scholarly journals Distinct Roles for the AAA ATPases NSF and p97 in the Secretory Pathway

2004 ◽  
Vol 15 (2) ◽  
pp. 637-648 ◽  
Author(s):  
Seema Dalal ◽  
Meredith F. N. Rosser ◽  
Douglas M. Cyr ◽  
Phyllis I. Hanson
Keyword(s):  
Membrane Trafficking ◽  
Mammalian Cells ◽  
Secretory Pathway ◽  
Atp Hydrolysis ◽  
Brefeldin A ◽  
Transmembrane Conductance Regulator ◽  
Organelle Biogenesis ◽  
Ubiquitinated Proteins ◽  
Organelle Assembly ◽  
Specific Assessment

NSF and p97 are related AAA proteins implicated in membrane trafficking and organelle biogenesis. p97 is also involved in pathways that lead to ubiquitin-dependent proteolysis, including ER-associated degradation (ERAD). In this study, we have used dominant interfering ATP-hydrolysis deficient mutants (NSF(E329Q) and p97(E578Q)) to compare the function of these AAA proteins in the secretory pathway of mammalian cells. Expressing NSF(E329Q) promotes disassembly of Golgi stacks into dispersed vesicular structures. It also rapidly inhibits glycosaminoglycan sulfation, reflecting disruption of intra-Golgi transport. In contrast, expressing p97(E578Q) does not affect Golgi structure or function; glycosaminoglycans are normally sulfated and secreted, as is the VSV-G ts045 protein. Instead, expression of p97(E578Q) causes ubiquitinated proteins to accumulate on ER membranes and slows degradation of the ERAD substrate cystic-fibrosis transmembrane-conductance regulator. In addition, expression of p97(E578Q) eventually causes the ER to swell. More specific assessment of effects of p97(E578Q) on organelle assembly shows that the Golgi apparatus disperses and reassembles normally after treatment with brefeldin A and during mitosis. These findings demonstrate that ATP-hydrolysis-dependent activities of NSF and p97 in the cell are not equivalent and suggest that only NSF is directly involved in regulating membrane fusion.

scholarly journals Specific and Nonspecific Membrane-binding Determinants Cooperate in Targeting Phosphatidylinositol Transfer Protein β-Isoform to the MammalianTrans-Golgi Network

2006 ◽  
Vol 17 (6) ◽  
pp. 2498-2512 ◽  
Author(s):  
Scott E. Phillips ◽  
Kristina E. Ile ◽  
Malika Boukhelifa ◽  
Richard P.H. Huijbregts ◽  
Vytas A. Bankaitis
Keyword(s):  
Membrane Trafficking ◽  
Mammalian Cells ◽  
Secretory Pathway ◽  
Membrane Binding ◽  
Bound State ◽  
Missense Mutations ◽  
Cis Acting ◽  
Domain Mapping ◽  
Phosphatidylinositol Transfer ◽  
Golgi Network

Phosphatidylinositol transfer proteins (PITPs) regulate the interface between lipid metabolism and specific steps in membrane trafficking through the secretory pathway in eukaryotes. Herein, we describe the cis-acting information that controls PITPβ localization in mammalian cells. We demonstrate PITPβ localizes predominantly to the trans-Golgi network (TGN) and that this localization is independent of the phospholipid-bound state of PITPβ. Domain mapping analyses show the targeting information within PITPβ consists of three short C-terminal specificity elements and a nonspecific membrane-binding element defined by a small motif consisting of adjacent tryptophan residues (the W202W203motif). Combination of the specificity elements with the W202W203motif is necessary and sufficient to generate an efficient TGN-targeting module. Finally, we demonstrate that PITPβ association with the TGN is tolerant to a range of missense mutations at residue serine 262, we describe the TGN localization of a novel PITPβ isoform with a naturally occurring S262Q polymorphism, and we find no other genetic or pharmacological evidence to support the concept that PITPβ localization to the TGN is obligately regulated by conventional protein kinase C (PKC) or the Golgi-localized PKC isoforms δ or ε. These latter findings are at odds with a previous report that conventional PKC-mediated phosphorylation of residue Ser262is required for PITPβ targeting to Golgi membranes.

scholarly journals A fluorescent lipid analogue can be used to monitor secretory activity and for isolation of mammalian secretion mutants.

1995 ◽  
Vol 6 (2) ◽  
pp. 135-150 ◽  
Author(s):  
N T Ktistakis ◽  
C Y Kao ◽  
R H Wang ◽  
M G Roth
Keyword(s):  
Chinese Hamster Ovary ◽  
Mammalian Cells ◽  
Secretory Pathway ◽  
Chinese Hamster Ovary Cells ◽  
Chinese Hamster ◽  
Brefeldin A ◽  
Secretory Activity ◽  
Specific Marker ◽  
Ovary Cells ◽  
Fluorescent Lipid

The use of reporter proteins to study the regulation of secretion has often been complicated by posttranslational processing events that influence the secretion of certain proteins, but are not part of the cellular mechanisms that specifically regulate secretion. This has been a particular limitation for the isolation of mammalian secretion mutants, which has typically been a slow process. To provide a reporter of secretory activity independent of protein processing events, cells were labeled with the fluorescent lipid analogue C5-DMB-ceramide (ceramide coupled to the fluorophore boron dipyrromethene difluoride) and its secretion was followed by fluorescence microscopy and fluorescence-activated cell sorting. Brefeldin A, which severely inhibits secretion in Chinese hamster ovary cells, blocked secretion of C5-DMB-ceramide. At high temperature, export of C5-DMB-ceramide was inhibited in HRP-1 cells, which have a conditional defect in secretion. Using C5-DMB-ceramide as a reporter of secretory activity, several different pulse-chase protocols were designed that selected mutant Chinese hamster ovary cells that were resistant to the drug brefeldin A and others that were defective in the transport of glycoproteins to the cell surface. Mutant cells of either type were identified in a mutagenized population at a frequency of 10(-6). Thus, the fluorescent lipid C5-DMB-ceramide can be used as a specific marker of secretory activity, providing an efficient, general approach for isolating mammalian cells with defects in the secretory pathway.

scholarly journals A tractable Drosophila cell system enables rapid identification of Acinetobacter baumannii host factors

2020 ◽  
Author(s):  
Qing-Ming Qin ◽  
Jianwu Pei ◽  
Gabriel Gomez ◽  
Allison Rice-Ficht ◽  
Thomas A. Ficht ◽  
...  
Keyword(s):  
Acinetobacter Baumannii ◽  
Membrane Trafficking ◽  
Mammalian Cells ◽  
Molecular Mechanisms ◽  
Model System ◽  
Host Factors ◽  
Host Cells ◽  
Bacterial Invasion ◽  
Organelle Biogenesis ◽  
Drosophila Cell

AbstractAcinetobacter baumannii is an important causative agent of nosocomial infections worldwide. The pathogen also readily acquires resistance to antibiotics, and pan-resistant strains have been reported. A. baumannii is widely regarded as an extracellular bacterial pathogen. However, accumulating evidence demonstrates that the pathogen can invade, survive or persist in infected mammalian cells. Unfortunately, the molecular mechanisms controlling these processes remain poorly understood. Here, we show that Drosophila S2 cells provide several attractive advantages as a model system for investigating the intracellular lifestyle of the pathogen, including susceptibility to bacterial intracellular replication and limited infection-induced host cell death. We also show that the Drosophila system can be used to rapidly identify host factors, including MAP kinase proteins, which confer susceptibility to intracellular parasitism. Finally, analysis of the Drosophila system suggested that host proteins that regulate organelle biogenesis and membrane trafficking contribute to regulating the intracellular lifestyle of the pathogen. Taken together, these findings establish a novel model system for elucidating interactions between A. baumannii and host cells, define new factors that regulate bacterial invasion or intracellular persistence, and identify subcellular compartments in host cells that interact with the pathogen.

The small GTP-binding protein rab6p is redistributed in the cytosol by brefeldin A

1993 ◽  
Vol 106 (3) ◽  
pp. 789-802 ◽  
Author(s):  
M. Roa ◽  
V. Cornet ◽  
C.Z. Yang ◽  
B. Goud
Keyword(s):  
Membrane Trafficking ◽  
Mammalian Cells ◽  
Brefeldin A ◽  
Atp Depletion ◽  
Cell Fractionation ◽  
Microtubule Organizing Center ◽  
Trans Golgi Network ◽  
Gtp Binding ◽  
Organizing Center ◽  
Golgi Network

Rab6 protein belongs to the Sec4/Ypt/rab subfamily of small GTP-binding proteins involved in intracellular membrane trafficking in yeast and mammalian cells. Its localization both in medial and trans-Golgi network prompted us to study the effects of brefeldin A (BFA) on rab6p redistribution. By two techniques, indirect immunofluorescence and cell fractionation, we investigated the fate of rab6p and compared it to other Golgi or trans-Golgi network markers in BHK-21 and NIH-3T3 cells. BFA, at 5 micrograms/ml, induced redistribution of rab6p according to a biphasic process: during the first 10–15 minutes, tubulo-vesicular structures--colabelled with a bona fide medial Golgi marker called CTR 433--were observed; these structures were then replaced by punctate diffuse staining, which was stable for up to 3 hours. The 110 kDa peripheral membrane protein beta-COP was released much more rapidly from the Golgi membranes, whereas the trans-Golgi network marker TGN 38 relocated to the microtubule organizing center. The kinetics of reversion of BFA action on these antigens was also followed by immunofluorescence. Consistent with these results, rab6 antigen, originally found as 40% in the cytosolic versus 60% in the particulate (P 150,000 g) fraction, became almost entirely cytosolic; moreover, it partitioned in the aqueous phase of Triton X-114 whereas the membrane fraction was detergent-soluble. Rab6p did not become part of the coatomers after its BFA-induced release from Golgi structures. Three requirements seemed to be necessary for such a release: integrity of the microtubules, presence of energy, and a hypothetical trimeric G protein, as revealed by the respective roles of nocodazole, ATP depletion, and sensitivity to aluminium fluoride. Finally, we have shown that BFA does not prevent attachment of newly synthesized rab6p to membranes.

Defects in early secretory pathway transport machinery components and neurodevelopmental disorders

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Bor Luen Tang
Keyword(s):  
Membrane Trafficking ◽  
Mammalian Cells ◽  
Secretory Pathway ◽  
Underlying Disease ◽  
Membrane Dynamics ◽  
Coat Proteins ◽  
Disease Manifestation ◽  
Vesicular Traffic ◽  
Early Secretory Pathway ◽  
Genes Encoding

Abstract The early secretory pathway, provisionally comprising of vesicular traffic between the endoplasmic reticulum (ER) and the Golgi apparatus, occurs constitutively in mammalian cells. Critical for a constant supply of secretory and plasma membrane (PM) materials, the pathway is presumably essential for general cellular function and survival. Neurons exhibit a high intensity in membrane dynamics and protein/lipid trafficking, with differential and polarized trafficking towards the somatodendritic and axonal PM domains. Mutations in genes encoding early secretory pathway membrane trafficking machinery components are known to result in neurodevelopmental or neurological disorders with disease manifestation in early life. Here, such rare disorders associated with autosomal recessive mutations in coat proteins, membrane tethering complexes and membrane fusion machineries responsible for trafficking in the early secretory pathway are summarily discussed. These mutations affected genes encoding subunits of coat protein complex I and II, subunits of transport protein particle (TRAPP) complexes, members of the YIP1 domain family (YIPF) and a SNAP receptor (SNARE) family member. Why the ubiquitously present and constitutively acting early secretory pathway machinery components could specifically affect neurodevelopment is addressed, with the plausible underlying disease etiologies and neuropathological mechanisms resulting from these mutations explored.

scholarly journals A Novel Quality Control Compartment Derived from the Endoplasmic Reticulum

2001 ◽  
Vol 12 (6) ◽  
pp. 1711-1723 ◽  
Author(s):  
Shiri Kamhi-Nesher ◽  
Marina Shenkman ◽  
Sandra Tolchinsky ◽  
Sharon Vigodman Fromm ◽  
Rachel Ehrlich ◽  
...  
Keyword(s):  
Quality Control ◽  
Endoplasmic Reticulum ◽  
Secretory Pathway ◽  
Brefeldin A ◽  
Degradation Process ◽  
Transmembrane Conductance Regulator ◽  
Heavy Chains ◽  
Tightly Coupled ◽  
Ubiquitin Proteasome ◽  
Control Compartment

Degradation of proteins that, because of improper or suboptimal processing, are retained in the endoplasmic reticulum (ER) involves retrotranslocation to reach the cytosolic ubiquitin-proteasome machinery. We found that substrates of this pathway, the precursor of human asialoglycoprotein receptor H2a and free heavy chains of murine class I major histocompatibility complex (MHC), accumulate in a novel preGolgi compartment that is adjacent to but not overlapping with the centrosome, the Golgi complex, and the ER-to-Golgi intermediate compartment (ERGIC). On its way to degradation, H2a associated increasingly after synthesis with the ER translocon Sec61. Nevertheless, it remained in the secretory pathway upon proteasomal inhibition, suggesting that its retrotranslocation must be tightly coupled to the degradation process. In the presence of proteasomal inhibitors, the ER chaperones calreticulin and calnexin, but not BiP, PDI, or glycoprotein glucosyltransferase, concentrate in the subcellular region of the novel compartment. The “quality control” compartment is possibly a subcompartment of the ER. It depends on microtubules but is insensitive to brefeldin A. We discuss the possibility that it is also the site for concentration and retrotranslocation of proteins that, like the mutant cystic fibrosis transmembrane conductance regulator, are transported to the cytosol, where they form large aggregates, the “aggresomes.”

scholarly journals Multiple pathways in the trafficking and assembly of connexin 26, 32 and 43 into gap junction intercellular communication channels

2001 ◽  
Vol 114 (21) ◽  
pp. 3845-3855 ◽  
Author(s):  
Patricia E. M. Martin ◽  
Geraldine Blundell ◽  
Shoeb Ahmad ◽  
Rachel J. Errington ◽  
W. Howard Evans
Keyword(s):  
Gap Junctions ◽  
Protein Trafficking ◽  
Mammalian Cells ◽  
Secretory Pathway ◽  
Transmembrane Domain ◽  
Fluorescent Proteins ◽  
Alternative Pathway ◽  
Brefeldin A ◽  
Junctional Communication ◽  
In Cells

The assembly of gap junctions was investigated in mammalian cells expressing connexin (Cx) 26, 32 and 43 fused to green, yellow or cyan fluorescent proteins (GFP, YFP, CFP). Targeting of Cx32-CFP and 43-GFP to gap junctions and gap junctional communication was inhibited in cells treated with Brefeldin A, a drug that disassembles the Golgi. However gap junctions constructed of Cx26-GFP were only minimally affected by Brefeldin A. Nocodazole, a microtubule disruptor, had little effect on the assembly of Cx43-GFP gap junctions, but perturbed assembly of Cx26-GFP gap junctions. Co-expression of Cx26-YFP and Cx32-CFP in cells treated with Brefeldin A resulted in assembly of gap junctions constructed of Cx26-YFP. Two amino acids that distinguish Cx26 from Cx32 in transmembrane domains were mutated in Cx32 to investigate underlying mechanisms determining trafficking routes to gap junctions. One mutation, Cx32I28L, conferred on it partial Cx26-like trafficking properties as well the post-translational membrane insertion characteristics of Cx26, suggesting that a key determinant regulating trafficking was present in the first transmembrane domain. The results provide a protein trafficking basis for specifying and regulating connexin composition of gap junctions and thus selectivity of intercellular signaling, with Cx32 and 43 trafficking through the secretory pathway and Cx26 also following an alternative pathway.

scholarly journals 1School of Life Science and Technology, ShanghaiTech University, Pudong, Shanghai 201210, China; [email protected] (X.Y.); [email protected] (Y.Q.)

2019 ◽  
Vol 20 (8) ◽  
pp. 2028 ◽  
Author(s):  
Yue ◽  
Qian ◽  
Gim ◽  
Lee
Keyword(s):  
Membrane Trafficking ◽  
Mammalian Cells ◽  
Secretory Pathway ◽  
Host Cells ◽  
Scaffolding Protein ◽  
Membrane Domain ◽  
Cellular Functions ◽  
Domain Organization ◽  
Bacterial Proliferation ◽  
Intracellular Organelles

Acyl-CoA-binding domain-containing 3 (ACBD3) is a multi-functional scaffolding protein, which has been associated with a diverse array of cellular functions, including steroidogenesis, embryogenesis, neurogenesis, Huntington’s disease (HD), membrane trafficking, and viral/bacterial proliferation in infected host cells. In this review, we aim to give a timely overview of recent findings on this protein, including its emerging role in membrane domain organization at the Golgi and the mitochondria. We hope that this review provides readers with useful insights on how ACBD3 may contribute to membrane domain organization along the secretory pathway and on the cytoplasmic surface of intracellular organelles, which influence many important physiological and pathophysiological processes in mammalian cells.

scholarly journals New factors for protein transport identified by a genome-wide CRISPRi screen in mammalian cells

2019 ◽  
Author(s):  
Laia Bassaganyas ◽  
Stephanie J. Popa ◽  
Max Horlbeck ◽  
Anupama Ashok ◽  
Sarah E. Stewart ◽  
...  
Keyword(s):  
Membrane Trafficking ◽  
Mammalian Cells ◽  
Secretory Pathway ◽  
Protein Transport ◽  
Basic Principles ◽  
Golgi Membranes ◽  
Genome Wide ◽  
A Genome ◽  
Powerful Strategy ◽  
Shed Light

AbstractProtein and membrane trafficking pathways are critical for cell and tissue homeostasis. Traditional genetic and biochemical approaches have shed light on basic principles underlying these processes. However, the list of factors required for secretory pathways function remains incomplete, and mechanisms involved in their adaptation poorly understood. Here, we present a powerful strategy based on a pooled genome-wide CRISPRi screen that allowed the identification of new factors involved in protein transport. Two newly identified factors, TTC17 and CCDC157, localized along the secretory pathway and were found to interact with resident proteins of ER-Golgi membranes. In addition, we uncovered that upon TTC17 knockdown, the polarized organization of Golgi cisternae was altered, creating glycosylation defects, and that CCDC157 is an important factor for the fusion of transport carriers to the Golgi complex. In conclusion, our work identified and characterized new actors in the mechanisms of protein transport and secretion, and opens stimulating perspectives for the use of our platform in physiological and pathological contexts.

scholarly journals New factors for protein transport identified by a genome-wide CRISPRi screen in mammalian cells

2019 ◽  
Vol 218 (11) ◽  
pp. 3861-3879 ◽  
Author(s):  
Laia Bassaganyas ◽  
Stephanie J. Popa ◽  
Max Horlbeck ◽  
Claudia Puri ◽  
Sarah E. Stewart ◽  
...  
Keyword(s):  
Membrane Trafficking ◽  
Mammalian Cells ◽  
Secretory Pathway ◽  
Protein Transport ◽  
Basic Principles ◽  
Golgi Membranes ◽  
Genome Wide ◽  
A Genome ◽  
Pathway Function ◽  
Powerful Strategy

Protein and membrane trafficking pathways are critical for cell and tissue homeostasis. Traditional genetic and biochemical approaches have shed light on basic principles underlying these processes. However, the list of factors required for secretory pathway function remains incomplete, and mechanisms involved in their adaptation poorly understood. Here, we present a powerful strategy based on a pooled genome-wide CRISPRi screen that allowed the identification of new factors involved in protein transport. Two newly identified factors, TTC17 and CCDC157, localized along the secretory pathway and were found to interact with resident proteins of ER-Golgi membranes. In addition, we uncovered that upon TTC17 knockdown, the polarized organization of Golgi cisternae was altered, creating glycosylation defects, and that CCDC157 is an important factor for the fusion of transport carriers to Golgi membranes. In conclusion, our work identified and characterized new actors in the mechanisms of protein transport and secretion and opens stimulating perspectives for the use of our platform in physiological and pathological contexts.

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