Involvement of the transmembrane protein p23 in biosynthetic protein transport

Rojo, Manuel; Pepperkok, Rainer; Emery, Grégory; Kellner, Roland; Stang, Espen; Parton, Robert G.; Grüenberg, Jean

doi:10.1016/s0248-4900(98)80302-x

Cited by 59 publications

(120 citation statements)

References 67 publications

(143 reference statements)

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“…Early endosomes also supported HPTS incorporation with either protocol (see Figures 5B and 6B, and Supplemental Figure S6D), as expected because the invagination process begins in early endosomes (Gruenberg and Stenmark, 2004;Piper and Katzmann, 2007). By contrast, a heavy membrane fraction recovered from the same gradient (see Figure 1A), which contained the plasma membrane and early biosynthetic membranes but not endosomes (Gu et al, 1997;Harder et al, 1997;Rojo et al, 1997), did not support HPTS incorporation with either protocol (data not shown). These observations demonstrate that HPTS was incorporated from the solution into membrane organelles, presumably late endosomes, and that this process required energy and depended on cytosolic factors.…”

Section: In Vitro Reconstitution Of Intraendosomal Buddingsupporting

confidence: 70%

In Vitro Budding of Intralumenal Vesicles into Late Endosomes Is Regulated by Alix and Tsg101

Falguières

Luyet

Bissig

et al. 2008

MBoC

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Endosomes along the degradation pathway leading to lysosomes accumulate membranes in their lumen and thus exhibit a characteristic multivesicular appearance. These lumenal membranes typically incorporate down-regulated EGF receptor destined for degradation, but the mechanisms that control their formation remain poorly characterized. Here, we describe a novel quantitative biochemical assay that reconstitutes the formation of lumenal vesicles within late endosomes in vitro. Vesicle budding into the endosome lumen was time-, temperature-, pH-, and energy-dependent and required cytosolic factors and endosome membrane components. Our light and electron microscopy analysis showed that the compartment supporting the budding process was accessible to endocytosed bulk tracers and EGF receptor. We also found that the EGF receptor became protected against trypsin in our assay, indicating that it was sorted into the intraendosomal vesicles that were formed in vitro. Our data show that the formation of intralumenal vesicles is ESCRT-dependent, because the process was inhibited by the K173Q dominant negative mutant of hVps4. Moreover, we find that the ESCRT-I subunit Tsg101 and its partner Alix control intralumenal vesicle formation, by acting as positive and negative regulators, respectively. We conclude that budding of the limiting membrane toward the late endosome lumen, which leads to the formation of intraendosomal vesicles, is controlled by the positive and negative functions of Tsg101 and Alix, respectively. INTRODUCTIONIn eukaryotic cells, molecules of the plasma membrane, ligands and solutes are internalized into early endosomes, from where they can be recycled back to the plasma membrane, transported to the trans-Golgi network, or targeted to late endosomes and lysosomes (Gruenberg, 2001;Maxfield and McGraw, 2004;Mayor and Pagano, 2007). The latter pathway is followed in particular by ubiquitinated signaling receptors that need to be down-regulated. These receptors are incorporated into invaginations of the early endosomal membrane that form within their lumen (Hurley and Emr, 2006), thus giving rise to nascent multivesicular bodies (MVBs) or endosomal carrier vesicles (ECVs; Gruenberg and Stenmark, 2004;Piper and Katzmann, 2007), which function as intermediates between early and late endosomes. Eventually, intralumenal vesicles are delivered to lysosomes, where they are degraded together with their receptor cargo.Major progress has been made in our understanding of the molecular mechanisms that control the sorting of ubiquitinated receptors, in particular the epidermal growth factor (EGF) receptor (Hurley and Emr, 2006;Slagsvold et al., 2006;Piper and Katzmann, 2007;Williams and Urbe, 2007). These receptors interact via the ubiquitin moiety with hepatocyte growth factor-regulated tyrosine kinase substrate (Hrs), which in turn binds clathrin and phosphatidyl-inositol-3-phosphate (PtdIns3P), thereby concentrating the receptor in early endosomal membrane domains (Raiborg et al., 2001;Urbe et al., 2003;Raiborg et al., ...

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Section: In Vitro Reconstitution Of Intraendosomal Buddingsupporting

confidence: 70%

In Vitro Budding of Intralumenal Vesicles into Late Endosomes Is Regulated by Alix and Tsg101

Falguières

Luyet

Bissig

et al. 2008

MBoC

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“…As has been noted for the majority of mammalian p24 proteins studied in cell culture (Stamnes et al, 1995;Sohn et al, 1996;Nickel et al, 1997;Rojo et al, 1997Rojo et al, , 2000Dominguez et al, 1998;Blum et al, 1999;Fü llekrug et al, 1999;Gommel et al, 1999;Jenne et al, 2002), the Drosophila Loj localizes predominantly to the early secretory pathway (Figs. 4M, 5J) but not the ER or the trans-Golgi (Figs.…”

Section: Drosophila P24 Protein Localizes To the Early Secretory Pathwaymentioning

confidence: 67%

“…Members of the p24 protein family localize to the ER and Golgi (Schimmöller et al, 1995;Stamnes et al, 1995;Belden and Barlowe, 1996;Elrod-Erickson and Kaiser, 1996;Sohn et al, 1996;Nickel et al, 1997;Rojo et al, 1997Dominguez et al, 1998;Kuehn et al, 1998;Blum et al, 1999;Fü llekrug et al, 1999;Gommel et al, 1999;Muñ iz et al, 2000;Bell et al, 2001;Jenne et al, 2002) and are major constituents of the COPI-and COPII-coated vesicles that cycle between these compartments (Schimöller et al, 1995;Stamnes et al,(reviewed in Rothman and Wieland, 1996;Schekman and Orci, 1996;Lee et al, 2004). Conserved phenylalanine residues in the carboxyl terminus of p24 proteins serve as an ER export signal Dominguez et al, 1998) and interact with the COPII coat complex (Dominguez et al, 1998;Kuehn et al, 1998).…”

Section: Introductionmentioning

confidence: 99%

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Drosophila melanogasterp24 genes have developmental, tissue‐specific, and sex‐specific expression patterns and functions

Boltz

Ellis

Carney

2006

Developmental Dynamics

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Genes encoding members of the p24 family of intracellular trafficking proteins are present throughout animal and plant lineages. However, very little is known about p24 developmental, spatial, or sex-specific expression patterns or how localized expression affects function. We investigated these problems in Drosophila melanogaster, which contains nine genes encoding p24 proteins. One of these genes, logjam (loj), is expressed in the adult female nervous system and ovaries and is essential for oviposition. Nervous system-specific expression of loj, but not ovary-specific expression, rescues the behavioral defect of mutants. The Loj protein localizes to punctate structures in the cellular cytoplasm. These structures colocalize with a marker specific to the intermediate compartment and cis-Golgi, consistent with experimental evidence from other systems suggesting that p24 proteins function in intracellular transport between the endoplasmic reticulum and Golgi. Our findings reveal that Drosophila p24 transcripts are developmentally and tissue-specifically expressed. CG31787 is male-specifically expressed gene that is present during the larval, pupal, and adult stages. Female CG9053 mRNA is limited to the head, whereas males express this gene widely. Together, our studies provide experimental evidence indicating that some p24 genes have sex-specific expression patterns and tissue-and sex-limited functions. Developmental Dynamics 236:544 -555, 2007.

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“…For improved covisualization of myctagged mitofusins and HA-OMP25 with mtGFP or mtRFP, cells were shortly fixed with paraformaldehyde (3% [wt/vol], 5 min) and permeabilized with cold methanol (Ϫ20°C, 5 min) as described previously (Rojo et al, 2002). All other immunohistochemical stainings were performed on cells fixed with paraformaldehyde (3% wt/vol, 20 min) and permeabilized with 0.1% Triton X-100 (5 min) as described previously (Rojo et al, 1997). Fixed cells were observed with an Axiophot microscope (Zeiss, Jena, Germany) and living cells with an inverted IX70 microscope equipped with a computerized shutter (Olympus, Tokyo, Japan).…”

Section: Antibodies Immunohistological Staining and Fluorescence MImentioning

confidence: 99%

Mitochondrial Fusion in Human Cells Is Efficient, Requires the Inner Membrane Potential, and Is Mediated by Mitofusins

Legros

Lombès

Frachon

et al. 2002

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583

399

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Mitochondrial fusion remains a largely unknown process despite its observation by live microscopy and the identification of few implicated proteins. Using green and red fluorescent proteins targeted to the mitochondrial matrix, we show that mitochondrial fusion in human cells is efficient and achieves complete mixing of matrix contents within 12 h. This process is maintained in the absence of a functional respiratory chain, despite disruption of microtubules or after significant reduction of cellular ATP levels. In contrast, mitochondrial fusion is completely inhibited by protonophores that dissipate the inner membrane potential. This inhibition, which results in rapid fragmentation of mitochondrial filaments, is reversible: small and punctate mitochondria fuse to reform elongated and interconnected ones upon withdrawal of protonophores. Expression of wild-type or dominant-negative dynamin-related protein 1 showed that fragmentation is due to dynamin-related protein 1-mediated mitochondrial division. On the other hand, expression of mitofusin 1 (Mfn1), one of the human Fzo homologues, increased mitochondrial length and interconnectivity. This process, but not Mfn1 targeting, was dependent on the inner membrane potential, indicating that overexpressed Mfn1 stimulates fusion. These results show that human mitochondria represent a single cellular compartment whose exchanges and interconnectivity are dynamically regulated by the balance between continuous fusion and fission reactions. INTRODUCTIONThe morphology and distribution of mitochondria differ significantly between the cells of different species and tissues. In addition, mitochondrial volume and morphology vary in function of cellular metabolism, are modulated during cell cycle and development, and during apoptosis (Stevens, 1981;Tzagoloff, 1982;Bereiter-Hahn and Voth, 1994;Church and Poyton, 1998;Diaz et al., 1999;Frank et al., 2001). Live microscopy has revealed that mitochondrial morphology is continuously remodeled by fission and fusion (Nunnari et al., 1997;Rizzuto et al., 1998). In yeast, selective inhibition of either process significantly modifies mitochondrial size and interconnectivity (Bleazard et al., 1999;Sesaki and Jensen, 1999). Among the best known proteins involved in mitochondrial dynamics are Fzo/ mitofusin, a transmembrane GTPase involved in fusion (Hales and Fuller, 1997;Hermann et al., 1998;Santel and Fuller, 2001;Rojo et al., 2002), and Dnm1p/dynamin-related protein 1 (Drp1), a dynamin-related protein involved in fission (Bleazard et al., 1999;Pitts et al., 1999;Smirnova et al., 2001).In yeast, mitochondrial fusion has been demonstrated by the diffusion and/or mixing of different matrix proteins during mating of haploid cells (Azpiroz and Butow, 1993;Nunnari et al., 1997). In contrast, mitochondrial fusion has not been studied with similar assays in human cells, and it is not known to what extent the apparent fusion events observed by live microscopy correspond to the formation of intermitochondrial junctions (Bakeeva et al., 1978;Amche...

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Involvement of the transmembrane protein p23 in biosynthetic protein transport

Cited by 59 publications

References 67 publications

In Vitro Budding of Intralumenal Vesicles into Late Endosomes Is Regulated by Alix and Tsg101

In Vitro Budding of Intralumenal Vesicles into Late Endosomes Is Regulated by Alix and Tsg101

Drosophila melanogasterp24 genes have developmental, tissue‐specific, and sex‐specific expression patterns and functions

Mitochondrial Fusion in Human Cells Is Efficient, Requires the Inner Membrane Potential, and Is Mediated by Mitofusins

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