Fusion Rapidly Follows Vesicle Transport to the Target Membrane in Protein Transport through the Golgi Apparatus in Vitro. A Re-evaluation of Transport Kinetics Based on the Finding that the Glycosylation Used to Mark Transport, and Not Transport Itself, is Rate Limiting in the Assay

1993 ◽  
pp. 45-51
Author(s):  
R. R. Hiebsch ◽  
B. W. Wattenberg
Keyword(s):  
Golgi Apparatus ◽  
Protein Transport ◽  
Vesicle Transport ◽  
Transport Kinetics ◽  
Target Membrane ◽  
Rate Limiting

scholarly journals Substrate Proteins Take Shape at an Improved Bacterial Translocon

2018 ◽  
Vol 201 (1) ◽  
Author(s):  
Donald Oliver
Keyword(s):  
Protein Transport ◽  
Protein Translocation ◽  
Membrane Vesicles ◽  
Transport Models ◽  
Content Type ◽  
Rate Limiting ◽  
Substrate Proteins

ABSTRACTCharacterization of Sec-dependent bacterial protein transport has often relied on anin vitroprotein translocation system comprised in part ofEscherichia coliinverted inner membrane vesicles or, more recently, purified SecYEG translocons reconstituted into liposomes using mostly a single substrate (proOmpA). A paper published in this issue (P. Bariya and L. Randall, J Bacteriol 201:e00493-18, 2019, https://doi.org/10.1128/JB.00493-18) finds that inclusion of SecA protein during SecYEG proteoliposome reconstitution dramatically improves the number of active translocons. This experimentally useful and intriguing result that may arise from SecA membrane integration properties is discussed here. Furthermore, determination of the rate-limiting transport step for nine different substrates implicates the mature region distal to the signal peptide in the observed rate constant differences, indicating that more nuanced transport models that respond to differences in protein sequence and structure are needed.

scholarly journals Identification of a 25-kD protein from yeast cytosol that operates in a prefusion step of vesicular transport between compartments of the Golgi.

1990 ◽  
Vol 110 (4) ◽  
pp. 947-954 ◽  
Author(s):  
B W Wattenberg ◽  
R R Hiebsch ◽  
L W LeCureux ◽  
M P White
Keyword(s):  
Monoclonal Antibodies ◽  
Golgi Apparatus ◽  
Active Component ◽  
Protein Transport ◽  
Transport Activity ◽  
Yeast Protein ◽  
Fusion Event ◽  
Transport Vesicles ◽  
Target Membrane ◽  
Cytosolic Factors

We have identified a 25-kD cytosolic yeast protein that mediates a late, prefusion step in transport of proteins between compartments of the Golgi apparatus. Activity was followed using the previously described cell free assay for protein transport between Golgi compartments as modified to detect late acting cytosolic factors (Wattenberg, B. W., and J. E. Rothman. 1986. J. Biol. Chem. 263:2208-2213). In the reaction mediated by this protein, transport vesicles that have become attached to the target membrane during a preincubation are processed in preparation for fusion. The ultimate fusion event does not require the addition of cytosolic proteins (Balch, W. E., W. G. Dunphy, W. A. Braell, and J. E. Rothman. 1984. Cell. 39:525-536). Although isolated from yeast, this protein has activity when assayed with mammalian membranes. This protein has been enriched over 150-fold from yeast cytosol, albeit not to complete homogeneity. The identity of a 25-kD polypeptide as the active component was confirmed by raising monoclonal antibodies to it. These antibodies were found to specifically inhibit transport activity. Because this is a protein operating in prefusion, it has been abbreviated POP.

scholarly journals Reconstitution of vesiculated Golgi membranes into stacks of cisternae: requirement of NSF in stack formation.

1995 ◽  
Vol 129 (3) ◽  
pp. 577-589 ◽  
Author(s):  
U Acharya ◽  
J M McCaffery ◽  
R Jacobs ◽  
V Malhotra
Keyword(s):  
High Speed ◽  
Protein Transport ◽  
Rat Kidney ◽  
Average Diameter ◽  
Cell Extract ◽  
Processing Enzymes ◽  
Golgi Membranes ◽  
Transport Vesicles ◽  
Target Membrane

We have developed an in vitro system to study the biochemical events in the fusion of ilimaquinone (IQ) induced vesiculated Golgi membranes (VGMs) into stacks of cisternae. The Golgi complex in intact normal rat kidney cells (NRK) is vesiculated by treatment with IQ. The cells are washed to remove the drug and then permeabilized by a rapid freeze-thaw procedure. VGMs of 60 nm average diameter assemble into stacks of Golgi cisternae by a process that is temperature dependent, requires ATP and a high speed supernatant from cell extract (cytosol), as revealed by immunofluorescence and electron microscopy. The newly assembled stacks are functionally active in vesicular protein transport and contain processing enzymes that carry out Golgi specific modifications of glycoproteins. The fusion of VGMs requires NSF, a protein known to promote fusion of transport vesicles with the target membrane in the exocytic and endocytic pathways. Immunoelectron microscopy using Golgi specific anti-mannosidase II antibody reveals that VGMs undergo sequential changes in their morphology, whereby they first fuse to form larger vesicles of 200-300-nm average diameter which subsequently extend into tubular elements and finally assemble into stacks of cisternae.

scholarly journals Bacterial Sec Protein Transport Is Rate-limited by Precursor Length: A Single Turnover Study

2009 ◽  
Vol 20 (19) ◽  
pp. 4256-4266 ◽  
Author(s):  
Fu-Cheng Liang ◽  
Umesh K. Bageshwar ◽  
Siegfried M. Musser
Keyword(s):  
Protein Transport ◽  
Atp Hydrolysis ◽  
Membrane Vesicles ◽  
Single Turnover ◽  
Rate Limiting Step ◽  
Limiting Step ◽  
Precursor Proteins ◽  
Inverted Membrane Vesicles ◽  
Rate Limiting

An in vitro real-time single turnover assay for the Escherichia coli Sec transport system was developed based on fluorescence dequenching. This assay corrects for the fluorescence quenching that occurs when fluorescent precursor proteins are transported into the lumen of inverted membrane vesicles. We found that 1) the kinetics were well fit by a single exponential, even when the ATP concentration was rate-limiting; 2) ATP hydrolysis occurred during most of the observable reaction period; and 3) longer precursor proteins transported more slowly than shorter precursor proteins. If protein transport through the SecYEG pore is the rate-limiting step of transport, which seems likely, these conclusions argue against a model in which precursor movement through the SecYEG translocon is mechanically driven by a series of rate-limiting, discrete translocation steps that result from conformational cycling of the SecA ATPase. Instead, we propose that precursor movement results predominantly from Brownian motion and that the SecA ATPase regulates pore accessibility.

scholarly journals Assembly of the B subunit pentamer of Escherichia coli heat-labile enterotoxin. Kinetics and molecular basis of rate-limiting steps in vitro.

1996 ◽  
Vol 271 (43) ◽  
pp. 27188
Author(s):  
Lloyd W. Ruddock ◽  
Jeremy J.F. Coen ◽  
Caroline Cheesman ◽  
Robert B. Freedman ◽  
Timothy R. Hirst
Keyword(s):  
Escherichia Coli ◽  
Molecular Basis ◽  
B Subunit ◽  
Heat Labile ◽  
Rate Limiting

scholarly journals Slow viral propagation during initial phase of infection leads to viral persistence in mice

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Haifeng C. Xu ◽  
Ruifeng Wang ◽  
Prashant V. Shinde ◽  
Lara Walotka ◽  
Anfei Huang ◽  
...  
Keyword(s):  
T Cell ◽  
Immune Evasion ◽  
Protein Transport ◽  
Adaptive Immune System ◽  
Viral Persistence ◽  
Lymphocytic Choriomeningitis ◽  
Type I ◽  
Viral Propagation

AbstractImmune evasion of pathogens can modify the course of infection and impact viral persistence and pathology. Here, using different strains of the lymphocytic choriomeningitis virus (LCMV) model system, we show that slower propagation results in limited type I interferon (IFN-I) production and viral persistence. Specifically, cells infected with LCMV-Docile exhibited reduced viral replication when compared to LCMV-WE and as a consequence, infection with LCMV-Docile resulted in reduced activation of bone marrow derived dendritic cells (BMDCs) and IFN-I production in vitro in comparison with LCMV-WE. In vivo, we observed a reduction of IFN-I, T cell exhaustion and viral persistence following infection of LCMV-Docile but not LCMV-WE. Mechanistically, block of intracellular protein transport uncovered reduced propagation of LCMV-Docile when compared to LCMV-WE. This reduced propagation was critical in blunting the activation of the innate and adaptive immune system. When mice were simultaneously infected with LCMV-Docile and LCMV-WE, immune function was restored and IFN-I production, T cell effector functions as well as viral loads were similar to that of mice infected with LCMV-WE alone. Taken together, this study suggests that reduced viral propagation can result in immune evasion and viral persistence.

scholarly journals Glycosphingolipids are required for sorting melanosomal proteins in the Golgi complex

2001 ◽  
Vol 155 (3) ◽  
pp. 369-380 ◽  
Author(s):  
Hein Sprong ◽  
Sophie Degroote ◽  
Tijs Claessens ◽  
Judith van Drunen ◽  
Viola Oorschot ◽  
...  
Keyword(s):  
Golgi Complex ◽  
Protein Transport ◽  
Transmembrane Domain ◽  
Direct Pathway ◽  
Mouse Melanoma Cell ◽  
Multicellular Organisms ◽  
Rate Limiting ◽  
Tyrosinase Related Protein ◽  
Mouse Melanoma Cell Line

A;lthough glycosphingolipids are ubiquitously expressed and essential for multicellular organisms, surprisingly little is known about their intracellular functions. To explore the role of glycosphingolipids in membrane transport, we used the glycosphingolipid-deficient GM95 mouse melanoma cell line. We found that GM95 cells do not make melanin pigment because tyrosinase, the first and rate-limiting enzyme in melanin synthesis, was not targeted to melanosomes but accumulated in the Golgi complex. However, tyrosinase-related protein 1 still reached melanosomal structures via the plasma membrane instead of the direct pathway from the Golgi. Delivery of lysosomal enzymes from the Golgi complex to endosomes was normal, suggesting that this pathway is not affected by the absence of glycosphingolipids. Loss of pigmentation was due to tyrosinase mislocalization, since transfection of tyrosinase with an extended transmembrane domain, which bypassed the transport block, restored pigmentation. Transfection of ceramide glucosyltransferase or addition of glucosylsphingosine restored tyrosinase transport and pigmentation. We conclude that protein transport from Golgi to melanosomes via the direct pathway requires glycosphingolipids.

scholarly journals Uric Acid Is a Genuine Metabolite of Penicillium cyclopium and Stimulates the Expression of Alkaloid Biosynthesis in This Fungus

2002 ◽  
Vol 68 (4) ◽  
pp. 1524-1533 ◽  
Author(s):  
Florian Helbig ◽  
Jörg Steighardt ◽  
Werner Roos
Keyword(s):  
Uric Acid ◽  
Low Molecular Weight ◽  
Alkaloid Production ◽  
Alkaloid Biosynthesis ◽  
Penicillium Cyclopium ◽  
Measurable Activity ◽  
Reduced Rate ◽  
Rate Limiting

ABSTRACT On searching for endogenous, low-molecular-weight effectors of benzodiazepine alkaloid biosynthesis in Penicillium cyclopium uric acid was isolated from ethanolic or autoclaved mycelial extracts of this fungus. The isolation was based on a three-step high-pressure liquid chromatography procedure guided by a microplate bioassay, and uric acid was identified by mass spectrometry and the uricase reaction. Conidiospore suspensions that were treated with this compound during the early phase of outgrowth developed emerged cultures with an enhanced rate of alkaloid production. Uric acid treatment did not increase the in vitro measurable activity of the rate-limiting biosynthetic enzyme, cyclopeptine synthetase. However, these cultures displayed a reduced rate of uptake of the alkaloid precursor l-phenylalanine into the vacuoles of the hyphal cells as assayed in situ. It is suggested that the depressed capacity of vacuolar uptake caused by the contact of outgrowing spores with uric acid liberated from hyphal cells results in an enhanced availability of the precursor l-phenylalanine in the cytoplasm and thus accounts at least in part for the increase in alkaloid production.

STEM-18. STROMAL EXTRACELLULAR VESICLES DRIVE GLIOMA STEM CELL REPROGRAMMING

2021 ◽  
Vol 23 (Supplement_6) ◽  
pp. vi24-vi25
Author(s):  
Lata Adnani ◽  
Brian Meehan ◽  
Jordan Kassouf ◽  
Cristiana Spinelli ◽  
Nadim Tawil ◽  
...  
Keyword(s):  
Molecular Subtype ◽  
Extracellular Vesicle ◽  
Host Cells ◽  
Tumour Mass ◽  
Membrane Structures ◽  
And Function ◽  
Rate Limiting ◽  
The Brain

Abstract Glioblastoma multiforme (GBM) represents the most frequent and lethal form of brain tumors originating from glioma stem cells (GSCs). GBM remains lethal because the rate limiting patho-mechanisms remain poorly understood. In this regard, few limitations involve the diversity 'between' cellular states and the molecular/cellular complexity 'within' the tumour mass. Using cell based- and mouse- models, we explored extracellular vesicle (EV) mediated interactions between cancer and stromal cells impacting phenotypes of GSCs as a function of their molecular subtype. EVs are spherical membrane structures that cells release to expel different molecular cargo (lipids, proteins, RNA, DNA), which can be transported across a distance in the brain and taken up by various ‘recipient’ cells resulting in reprogramming of the recipient cell's content and function. In vivo, GSCs altered their pattern of NOTCH signalling and molecular phenotype as a function of proximity to non-transformed host cells in the brain. In vitro stromal EVs altered GSC sphere forming capacity, proteome and expression of mesenchymal markers. Thus, EV mediated tumour-stromal interactions could represent a biological switch and a novel targeting point in the biology of GBM.

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