of endospanin-1 as a regulator of OB-R function was evaluated in mice. The expression of a lentivirus-delivered short hairpin RNA (shRNA) directed against endospanin-1 in the arcuate nucleus of the hypothalamus prevented the...

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“…Mammals have a single OB-RGRP homologue called LEPROTL1 (leptin receptor overlapping transcript-like 1), that has 70% amino acid sequence similarity with OB-RGRP and whose gene maps on chromosome 8 in humans (10). In yeast, Vps55p, a functional homologue of OB-RGRP, plays a role in protein transport from the Golgi to the vacuole and in the late endocytic pathway (11). LEPROTL1 and OB-RGRP may, by analogy, be involved in protein trafficking.…”

mentioning

confidence: 99%

Silencing of OB-RGRP in mouse hypothalamic arcuate nucleus increases leptin receptor signaling and prevents diet-induced obesity

Couturier

Sarkis

Séron

et al. 2007

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

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106

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Obesity is a major public health problem and is often associated with type 2 diabetes mellitus, cardiovascular disease, and metabolic syndrome. Leptin is the crucial adipostatic hormone that controls food intake and body weight through the activation of specific leptin receptors (OB-R) in the hypothalamic arcuate nucleus (ARC). However, in most obese patients, high circulating levels of leptin fail to bring about weight loss. The prevention of this ''leptin resistance'' is a major goal for obesity research. We report here a successful prevention of diet-induced obesity (DIO) by silencing a negative regulator of OB-R function, the OB-R gene-related protein (OB-RGRP), whose transcript is genetically linked to the OB-R transcript. We provide in vitro evidence that OB-RGRP controls OB-R function by negatively regulating its cell surface expression. In the DIO mouse model, obesity was prevented by silencing OB-RGRP through stereotactic injection of a lentiviral vector encoding a shRNA directed against OB-RGRP in the ARC. This work demonstrates that OB-RGRP is a potential target for obesity treatment. Indeed, regulators of the receptor could be more appropriate targets than the receptor itself. This finding could serve as the basis for an approach to identifying potential new therapeutic targets for a variety of diseases, including obesity.leptin receptor overlapping transcript ͉ leptin resistance ͉ gene therapy ͉ receptor trafficking ͉ metabolic syndrome L eptin and its receptor (OB-R) were initially identified and characterized because of their involvement in the regulation of energy balance, metabolism, and neuroendocrine responses to food intake (1). Subsequently, leptin has also been shown to be important in wound healing (2), angiogenesis (3), and bone mass and immune system regulation (4, 5). OB-R belongs to the class I cytokine receptor family, which typically uses the JAK/STAT signaling pathway (6). The human OB-R gene on chromosome 1 generates multiple transcripts. Several of these transcripts encode at least five OB-R isoforms, including the short OB-Ra isoform and the long signaling-competent OB-Rb isoform (1). An additional transcript is generated from the same locus encoding a protein called OB-RGRP [or leptin receptor overlapping transcript (LEPROT)], which does not share any sequence similarity with OB-R (7). In situ hybridization experiments show coexpression of the OB-R transcript and the associated OB-RGRP transcript in the mouse brain, including hypothalamic regions involved in body weight regulation (8). Evolutionarily conserved coexpression of two ORFs is often observed in prokaryotes and viruses; however, there are few known cases in eukaryotes (9). Mammals have a single OB-RGRP homologue called LEPROTL1 (leptin receptor overlapping transcript-like 1), that has 70% amino acid sequence similarity with OB-RGRP and whose gene maps on chromosome 8 in humans (10). In yeast, Vps55p, a functional homologue of OB-RGRP, plays a role in protein transport from the Golgi to the vacuole and in the late endoc...

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Yeast Vps55p, a Functional Homolog of Human Obesity Receptor Gene-related Protein, Is Involved in Late Endosome to Vacuole Trafficking

Cited by 43 publications

References 77 publications

Global Analysis of Yeast Endosomal Transport Identifies the Vps55/68 Sorting Complex

Global Analysis of Yeast Endosomal Transport Identifies the Vps55/68 Sorting Complex

Endospanins Regulate a Postinternalization Step of the Leptin Receptor Endocytic Pathway

Silencing of OB-RGRP in mouse hypothalamic arcuate nucleus increases leptin receptor signaling and prevents diet-induced obesity

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