scholarly journals Yeast Kex1p is a Golgi-associated membrane protein: deletions in a cytoplasmic targeting domain result in mislocalization to the vacuolar membrane.

1992 ◽  
Vol 119 (6) ◽  
pp. 1459-1468 ◽  
Author(s):  
A Cooper ◽  
H Bussey
Keyword(s):  
Golgi Apparatus ◽  
Membrane Protein ◽  
Secretory Pathway ◽  
Vacuolar Membrane ◽  
Unexpected Finding ◽  
Type I ◽  
Dependent Manner ◽  
Wild Type ◽  
Carboxy Terminal Domain ◽  
Carboxy Terminal

We have investigated the localization of Kex1p, a type I transmembrane carboxypeptidase involved in precursor processing within the yeast secretory pathway. Indirect immunofluorescence demonstrated the presence of Kex1p in a punctate organelle resembling the yeast Golgi apparatus as identified by Kex2p and Sec7p (Franzusoff, A., K. Redding, J. Crosby, R. S. Fuller, and R. Schekman. 1991. J. Cell Biol. 112:27-37). Glycosylation studies of Kex1p were consistent with a Golgi location, as Kex1p was progressively N-glycosylated in an MNN1-dependent manner. To address the basis of Kex1p targeting to the Golgi apparatus, we examined the cellular location of a series of carboxy-terminal truncations of the protein. The results indicate that a cytoplasmically exposed carboxy-terminal domain is required for retention of this membrane protein within the Golgi apparatus. Deletions of the retention region or overproduction of wild-type Kex1p led to mislocalization of Kex1p to the vacuolar membrane. This unexpected finding is discussed in terms of models involving either the vacuole as a default destination for membrane proteins, or by endocytosis to the vacuole following their default localization to the plasma membrane.

scholarly journals The Carboxy-Terminal Domain of Glycoprotein N of Human Cytomegalovirus Is Required for Virion Morphogenesis

2007 ◽  
Vol 81 (10) ◽  
pp. 5212-5224 ◽  
Author(s):  
Michael Mach ◽  
Karolina Osinski ◽  
Barbara Kropff ◽  
Ursula Schloetzer-Schrehardt ◽  
Magdalena Krzyzaniak ◽  
...  
Keyword(s):  
Human Cytomegalovirus ◽  
Critical Role ◽  
Point Mutations ◽  
Cysteine Residue ◽  
Cysteine Residues ◽  
Type I ◽  
Terminal Domain ◽  
Carboxy Terminal Domain ◽  
Carboxy Terminal ◽  
Assembly Compartment

ABSTRACT Glycoproteins M and N (gM and gN, respectively) are among the few proteins that are conserved across the herpesvirus family. The function of the complex is largely unknown. Whereas deletion from most alphaherpesviruses has marginal effects on the replication of the respective viruses, both proteins are essential for replication of human cytomegalovirus (HCMV). We have constructed a series of mutants in gN to study the function of this protein. gN of HCMV is a type I glycoprotein containing a short carboxy-terminal domain of 14 amino acids, including two cysteine residues directly adjacent to the predicted transmembrane anchor at positions 125 and 126. Deletion of the entire carboxy-terminal domain as well as substitution with the corresponding region from alpha herpesviruses or mutations of both cysteine residues resulted in a replication-incompetent virus. Recombinant viruses containing point mutations of either cysteine residue could be generated. These viruses were profoundly defective for replication. Complex formation of the mutant gNs with gM and transport of the complex to the viral assembly compartment appeared unaltered compared to the wild type. However, in infected cells, large numbers of capsids accumulated in the cytoplasm that failed to acquire an envelope. Transiently expressed gN was shown to be modified by palmitic acid at both cysteine residues. In summary, our data suggest that the carboxy-terminal domain of gN plays a critical role in secondary envelopment of HCMV and that palmitoylation of gN appears to be essential for function in secondary envelopment of HCMV and virus replication.

scholarly journals The Helicobacter pylori Autotransporter ImaA (HP0289) Modulates the Immune Response and Contributes to Host Colonization

2012 ◽  
Vol 80 (7) ◽  
pp. 2286-2296 ◽  
Author(s):  
William E. Sause ◽  
Andrea R. Castillo ◽  
Karen M. Ottemann
Keyword(s):  
Immune Response ◽  
Helicobacter Pylori ◽  
Membrane Protein ◽  
Outer Membrane ◽  
Outer Membrane Protein ◽  
Dependent Manner ◽  
Wild Type ◽  
Content Type ◽  
H Pylori ◽  
Murine Infections

ABSTRACTThe human pathogenHelicobacter pyloriemploys a diverse collection of outer membrane proteins to colonize, persist, and drive disease within the acidic gastric environment. In this study, we sought to elucidate the function of the host-induced geneHP0289, which encodes an uncharacterized outer membrane protein. We first generated an isogenicH. pylorimutant that lacksHP0289and found that the mutant has a colonization defect in single-strain infections and is greatly outcompeted in mouse coinfection experiments with wild-typeH. pylori. Furthermore, we used protease assays and biochemical fractionation coupled with an HP0289-targeted peptide antibody to verify that the HP0289 protein resides in the outer membrane. Our previous findings showed that theHP0289promoter is upregulated in the mouse stomach, and here we demonstrate thatHP0289expression is induced under acidic conditions in an ArsRS-dependent manner. Finally, we have shown that theHP0289mutant induces greater expression of the chemokine interleukin-8 (IL-8) and the cytokine tumor necrosis factor alpha (TNF-α) in gastric carcinoma cells (AGS). Similarly, transcription of the IL-8 homolog keratinocyte-derived chemokine (KC) is elevated in murine infections with the HP0289 mutant than in murine infections with wild-typeH. pylori. On the basis of this phenotype, we renamed HP0289 ImaA forimmunomodulatoryautotransporter protein. Our work has revealed that genes inducedin vivoplay an important role inH. pyloripathogenesis. Specifically, the outer membrane protein ImaA modulates a component of the host inflammatory response, and thus may allowH. pylorito fine tune the host immune response based on ImaA expression.

scholarly journals MLN64 Is Involved in Actin-mediated Dynamics of Late Endocytic Organelles

2005 ◽  
Vol 16 (8) ◽  
pp. 3873-3886 ◽  
Author(s):  
Maarit Hölttä-Vuori ◽  
Fabien Alpy ◽  
Kimmo Tanhuanpää ◽  
Eija Jokitalo ◽  
Aino-Liisa Mutka ◽  
...  
Keyword(s):  
Membrane Protein ◽  
Unknown Function ◽  
Cell Periphery ◽  
Dependent Manner ◽  
Protein Overexpression ◽  
Wild Type ◽  
Functional Connection ◽  
Late Endosomes ◽  
Endosomal Membranes ◽  
Cholesterol Binding

MLN64 is a late endosomal cholesterol-binding membrane protein of an unknown function. Here, we show that MLN64 depletion results in the dispersion of late endocytic organelles to the cell periphery similarly as upon pharmacological actin disruption. The dispersed organelles in MLN64 knockdown cells exhibited decreased association with actin and the Arp2/3 complex subunit p34-Arc. MLN64 depletion was accompanied by impaired fusion of late endocytic organelles and delayed cargo degradation. MLN64 overexpression increased the number of actin and p34-Arc-positive patches on late endosomes, enhanced the fusion of late endocytic organelles in an actin-dependent manner, and stimulated the deposition of sterol in late endosomes harboring the protein. Overexpression of wild-type MLN64 was capable of rescuing the endosome dispersion in MLN64-depleted cells, whereas mutants of MLN64 defective in cholesterol binding were not, suggesting a functional connection between MLN64-mediated sterol transfer and actin-dependent late endosome dynamics. We propose that local sterol enrichment by MLN64 in the late endosomal membranes facilitates their association with actin, thereby governing actin-dependent fusion and degradative activity of late endocytic organelles.

Role of common cytokine receptor γ chain (γc)– and Jak3-dependent signaling in the proliferation and survival of murine mast cells

Blood ◽  
2000 ◽  
Vol 96 (6) ◽  
pp. 2172-2180 ◽  
Author(s):  
Kotaro Suzuki ◽  
Hiroshi Nakajima ◽  
Norihiko Watanabe ◽  
Shin-ichiro Kagami ◽  
Akira Suto ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Mast Cells ◽  
Cytokine Receptor ◽  
Type I ◽  
Dependent Manner ◽  
Type Ii ◽  
Wild Type ◽  
Peritoneal Mast Cells ◽  
The Common

Abstract The regulatory roles of the common cytokine receptor γ chain (γc)– and Jak3-dependent signaling in the proliferation and survival of mast cells were determined using γc-deficient (γc−) and Jak3-deficient (Jak3−) mice. Although the mast cells in γc− and Jak3− mice were morphologically indistinguishable from those in wild-type mice, the number of peritoneal mast cells was decreased in γc− and Jak3− mice as compared with that in wild-type mice. Among γc-related cytokines, interleukin (IL)-4 and IL-9, but not IL-2, IL-7, or IL-15, enhanced the proliferation and survival of bone marrow–derived mast cells (BMMCs) from wild-type mice. However, the effects of IL-4 and IL-9 were absent in BMMCs from γc− and Jak3−mice. In addition, IL-4Rα, γc, and Jak3, but not IL-2Rβ or IL-7Rα, were expressed in BMMCs. In contrast, IL-13 did not significantly induce the proliferation and survival of BMMCs even from wild-type mice, and IL-13Rα1 was not expressed in BMMCs. Furthermore, IL-4 phosphorylated the 65-kd isoform of Stat6 in BMMCs from wild-type mice but not from γc− and Jak3− mice. These results indicate that γc- and Jak3-dependent signaling is essential for IL-4– and IL-9–induced proliferation and survival of murine mast cells, that the effects of IL-4 are mediated by type I IL-4R and that type II IL-4R is absent on mast cells, and that IL-4 phosphorylates the 65-kd isoform of Stat6 in mast cells in a γc- and Jak3-dependent manner.

scholarly journals Regulation of ATR activity by the RNA polymerase II phosphatase PNUTS-PP1

2018 ◽  
Author(s):  
Helga B. Landsverk ◽  
Lise E. Sandquist ◽  
Gro Elise Rødland ◽  
Beata Grallert ◽  
Laura Trinkle-Mulcahy ◽  
...  
Keyword(s):  
Rna Polymerase Ii ◽  
Ataxia Telangiectasia ◽  
Replication Stress ◽  
Dependent Manner ◽  
Ataxia Telangiectasia Mutated ◽  
Carboxy Terminal Domain ◽  
Key Factor ◽  
Carboxy Terminal ◽  
Atr Kinase ◽  
Insight Into

AbstractAtaxia telangiectasia mutated and Rad3-related (ATR) kinase is a key factor activated by DNA damage and replication stress. Here, we show that ATR signaling is increased in human cells after depletion of the RNAPII phosphatase PNUTS-PP1, which dephosphorylates RNAPII on Ser 5 of its carboxy-terminal domain (CTD) (pRNAPII S5). Increased ATR signaling was observed in the presence and absence of ionizing radiation or replication stress and even in G1 phase after depletion of PNUTS. Vice versa, ATR signaling was reduced, in a PNUTS dependent manner, after inhibition of the CDK7 kinase mediating pRNAPII S5. Furthermore, CDC73, a well-known RNAPII-CTD binding protein, was required for the high ATR signaling after depletion of PNUTS and co-immunoprecipitated with RNAPII and ATR. These results suggest a novel pathway involving RNAPII, PNUTS-PP1 and CDC73 in ATR signaling and give new insight into the diverse functions of ATR.

scholarly journals Chk2 Activation Dependence on Nbs1 after DNA Damage

2001 ◽  
Vol 21 (15) ◽  
pp. 5214-5222 ◽  
Author(s):  
Giacomo Buscemi ◽  
Camilla Savio ◽  
Laura Zannini ◽  
Francesca Miccichè ◽  
Debora Masnada ◽  
...  
Keyword(s):  
Dna Damage ◽  
Cell Cycle Progression ◽  
Phosphorylation Site ◽  
Nijmegen Breakage Syndrome ◽  
Mutant Form ◽  
Dependent Manner ◽  
Wild Type ◽  
Normal Cells ◽  
Chromosome Fragility ◽  
Carboxy Terminal

ABSTRACT The checkpoint kinase Chk2 has a key role in delaying cell cycle progression in response to DNA damage. Upon activation by low-dose ionizing radiation (IR), which occurs in an ataxia telangiectasia mutated (ATM)-dependent manner, Chk2 can phosphorylate the mitosis-inducing phosphatase Cdc25C on an inhibitory site, blocking entry into mitosis, and p53 on a regulatory site, causing G1 arrest. Here we show that the ATM-dependent activation of Chk2 by γ- radiation requires Nbs1, the gene product involved in the Nijmegen breakage syndrome (NBS), a disorder that shares with AT a variety of phenotypic defects including chromosome fragility, radiosensitivity, and radioresistant DNA synthesis. Thus, whereas in normal cells Chk2 undergoes a time-dependent increased phosphorylation and induction of catalytic activity against Cdc25C, in NBS cells null for Nbs1 protein, Chk2 phosphorylation and activation are both defective. Importantly, these defects in NBS cells can be complemented by reintroduction of wild-type Nbs1, but neither by a carboxy-terminal deletion mutant of Nbs1 at amino acid 590, unable to form a complex with and to transport Mre11 and Rad50 in the nucleus, nor by an Nbs1 mutated at Ser343 (S343A), the ATM phosphorylation site. Chk2 nuclear expression is unaffected in NBS cells, hence excluding a mislocalization as the cause of failed Chk2 activation in Nbs1-null cells. Interestingly, the impaired Chk2 function in NBS cells correlates with the inability, unlike normal cells, to stop entry into mitosis immediately after irradiation, a checkpoint abnormality that can be corrected by introduction of the wild-type but not the S343A mutant form of Nbs1. Altogether, these findings underscore the crucial role of a functional Nbs1 complex in Chk2 activation and suggest that checkpoint defects in NBS cells may result from the inability to activate Chk2.

scholarly journals Retrograde Shiga Toxin Trafficking Is Regulated by ARHGAP21 and Cdc42

2009 ◽  
Vol 20 (20) ◽  
pp. 4303-4312 ◽  
Author(s):  
Heidi Hehnly ◽  
Katrina Marie Longhini ◽  
Ji-Long Chen ◽  
Mark Stamnes
Keyword(s):  
Golgi Apparatus ◽  
Shiga Toxin ◽  
Rho Gtpases ◽  
Secretory Pathway ◽  
Retrograde Transport ◽  
Protein Translation ◽  
Dependent Manner ◽  
Intestinal Epithelial ◽  
Food Borne ◽  
Cytoskeletal Dynamics

Shiga-toxin–producing Escherichia coli remain a food-borne health threat. Shiga toxin is endocytosed by intestinal epithelial cells and transported retrogradely through the secretory pathway. It is ultimately translocated to the cytosol where it inhibits protein translation. We found that Shiga toxin transport through the secretory pathway was dependent on the cytoskeleton. Recent studies reveal that Shiga toxin activates signaling pathways that affect microtubule reassembly and dynein-dependent motility. We propose that Shiga toxin alters cytoskeletal dynamics in a way that facilitates its transport through the secretory pathway. We have now found that Rho GTPases regulate the endocytosis and retrograde motility of Shiga toxin. The expression of RhoA mutants inhibited endocytosis of Shiga toxin. Constitutively active Cdc42 or knockdown of the Cdc42-specific GAP, ARHGAP21, inhibited the transport of Shiga toxin to the juxtanuclear Golgi apparatus. The ability of Shiga toxin to stimulate microtubule-based transferrin transport also required Cdc42 and ARHGAP21 function. Shiga toxin addition greatly decreases the levels of active Cdc42-GTP in an ARHGAP21-dependent manner. We conclude that ARHGAP21 and Cdc42-based signaling regulates the dynein-dependent retrograde transport of Shiga toxin to the Golgi apparatus.

Effect of mutations in the general secretory pathway on outer membrane protein and surface layer assembly in Aeromonas spp.

1995 ◽  
Vol 41 (6) ◽  
pp. 525-532 ◽  
Author(s):  
S Peter Howard ◽  
Heather G. Meiklejhon
Keyword(s):  
Surface Layer ◽  
Membrane Protein ◽  
Outer Membrane ◽  
Outer Membrane Protein ◽  
Secretory Pathway ◽  
Immunoblot Analysis ◽  
Surface Proteins ◽  
Wild Type ◽  
Extracellular Secretion ◽  
In The Wild

Mutations in the exeC-N operon of Aeromonas hydrophila, which block extracellular protein secretion, also result in large decreases in the level of the major outer membrane porin, protein II. Immunoblot analysis demonstrated that the porin missing from the outer membrane of the mutant was not accumulating elsewhere in the cell. Pulse-chase and immunoprecipitation analyses showed that the porin was as stable in the mutant as in the wild type, but that far less porin was synthesized in the exe mutants. The relationship between extracellular secretion involving the exe genes and the assembly of other outer membrane and surface proteins was also examined. Both the wild type and exeE mutants of A. hydrophila were capable of assembling the protein I and protein III porins under inducing conditions. Aeromonas sohria As9071, which contains a surface array protein, could secrete A. hydrophila aerolysin and required homologues of the A. hydrophila exe genes to do so; however, an exe− derivative of this bacteria was unaffected in its ability to assemble its surface array. These results demonstrate that the exe genes are not required for general outer membrane protein assembly in these bacteria, but that the synthesis of protein II is specifically downregulated in the exe mutants.Key words: extracellular secretion, outer membrane assembly, surface layer, Aeromonas.

Scavenger receptor class A type I/II (CD204) null mice fail to develop fibrosis following silica exposure

2005 ◽  
Vol 289 (2) ◽  
pp. L186-L195 ◽  
Author(s):  
Celine A. Beamer ◽  
Andrij Holian
Keyword(s):  
Scavenger Receptor ◽  
Lavage Fluid ◽  
Type I ◽  
Dependent Manner ◽  
Wild Type ◽  
Focal Lesions ◽  
Silica Exposure ◽  
Class A

Alveolar macrophages express the class A scavenger receptor (CD204) (Babaev VR, Gleaves LA, Carter KJ, Suzuki H, Kodama T, Fazio S, and Linton MF. Arterioscler Thromb Vasc Biol 20: 2593–2599, 2000); yet its role in vivo in lung defense against environmental particles has not been clearly defined. In the current study, CD204 null mice (129Sv background) were used to investigate the link between CD204 and downstream events of inflammation and fibrosis following silica exposure in vivo. CD204−/− macrophages were shown to recognize and uptake silica in vitro, although this response was attenuated compared with 129Sv wild-type mice. The production of tumor necrosis factor-α in lavage fluid was significantly enhanced in CD204 null mice compared with wild-type mice following silica exposure. Moreover, after exposure to environmental particles, CD204−/− macrophages exhibited improved cell viability in a dose-dependent manner compared with wild-type macrophages. Finally, histopathology from a murine model of chronic silicosis in 129Sv wild-type mice displayed typical focal lesions, interstitial thickening with increased connective tissue matrix, and cellular infiltrate into air space. In contrast, CD204−/− mice exhibited little to no deposition of collagen, yet they demonstrated enhanced accumulation of inflammatory cells largely composed of neutrophils. Our findings point to an important role of CD204 in mounting an efficient and appropriately regulated immune response against inhaled particles. Furthermore, these results indicate that the functions of CD204 are critical to the development of fibrosis and the resolution of inflammation.

scholarly journals TF protein of Sindbis virus antagonizes host type I interferon responses in a palmitoylation-dependent manner

2019 ◽  
Author(s):  
Rogers KJ. ◽  
Jones-Burrage S. ◽  
Maury W. ◽  
Mukhopadhyay S.
Keyword(s):  
Sindbis Virus ◽  
Interferon Response ◽  
Type I ◽  
Dependent Manner ◽  
Wild Type ◽  
Particle Assembly ◽  
Viral Loads ◽  
Interferon Responses ◽  
Deficient Mice

AbstractSindbis virus (SINV) produces the small membrane protein TF from the 6K gene via a (−1) programmed ribosomal frameshifting. While several groups have shown that TF-deficient virus exhibits reduced virulence, mechanism(s) by which this occurs remain unknown. Here, we demonstrate a role for TF in antagonizing the host interferon response. Using wild-type and type 1 interferon receptor-deficient mice and primary cells derived from these animals, we show that TF controls the induction of the host interferon responses at early times during infection. Loss of TF production leads to elevated interferon and a concurrent reduction in viral loads with a loss of pathogenicity. Palmitoylation of TF has been shown to be important for particle assembly and morphology. We find that palmitoylation of TF also contributes to the ability of TF to antagonize host interferon responses as dysregulated palmitoylation of TF reduces virulence in a manner similar to loss of TF.

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