scholarly journals Atypical parkinsonism–associated retromer mutant alters endosomal sorting of specific cargo proteins

2016 ◽  
Vol 214 (4) ◽  
pp. 389-399 ◽  
Author(s):  
Kirsty J. McMillan ◽  
Matthew Gallon ◽  
Adam P. Jellett ◽  
Thomas Clairfeuille ◽  
Frances C. Tilley ◽  
...  
Keyword(s):  
Membrane Proteins ◽  
Neurodegenerative Disease ◽  
Quantitative Proteomics ◽  
Protein Complexes ◽  
Integral Membrane Proteins ◽  
Atypical Parkinsonism ◽  
Endosomal Sorting ◽  
Retromer Complex ◽  
Cargo Proteins ◽  
Cargo Sorting

The retromer complex acts as a scaffold for endosomal protein complexes that sort integral membrane proteins to various cellular destinations. The retromer complex is a heterotrimer of VPS29, VPS35, and VPS26. Two of these paralogues, VPS26A and VPS26B, are expressed in humans. Retromer dysfunction is associated with neurodegenerative disease, and recently, three VPS26A mutations (p.K93E, p.M112V, and p.K297X) were discovered to be associated with atypical parkinsonism. Here, we apply quantitative proteomics to provide a detailed description of the retromer interactome. By establishing a comparative proteomic methodology, we identify how this interactome is perturbed in atypical parkinsonism-associated VPS26A mutants. In particular, we describe a selective defect in the association of VPS26A (p.K297X) with the SNX27 cargo adaptor. By showing how a retromer mutant leads to altered endosomal sorting of specific PDZ ligand–containing cargo proteins, we reveal a new mechanism for perturbed endosomal cargo sorting in atypical parkinsonism.

scholarly journals Constitutively active ESCRT-II suppresses the MVB-sorting phenotype of ESCRT-0 and ESCRT-I mutants

2015 ◽  
Vol 26 (3) ◽  
pp. 554-568 ◽  
Author(s):  
Shrawan Kumar Mageswaran ◽  
Natalie K. Johnson ◽  
Greg Odorizzi ◽  
Markus Babst
Keyword(s):  
Protein Complexes ◽  
Deletion Strain ◽  
Endosomal Sorting ◽  
Cargo Proteins ◽  
Redundant Functions ◽  
Cargo Sorting ◽  
Constitutively Active

The endosomal sorting complex required for transport (ESCRT) protein complexes function at the endosome in the formation of intraluminal vesicles (ILVs) containing cargo proteins destined for the vacuolar/lysosomal lumen. The early ESCRTs (ESCRT-0 and -I) are likely involved in cargo sorting, whereas ESCRT-III and Vps4 function to sever the neck of the forming ILVs. ESCRT-II links these functions by initiating ESCRT-III formation in an ESCRT-I–regulated manner. We identify a constitutively active mutant of ESCRT-II that partially suppresses the phenotype of an ESCRT-I or ESCRT-0 deletion strain, suggesting that these early ESCRTs are not essential and have redundant functions. However, the ESCRT-III/Vps4 system alone is not sufficient for ILV formation but requires cargo sorting mediated by one of the early ESCRTs.

scholarly journals ESCRT ubiquitin-binding domains function cooperatively during MVB cargo sorting

2009 ◽  
Vol 185 (2) ◽  
pp. 213-224 ◽  
Author(s):  
S. Brookhart Shields ◽  
Andrea J. Oestreich ◽  
Stanley Winistorfer ◽  
Doris Nguyen ◽  
Johanna A. Payne ◽  
...  
Keyword(s):  
Membrane Proteins ◽  
Structural Information ◽  
Multivesicular Bodies ◽  
Endosomal Sorting ◽  
Binding Domains ◽  
Ubiquitin Binding ◽  
Cargo Sorting

Ubiquitin (Ub) sorting receptors facilitate the targeting of ubiquitinated membrane proteins into multivesicular bodies (MVBs). Ub-binding domains (UBDs) have been described in several endosomal sorting complexes required for transport (ESCRT). Using available structural information, we have investigated the role of the multiple UBDs within ESCRTs during MVB cargo selection. We found a novel UBD within ESCRT-I and show that it contributes to MVB sorting in concert with the known UBDs within the ESCRT complexes. These experiments reveal an unexpected level of coordination among the ESCRT UBDs, suggesting that they collectively recognize a diverse set of cargo rather than act sequentially at discrete steps.

scholarly journals Hse1, a Component of the Yeast Hrs-STAM Ubiquitin-sorting Complex, Associates with Ubiquitin Peptidases and a Ligase to Control Sorting Efficiency into Multivesicular Bodies

2007 ◽  
Vol 18 (1) ◽  
pp. 324-335 ◽  
Author(s):  
Jihui Ren ◽  
Younghoon Kee ◽  
Jon M. Huibregtse ◽  
Robert C. Piper
Keyword(s):  
Functional Analysis ◽  
Membrane Proteins ◽  
Ubiquitin Ligase ◽  
Integral Membrane Proteins ◽  
Multivesicular Bodies ◽  
C Terminus ◽  
Cargo Proteins ◽  
Sorting Receptor ◽  
Sorting Efficiency ◽  
Novel Protein

Ubiquitinated integral membrane proteins are delivered to the interior of the lysosome/vacuole for degradation. This process relies on specific ubiquitination of potential cargo and recognition of that Ub-cargo by sorting receptors at multiple compartments. We show that the endosomal Hse1-Vps27 sorting receptor binds to ubiquitin peptidases and the ubiquitin ligase Rsp5. Hse1 is linked to Rsp5 directly via a PY element within its C-terminus and through a novel protein Hua1, which recruits a complex of Rsp5, Rup1, and Ubp2. The SH3 domain of Hse1 also binds to the deubiquitinating protein Ubp7. Functional analysis shows that when both modes of Rsp5 association with Hse1 are altered, sorting of cargo that requires efficient ubiquitination for entry into the MVB is blocked, whereas sorting of cargo containing an in-frame addition of ubiquitin is normal. Further deletion of Ubp7 restores sorting of cargo when the Rsp5:Hse1 interaction is compromised suggesting that both ubiquitin ligases and peptidases associate with the Hse1-Vps27 sorting complex to control the ubiquitination status and sorting efficiency of cargo proteins. Additionally, we find that disruption of UBP2 and RUP1 inhibits MVB sorting of some cargos suggesting that Rsp5 requires association with Ubp2 to properly ubiquitinate cargo for efficient MVB sorting.

The role of ESCRT proteins in attenuation of cell signalling

2009 ◽  
Vol 37 (1) ◽  
pp. 137-142 ◽  
Author(s):  
Lina M. Rodahl ◽  
Susanne Stuffers ◽  
Viola H. Lobert ◽  
Harald Stenmark
Keyword(s):  
Cell Proliferation ◽  
Growth Factor ◽  
Membrane Proteins ◽  
Protein Complexes ◽  
Cell Signalling ◽  
Control Cell ◽  
Endosomal Sorting ◽  
Tumour Suppression ◽  
Multivesicular Endosomes

The ESCRT (endosomal sorting complex required for transport) machinery consists of four protein complexes that mediate sorting of ubiquitinated membrane proteins into the intraluminal vesicles of multivesicular endosomes, thereby targeting them for degradation in lysosomes. In the present paper, we review how ESCRT-mediated receptor down-regulation affects signalling downstream of Notch and growth factor receptors, and how ESCRTs may control cell proliferation, survival and cytoskeletal functions and contribute to tumour suppression.

scholarly journals Mistargeting of secretory cargo in retromer-deficient cells

2020 ◽  
Author(s):  
Sarah D. Neuman ◽  
Erica L. Terry ◽  
Jane E. Selegue ◽  
Amy T. Cavanagh ◽  
Arash Bashirullah
Keyword(s):  
Membrane Proteins ◽  
Salivary Glands ◽  
Secretory Granule ◽  
Complex Function ◽  
Secretory Cells ◽  
Regulated Exocytosis ◽  
Retromer Complex ◽  
Cargo Proteins ◽  
Granule Membrane ◽  
Granule Membrane Proteins

ABSTRACTIntracellular trafficking is a basic and essential cellular function required for delivery of proteins to the appropriate subcellular destination; this process is especially demanding in professional secretory cells, which synthesize and secrete massive quantities of cargo proteins via regulated exocytosis. The Drosophila larval salivary glands are professional secretory cells that synthesize and secrete mucin proteins at the onset of metamorphosis. Using the larval salivary glands as a model system, we have identified a role for the highly conserved retromer complex in trafficking of secretory granule membrane proteins. We demonstrate that retromer-dependent trafficking via endosomal tubules is induced at the onset of secretory granule biogenesis, and that recycling via endosomal tubules is required for delivery of essential secretory granule membrane proteins to nascent granules. Without retromer function, nascent granules do not contain the proper membrane proteins; as a result, cargo from these defective granules is mistargeted to Rab7-positive endosomes, where it progressively accumulates to generate dramatically enlarged endosomes. Retromer complex dysfunction is strongly associated with Alzheimer’s disease, characterized by accumulation of amyloid β (Aβ). We show that amyloid precursor protein (APP) undergoes regulated exocytosis and accumulates within enlarged endosomes in retromer-deficient cells. These results highlight recycling of secretory granule membrane proteins as a critical step during secretory granule maturation and provide new insights into our understanding of retromer complex function in secretory cells. Our data also suggests that misrouting of secretory cargo, including APP, may contribute to the progressive nature of neurodegenerative disease.SUMMARY STATEMENTRetromer complex dysfunction is implicated in neurodegeneration. Here the authors show a new role for the retromer complex in recycling of secretory membrane and cargo proteins during regulated exocytosis.

scholarly journals Did2 coordinates Vps4-mediated dissociation of ESCRT-III from endosomes

2006 ◽  
Vol 175 (5) ◽  
pp. 715-720 ◽  
Author(s):  
Daniel P. Nickerson ◽  
Matthew West ◽  
Greg Odorizzi
Keyword(s):  
Vesicle Formation ◽  
Multivesicular Bodies ◽  
Vesicle Budding ◽  
Endosomal Sorting ◽  
Essential Step ◽  
Adenosine Triphosphatases ◽  
Cargo Proteins ◽  
Endosomal Membranes ◽  
Cargo Sorting

The sorting of transmembrane cargo proteins into the lumenal vesicles of multivesicular bodies (MVBs) depends on the recruitment of endosomal sorting complexes required for transport (ESCRTs) to the cytosolic face of endosomal membranes. The subsequent dissociation of ESCRT complexes from endosomes requires Vps4, a member of the AAA family of adenosine triphosphatases. We show that Did2 directs Vps4 activity to the dissociation of ESCRT-III but has no role in the dissociation of ESCRT-I or -II. Surprisingly, vesicle budding into the endosome lumen occurs in the absence of Did2 function even though Did2 is required for the efficient sorting of MVB cargo proteins into lumenal vesicles. This uncoupling of MVB cargo sorting and lumenal vesicle formation suggests that the Vps4-mediated dissociation of ESCRT-III is an essential step in the sorting of cargo proteins into MVB vesicles but is not a prerequisite for the budding of vesicles into the endosome lumen.

scholarly journals Molecular interactions of the M and E integral membrane proteins of SARS-CoV-2

2021 ◽  
Author(s):  
Viviana Monje-Galvan ◽  
Gregory A. Voth
Keyword(s):  
Membrane Proteins ◽  
Protein Interactions ◽  
Protein Complexes ◽  
Integral Membrane Proteins ◽  
Protein Protein Interactions ◽  
Novel Treatments ◽  
Cellular Processes ◽  
Ongoing Work ◽  
Lipid Environment ◽  
Lipid Protein Interactions

AbstractSpecific lipid-protein interactions are key for cellular processes, and even more so for the replication of pathogens. The COVID-19 pandemic has drastically changed our lives and cause the death of nearly three million people worldwide, as of this writing. SARS-CoV-2 is the virus that causes the disease and has been at the center of scientific research over the past year. Most of the research on the virus is focused on key players during its initial attack and entry into the cellular host; namely the S protein, its glycan shield, and its interactions with the ACE2 receptors of human cells. As cases continue to raise around the globe, and new mutants are identified, there is an urgent need to understand the mechanisms of this virus during different stages of its life cycle. Here, we consider two integral membrane proteins of SARS-CoV-2 known to be important for viral assembly and infectivity. We have used microsecond-long all-atom molecular dynamics to examine the lipid-protein and protein-protein interactions of the membrane (M) and envelope (E) structural proteins of SARS-CoV-2 in a complex membrane model. We contrast the two proposed protein complexes for each of these proteins, and quantify their effect on their local lipid environment. This ongoing work also aims to provide molecular-level understanding of the mechanisms of action of this virus to possibly aid in the design of novel treatments.

Image Analysis of Intramembrane Particles in Freeze-Fractured Biomembranes Using Computer Simulation Techniques

1975 ◽  
Vol 33 ◽  
pp. 214-215
Author(s):  
D.J. Benefiel ◽  
R.S. Weinstein
Keyword(s):  
Membrane Proteins ◽  
Freeze Fracture ◽  
Integral Membrane Proteins ◽  
Systematic Evaluation ◽  
Intramembrane Particles ◽  
Modeling Methods ◽  
Simulation Techniques ◽  
Freeze Fracture Electron Microscopy ◽  
Fracture Electron ◽  
Computer Simulation Techniques

Intramembrane particles (IMP or MAP) are components of most biomembranes. They are visualized by freeze-fracture electron microscopy, and they probably represent replicas of integral membrane proteins. The presence of MAP in biomembranes has been extensively investigated but their detailed ultrastructure has been largely ignored. In this study, we have attempted to lay groundwork for a systematic evaluation of MAP ultrastructure. Using mathematical modeling methods, we have simulated the electron optical appearances of idealized globular proteins as they might be expected to appear in replicas under defined conditions. By comparing these images with the apearances of MAPs in replicas, we have attempted to evaluate dimensional and shape distortions that may be introduced by the freeze-fracture technique and further to deduce the actual shapes of integral membrane proteins from their freezefracture images.

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