Spread of HTLV-I Between Lymphocytes by Virus-Induced Polarization of the Cytoskeleton

Sun

Journal of Biological Chemistry

2007

Human T cell leukemia virus type 1 (HTLV-1) is the etiological agent of adult T cell leukemia. HTLV-1 encodes a trans-activating protein, Tax, which is largely responsible for the oncogenic properties of the virus. Tax promotes T cell transformation by deregulating the activity of various cellular factors, including the transcription factor NF-B. Tax activates the I B kinase (IKK) via physical interaction with the regulatory subunit, IKK␥, although it is unknown precisely how Tax activates the IKK complex. Here we show that Tax modulates the cellular localization of the IKK complex. The IKKs relocalize from a broad distribution in the cytoplasm to concentrated perinuclear "hot spots" in both HTLV-1-transformed lines and in Tax-expressing Jurkat cells. Relocalization of IKK is not observed with Tax mutants unable to activate NF-B, suggesting that only activated forms of IKK are relocalized. However, relocalization of IKK is strictly dependent on Tax expression because it does not occur in ATL cell lines that lack Tax expression or in Jurkat cells treated with phorbol 12-myristate 13-acetate and ionomycin. Furthermore, IKK␥ is required for redistribution because cells lacking IKK␥ were unable to relocalize IKK␣ upon expression of Tax. We also find that Tax ubiquitination likely regulates IKK relocalization because mutation of three critical lysine residues in Tax renders it unable to relocalize IKK and activate the canonical and noncanonical NF-B pathways. Finally, we have observed that the perinuclear IKK in Tax-expressing cells colocalizes with the Golgi, and disruption of Golgi with either nocodazole or brefeldin A leads to a redistribution of IKK to the cytoplasm. Together, these results demonstrate that Tax induces relocalization of the IKK complex in a ubiquitin-dependent manner, and dynamic changes in the subcellular localization of the IKK complex may be critical for Tax function.The human T cell leukemia virus type I (HTLV-1) 3 is associated with adult T cell leukemia (ATL), an aggressive malignancy of CD4 ϩ T cells, and a neuroinflammatory disease known as HTLV-1-associated myelopathy/tropical spastic paraparesis (1). The HTLV-1 genome encodes a regulatory protein Tax in the pX region that plays a central role in HTLV-1-associated disease (2). Tax acts as a trans-activating protein that is critical for the expression of viral genes and also deregulates the expression of cellular genes. Tax regulates the expression of cellular genes by modulating signaling pathways such as NF-B, AP-1, CREB, and nuclear factor of activated T cells (3). Tax activation of NF-B is required for immortalization of T lymphocytes (4). Further, pharmacologic inhibition of NF-B leads to apoptosis of HTLV-1 transformed T cell lines and ATL cells (5).NF-B represents a family of transcription factors that regulate a wide variety of genes controlling cell survival, development, differentiation, and activation. NF-B family members include RelA (p65), c-Rel, RelB, p50, and p52, all of which contain a 300-amino acid Rel homology domain th...

Section: Discussionmentioning

confidence: 99%

Activation of NF-κB by the Human T Cell Leukemia Virus Type I Tax Oncoprotein Is Associated with Ubiquitin-dependent Relocalization of IκB Kinase

Sun

Journal of Biological Chemistry

2007

“…As 1 example, with our model that adjusted for the frequencies of the other class II haplotypes, In contrast to individual types, we did have good statistical power to assess whether more common types were associated with disease risk. Given that HTLV-I is tightly cell associated and viral protein is expressed on the cell surface, 11 HLA can be postulated to play an important role in recognizing such cells as foreign and mounting an effective immune response against them. Indeed, Biggar et al noted that concordance in HLA class I alleles between a mother and her infant was a strong risk factor for transmission by breast feeding.…”

Section: Discussionmentioning

confidence: 99%

“…8 Moreover, HIV viral load is significantly lower with rare HLA class I supertypes and perhaps alleles. 9,10 HTLV-I is transmitted primarily by cell-to-cell contact, 11 and transmission from mother to infant is directly related to burden of infection in the mother (proviral load) 12 and is significantly increased for mothers and infants who are highly HLA concordant. 13 In the present study, we examined HLA gene polymorphisms of 305 Jamaican subjects with HTLV-I infection, postulating that people with higher prevalence HLA types may develop an immune response against a narrower range of cell-associated viral or neoplastic antigens and consequently may be at higher risk of ATL or HAM/TSP.…”

mentioning

confidence: 99%

Risk of human T‐lymphotropic virus type I‐associated diseases in Jamaica with common HLA types

Goedert

Gao

et al. 2007

Intl Journal of Cancer

Human T‐lymphotropic virus‐I (HTLV‐I) causes adult T‐cell leukemia/lymphoma (ATL) and HTLV‐associated myelopathy/tropical spastic paraparesis (HAM/TSP). We postulated a higher disease risk for people with common human leukocyte antigen (HLA) types, due to a narrower immune response against viral or neoplastic antigens, compared to people with uncommon types. HLA class‐I (A,B) and class‐II (DRB1, DQB1) allele and haplotype frequencies in 56 ATL patients, 59 HAM/TSP patients and 190 population‐based, asymptomatic HTLV‐I‐infected carriers were compared by logistic regression overall (score test) and with odds ratios (ORs) for common types (prevalence >50% of asymptomatic carriers) and by prevalence quartile. HTLV‐I proviral load between asymptomatic carriers with common versus uncommon types was compared by t‐test. ATL differed from asymptomatic carriers in overall DQB1 allele and class‐I haplotype frequencies (p ≤≤ 0.04). ATL risk was increased significantly with common HLA‐B (OR 2.25, 95% CI 1.19–4.25) and DRB1 (OR 2.11, 95% CI 1.13–3.40) alleles. Higher prevalence HLA‐B alleles were associated with higher ATL risk (OR 1.14 per quartile, ptrend = 0.02). Asymptomatic carriers with common HLA‐B alleles had marginally higher HTLV‐I proviral load (p = 0.057). HAM/TSP risk did not differ consistently with common HLA types. Thus, ATL risk, but not HAM/TSP risk, was increased with higher prevalence HLA‐B alleles. Perhaps breadth of cellular immunity affects risk of this viral leukemia/lymphoma. © 2007 Wiley‐Liss, Inc.

“…In the case of the human immunodeficiency virus (HIV) and the human T cell lymphoma virus these cell-cell contacts share features with immunological synapses and have been designated infectious or virological synapses (13,14,19,29,41). Using the murine leukemia virus (MLV) as a model system, we demonstrated that the interaction between the viral Env glycoprotein (Env), expressed on the infected cell and the viral receptor, expressed on the uninfected target cell, leads to the establishment of cell-cell contacts (32,45).…”

mentioning

confidence: 99%

Viral Determinants of Polarized Assembly for the Murine Leukemia Virus

Jin

Mothes

2011

J Virol

Retrovirus transmission via direct cell-cell contact is more efficient than diffusion through the extracellular milieu. This is believed to be due to the ability of viruses to efficiently coordinate several steps of the retroviral life cycle at cell-cell contact sites (D. Viruses exploit and manipulate cell-cell contacts for efficient spreading (12,18,32,37,43). In the case of the human immunodeficiency virus (HIV) and the human T cell lymphoma virus these cell-cell contacts share features with immunological synapses and have been designated infectious or virological synapses (13,14,19,29,41). Using the murine leukemia virus (MLV) as a model system, we demonstrated that the interaction between the viral Env glycoprotein (Env), expressed on the infected cell and the viral receptor, expressed on the uninfected target cell, leads to the establishment of cell-cell contacts (32, 45). Importantly, following the establishment of cellcell adhesion, assembly was polarized toward the cell-cell contact (16). These data suggested that the infected cell can "sense" the uninfected cell and direct the viral components needed to assemble viruses toward the uninfected cell. Sensing of the target cell turned out to be mediated by the accumulation of Env and receptor at the cell-cell interface and depending on the presence of a cytoplasmic tail (C-tail) of Env, MLV Gag was recruited toward the site of cell-cell contact. Here, we identify a tyrosine residue within the C-tail of Env and matrix within Gag as the viral determinants responsible for this process.C MATERIALS AND METHODSPlasmids and reagents. Mutant MLV envelope expression vectors were generated by site-directed mutagenesis based on the Friend MLV envelope expression vector previously described (16,46). MLV Gag-GFP expression vector was made by fusing enhanced green fluorescent protein (eGFP) to C-terminal of Gag and deleting a large fragment of Pol in full-length Friend57 MLV expression vector pLRB303 (23,35). Individual domains of MLV Gag-GFP were deleted or replaced by a standard overlapping PCR approach. MLV Gag-YFP expression vector was previously described (46). Chimeric MLV Gag with MA swapped with HIV MA was kindly provided by Marc Johnson, University of Missouri. HIV Gag-GFP expression vector and chimeric HIV Gag with MA swapped with MLV MA were described previously (17). HEK293 and XC cells were previously described (16).Visualizing virus cell-to-cell transmission. HEK293 cells were transfected with indicated plasmids by FuGENE 6 and cocultured 4 h posttransfection with XC cells expressing mCherry or cyan fluorescent protein (CFP)-tagged mCAT-1 as previously described (16). The formation of MLV synapses was reproducibly observed 2 to 6 postinitiation of cocultures for MLV generated by the tripartite system (MLV GagPol, Gag-YFP, MLV LTR, and MLV Env) or 4 to 10 h postinitiation of cocultures for MLV generated using proviral pLRB303-derived constructs. Imaging of fixed samples, as well as live-cell imaging, was performed using spinning disc confocal microscopy as ...