scholarly journals Jaagsiekte Sheep Retrovirus Utilizes a pH-Dependent Endocytosis Pathway for Entry

2007 ◽  
Vol 82 (5) ◽  
pp. 2555-2559 ◽  
Author(s):  
Pascale Bertrand ◽  
Marceline Côté ◽  
Yi-Min Zheng ◽  
Lorraine M. Albritton ◽  
Shan-Lu Liu
Keyword(s):  
Leukemia Virus ◽  
Low Ph ◽  
Dominant Negative ◽  
Moloney Murine Leukemia Virus ◽  
Dominant Negative Mutant ◽  
Jaagsiekte Sheep Retrovirus ◽  
Early Entry ◽  
Ph Inactivation ◽  
Endocytosis Pathway ◽  
Ph Dependent

ABSTRACT Using Moloney murine leukemia virus pseudovirions bearing the envelope protein of Jaagsiekte sheep retrovirus (JSRV), we report here that entry was weakly inhibited by lysosomotropic agents but was profoundly blocked by bafilomycin A1 (BafA1). Kinetics studies revealed that JSRV entry is a slow process and was substantially blocked by a dominant-negative mutant of dynamin. Interestingly, a low-pH pulse overcame the BafA1 block to JSRV infection, although this occurred only if virus-bound cells were preincubated at 37°C, consistent with a very early entry event such as endocytosis being required before the low-pH-dependent step occurs. Moreover, JSRV pseudovirions were resistant to low-pH inactivation. Altogether, this study reveals that JSRV utilizes a pH-dependent, dynamin-associated endocytosis pathway for entry that differs from the classical pH-dependent entry pathway of vesicular stomatitis virus.

scholarly journals Functional Entry of Baculovirus into Insect and Mammalian Cells Is Dependent on Clathrin-Mediated Endocytosis

2006 ◽  
Vol 80 (17) ◽  
pp. 8830-8833 ◽  
Author(s):  
Gang Long ◽  
Xiaoyu Pan ◽  
Richard Kormelink ◽  
Just M. Vlak
Keyword(s):  
Electron Microscopy ◽  
Mammalian Cells ◽  
Low Ph ◽  
Coated Pits ◽  
Immuno Electron Microscopy ◽  
Endocytosis Pathway ◽  
Ph Dependent ◽  
Budded Virus

ABSTRACT Entry of the budded virus form of baculoviruses into insect and mammalian cells is generally thought to occur through a low-pH-dependent endocytosis pathway, possibly through clathrin-coated pits. This insight is primarily based on (immuno)electron microscopy studies but requires biochemical support to exclude the use of other pathways. Here, we demonstrate using various inhibitors that functional entry of baculoviruses into insect and mammalian cells is primarily dependent on clathrin-mediated endocytosis. Our results further suggest that caveolae are somehow involved in baculovirus entry in mammalian cells. A caveolar endocytosis inhibitor, genistein, enhances baculovirus transduction in these cells considerably.

scholarly journals Effects of Mutant Ubiquitin on ts1 Retrovirus-Mediated Neuropathology

2003 ◽  
Vol 77 (13) ◽  
pp. 7193-7201 ◽  
Author(s):  
Mei Zhang ◽  
Sherry Thurig ◽  
Maria Tsirigotis ◽  
Paul K. Y. Wong ◽  
Kenneth R. Reuhl ◽  
...  
Keyword(s):  
Transgenic Mice ◽  
Therapeutic Potential ◽  
Leukemia Virus ◽  
Lewy Bodies ◽  
Dominant Negative ◽  
Dominant Negative Mutant ◽  
Spongiform Encephalopathy ◽  
Temperature Sensitive ◽  
Transgenic Mouse Line

ABSTRACT ts1 is a temperature-sensitive mutant of Moloney murine leukemia virus that induces a rapid spongiform encephalopathy in mice infected as newborns. The pathological features include the formation of ubiquitinated inclusions resembling Lewy bodies. To determine how perturbation of the ubiquitin-proteasome pathway might affect ts1-mediated neurodegeneration, the virus was introduced into transgenic mice in which the assembly of ubiquitin chains was compromised by the expression of dominant-negative mutant ubiquitin. The onset of symptoms was greatly delayed in a transgenic mouse line expressing K48R mutant ubiquitin; no such delay was observed in mice expressing a wild-type ubiquitin transgene or K63R mutant ubiquitin. The extended latency was found to correlate with a delayed increase in viral titers. Pathological findings in K48R transgenic mice at 60 days were found to be similar to those in the other strains at 30 days, suggesting that while delayed, the neurodegenerative process in K48R mice was otherwise similar. These data demonstrate the sensitivity of retroviral replication to the partial disruption of ubiquitin-mediated proteolysis in vivo, a finding that may have therapeutic potential.

scholarly journals Receptor-Mediated Moloney Murine Leukemia Virus Entry Can Occur Independently of the Clathrin-Coated-Pit-Mediated Endocytic Pathway

1999 ◽  
Vol 73 (7) ◽  
pp. 5994-6005 ◽  
Author(s):  
Sunyoung Lee ◽  
Yi Zhao ◽  
W. French Anderson
Keyword(s):  
Hela Cells ◽  
Murine Leukemia Virus ◽  
Leukemia Virus ◽  
Dominant Negative ◽  
Endocytic Pathway ◽  
Moloney Murine Leukemia Virus ◽  
Wild Type ◽  
293 Cells ◽  
Immunofluorescence Labeling ◽  
Murine Leukemia

ABSTRACT To investigate receptor-mediated Moloney murine leukemia virus (MoMuLV) entry, the green fluorescent protein (GFP)-tagged ecotropic receptor designated murine cationic amino acid transporter (MCAT-1) (MCAT-1-GFP) was constructed and expressed in 293 cells (293/MCAT-1-GFP). 293/MCAT-1-GFP cells displayed green fluorescence primarily at the cell membrane and supported wild-type levels of MoMuLV vector binding and transduction. Using immunofluorescence labeling and confocal microscopy, it was demonstrated that the surface envelope protein (SU) gp70 of MoMuLV virions began to appear inside cells 5 min after virus binding and was colocalized with MCAT-1-GFP. However, clathrin was not colocalized with MCAT-1-GFP, suggesting that MoMuLV entry, mediated by MCAT-1, does not involve clathrin. Double immunofluorescence labeling of SU and clathrin in 293 cells expressing untagged receptor (293/MCAT-1) gave the same results, i.e., SU and clathrin did not colocalize. In addition, we examined the transduction ability of MoMuLV vector on HeLa cells overexpressing the dominant-negative GTPase mutant of dynamin (K44A). HeLa cells overexpressing mutant dynamin have a severe block in endocytosis by the clathrin-coated-pit pathway. No significant titer difference was observed when MoMuLV vector was tranduced into HeLa cells overexpressing either wild-type or mutant dynamin, while the transduction ability of vesicular stomatitis virus glycoprotein pseudotyped vector into HeLa cells overexpressing mutant dynamin was decreased significantly. Taken together, these data suggest that MoMuLV entry does not occur through the clathrin-coated-pit-mediated endocytic pathway.

scholarly journals Late Domain-Independent Rescue of a Release-Deficient Moloney Murine Leukemia Virus by the Ubiquitin Ligase Itch

2009 ◽  
Vol 84 (2) ◽  
pp. 704-715 ◽  
Author(s):  
Joshua A. Jadwin ◽  
Victoria Rudd ◽  
Paola Sette ◽  
Swathi Challa ◽  
Fadila Bouamr
Keyword(s):  
Ubiquitin Ligase ◽  
Murine Leukemia Virus ◽  
Leukemia Virus ◽  
Dominant Negative ◽  
Moloney Murine Leukemia Virus ◽  
Independent Manner ◽  
Gag Proteins ◽  
Aaa Atpase ◽  
Domain Independent ◽  
Murine Leukemia

ABSTRACT Moloney murine leukemia virus (MoMLV) Gag utilizes its late (L) domain motif PPPY to bind members of the Nedd4-like ubiquitin ligase family. These interactions recruit components of the cell's budding machinery that are critical for virus release. MoMLV Gag contains two additional L domains, PSAP and LYPAL, that are believed to drive residual MoMLV release via interactions with cellular proteins Tsg101 and Alix, respectively. We found that overexpression of Tsg101 or Alix failed to rescue the release of PPPY-deficient MoMLV via these other L domains. However, low-level expression of the ubiquitin ligase Itch potently rescued the release and infectivity of MoMLV lacking PPPY function. In contrast, other ubiquitin ligases such as WWP1, Nedd4.1, Nedd4.2, and Nedd4.2s did not rescue this release-deficient virus. Efficient rescue required the ubiquitin ligase activity of Itch and an intact C2 domain but not presence of the endophilin-binding site. Additionally, we found Itch to immunoprecipitate with MoMLV Gag lacking the PPPY motif and to be incorporated into rescued MoMLV particles. The PSAP and LYPAL motifs were dispensable for Itch-mediated virus rescue, and their absence did not affect the incorporation of Itch into the rescued particles. Itch-mediated rescue of release-defective MoMLV was sensitive to inhibition by dominant-negative versions of ESCRT-III components and the VPS4 AAA ATPase, indicating that Itch-mediated correction of MoMLV release defects requires the integrity of the host vacuolar sorting protein pathway. RNA interference knockdown of Itch suppressed the residual release of the MoMLV lacking the PPPY motif. Interestingly, Itch stimulation of the PPPY-deficient MoMLV release was accompanied by the enhancement of Gag ubiquitination and the appearance of new ubiquitinated Gag proteins in virions. Together, these results suggest that Itch can facilitate MoMLV release in an L domain-independent manner via a mechanism that requires the host budding machinery and involves Gag ubiquitination.

scholarly journals Acid-Resistant Bovine Pestivirus Requires Activation for pH-Triggered Fusion during Entry

2005 ◽  
Vol 79 (7) ◽  
pp. 4191-4200 ◽  
Author(s):  
Thomas Krey ◽  
Heinz-Jürgen Thiel ◽  
Till Rümenapf
Keyword(s):  
Disulfide Bonds ◽  
Low Ph ◽  
Dominant Negative ◽  
Dominant Negative Mutant ◽  
Acidic Ph ◽  
Diarrhea Virus ◽  
Endosomal Membrane ◽  
Endosomal Acidification ◽  
Mdbk Cells ◽  
Low Efficiency

ABSTRACT The route of internalization of the pestivirus bovine viral diarrhea virus (BVDV) was studied by using different chemical and biophysical inhibitors of endocytosis. Expression of the dominant-negative mutant DynK44A of the GTPase dynamin in MDBK cells, as well as the treatment of the cells with chlorpromazine and β-methyl-cyclodextrin inhibited BVDV entry. BVDV infection was also abolished by potassium (K+) depletion, hyperosmolarity, and different inhibitors of endosomal acidification. We conclude that BVDV likely enters the cell by clathrin-dependent endocytosis and that acidification initiates fusion with the endosomal membrane. Further studies revealed that BVDV was unable to undergo “fusion from without” at low pH. The finding that low pH is not sufficient to force adsorbed BVDV into fusion with the plasma membrane is compatible with the remarkable resistance of pestiviruses to inactivation by low pH. The importance of the abundant intra- and intermolecular disulfide bonds in BVDV glycoproteins for virus stability was studied by the use of reducing agents. The combination of dithiothreitol and acidic pH led to partial inactivation of BVDV and allowed fusion from without at low efficiency. Evidence is provided here that acid-resistant BVDV is destabilized during endocytosis to become fusogenic at an endosomal acidic pH. We suggest that destabilization of the virion occurs by breakage of disulfide bonds in the glycoproteins by an unknown mechanism.

Zebrafish Meis functions to stabilize Pbx proteins and regulate hindbrain patterning

Development ◽  
2001 ◽  
Vol 128 (21) ◽  
pp. 4139-4151 ◽  
Author(s):  
Andrew Jan Waskiewicz ◽  
Holly A. Rikhof ◽  
Rafael E. Hernandez ◽  
Cecilia B. Moens
Keyword(s):  
Dna Binding ◽  
Hox Genes ◽  
Integration Site ◽  
Leukemia Virus ◽  
Dominant Negative ◽  
Dominant Negative Mutant ◽  
Hox Proteins ◽  
Protein Levels ◽  
Vertebrate Orthologs ◽  
And Function

Homeodomain-containing Hox proteins regulate segmental identity in Drosophila in concert with two partners known as Extradenticle (Exd) and Homothorax (Hth). These partners are themselves DNA-binding, homeodomain proteins, and probably function by revealing the intrinsic specificity of Hox proteins. Vertebrate orthologs of Exd and Hth, known as Pbx and Meis (named for a myeloid ecotropic leukemia virus integration site), respectively, are encoded by multigene families and are present in multimeric complexes together with vertebrate Hox proteins. Previous results have demonstrated that the zygotically encoded Pbx4/Lazarus (Lzr) protein is required for segmentation of the zebrafish hindbrain and proper expression and function of Hox genes. We demonstrate that Meis functions in the same pathway as Pbx in zebrafish hindbrain development, as expression of a dominant-negative mutant Meis results in phenotypes that are remarkably similar to that of lzr mutants. Surprisingly, expression of Meis protein partially rescues the lzr– phenotype. Lzr protein levels are increased in embryos overexpressing Meis and are reduced for lzr mutants that cannot bind to Meis. This implies a mechanism whereby Meis rescues lzr mutants by stabilizing maternally encoded Lzr. Our results define two functions of Meis during zebrafish hindbrain segmentation: that of a DNA-binding partner of Pbx proteins, and that of a post-transcriptional regulator of Pbx protein levels.

Sign in / Sign up

Export Citation Format

Share Document