scholarly journals Direct Binding to Rsp5 Mediates Ubiquitin-independent Sorting of Sna3 via the Multivesicular Body Pathway

2007 ◽  
Vol 18 (2) ◽  
pp. 697-706 ◽  
Author(s):  
Matthew W. McNatt ◽  
Ian McKittrick ◽  
Matthew West ◽  
Greg Odorizzi
Keyword(s):  
Multivesicular Body ◽  
Integral Membrane Proteins ◽  
Multivesicular Bodies ◽  
Wild Type ◽  
Independent Function ◽  
Broad Distribution ◽  
Ww Domains ◽  
Cargo Protein ◽  
Cytosolic Domains ◽  
Direct Binding

The sorting of most integral membrane proteins into the lumenal vesicles of multivesicular bodies (MVBs) is dependent on the attachment of ubiquitin (Ub) to their cytosolic domains. However, Ub is not required for sorting of Sna3, an MVB vesicle cargo protein in yeast. We show that Sna3 circumvents Ub-mediated recognition by interacting directly with Rsp5, an E3 Ub ligase that catalyzes monoubiquitination of MVB vesicle cargoes. The PPAY motif in the C-terminal cytosolic domain of Sna3 binds the WW domains in Rsp5, and Sna3 is polyubiquitinated as a consequence of this association. However, Ub does not appear to be required for transport of Sna3 via the MVB pathway because its sorting occurs under conditions in which its ubiquitination is impaired. Consistent with Ub-independent function of the MVB pathway, we show by electron microscopy that the formation of MVB vesicles does not require Rsp5 E3 ligase activity. However, cells expressing a catalytically disabled form of Rsp5 have a greater frequency of smaller MVB vesicles compared with the relatively broad distribution of vesicles seen in MVBs of wild-type cells, suggesting that the formation of MVB vesicles is influenced by Rsp5-mediated ubiquitination.

scholarly journals Direct Binding to Rsp5p Regulates Ubiquitination-independent Vacuolar Transport of Sna3p

2007 ◽  
Vol 18 (5) ◽  
pp. 1781-1789 ◽  
Author(s):  
Hadiya Watson ◽  
Juan S. Bonifacino
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Ubiquitin Ligase ◽  
Adaptor Protein ◽  
Direct Interaction ◽  
Integral Membrane Proteins ◽  
Multivesicular Bodies ◽  
Hect Domain ◽  
Ww Domains ◽  
Cytosolic Domains ◽  
Direct Binding

The sorting of integral membrane proteins such as carboxypeptidase S (Cps1p) into the luminal vesicles of multivesicular bodies (MVBs) in Saccharomyces cerevisiae requires ubiquitination of their cytosolic domains by the ubiquitin ligases Rsp5p and/or Tul1p. An exception is Sna3p, which does not require ubiquitination for entry into MVBs. The mechanism underlying this ubiquitination-independent MVB sorting pathway has not yet been characterized. Here, we show that Sna3p sorting into the MVB pathway depends on a direct interaction between a PPAY motif within its C-terminal cytosolic tail and the WW domains of Rsp5p. Disruption of this interaction inhibits vacuolar targeting of Sna3p and causes its accumulation in a compartment that overlaps only partially with MVBs. Surprisingly, Sna3p does require a functional ubiquitin-ligase HECT domain within Rsp5p; however, the dependence of Sna3p on HECT domain activity is distinct from that of Cps1p. Last, we show that Sna3p requires neither Tul1p nor the transmembrane adaptor protein Bsd2p for its MVB sorting. Our data demonstrate that Sna3p follows a novel ubiquitination-independent, but Rsp5p-mediated, sorting pathway to the vacuole.

scholarly journals Bro1 coordinates deubiquitination in the multivesicular body pathway by recruiting Doa4 to endosomes

2004 ◽  
Vol 166 (5) ◽  
pp. 717-729 ◽  
Author(s):  
Natalie Luhtala ◽  
Greg Odorizzi
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Multivesicular Body ◽  
Integral Membrane Proteins ◽  
Surface Receptors ◽  
Cargo Protein ◽  
Cargo Proteins ◽  
Late Step ◽  
Endosomal Membranes ◽  
Multivesicular Endosomes ◽  
Mutant Cells

Ubiquitination directs the sorting of cell surface receptors and other integral membrane proteins into the multivesicular body (MVB) pathway. Cargo proteins are subsequently deubiquitinated before their enclosure within MVB vesicles. In Saccharomyces cerevisiae, Bro1 functions at a late step of MVB sorting and is required for cargo protein deubiquitination. We show that the loss of Bro1 function is suppressed by the overexpression of DOA4, which encodes the ubiquitin thiolesterase required for the removal of ubiquitin from MVB cargoes. Overexpression of DOA4 restores cargo protein deubiquitination and sorting via the MVB pathway and reverses the abnormal endosomal morphology typical of bro1 mutant cells, resulting in the restoration of multivesicular endosomes. We further demonstrate that Doa4 interacts with Bro1 on endosomal membranes and that the recruitment of Doa4 to endosomes requires Bro1. Thus, our results point to a key role for Bro1 in coordinating the timing and location of deubiquitination by Doa4 in the MVB pathway.

scholarly journals YPXL/I Is a Protein Interaction Motif Recognized by Aspergillus PalA and Its Human Homologue, AIP1/Alix

2003 ◽  
Vol 23 (5) ◽  
pp. 1647-1655 ◽  
Author(s):  
Olivier Vincent ◽  
Lynne Rainbow ◽  
Joan Tilburn ◽  
Herbert N. Arst, ◽  
Miguel A. Peñalva
Keyword(s):  
Transcription Factor ◽  
Signal Transduction Pathway ◽  
Multivesicular Body ◽  
Binding Motif ◽  
Wild Type ◽  
Proteolytic Activation ◽  
Protease Cleavage ◽  
Proteolytic Cascade ◽  
Direct Binding ◽  
Mammalian Homologue

ABSTRACT The zinc finger transcription factor PacC undergoes two-step proteolytic activation in response to alkaline ambient pH. PalA is a component of the fungal ambient pH signal transduction pathway. Its mammalian homologue AIP1/Alix interacts with the apoptosis-linked protein ALG-2. We show that both PalA and AIP1/Alix recognize a protein-protein binding motif that we denote YPXL/I, where Tyr, Pro, and Leu/Ile are crucial for its interactive properties. Two such motifs flanking the signaling protease cleavage site mediate direct binding of PalA to PacC, required for the first and only pH-regulated cleavage of this transcription factor. PalA can bind the “closed” (i.e., wild-type full-length) conformer of PacC, suggesting that PalA binding constitutes the first stage in the two-step proteolytic cascade, recruiting or facilitating access of the signaling protease, presumably PalB. In addition to recognizing YPXL/I motifs, both PalA and AIP1/Alix interact with the Aspergillus class E Vps protein Vps32 homologue, a member of a protein complex involved in the early steps of the multivesicular body pathway, suggesting that this interaction is an additional feature of proteins of the PalA/AIP1/Alix family.

scholarly journals Rsp5p, a New Link between the Actin Cytoskeleton and Endocytosis in the Yeast Saccharomyces cerevisiae

2002 ◽  
Vol 22 (20) ◽  
pp. 6946-6948 ◽  
Author(s):  
Joanna Kamińska ◽  
Beata Gajewska ◽  
Anita K. Hopper ◽  
Teresa ˙Zołądek
Keyword(s):  
Saccharomyces Cerevisiae ◽  
Actin Cytoskeleton ◽  
Cytoskeletal Proteins ◽  
Wild Type ◽  
Yeast Saccharomyces Cerevisiae ◽  
Ww Domains ◽  
Ubiquitin Protein Ligase ◽  
Growth Defects ◽  
Genes Encoding ◽  
Cytoskeleton Dynamics

ABSTRACT Rsp5p is an ubiquitin-protein ligase of Saccharomyces cerevisiae that has been implicated in numerous processes including transcription, mitochondrial inheritance, and endocytosis. Rsp5p functions at multiple steps of endocytosis, including ubiquitination of substrates and other undefined steps. We propose that one of the roles of Rsp5p in endocytosis involves maintenance and remodeling of the actin cytoskeleton. We report the following. (i) There are genetic interactions between rsp5 and several mutant genes encoding actin cytoskeletal proteins. rsp5 arp2, rsp5 end3, and rsp5 sla2 double mutants all show synthetic growth defects. Overexpressed wild-type RSP5 or mutant rsp5 genes with lesions of some WW domains suppress growth defects of arp2 and end3 cells. The defects in endocytosis, actin cytoskeleton, and morphology of arp2 are also suppressed. (ii) Rsp5p and Sla2p colocalize in abnormal F-actin-containing clumps in arp2 and pan1 mutants. Immunoprecipitation experiments confirmed that Rsp5p and Act1p colocalize in pan1 mutants. (iii) Rsp5p and Sla2p coimmunoprecipitate and partially colocalize to punctate structures in wild-type cells. These studies provide the first evidence for an interaction of an actin cytoskeleton protein with Rsp5p. (iv) rsp5-w1 mutants are resistant to latrunculin A, a drug that sequesters actin monomers and depolymerizes actin filaments, consistent with the fact that Rsp5p is involved in actin cytoskeleton dynamics.

scholarly journals Novel Interactions of ESCRT-III with LIP5 and VPS4 and their Implications for ESCRT-III Disassembly

2008 ◽  
Vol 19 (6) ◽  
pp. 2661-2672 ◽  
Author(s):  
Soomin Shim ◽  
Samuel A. Merrill ◽  
Phyllis I. Hanson
Keyword(s):  
Atpase Activity ◽  
Binding Site ◽  
Binding Sites ◽  
Essential Role ◽  
Multivesicular Body ◽  
The Other ◽  
Aaa Atpase ◽  
Direct Binding ◽  
Novel Interactions

The AAA+ ATPase VPS4 plays an essential role in multivesicular body biogenesis and is thought to act by disassembling ESCRT-III complexes. VPS4 oligomerization and ATPase activity are promoted by binding to LIP5. LIP5 also binds to the ESCRT-III like protein CHMP5/hVps60, but how this affects its function remains unclear. Here we confirm that LIP5 binds tightly to CHMP5, but also find that it binds well to additional ESCRT-III proteins including CHMP1B, CHMP2A/hVps2–1, and CHMP3/hVps24 but not CHMP4A/hSnf7–1 or CHMP6/hVps20. LIP5 binds to a different region within CHMP5 than within the other ESCRT-III proteins. In CHMP1B and CHMP2A, its binding site encompasses sequences at the proteins' extreme C-termini that overlap with “MIT interacting motifs” (MIMs) known to bind to VPS4. We find unexpected evidence of a second conserved binding site for VPS4 in CHMP2A and CHMP1B, suggesting that LIP5 and VPS4 may bind simultaneously to these proteins despite the overlap in their primary binding sites. Finally, LIP5 binds preferentially to soluble CHMP5 but instead to polymerized CHMP2A, suggesting that the newly defined interactions between LIP5 and ESCRT-III proteins may be regulated by ESCRT-III conformation. These studies point to a role for direct binding between LIP5 and ESCRT-III proteins that is likely to complement LIP5's previously described ability to regulate VPS4 activity.

scholarly journals Tumour susceptibility gene 101 and the vacuolar protein sorting pathway are required for the release of hepatitis E virions

2011 ◽  
Vol 92 (12) ◽  
pp. 2838-2848 ◽  
Author(s):  
Shigeo Nagashima ◽  
Masaharu Takahashi ◽  
Suljid Jirintai ◽  
Toshinori Tanaka ◽  
Tsutomu Nishizawa ◽  
...  
Keyword(s):  
Susceptibility Gene ◽  
Multivesicular Body ◽  
Hepatitis E ◽  
Negative Control ◽  
Dominant Negative ◽  
Wild Type ◽  
Orf3 Protein ◽  
Virus Particles ◽  
Virion Release ◽  
Vacuolar Protein

We have previously demonstrated that an intact PSAP motif in the ORF3 protein is required for the formation and release of membrane-associated hepatitis E virus (HEV) particles with ORF3 proteins on their surface. In this study, we investigated the direct interaction between the ORF3 protein and tumour susceptibility gene 101 (Tsg101), a cellular factor involved in the budding of viruses containing the P(T/S)AP late-domain, in PLC/PRF/5 cells expressing the wild-type or PSAP-mutated ORF3 protein and Tsg101 by co-immunoprecipitation. Tsg101 bound to wild-type ORF3 protein, but not to the PSAP-inactive ORF3 protein. To examine whether HEV utilizes the multivesicular body (MVB) pathway to release the virus particles, we analysed the efficiency of virion release from cells upon introduction of small interfering RNA (siRNA) against Tsg101 or dominant-negative (DN) mutants of Vps4 (Vps4A and Vps4B). The relative levels of virus particles released from cells depleted of Tsg101 decreased to 6.4 % of those transfected with negative control siRNA. Similarly, virion egress was significantly reduced by the overexpression of DN forms (Vps4AEQ or Vps4BEQ). The relative levels of virus particles released from cells expressing Vps4AEQ and Vps4BEQ were 19.2 and 15.6 %, respectively, while the overexpression of wild-type Vps4A and Vps4B did not alter the levels of virus release. These results indicate that the ORF3 protein interacts with Tsg101 through the PSAP motifs in infected cells, and that Tsg101 and the enzymic activities of Vps4A and Vps4B are involved in HEV release, thus suggesting that HEV requires the MVB pathway for egress of virus particles.

scholarly journals Fibrinogen Hershey IV: A novel dysfibrinogen with a γV411I mutation in the integrin αIIbβ3 binding site

2008 ◽  
Vol 99 (06) ◽  
pp. 1008-1012 ◽  
Author(s):  
Veronica Flood ◽  
Hamid Al-Mondhiry ◽  
Chantelle Rein ◽  
Kristine Alexander ◽  
Rehana Lovely ◽  
...  
Keyword(s):  
Platelet Aggregation ◽  
Biological Effects ◽  
Terminal Segment ◽  
Wild Type ◽  
Binding Assays ◽  
Normal Platelet ◽  
Platelet Receptor ◽  
Direct Binding ◽  
Aggregation Inhibition ◽  
Carboxyl Terminal

SummaryThe carboxyl terminal segment of the fibrinogen γ chain from γ408–4ll plays a crucial role in platelet aggregation via interactions with the platelet receptor αIIbβ3. We describe here the first naturally-occurring fibrinogen point mutation affecting this region and demonstrate its effects on platelet interactions. DNA sequencing was used to sequence the proband DNA, and platelet aggregation and direct binding assays were used to quantitate the biological effects of fibrinogen Hershey IV. The Hershey IV proband was found to be heterozygous for two mutations, γV411I and γR275C. Little difference in aggregation was seen when fibrinogen Hershey IV was compared to normal fibrinogen. However, less aggregation inhibition was observed using a competing synthetic dodecapeptide containing the V411I mutation as compared to the wild-type dodecapeptide. Purified fibrinogen Hershey IV also bound to purified platelet αIIbβ3 with a lower affinity than wild-type fibrinogen. These findings show that the γV411I mutation results in a decreased ability to bind platelets. In the heterozygous state, however, the available wild-type fibrinogen appears to be sufficient to support normal platelet aggregation.

scholarly journals Abnormal Lysosomal Positioning and Small Extracellular Vesicle Secretion in Arterial Stiffening and Calcification of Mice Lacking Mucolipin 1 Gene

2020 ◽  
Vol 21 (5) ◽  
pp. 1713 ◽  
Author(s):  
Owais M. Bhat ◽  
Xinxu Yuan ◽  
Sarah Camus ◽  
Fadi N. Salloum ◽  
Pin-Lan Li
Keyword(s):  
Multivesicular Body ◽  
Extracellular Vesicle ◽  
Annexin Ii ◽  
High Dose ◽  
Wild Type ◽  
Phenotypic Switch ◽  
Arterial Stiffening ◽  
Vesicle Secretion ◽  
Arterial Medial Calcification ◽  
Medial Calcification

Recent studies have shown that arterial medial calcification is mediated by abnormal release of exosomes/small extracellular vesicles from vascular smooth muscle cells (VSMCs) and that small extracellular vesicle (sEV) secretion from cells is associated with lysosome activity. The present study was designed to investigate whether lysosomal expression of mucolipin-1, a product of the mouse Mcoln1 gene, contributes to lysosomal positioning and sEV secretion, thereby leading to arterial medial calcification (AMC) and stiffening. In Mcoln1−/− mice, we found that a high dose of vitamin D (Vit D; 500,000 IU/kg/day) resulted in increased AMC compared to their wild-type littermates, which was accompanied by significant downregulation of SM22-α and upregulation of RUNX2 and osteopontin in the arterial media, indicating a phenotypic switch to osteogenic. It was also shown that significantly decreased co-localization of lysosome marker (Lamp-1) with lysosome coupling marker (Rab 7 and ALG-2) in the aortic wall of Mcoln1−/− mice as compared to their wild-type littermates. Besides, Mcoln1−/− mice showed significant increase in the expression of exosome/ sEV markers, CD63, and annexin-II (AnX2) in the arterial medial wall, accompanied by significantly reduced co-localization of lysosome marker (Lamp-1) with multivesicular body (MVB) marker (VPS16), suggesting a reduction of the lysosome-MVB interactions. In the plasma of Mcoln1−/− mice, the number of sEVs significantly increased as compared to the wild-type littermates. Functionally, pulse wave velocity (PWV), an arterial stiffening indicator, was found significantly increased in Mcoln1−/− mice, and Vit D treatment further enhanced such stiffening. All these data indicate that the Mcoln1 gene deletion in mice leads to abnormal lysosome positioning and increased sEV secretion, which may contribute to the arterial stiffness during the development of AMC.

scholarly journals Soluble Receptor Potentiates Receptor-Independent Infection by Murine Coronavirus

2002 ◽  
Vol 76 (3) ◽  
pp. 950-958 ◽  
Author(s):  
Fumihiro Taguchi ◽  
Shutoku Matsuyama
Keyword(s):  
Monoclonal Antibody ◽  
Hepatitis Virus ◽  
Active Form ◽  
Mouse Hepatitis Virus ◽  
Soluble Receptor ◽  
Wild Type ◽  
S Protein ◽  
Bhk Cells ◽  
Direct Binding ◽  
Mediate Cell

ABSTRACT Mouse hepatitis virus (MHV) infection spreads from MHV-infected DBT cells, which express the MHV receptor CEACAM1 (MHVR), to BHK cells, which are devoid of the receptor, by intercellular membrane fusion (MHVR-independent fusion). This mode of infection is a property of wild-type (wt) JHMV cl-2 virus but is not seen in cultures infected with the mutant virus JHMV srr7. In this study, we show that soluble MHVR (soMHVR) potentiates MHVR-independent fusion in JHMV srr7-infected cultures. Thus, in the presence of soMHVR, JHMV srr7-infected DBT cells overlaid onto BHK cells induce BHK cell syncytia and the spread of JHMV srr7 infection. This does not occur in the absence of soMHVR. soMHVR also enhanced wt virus MHVR-independent fusion. These effects were dependent on the concentration of soMHVR in the culture and were specifically blocked by the anti-MHVR monoclonal antibody CC1. Together with these observations, direct binding of soMHVR to the virus spike (S) glycoprotein as revealed by coimmunoprecipitation demonstrated that the effect is mediated by the binding of soMHVR to the S protein. Furthermore, fusion of BHK cells expressing the JHMV srr7 S protein was also induced by soMHVR. These results indicated that the binding of soMHVR to the S protein expressed on the DBT cell surface potentiates the fusion of MHV-infected DBT cells with nonpermissive BHK cells. We conclude that the binding of soMHVR to the S protein converts the S protein to a fusion-active form competent to mediate cell-cell fusion, in a fashion similar to the fusion of virus and cell membranes.

scholarly journals Molecular mechanism to recruit galectin-3 into multivesicular bodies for polarized exosomal secretion

2018 ◽  
Vol 115 (19) ◽  
pp. E4396-E4405 ◽  
Author(s):  
Sebastian Bänfer ◽  
Dominik Schneider ◽  
Jenny Dewes ◽  
Maximilian T. Strauss ◽  
Sven-A. Freibert ◽  
...  
Keyword(s):  
Secretory Pathway ◽  
Direct Interaction ◽  
Multivesicular Body ◽  
Dominant Negative ◽  
Amino Terminus ◽  
Multivesicular Bodies ◽  
Dramatic Decrease ◽  
Endosomal Sorting ◽  
Galectin 3 ◽  
Binding Lectin

The beta-galactoside binding lectin galectin-3 (Gal3) is found intracellularly and in the extracellular space. Secretion of this lectin is mediated independently of the secretory pathway by a not yet defined nonclassical mechanism. Here, we found Gal3 in the lumen of exosomes. Superresolution and electron microscopy studies visualized Gal3 recruitment and sorting into intraluminal vesicles. Exosomal Gal3 release depends on the endosomal sorting complex required for transport I (ESCRT-I) component Tsg101 and functional Vps4a. Either Tsg101 knockdown or expression of dominant-negative Vps4aE228Q causes an intracellular Gal3 accumulation at multivesicular body formation sites. In addition, we identified a highly conserved tetrapeptide P(S/T)AP motif in the amino terminus of Gal3 that mediates a direct interaction with Tsg101. Mutation of the P(S/T)AP motif results in a loss of interaction and a dramatic decrease in exosomal Gal3 secretion. We conclude that Gal3 is a member of endogenous non-ESCRT proteins which are P(S/T)AP tagged for exosomal release.

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