scholarly journals Wolbachia endosymbionts subvert the endoplasmic reticulum to acquire host membranes without triggering ER stress

2018 ◽  
Author(s):  
Nour Fattouh ◽  
Chantal Cazevieille ◽  
Frédéric Landmann
Keyword(s):  
Endoplasmic Reticulum ◽  
Golgi Apparatus ◽  
Host Cell ◽  
Pathogenic Bacteria ◽  
Secretory Pathway ◽  
Immune Surveillance ◽  
Lipid Synthesis ◽  
Time Lapse ◽  
Intracellular Bacteria ◽  
Arthropod Species

AbstractThe reproductive parasite Wolbachia are the most common endosymbionts on earth, present in a plethora of arthropod species. They have been introduced into mosquitos to successfully prevent the spread of vector-borne diseases, yet the strategies of host cell subversion underlying their obligate intracellular lifestyle remain to be explored in depth in order to gain insights into the mechanisms of pathogen-blocking. Like some other intracellular bacteria, Wolbachia reside in a host-derived vacuole in order to replicate and escape the immune surveillance. Using here the pathogen-blocking Wolbachia strain from Drosophila melanogaster, introduced into two different Drosophila cell lines, we show that Wolbachia subvert the endoplasmic reticulum to acquire their vacuolar membrane and colonize the host cell at high density. Wolbachia redistribute the endoplasmic reticulum to increase contact sites, and time lapse experiments reveal tight coupled dynamics suggesting important signalling events or nutrient uptake. They however do not affect the tubular or cisternal morphologies. A fraction of endoplasmic reticulum becomes clustered, allowing the endosymbionts to reside in between the endoplasmic reticulum and the Golgi apparatus, possibly modulating the traffic between these two organelles. Gene expression analyses and immunostaining studies suggest that Wolbachia achieve persistent infections at very high titers without triggering endoplasmic reticulum stress or enhanced ERAD-driven proteolysis, suggesting that amino acid salvage is achieved through modulation of other signalling pathways.Author summaryWolbachia are a genus of intracellular bacteria living in symbiosis with millions of arthropod species. They have the ability to block the transmission of arboviruses when introduced into mosquito vectors, by interfering with the cellular resources exploited by these viruses. Despite the biomedical interest of this symbiosis, little is known about the mechanisms by which Wolbachia survive and replicate in the host cell. We show here that the membrane composing the Wolbachia vacuole is acquired from the endoplasmic reticulum, a central organelle required for protein and lipid synthesis, and from which originates a vesicular trafficking toward the Golgi apparatus and the secretory pathway. Wolbachia modify the distribution of this organelle to increase their interactions with this source of membrane and likely of nutrients as well. In contrast to some intracellular pathogenic bacteria, the effect of Wolbachia on the cell homeostasis does not induce a stress on the endoplasmic reticulum. One of the consequences of such a stress would be an increased proteolysis used to relieve the cell from an excess of misfolded proteins. Incidentally, this shows that Wolbachia do not acquire amino acids from the host cell through this strategy.

scholarly journals The unfolded protein response coordinates the production of endoplasmic reticulum protein and endoplasmic reticulum membrane.

1997 ◽  
Vol 8 (9) ◽  
pp. 1805-1814 ◽  
Author(s):  
J S Cox ◽  
R E Chapman ◽  
P Walter
Keyword(s):  
Endoplasmic Reticulum ◽  
Unfolded Protein Response ◽  
Secretory Pathway ◽  
Lipid Synthesis ◽  
Secretory Proteins ◽  
Endoplasmic Reticulum Membrane ◽  
Yeast Saccharomyces Cerevisiae ◽  
Unfolded Protein ◽  
The Unfolded Protein Response ◽  
Protein Response

The endoplasmic reticulum (ER) is a multifunctional organelle responsible for production of both lumenal and membrane components of secretory pathway compartments. Secretory proteins are folded, processed, and sorted in the ER lumen and lipid synthesis occurs on the ER membrane itself. In the yeast Saccharomyces cerevisiae, synthesis of ER components is highly regulated: the ER-resident proteins by the unfolded protein response and membrane lipid synthesis by the inositol response. We demonstrate that these two responses are intimately linked, forming different branches of the same pathway. Furthermore, we present evidence indicating that this coordinate regulation plays a role in ER biogenesis.

scholarly journals Brefeldin A inhibits transport of the glycophorin-binding protein from Plasmodium falciparum into the host erythrocyte

1994 ◽  
Vol 300 (3) ◽  
pp. 821-826 ◽  
Author(s):  
J Benting ◽  
D Mattei ◽  
K Lingelbach
Keyword(s):  
Plasmodium Falciparum ◽  
Golgi Apparatus ◽  
Host Cell ◽  
Protein Secretion ◽  
Secretory Pathway ◽  
Binding Protein ◽  
Brefeldin A ◽  
Cell Cytoplasm ◽  
Parasite Cell ◽  
Host Cell Cytoplasm

Plasmodium falciparum, a protozoan parasite of the human erythrocyte, causes the most severe form of malaria. During its intraerythrocytic development, the parasite synthesizes proteins which are exported into the host cell. The compartments involved in the secretory pathway of P. falciparum are still poorly characterized. A Golgi apparatus has not been identified, owing to the lack of specific protein markers and Golgi-specific post-translational modifications in the parasite. The fungal metabolite brefeldin A (BFA) is known to inhibit protein secretion in higher eukaryotes by disrupting the integrity of the Golgi apparatus. We have used the parasite-encoded glycophorin-binding protein (GBP), a soluble protein found in the host cell cytoplasm, as a marker to investigate the effects of BFA on protein secretion in the intracellular parasite. In the presence of BFA, GBP was not transported into the erythrocyte, but remained inside the parasite cell. The effect caused by BFA was reversible, and the protein could be chased into the host cell cytoplasm within 30 min. Transport of GBP from the BFA-sensitive site into the host cell did not require protein synthesis. Similar observations were made when infected erythrocytes were incubated at 15 degrees C. Incubation at 20 degrees C resulted in a reduction rather than a complete block of protein export. The relevance of our findings to the identification of compartments involved in protein secretion from the parasite cell is discussed.

scholarly journals Activation of Mammalian Unfolded Protein Response Is Compatible with the Quality Control System Operating in the Endoplasmic Reticulum

2004 ◽  
Vol 15 (6) ◽  
pp. 2537-2548 ◽  
Author(s):  
Satomi Nadanaka ◽  
Hiderou Yoshida ◽  
Fumi Kano ◽  
Masayuki Murata ◽  
Kazutoshi Mori
Keyword(s):  
Quality Control ◽  
Endoplasmic Reticulum ◽  
Control System ◽  
Golgi Apparatus ◽  
Er Stress ◽  
Unfolded Protein Response ◽  
Secretory Pathway ◽  
Unfolded Proteins ◽  
Unfolded Protein ◽  
Protein Response

Newly synthesized secretory and transmembrane proteins are folded and assembled in the endoplasmic reticulum (ER) where an efficient quality control system operates so that only correctly folded molecules are allowed to move along the secretory pathway. The productive folding process in the ER has been thought to be supported by the unfolded protein response (UPR), which is activated by the accumulation of unfolded proteins in the ER. However, a dilemma has emerged; activation of ATF6, a key regulator of mammalian UPR, requires intracellular transport from the ER to the Golgi apparatus. This suggests that unfolded proteins might be leaked from the ER together with ATF6 in response to ER stress, exhibiting proteotoxicity in the secretory pathway. We show here that ATF6 and correctly folded proteins are transported to the Golgi apparatus via the same route and by the same mechanism under conditions of ER stress, whereas unfolded proteins are retained in the ER. Thus, activation of the UPR is compatible with the quality control in the ER and the ER possesses a remarkable ability to select proteins to be transported in mammalian cells in marked contrast to yeast cells, which actively utilize intracellular traffic to deal with unfolded proteins accumulated in the ER.

scholarly journals The propeptide of preprosomatostatin mediates intracellular transport and secretion of alpha-globin from mammalian cells.

1989 ◽  
Vol 108 (5) ◽  
pp. 1647-1655 ◽  
Author(s):  
T J Stoller ◽  
D Shields
Keyword(s):  
Amino Acids ◽  
Endoplasmic Reticulum ◽  
Golgi Apparatus ◽  
Signal Peptide ◽  
Mammalian Cells ◽  
Intracellular Transport ◽  
Secretory Pathway ◽  
Gh3 Cells ◽  
Alpha Globin ◽  
Regulated Secretory Pathway

We have investigated the role of the somatostatin propeptide in mediating intracellular transport and sorting to the regulated secretory pathway. Using a retroviral expression vector, two fusion proteins were expressed in rat pituitary (GH3) cells: a control protein consisting of the beta-lactamase signal peptide fused to chimpanzee alpha-globin (142 amino acids); and a chimera of the somatostatin signal peptide and proregion (82 amino acids) fused to alpha-globin. Control globin was translocated into the endoplasmic reticulum as determined by accurate cleavage of its signal peptide; however, alpha-globin was not secreted but was rapidly and quantitatively degraded intracellularly with a t 1/2 of 4-5 min. Globin degradation was insensitive to chloroquine, a drug which inhibits lysosomal proteases, but was inhibited at 16 degrees C suggesting proteolysis occurred during transport to the cis-Golgi apparatus. In contrast to the control globin, approximately 30% of the somatostatin propeptide-globin fusion protein was transported to the distal elements of the Golgi apparatus where it was endoproteolytically processed. Processing of the chimera occurred in an acidic intracellular compartment since cleavage was inhibited by 25 microM chloroquine. 60% of the transported chimera was cleaved at the Arg-Lys processing site in native prosomatostatin yielding "mature" alpha-globin. Most significantly, approximately 50% of processed alpha-globin was sorted to the regulated pathway and secreted in response to 8-Br-cAMP. We conclude that the somatostatin propeptide mediated transport of alpha-globin from the endoplasmic reticulum to the trans-Golgi network by protecting molecules from degradation and in addition, facilitated packaging of alpha-globin into vesicles whose secretion was stimulated by cAMP.

scholarly journals Eradication of Intracellular Salmonellaenterica Serovar Typhimurium with a Small-Molecule, Host Cell-Directed Agent

2009 ◽  
Vol 53 (12) ◽  
pp. 5236-5244 ◽  
Author(s):  
Hao-Chieh Chiu ◽  
Samuel K. Kulp ◽  
Shilpa Soni ◽  
Dasheng Wang ◽  
John S. Gunn ◽  
...  
Keyword(s):  
Host Cell ◽  
Small Molecule ◽  
Pathogenic Bacteria ◽  
Intracellular Survival ◽  
Resistant Bacteria ◽  
Intracellular Bacteria ◽  
Akt Kinase ◽  
Antibiotic Resistant ◽  
Serovar Typhimurium ◽  
Host Cell Factors

ABSTRACTEradication of intracellular pathogenic bacteria with host-directed chemical agents has been an anticipated innovation in the treatment of antibiotic-resistant bacteria. We previously synthesized and characterized a novel small-molecule agent, AR-12, that induces autophagy and inhibits the Akt kinase in cancer cells. As both autophagy and the Akt kinase have been shown recently to play roles in the intracellular survival of several intracellular bacteria, includingSalmonellaentericaserovar Typhimurium, we investigated the effect of AR-12 on the intracellular survival ofSalmonellaserovar Typhimurium in macrophages. Our results show that AR-12 induces autophagy in macrophages, as indicated by increased autophagosome formation, and potently inhibits the survival of serovar Typhimurium in macrophages in association with increased colocalization of intracellular bacteria with autophagosomes. Intracellular bacterial growth was partially rescued in the presence of AR-12 by the short hairpin RNA-mediated knockdown of Beclin-1 or Atg7 in macrophages. Moreover, AR-12 inhibits Akt kinase activity in infected macrophages, which we show to be important for its antibacterial effect as the enforced expression of constitutively activated Akt1 in these cells reverses the AR-12-induced inhibition of intracellular serovar Typhimurium survival. Finally, oral administration of AR-12 at 2.5 mg/kg/day to serovar Typhimurium-infected mice reduced hepatic and splenic bacterial burdens and significantly prolonged survival. These findings show that AR-12 represents a proof of principle that the survival of intracellular bacteria can be suppressed by small-molecule agents that target both innate immunity and host cell factors modulated by bacteria.

scholarly journals How a Cytokine Is Chaperoned through the Secretory Pathway by Complexing with Its Own Receptor: Lessons from Interleukin-15 (IL-15)/IL-15 Receptor α

2008 ◽  
Vol 28 (15) ◽  
pp. 4851-4861 ◽  
Author(s):  
Erwin H. Duitman ◽  
Zane Orinska ◽  
Elena Bulanova ◽  
Ralf Paus ◽  
Silvia Bulfone-Paus
Keyword(s):  
Endoplasmic Reticulum ◽  
Golgi Apparatus ◽  
Secretory Pathway ◽  
Model System ◽  
Cytokine Receptor ◽  
High Affinity ◽  
High Affinity Receptor ◽  
Interleukin 15 ◽  
Affinity Receptor ◽  
Ligand Transport

ABSTRACTWhile it is well appreciated that receptors for secreted cytokines transmit ligand-induced signals, little is known about additional roles for cytokine receptor components in the control of ligand transport and secretion. Here, we show that interleukin-15 (IL-15) translocation into the endoplasmic reticulum occurs independently of the presence of IL-15 receptor α (IL-15Rα). Subsequently, however, IL-15 is transported through the Golgi apparatus only in association with IL-15Rα and then is secreted. This intracellular IL-15/IL-15Rα complex already is formed in the endoplasmic reticulum and, thus, enables the further trafficking of complexed IL-15 through the secretory pathway. Just transfecting IL-15Rα in cells, which transcribe but normally do not secrete IL-15, suffices to induce IL-15 secretion. Thus, we provide the first evidence of how a cytokine is chaperoned through the secretory pathway by complexing with its own high-affinity receptor and show that IL-15/IL-15Rα offers an excellent model system for the further exploration of this novel mechanism for the control of cytokine secretion.

Molecular chaperones in pancreatic tissue: the presence of cpn10, cpn60 and hsp70 in distinct compartments along the secretory pathway of the acinar cells

1994 ◽  
Vol 107 (3) ◽  
pp. 539-549 ◽  
Author(s):  
C.S. Velez-Granell ◽  
A.E. Arias ◽  
J.A. Torres-Ruiz ◽  
M. Bendayan
Keyword(s):  
Endoplasmic Reticulum ◽  
Golgi Apparatus ◽  
Secretory Pathway ◽  
Secretory Granules ◽  
Acinar Cells ◽  
Pancreatic Tissue ◽  
Secretory Proteins ◽  
Trans Golgi Network ◽  
Hsp70 Protein ◽  
Golgi Network

Three chaperones, the chaperonins cpn10 and cpn60, and the hsp70 protein, were revealed by immunochemistry and cytochemistry in pancreatic rat acinar cells. Western immunoblotting analysis of rat pancreas homogenates has shown that antibodies against cpn10, cpn60 and hsp70 protein recognize single protein bands of 25 kDa, 60 kDa and 70 kDa, respectively. Single bands for the cpn10 and cpn60 were also detected in pancreatic juice. Immunofluorescence studies on rat pancreatic tissue revealed a strong positive signal in the apical region of the acinar cells for cpn10 and cpn60, while an immunoreaction was detected at the juxtanuclear Golgi region with the anti-hsp70 antibody. Immunocytochemical gold labeling confirmed the presence of these three chaperones in distinct cell compartments of pancreatic acinar cells. Chaperonin 10 and cpn60 were located in the endoplasmic reticulum, Golgi apparatus, condensing vacuoles and secretory granules. Interestingly, the labeling for both cpn10 and cpn60 followed the increasing concentration gradient of secretory proteins along the RER-Golgi-granule secretory pathway. On the contrary, the labeling for hsp70 was mainly concentrated in the endoplasmic reticulum and the Golgi apparatus. In the latter, the hsp70 was found to be primary located in the trans-most cisternae and to colocalize with acid phosphatase in the trans-Golgi network. The three chaperones were also present in mitochondria. In view of the role played by the chaperones in the proper folding, sorting and aggregation of proteins, we postulate that hsp70 assists the adequate sorting and packaging of proteins from the ER to the trans-Golgi network while cpn10 and cpn60 play key roles in the proper packaging and aggregation of secretory proteins as well as, most probably, in the prevention of early enzyme activation in secretory granules.

scholarly journals Biosynthesis of high density lipoprotein by chicken liver: conjugation of nascent lipids with apoprotein A1.

1984 ◽  
Vol 99 (6) ◽  
pp. 1917-1926 ◽  
Author(s):  
D Banerjee ◽  
C M Redman
Keyword(s):  
Endoplasmic Reticulum ◽  
Golgi Apparatus ◽  
Smooth Endoplasmic Reticulum ◽  
Lipid Synthesis ◽  
Density Lipoprotein ◽  
Plasma Lipoproteins ◽  
Golgi Cell ◽  
Intracellular Organelles ◽  
Apoprotein A1 ◽  
Cell Fractions

To study the assembly of newly synthesized lipids with apoprotein A1, we administered [2-3H]glycerol to young chickens and determined the hepatic intracellular sites of lipid synthesis and association of nascent lipids with apoprotein A1. [2-3H]glycerol was rapidly incorporated into hepatic lipids, reaching maximal levels at 5 min, and this preceded the appearance of lipid radioactivity in the plasma. The liver was fractionated into rough and smooth endoplasmic reticulum and Golgi cell fractions. The isolated cell fractions were further subfractionated into membrane and soluble (content) fractions by treatment with 0.1 M Na2CO3, pH 11.3. At various times, the lipid radioactivity was measured in each of the intracellular organelles, in immunoprecipitable apoprotein A1, and in materials that floated at buoyant densities similar to those of plasma lipoproteins. Maximal incorporation occurred at 1 min in the rough endoplasmic reticulum, at 3-5 min in the smooth endoplasmic reticulum, and at 5 min in the Golgi cell fractions. The majority (66-93%) of radioactive glycerol was incorporated into triglycerides with smaller (4-27%) amounts into phospholipids. About 80% of the lipid radioactivity in the endoplasmic reticulum and 70% of that in the Golgi cell fractions was in the membranes. The radioactive lipids in the content subfraction were distributed in various density classes with most nascent lipids floating at a density less than or equal to 1.063 g/ml. Apoprotein A1 from the Golgi apparatus, obtained by immunoprecipitation, contained sixfold more nascent lipids than did that from the endoplasmic reticulum. These data indicate that [2-3H]glycerol is quickly incorporated into lipids of the endoplasmic reticulum and the Golgi cell fractions, that most of the nascent lipids are conjugated with apoproteins A1 in the Golgi apparatus, and that very little association of nascent lipid to apoprotein A1 occurs in the endoplasmic reticulum.

scholarly journals A membrane glycoprotein, Sec12p, required for protein transport from the endoplasmic reticulum to the Golgi apparatus in yeast.

1988 ◽  
Vol 107 (3) ◽  
pp. 851-863 ◽  
Author(s):  
A Nakano ◽  
D Brada ◽  
R Schekman
Keyword(s):  
Amino Acids ◽  
Endoplasmic Reticulum ◽  
Golgi Apparatus ◽  
Membrane Fraction ◽  
Secretory Pathway ◽  
Protein Transport ◽  
Genomic Library ◽  
Membrane Glycoprotein ◽  
Mobility Shift ◽  
Cloned Gene

SEC12, a gene that is required for secretory, membrane, and vacuolar proteins to be transported from the endoplasmic reticulum to the Golgi apparatus, has been cloned from a genomic library by complementation of a sec12 ts mutation. Genetic analysis has shown that the cloned gene integrates at the SEC12 locus and that a null mutation at the locus is lethal. The DNA sequence predicts a protein of 471 amino acids containing a hydrophobic stretch of 19 amino acids near the COOH terminus. To characterize the gene product (Sec12p) in detail, a lacZ-SEC12 gene fusion has been constructed and a polyclonal antibody raised against the hybrid protein. The antibody recognizes Sec12p as a approximately 70-kD protein that sediments in a mixed membrane fraction that includes endoplasmic reticulum. Sec12p is not removed from the membrane fraction by treatment at high pH and high salt and is not degraded by exogenous protease unless detergent is present. Glycosylation of Sec12p during biogenesis is indicated by an electrophoretic mobility shift of the protein that is influenced by tunicamycin and by imposition of an independent secretory pathway block. We suggest that Sec12p is an integral membrane glycoprotein with a prominent domain that faces the cytoplasm where it functions to promote protein transport to the Golgi apparatus. In the process of transport, Sec12p itself may migrate to the Golgi apparatus and function in subsequent transport events.

scholarly journals BPIFB6 Regulates Secretory Pathway Trafficking and Enterovirus Replication

2016 ◽  
Vol 90 (10) ◽  
pp. 5098-5107 ◽  
Author(s):  
Stefanie Morosky ◽  
Nicholas J. Lennemann ◽  
Carolyn B. Coyne
Keyword(s):  
Endoplasmic Reticulum ◽  
Host Cell ◽  
Golgi Complex ◽  
Secretory Pathway ◽  
Type I Diabetes ◽  
Enterovirus 71 ◽  
Type I ◽  
Virus Infections ◽  
Cell Functions ◽  
Coxsackievirus B

ABSTRACTBactericidal/permeability-increasing protein (BPI) fold-containing family B, member 3 (BPIFB3) is an endoplasmic reticulum (ER)-localized host factor that negatively regulates coxsackievirus B (CVB) replication through its control of the autophagic pathway. Here, we show that another member of the BPIFB family, BPIFB6, functions as a positive regulator of CVB, and other enterovirus, replication by controlling secretory pathway trafficking and Golgi complex morphology. We show that similar to BPIFB3, BPIFB6 localizes exclusively to the ER, where it associates with other members of the BPIFB family. However, in contrast to our findings that RNA interference (RNAi)-mediated silencing of BPIFB3 greatly enhances CVB replication, we show that silencing of BPIFB6 expression dramatically suppresses enterovirus replication in a pan-viral manner. Mechanistically, we show that loss of BPIFB6 expression induces pronounced alterations in retrograde and anterograde trafficking, which correlate with dramatic fragmentation of the Golgi complex. Taken together, these data implicate BPIFB6 as a key regulator of secretory pathway trafficking and viral replication and suggest that members of the BPIFB family participate in diverse host cell functions to regulate virus infections.IMPORTANCEEnterovirus infections are associated with a number of severe pathologies, such as aseptic meningitis, dilated cardiomyopathy, type I diabetes, paralysis, and even death. These viruses, which include coxsackievirus B (CVB), poliovirus (PV), and enterovirus 71 (EV71), co-opt the host cell secretory pathway, which controls the transport of proteins from the endoplasmic reticulum to the Golgi complex, to facilitate their replication. Here we report on the identification of a novel regulator of the secretory pathway, bactericidal/permeability-increasing protein (BPI) fold-containing family B, member 6 (BPIFB6), whose expression is required for enterovirus replication. We show that loss of BPIFB6 expression correlates with pronounced defects in the secretory pathway and greatly reduces the replication of CVB, PV, and EV71. Our results thus identify a novel host cell therapeutic target whose function could be targeted to alter enterovirus replication.

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