The kinetics of vimentin RNA and protein expression in interleukin 2-stimulated T lymphocytes

Akt, 14-3-3ζ, and vimentin mediate a drug-resistant invasive phenotype in diffuse large B-cell lymphoma

Development of resistance to the CHOP chemotherapeutic regimen (cyclophosphamide, doxorubicin, vincristine, prednisone) remains a major cause of treatment failure and mortality in approximately 40% of patients with diffuse large B-cell lymphoma (DLBCL). We established CHOP-resistant DLBCL cells as a model system to investigate molecular mechanisms involved in multidrug resistance. Two-dimensional differential in-gel (DIGE) analysis identified 10 differentially expressed proteins between CHOP-sensitive and -resistant DLBCL cells that play roles in glycolysis (triosephosphate isomerase-1, enolase-1), cytoskeletal structure (ezrin, vimentin, tubulin-specific chaperone B), purine biosynthesis (serine hydroxymethyltransferase), calcium binding (sorcin), and apoptosis (p53, 14-3-3ζ, Akt). Akt, 14-3-3ζ, and vimentin were up-regulated in CHOP-resistant DLBCL cells. We showed previously that siRNA-mediated knockdown of 14-3-3ζ reversed CHOP resistance in DLBCL cells (Maxwell et al., J Biol Chem 2009;284:22379-22389). Here we show that chemical inhibition of Akt overcomes CHOP resistance in DLBCL cells. CHOP-resistant cells exhibited a five-fold greater ability to invade collagen matrices compared with CHOP-sensitive cells. Knockdown of vimentin by siRNA or withaferin A repressed the invasiveness of CHOP-resistant cells in collagen matrices. Increased expressions of Akt, 14-3-3ζ, and vimentin were observed by Western blotting in primary DLBCL tissues relative to normal lymphatic tissue. The data implicate activation of an Akt-14-3-3ζ signaling pathway in promoting a multidrug-resistant phenotype associated with a vimentin-dependent invasive behavior in DLBCL cells.

BCL11B is a general transcriptional repressor of the HIV-1 long terminal repeat in T lymphocytes through recruitment of the NuRD complex

In this study we provide evidence that the transcription factor BCL11B represses expression from the HIV-1 long terminal repeat (LTR) in T lymphocytes through direct association with the HIV-1 LTR. We also demonstrate that the NuRD corepressor complex mediates BCL11B transcriptional repression of the HIV-1 LTR. In addition, BCL11B and the NuRD complex repressed TAT-mediated transactivation of the HIV-1 LTR in T lymphocytes, pointing to a potential role in initiation of silencing. In support of all the above results, we demonstrate that BCL11B affects HIV-1 replication and virus production, most likely by blocking LTR transcriptional activity. BCL11B showed specific repression for the HIV-1 LTR sequences isolated from seven different HIV-1 subtypes, demonstrating that it is a general transcriptional repressor for all LTRs.

14-3-3 proteins as potential oncogenes

14-3-3 proteins are a family of highly conserved cellular proteins that play key roles in the regulation of central physiological pathways. More than 200 14-3-3 target proteins have been identified, including proteins involved in mitogenic and cell survival signaling, cell cycle control and apoptotic cell death. Importantly, the involvement of 14-3-3 proteins in the regulation of various oncogenes and tumor suppressor genes points to a potential role in human cancer. The present review summarizes current findings implicating a 14-3-3 role in cancer while discussing potential mechanisms and points of action of 14-3-3 during cancer development and progression.

Anti-idiotypic antibody to the V3 domain of gp120 binds to vimentin: a possible role of intermediate filaments in the early steps of HIV-1 infection cycle

Although the CD4 molecule is the major cellular receptor for human immunodeficiency virus (HIV), several lines of evidence suggest participation of additional molecules that are engaged after the binding of HIV to the CD4 receptor and that may facilitate viral entry into the target cell. Some of the post-CD4 binding, perfusion events involve the third hypervariable region (V3 loop) of the viral envelope protein gp120. To identify cellular proteins that interact with the V3 loop, we chose as a probe an antiidiotypic monoclonal antibody (MAb), anti-id2, which was prepared against the neutralizing MAb 110.4 that binds the V3 domain in the envelope glycoprotein gp120 of the LAI isolate of HIV-1. Anti-id2 reacted specifically with a 55- to 60-kDa protein in human T cell and monocytoid cell lines, and in a mouse melanoma cell line. This protein was identified immunologically and by protein sequence analysis as vimentin, an intermediate filament protein of lymphoid and other cells of mesodermal origin. Antiserum raised against vimentin inhibited nuclear translocation of HIV-1 DNA following infection of monocytes and CD4+ T cells with live virus, and reduced the amount of HIV-1 gag-specific RNA in the nuclei of monocytes following inoculation with HIV-1 pseudovirions. These data suggest that vimentin may participate in the early steps of HIV-1 replication, perhaps during the uptake of HIV-1 preintegration complexes into the nuclear compartment.

Growth-regulated expression of vimentin in hamster fibroblasts is a result of increased transcription

We have previously shown that vimentin is a growth-regulated gene whose mRNA levels increase after serum stimulation of quiescent hamster fibroblasts. In this study, the control of the growth-regulated expression of vimentin was determined in ts13 cells induced to proliferate by serum. Both transcriptional and post-transcriptional mechanisms of regulation were examined by determining transcriptional rates, cytoplasmic transcript abundance, transcript stability, and protein abundance. We observed a fourfold increase in vimentin transcripts in the cytoplasm of serum-stimulated ts13 cells. Since transcripts are stable in both quiescent and stimulated cells, this induction of vimentin expression is a result of a fivefold increase in vimentin-specific transcriptional activity. As a result of this increased transcript availability, the abundance of polymerized vimentin protein increased following serum stimulation of quiescent fibroblasts. Overall, the induction of vimentin expression in fibroblasts by serum is a consequence of increased vimentin-specific transcriptional activity. The significance of this with regard to cytoskeletal organization and cell division is discussed.