scholarly journals Three YXXL Sequences of a Bovine Leukemia Virus Transmembrane Protein are Independently Required for Fusion Activity by Controlling Expression on the Cell Membrane

Viruses ◽  
2019 ◽  
Vol 11 (12) ◽  
pp. 1140 ◽  
Author(s):  
Ryosuke Matsuura ◽  
Kazunori Inabe ◽  
Hiroyuki Otsuki ◽  
Kazuo Kurokawa ◽  
Naoshi Dohmae ◽  
...  
Keyword(s):  
Life Cycle ◽  
Cell Surface ◽  
Bovine Leukemia Virus ◽  
Transmembrane Protein ◽  
Leukemia Virus ◽  
Viral Life Cycle ◽  
Neoplastic Disease ◽  
Single Mutation ◽  
Early Endosomes ◽  
Env Protein

Bovine leukemia virus (BLV), which is closely related to human T-cell leukemia viruses, is the causative agent of enzootic bovine leukosis, the most common neoplastic disease of cattle. The transmembrane subunit of the BLV envelope glycoprotein, gp30, contains three completely conserved YXXL sequences that fit an endocytic sorting motif. The two N-terminal YXXL sequences are reportedly critical for viral infection. However, their actual function in the viral life cycle remains undetermined. Here, we identified the novel roles of each YXXL sequence. Syncytia formation ability was upregulated by a single mutation of the tyrosine (Tyr) residue in any of the three YXXL sequences, indicating that each YXXL sequence is independently able to regulate the fusion event. The alteration resulted from significantly high expression of gp51 on the cell surface, thereby decreasing the amount of gp51 in early endosomes and further revealing that the three YXXL sequences are independently required for internalization of the envelope (Env) protein, following transport to the cell surface. Moreover, the 2nd and 3rd YXXL sequences contributed to Env protein incorporation into the virion by functionally distinct mechanisms. Our findings provide new insights regarding the three YXXL sequences toward the BLV viral life cycle and for developing new anti-BLV drugs.

scholarly journals Dileucine and YXXL Motifs in the Cytoplasmic Tail of the Bovine Leukemia Virus Transmembrane Envelope Protein Affect Protein Expression on the Cell Surface

2004 ◽  
Vol 78 (15) ◽  
pp. 8301-8311 ◽  
Author(s):  
Sinisa Novakovic ◽  
Earl T. Sawai ◽  
Kathryn Radke
Keyword(s):  
Cell Surface ◽  
Bovine Leukemia Virus ◽  
Leukemia Virus ◽  
Surface Display ◽  
Chimeric Protein ◽  
Surface Expression ◽  
Terminal Segment ◽  
Cell Surface Expression ◽  
Chimeric Proteins ◽  
Env Protein

ABSTRACT Several retroviruses downmodulate the cell surface expression of envelope (Env) proteins through peptide sequences located in the cytoplasmic tail of the transmembrane (TM) subunit. We investigated whether cell surface expression of a chimeric protein containing the cytoplasmic domain of the TM protein (CTM) of bovine leukemia virus (BLV) was regulated by two membrane-proximal dileucine motifs or by tyrosine Y487 or Y498 in YXXL motifs. A chimeric protein composed of the extracellular and membrane-spanning portions of human CD8-α plus a wild-type (wt) BLV CTM was detectable on the surface of only 40% of the cells in which it was transiently expressed. Replacement of either dileucine pair with alanines increased the level of surface display of chimeric proteins. Nearly all cells became surface positive when both dileucine motifs were altered simultaneously and when either an N-terminal segment containing both dileucine motifs or a C-terminal segment containing all YXXL motifs was deleted. In contrast, replacement of Y487 or Y498 with alanine or phenylalanine enabled only small increases in surface display compared with wt levels. Chimeric proteins had similar stabilities but were downmodulated from the cell surface at three different rates. Point mutants segregated into each of the three groups of proteins categorized according to these different rates. Interestingly, Y487 mutants were downmodulated less efficiently than Y498 mutants, which behaved like wt. CD8-CTM chimeric proteins were phosphorylated on serine residues, but the native BLV Env protein was not phosphorylated either in transfected cells or in a lymphoid cell line constitutively producing BLV. Thus, both dileucine and YXXL motifs within the BLV CTM contribute to downmodulation of a protein containing this domain. Interactions with other proteins may influence surface exposure of Env protein complexes in virus-infected cells, assisting in viral evasion of adaptive immunity.

scholarly journals The Mouse Homolog of the Bovine Leukemia Virus Receptor Is Closely Related to the δ Subunit of Adaptor-Related Protein Complex AP-3, Not Associated with the Cell Surface

1998 ◽  
Vol 72 (1) ◽  
pp. 593-599 ◽  
Author(s):  
Takako Suzuki ◽  
Hidetoshi Ikeda
Keyword(s):  
Amino Acids ◽  
Cell Surface ◽  
Protein Complex ◽  
Bovine Leukemia Virus ◽  
Transmembrane Protein ◽  
Leukemia Virus ◽  
Adaptor Protein ◽  
Type I ◽  
Related Protein ◽  
Virus Receptor

ABSTRACT A mouse cDNA (mBLVR1) which was highly homologous to the bovine cDNA of the bovine leukemia virus receptor (BLVR) gene was cloned. The mBLVR1 cDNA, of 4,730 bp, covered nearly the full length of the mRNA (about 5 kb) and included an open reading frame (ORF) encoding a protein of 1,199 amino acids. While the bovine BLVR protein was thought to be a type I transmembrane protein, the deduced protein coded by mBLVR1 did not appear to be a typical transmembrane protein. The ORF of mBLVR1 ended at a site 280 amino acids upstream of the termination codon of the bovine BLVR ORF, so the deduced mouse BLVR protein lacked the corresponding transmembrane and cytoplasmic regions of the predicted bovine BLVR protein. No significant hydrophobic region was found in the mouse protein. Recently, a human cDNA which was highly homologous (69.6% homology) to the mouse BLVR gene was reported. The cDNA encodes the δ subunit of the human adaptor-related protein complex AP-3, which aligned almost collinearly with the mouse BLVR protein. AP-3 and all other related adaptor protein complexes have been shown to be associated with intracellular vesicles but not with the cell surface. Thus, the mouseBLVR homolog appeared to be the mouse AP-3 δ subunit itself or closely related to it, but the bovine BLVR gene seemed slightly different from the adaptor subunit gene family.

scholarly journals Retroviral Restriction Factors Fv1 and TRIM5α Act Independently and Can Compete for Incoming Virus before Reverse Transcription

2006 ◽  
Vol 80 (5) ◽  
pp. 2100-2105 ◽  
Author(s):  
Luca D. Passerini ◽  
Zuzana Keckesova ◽  
Greg J. Towers
Keyword(s):  
Life Cycle ◽  
Reverse Transcription ◽  
Murine Leukemia Virus ◽  
Leukemia Virus ◽  
Viral Life Cycle ◽  
Human Cells ◽  
Restriction Factors ◽  
Retroviral Infection ◽  
The Relationship ◽  
Murine Leukemia

ABSTRACT The restriction factors Fv1 and TRIM5α provide dominant blocks to retroviral infection, targeting incoming capsids at a postentry, preintegration step. They both restrict N-tropic murine leukemia virus with similar specificity yet act at different points in the viral life cycle. TRIM5α-restricted virus is usually unable to reverse transcribe, whereas Fv1-restricted virus reverse transcribes normally. Here we investigate the relationship between these two restriction factors by expressing Fv1 alleles in human cells. We demonstrate that Fv1 is able to compete with TRIM5α for virus before reverse transcription. In human cells expressing Fv1b, N-tropic restricted virus becomes less infectious but reverse transcribes more efficiently, indicating competition between the two antiviral molecules and protection of the virus from TRIM5α by Fv1. Our findings suggest that, like TRIM5α, Fv1 interacts with virus before reverse transcription, but the consequences of this interaction are not realized until a later stage of the life cycle. We also demonstrate that Fv1 is functionally independent of TRIM5α when expressed in human cells.

scholarly journals CAT1/SLC7A1 acts as a cellular receptor for bovine leukemia virus infection

2019 ◽  
Author(s):  
Lanlan Bai ◽  
Hirotaka Sato ◽  
Yoshinao Kubo ◽  
Satoshi Wada ◽  
Yoko Aida
Keyword(s):  
Cell Surface ◽  
Envelope Glycoprotein ◽  
Bovine Leukemia Virus ◽  
Virus Entry ◽  
Leukemia Virus ◽  
Cellular Receptor ◽  
Cationic Amino Acid Transporter ◽  
Cell Leukemia ◽  
Cationic Amino Acid ◽  
Human T Cell

AbstractBovine leukemia virus (BLV) is the causative agent of enzootic bovine leukosis, the most common neoplastic disease of cattle, which is closely related to human T-cell leukemia viruses. BLV has spread worldwide and causes a serious problem for the cattle industry. The cellular receptor specifically binds with viral envelope glycoprotein (Env) and this attachment mediates cell fusion to lead virus entry. BLV Env reportedly binds to cationic amino acid transporter 1 (CAT1)/SLC7A1, but whether the CAT1/SLC7A1 is an actual receptor for BLV remains unknown. Here, we showed that CAT1 functioned as an infection receptor, interacting with BLV particles. Cells expressing undetectable CAT1 levels were resistant to BLV infection but became highly susceptible upon CAT1 overexpression. CAT1 exhibited specific binding to BLV particles on the cell surface and co-localized with the Env in endomembrane compartments and membrane. Knockdown of CAT1 in permissive cells significantly reduced binding to BLV particles and BLV infection. In addition, bovine serum with neutralizing activity from a BLV-infected cattle inhibited BLV particles. Expression of CAT1 from various species demonstrated no species-specificity for BLV infection, implicating CAT1 as a functional BLV receptor responsible for its broad host range. These findings provide insights for BLV infection and for developing new strategies for treating BLV and preventing its spread.Author SummaryBovine leukemia virus (BLV), which can infect a variety of animal species and induce lymphoma in cattle, is a member of the familyRetroviridae. BLV induces huge economic losses by not only lymphoma but also subclinical forms of the disease. In addition, BLV is frequently used as an animal model of human T-cell leukemia virus (HTLV), as BLV has many similar characteristics to HTLV. Thus, understanding BLV pathogenesis contribute to resolve not only BLV-but also HTLV-induced problems. Retroviral envelope glycoprotein (Env) is specifically recognized by the cellular receptor at cell surface, which induces a conformational changes between viral and cell membrane to entry. Thus, the elucidation of cellular receptor for BLV infection is very important for virus entry. However, the BLV receptor has not been identified yet. In the current study, we found that BLV Env protein binds to cationic amino acid transporter 1 (CAT1)/SLC7A1 at cell surface, artificial expression of CAT1 in CAT1-negative cells confers the cells susceptible to BLV infection, and CAT1-silencing significantly reduces BLV infection, concluding that CAT1 is the BLV receptor. These findings will have far reaching great advantages of insights in the retrovirus study.

scholarly journals Comprehensive Mutational Analysis of the Moloney Murine Leukemia Virus Envelope Protein

2001 ◽  
Vol 75 (23) ◽  
pp. 11851-11862 ◽  
Author(s):  
S. Michael Rothenberg ◽  
Mari N. Olsen ◽  
Louise Chang Laurent ◽  
Rachel Adams Crowley ◽  
Patrick O. Brown
Keyword(s):  
Cell Surface ◽  
Receptor Binding ◽  
Leukemia Virus ◽  
Moloney Murine Leukemia Virus ◽  
Receptor Binding Domain ◽  
Amino Terminal ◽  
Carboxy Terminal Region ◽  
Env Protein ◽  
Carboxy Terminal ◽  
Murine Leukemia

ABSTRACT The envelope (Env) protein of Moloney murine leukemia virus is the primary mediator of viral entry. We constructed a large pool of insertion mutations in the env gene and analyzed the fitness of each mutant in completing two critical steps in the virus life cycle: (i) the expression and delivery of the Env protein to the cell surface during virion assembly and (ii) the infectivity of virions displaying the mutant proteins. The majority of the mutants were poorly expressed at the producer cell surface, suggesting folding defects due to the presence of the inserted residues. The mutants with residual infectivity had insertions either in the amino-terminal signal sequence region, two disulfide-bonded loops in the receptor binding domain, discrete regions of the carboxy-terminal region of the surface subunit (SU), or the cytoplasmic tail. Insertions that allowed the mutants to reach the cell surface but not to mediate detectable infection were located within the amino-terminal sequence of the mature Env, within the SU carboxy-terminal region, near putative receptor binding residues, and throughout the fusion peptide. Independent analysis of select mutants in this group allowed more precise identification of the defect in Env function. Mapping of mutant phenotypes to a structural model of the receptor-binding domain provides insights into the protein's functional organization. The high-resolution functional map reported here will be valuable for the engineering of the Env protein for a variety of uses, including gene therapy.

scholarly journals Even Attenuated Bovine Leukemia Virus Proviruses Can Be Pathogenic in Sheep

2007 ◽  
Vol 81 (18) ◽  
pp. 10195-10200 ◽  
Author(s):  
Arnaud Florins ◽  
Nicolas Gillet ◽  
Mathieu Boxus ◽  
Pierre Kerkhofs ◽  
Richard Kettmann ◽  
...  
Keyword(s):  
Bovine Leukemia Virus ◽  
Reverse Genetics ◽  
Transmembrane Protein ◽  
Direct Sequencing ◽  
Leukemia Virus ◽  
Wild Type ◽  
Gene Sequences

ABSTRACT Based on a reverse genetics approach, we previously reported that bovine leukemia virus (BLV) mutants harboring deletions in the accessory R3 and G4 genes persist at very low proviral loads and are unable to induce leukemia or lymphoma in sheep, indicating that these R3 and G4 gene sequences are required for pathogenesis. We now show that lymphoma can occur, albeit infrequently (1 case of 20) and after extended periods of latency (7 years). Direct sequencing and reinfection experiments demonstrated that lymphomagenesis was not due to the reversion of the mutant to the wild type. Similar observations with another type of attenuated mutant impaired in the transmembrane protein (TM) YXXL signaling motifs were made. We conclude that the R3 and G4 genes and the TM YXXL motifs are not strictly required for pathogenesis but that their integrity contributes to disease frequency and latency.

Exosomal sorting of the cytoplasmic domain of bovine leukemia virus TM Env protein

2009 ◽  
Vol 33 (1) ◽  
pp. 36-48 ◽  
Author(s):  
A DEGASSART ◽  
B TRENTIN ◽  
M MARTIN ◽  
A HOCQUELLET ◽  
P BETTEBOBILLO ◽  
...  
Keyword(s):  
Bovine Leukemia Virus ◽  
Leukemia Virus ◽  
Cytoplasmic Domain ◽  
Env Protein ◽  
Exosomal Sorting

scholarly journals Relationship between Allelic Heterozygosity in BoLA-DRB3 and Proviral Loads in Bovine Leukemia Virus-Infected Cattle

Animals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 647
Author(s):  
Hala El Daous ◽  
Shuya Mitoma ◽  
Eslam Elhanafy ◽  
Huyen Thi Nguyen ◽  
Ngan Thi Mai ◽  
...  
Keyword(s):  
Polymerase Chain Reaction ◽  
Bovine Leukemia Virus ◽  
Negative Binomial ◽  
Leukemia Virus ◽  
Negative Binomial Regression ◽  
Enzyme Linked Immunosorbent Assay ◽  
Neoplastic Disease ◽  
Infected Cattle ◽  
Chain Reaction ◽  
Polymerase Chain

Enzootic bovine leukosis is a lethal neoplastic disease caused by bovine leukemia virus (BLV), belongs to family Retroviridae. The BLV proviral load (PVL) represents the quantity of BLV genome that has integrated into the host’s genome in BLV-infected cells. Bovine leukocyte antigen (BoLA) class II allelic polymorphisms are associated with PVLs in BLV-infected cattle. We sought to identify relationships between BoLA-DRB3 allelic heterozygosity and BLV PVLs among different cattle breeds. Blood samples from 598 BLV-infected cattle were quantified to determine their PVLs by real-time polymerase chain reaction. The results were confirmed by a BLV-enzyme-linked immunosorbent assay. Restriction fragment length polymorphism-polymerase chain reaction identified 22 BoLA-DRB3 alleles. Multivariate negative binomial regression modeling was used to test for associations between BLV PVLs and BoLA-DRB3 alleles. BoLA-DRB3.2*3, *7, *8, *11, *22, *24, and *28 alleles were significantly associated with low PVLs. BoLA-DRB3.2*10 was significantly associated with high PVLs. Some heterozygous allele combinations were associated with low PVLs (*3/*28, *7/*8, *8/*11, *10/*11, and *11/*16); others were associated with high PVLs (*1/*41, *10/*16, *10/*41, *16/*27, and *22/*27). Interestingly, the BoLA-DRB3.2*11 heterozygous allele was always strongly and independently associated with low PVLs. This is the first reported evidence of an association between heterozygous allelic combinations and BLV PVLs.

Sign in / Sign up

Export Citation Format

Share Document