Faculty Opinions recommendation of Ubiquitin-dependent sorting into the multivesicular body pathway requires the function of a conserved endosomal protein sorting complex, ESCRT-I.

ABSTRACT The budding of many enveloped RNA viruses, including human immunodeficiency virus type 1 (HIV-1), requires some of the same cellular machinery as vesicle formation at the multivesicular body (MVB). In Saccharomyces cerevisiae, the ESCRT-II complex performs a central role in MVB protein sorting and vesicle formation, as it is recruited by the upstream ESCRT-I complex and nucleates assembly of the downstream ESCRT-III complex. Here, we report that the three subunits of human ESCRT-II, EAP20, EAP30, and EAP45, have a number of properties in common with their yeast orthologs. Specifically, EAP45 bound ubiquitin via its N-terminal GRAM-like ubiquitin-binding in EAP45 (GLUE) domain, both EAP45 and EAP30 bound the C-terminal domain of TSG101/ESCRT-I, and EAP20 bound the N-terminal half of CHMP6/ESCRT-III. Consistent with its expected role in MVB vesicle formation, (i) human ESCRT-II localized to endosomal membranes in a VPS4-dependent fashion and (ii) depletion of EAP20/ESCRT-II and CHMP6/ESCRT-III inhibited lysosomal targeting and downregulation of the epidermal growth factor receptor, albeit to a lesser extent than depletion of TSG101/ESCRT-I. Nevertheless, HIV-1 release and infectivity were not reduced by efficient small interfering RNA depletion of EAP20/ESCRT-II or CHMP6/ESCRT-III. These observations indicate that there are probably multiple pathways for protein sorting/MVB vesicle formation in human cells and that HIV-1 does not utilize an ESCRT-II-dependent pathway to leave the cell.

Download Full-text

ESCRTs and human disease

Biochemical Society Transactions ◽

10.1042/bst0370167 ◽

2009 ◽

Vol 37 (1) ◽

pp. 167-172 ◽

Cited By ~ 65

Author(s):

Suraj Saksena ◽

Scott D. Emr

Keyword(s):

Human Disease ◽

Protein Sorting ◽

Critical Role ◽

Multivesicular Body ◽

Human Diseases ◽

Down Regulation ◽

Endosomal Sorting ◽

Retroviral Budding

The ESCRT (endosomal sorting complex required for transport) machinery plays a critical role in receptor down-regulation, retroviral budding, and other normal and pathological processes. The ESCRT components are conserved in all five major subgroups of eukaryotes. This review summarizes the growing number of links identified between ESCRT-mediated protein sorting in the MVB (multivesicular body) pathway and various human diseases.

Download Full-text

Faculty Opinions recommendation of Ent5p is required with Ent3p and Vps27p for ubiquitin-dependent protein sorting into the multivesicular body.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.1019464.218577 ◽

2004 ◽

Author(s):

Robert Michell

Keyword(s):

Protein Sorting ◽

Multivesicular Body ◽

Dependent Protein

Download Full-text

Involvement of Specific COPI Subunits in Protein Sorting from the Late Endosome to the Vacuole in Yeast

Molecular and Cellular Biology ◽

10.1128/mcb.00577-06 ◽

2006 ◽

Vol 27 (2) ◽

pp. 526-540 ◽

Cited By ~ 43

Author(s):

Galina Gabriely ◽

Rachel Kama ◽

Jeffrey E. Gerst

Keyword(s):

Mammalian Cells ◽

Secretory Pathway ◽

Protein Sorting ◽

Multivesicular Body ◽

Carboxypeptidase Y ◽

Direct Role ◽

Vacuolar Protein Sorting ◽

Early Secretory Pathway ◽

Physical Interactions ◽

Vacuolar Protein

ABSTRACT Although COPI function on the early secretory pathway in eukaryotes is well established, earlier studies also proposed a nonconventional role for this coat complex in endocytosis in mammalian cells. Here we present results that suggest an involvement for specific COPI subunits in the late steps of endosomal protein sorting in Saccharomyces cerevisiae. First, we found that carboxypeptidase Y (CPY) was partially missorted to the cell surface in certain mutants of the COPIB subcomplex (COPIb; Sec27, Sec28, and possibly Sec33), which indicates an impairment in endosomal transport. Second, integral membrane proteins destined for the vacuolar lumen (i.e., carboxypeptidase S [CPS1]; Fur4, Ste2, and Ste3) accumulated at an aberrant late endosomal compartment in these mutants. The observed phenotypes for COPIb mutants resemble those of class E vacuolar protein sorting (vps) mutants that are impaired in multivesicular body (MVB) protein sorting and biogenesis. Third, we observed physical interactions and colocalization between COPIb subunits and an MVB-associated protein, Vps27. Together, our findings suggest that certain COPI subunits could have a direct role in vacuolar protein sorting to the MVB compartment.

Download Full-text

Cdc48 and ubiquilins confer selective anterograde protein sorting and entry into the multivesicular body in yeast

Molecular Biology of the Cell ◽

10.1091/mbc.e17-11-0652 ◽

2018 ◽

Vol 29 (8) ◽

pp. 948-963 ◽

Cited By ~ 4

Author(s):

Rachel Kama ◽

Galina Gabriely ◽

Vydehi Kanneganti ◽

Jeffrey E. Gerst

Keyword(s):

Protein Sorting ◽

Multivesicular Body ◽

Linkage Groups ◽

Disease Pathogenesis ◽

Proteolytic Activation ◽

Ubiquitinated Proteins ◽

Independent Functions ◽

Specific Proteins ◽

Lateral Sclerosis ◽

Human Neurodegenerative Disease

Cdc48/p97 is known primarily for the retrotranslocation of misfolded proteins in endoplasmic reticulum (ER)-associated protein degradation (ERAD). Here we uncover a novel function for both Cdc48 and the conserved ubiquitin-associated/ubiquitin-like ubiquitin receptor (ubiquilin) proteins in yeast (e.g., Ddi1, Dsk2, and Rad23), which deliver ubiquitinated proteins to the proteasome for degradation. We show that Cdc48, its core adaptors Npl4 and Ufd1, and the ubiquilins confer the constitutive anterograde delivery of carboxypeptidase S (Cps1), a membranal hydrolase, to the multivesicular body (MVB) and vacuolar lumen. Cdc48 and Ddi1 act downstream of Rsp5-dependent Cps1 ubiquitination to facilitate the disassembly of insoluble Cps1 oligomers and upstream of ESCRT-0 to facilitate the entry of soluble protein into the MVB. Consequentially, detergent-insoluble Cps1 accumulates in cells bearing mutations in CDC48, DDI1, and all three ubiquilins (ddi1Δ, dsk2Δ, rad23Δ). Thus, Cdc48 and the ubiquilins have ERAD- and proteasome-independent functions in the anterograde delivery of specific proteins to the yeast vacuole for proteolytic activation. As Cdc48/p97 and the ubiquilins are major linkage groups associated with the onset of human neurodegenerative disease (e.g., amytrophic lateral sclerosis, Alzheimer’s, and Paget’s disease of the bone), there may be a connection between their involvement in anterograde protein sorting and disease pathogenesis.

Download Full-text

Peroxisome biogenesis and the formation of multivesicular peroxisomes during tombusvirus infection: a role for ESCRT?This review is one of a selection of papers published in the Special Issue on Plant Cell Biology.

Canadian Journal of Botany ◽

10.1139/b06-005 ◽

2006 ◽

Vol 84 (4) ◽

pp. 551-564 ◽

Cited By ~ 8

Author(s):

Robert T. Mullen ◽

Andrew W. McCartney ◽

C. Robb Flynn ◽

Graham S.T. Smith

Keyword(s):

Cell Biology ◽

Molecular Mechanisms ◽

Protein Sorting ◽

Multivesicular Body ◽

Peroxisomal Membrane ◽

Viral Pathogens ◽

Endosomal Sorting ◽

Metabolic Functions ◽

Membrane Bound ◽

Vacuolar Protein

Peroxisomes are highly dynamic organelles with regard to their metabolic functions, shapes, distribution, movements, and biogenesis. They are also important as sites for the development of some viral pathogens. It has long been known that certain members of the tombusvirus family recruit peroxisomes for viral RNA replication and that this process is accompanied by dramatic changes in peroxisome morphology, the most remarkable of which is the extensive inward vesiculation of the peroxisomal boundary membrane leading to the formation of a peroxisomal multivesicular body (pMVB). While it is unclear how the internal vesicles of a pMVB form, they appear to serve in effectively concentrating viral membrane-bound replication complexes and protecting nascent viral RNAs from host-cell defences. Here, we review briefly the biogenesis of peroxisomes and pMVBs and discuss recent studies that have begun to shed light on how components of the tombusvirus replicase exploit the molecular mechanisms involved in peroxisome membrane protein sorting. We also address the question of what controls invagination and vesicle formation at the peroxisomal membrane during pMVB biogenesis. We propose that tombusviruses exploit protein constituents of the class E vacuolar protein-sorting pathway referred to as ESCRT (endosomal sorting complex required for transport) in the formation of pMVBs. This new pMVB–ESCRT hypothesis reconciles current paradigms of pMVB biogenesis with the role of ESCRT in endosomal multivesicular body formation and the ability of enveloped RNA viruses, including HIV, to appropriate the ESCRT machinery to execute their budding programme from cells.

Download Full-text