HIV-1 subverts antigen processing in dendritic cells (DCs) resulting in viral uptake, infection, and transfer to T cells. Although DCs bound monomeric gp120 and HIV-1 similarly, virus rarely colocalized with endolysosomal markers, unlike gp120, suggesting HIV-1 alters endolysosomal trafficking. Virus within DC intracellular compartments rapidly moved to DC-CD4 ؉ lymphocyte synapses when introduced to CD4 ؉ lymphocyte cultures.Although viral harboring and transfer from nonlysosomal compartments was transient, given DC-associated virus protein, nucleic acids, and infectious HIV-1 transfer to CD4 ؉ , lymphocytes decayed within 24 hours. However a second long-term transfer phase was apparent in immature DCs after 48 hours as a zidovudinesensitive rise in proviral DNA. Therefore, DCs transfer HIV-1 to CD4 ؉ lymphocytes in 2 distinct phases. Immature and mature DCs first divert virus from the endolysosomal pathway to the DC-T-cell synapse. Secondly, the later transfer phase from immature DCs is through de novo HIV-1 production. Thus, the controversy of DCs being infected or not infected for the mechanics of viral transfer to CD4 ؉ lymphocytes can be addressed as a function of time.

MURR1 is a multifunctional protein that inhibits nuclear factor B (NF-B), a transcription factor with pleiotropic functions affecting innate and adaptive immunity, apoptosis, cell cycle regulation, and oncogenesis. Here we report the discovery of a new family of proteins with homology to MURR1. These proteins form multimeric complexes and were identified in a biochemical screen for MURR1-associated factors. The family is defined by the presence of a conserved and unique motif termed the COMM (copper metabolism gene MURR1) domain, which functions as an interface for proteinprotein interactions. Like MURR1, several of these factors also associate with and inhibit NF-B. The proteins designated as COMMD or COMM domain containing 1-10 are extensively conserved in multicellular eukaryotic organisms and define a novel family of structural and functional homologs of MURR1. The prototype of this family, MURR1/COMMD1, suppresses NF-B not by affecting nuclear translocation or binding of NF-B to cognate motifs; rather, it functions in the nucleus by affecting the association of NF-B with chromatin.NF-B is a dimeric complex formed by members of a highly conserved family of proteins that share a defining motif designated the Rel homology domain (RHD).1 Through transcriptional regulation of many gene products, NF-B participates in a number of biological processes including innate and adaptive immune responses, programmed cell death, cell cycle progression, and oncogenesis (1-6). Additionally, by its ability to regulate transcription of various viral genomes including human immunodeficiency virus-1 (HIV-1) (7-10), NF-B also participates in viral cycle progression.Studies into the regulation of NF-B activation have largely focused on the role of cytoplasmic sequestration of the NF-B complex as a mainstay level of control. In most cells NF-B is localized in the cytoplasm through the interaction of the complex with members of the IB family (11). These proteins contain ankyrin repeats that allow their interaction with NF-B and mask the nuclear localization signal present in the RHD. Phosphorylation of IB by a multimeric kinase known as the IB kinase complex targets these proteins for ubiquitination and proteasomal degradation (3,12). This allows the translocation of NF-B to the nucleus where it binds to cognate DNA sequences present in an array of gene promoters.MURR1 is a recently identified factor that has been shown to participate in two apparently distinct activities, regulation of the transcription factor NF-B and control of copper metabolism (13). Mutations in MURR1 are responsible for copper toxicosis in an inbred canine strain (Bedlington terriers) (14), and an interaction between MURR1 and the copper transporter ATP7B (15) has been recently reported.In addition to its role in copper metabolism in mammals, more recent studies implicate MURR1 in the regulation of the transcription factor NF-B (13, 16). MURR1 was found to be a broad inhibitor of NF-B, affecting B-responsive transcription from endogenous and viral promoters in...

XIAP is a potent suppressor of apoptosis that directly inhibits specific members of the caspase family of cysteine proteases. Here we demonstrate a novel role for XIAP in the control of intracellular copper levels. XIAP was found to interact with MURR1, a factor recently implicated in copper homeostasis. XIAP binds to MURR1 in a manner that is distinct from that utilized by XIAP to bind caspases, and consistent with this, MURR1 did not affect the antiapoptotic properties of XIAP. However, cells and tissues derived from Xiap-deficient mice were found to contain reduced copper levels, while suppression of MURR1 resulted in increased intracellular copper in cultured cells. Consistent with these opposing effects, XIAP was observed to negatively regulate MURR1 protein levels by the formation of K48 polyubiquitin chains on MURR1 that promote its degradation. These findings represent the first described phenotypic alteration in Xiap-deficient mice and demonstrate that XIAP can function through MURR1 to regulate copper homeostasis.

AbstractMacrophages are key target cells for HIV-1. HIV-1BaL induced a subset of interferon-stimulated genes in monocyte-derived macrophages (MDMs), which differed from that in monocyte-derived dendritic cells and CD4 T cells, without inducing any interferons. Inhibition of type I interferon induction was mediated by HIV-1 inhibition of interferon-regulated factor (IRF3) nuclear translocation. In MDMs, viperin was the most up-regulated interferon-stimulated genes, and it significantly inhibited HIV-1 production. HIV-1 infection disrupted lipid rafts via viperin induction and redistributed viperin to CD81 compartments, the site of HIV-1 egress by budding in MDMs. Exogenous farnesol, which enhances membrane protein prenylation, reversed viperin-mediated inhibition of HIV-1 production. Mutagenesis analysis in transfected cell lines showed that the internal S-adenosyl methionine domains of viperin were essential for its antiviral activity. Thus viperin may contribute to persistent noncytopathic HIV-1 infection of macrophages and possibly to biologic differences with HIV-1–infected T cells.

Curcumin is a natural product currently in human clinical trials for a variety of neoplastic, preneoplastic, and inflammatory conditions. We previously observed that, in cultured cells, curcumin exhibits properties of an iron chelator. To test whether the chelator activity of curcumin is sufficient to induce iron deficiency in vivo, mice were placed on diets containing graded concentrations of both iron and curcumin for 26 weeks.

Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) is a member of the tumor necrosis factor ␣ family of cytokines that preferentially induces apoptosis in transformed cells, making it a promising cancer therapy. However, many neoplasms are resistant to TRAIL-induced apoptosis by mechanisms that are poorly understood. We demonstrate that the expression of the small heat shock protein ␣B-crystallin (but not other heat shock proteins or apoptosis-regulating proteins) correlates with TRAIL resistance in a panel of human cancer cell lines. Stable expression of wild-type ␣B-crystallin, but not a pseudophosphorylation mutant impaired in its assembly and chaperone function, protects cancer cells from TRAIL-induced caspase-3 activation and apoptosis in vitro. Furthermore, selective inhibition of ␣B-crystallin expression by RNA interference sensitizes cancer cells to TRAIL. In addition, wild-type ␣B-crystallin promotes xenograft tumor growth and inhibits TRAIL-induced apoptosis in vivo in nude mice, whereas a pseudophosphorylation ␣B-crystallin mutant impaired in its anti-apoptotic function inhibits xenograft tumor growth. Collectively, these findings indicate that ␣B-crystallin is a novel regulator of TRAILinduced apoptosis and tumor growth. Moreover, these results demonstrate that targeted inhibition of ␣B-crystallin promotes TRAIL-induced apoptosis, thereby suggesting a novel strategy to overcome TRAIL resistance in cancer.Tumor necrosis factor-related apoptosis-inducing ligand (TRAIL), 1 also known as Apo2L, is a promising antitumor agent currently in preclinical studies that preferentially induces apoptosis in cancer cells, but not normal cells (1, 2). Like other members of the tumor necrosis factor family of cytokines, TRAIL is a type II transmembrane protein with an extracellular carboxyl terminus that mediates trimerization and receptor binding (3, 4). TRAIL plays a critical role in immune surveillance against tumors: TRAIL-deficient mice are more sensitive to chemical carcinogens and more susceptible to metastasis from mammary carcinoma xenografts (5). Recombinant soluble TRAIL induces apoptosis in many cancer cells in vitro and in vivo, and the native recombinant protein (amino acids 114 -281) appears to be quite tumor-selective (1, 6, 7). In addition, an antibody against one of the receptors of TRAIL (DR5) potently induces apoptosis in human hepatocellular carcinomas in vitro and in vivo, but not in normal human hepatocytes, thereby suggesting an additional therapeutic strategy to activate TRAIL apoptotic signaling (8). Although the mechanisms underlying the differential sensitivity of cancer and normal cells to TRAIL-induced apoptosis are poorly understood, the potential tumor selectivity of TRAIL distinguishes it from many other cancer therapies.TRAIL-induced apoptosis is mediated by the death-inducing signaling complex (DISC), which is composed of the TRAIL death receptors (DR4 and DR5), Fas-associated death domain (FADD), and the apical procaspases-8 and -10 (2). Trimeric TRAIL binds to its dea...

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While high shear alignment has been shown to improve the mechanical properties of single-wall carbon nanotube (SWNT)-polymer composites, this method does not allow for control over the electrical and dielectric properties of the composite and often results in degradation of these properties. Here, we report a novel method to actively align SWNTs in a polymer matrix, which permits control over the degree of alignment of the SWNTs without the side effects of shear alignment. In this process, SWNTs were aligned via AC field-induced dipolar interactions among the nanotubes in a liquid matrix followed by immobilization by photopolymerization under continued application of the electric field. Alignment of SWNTs was controlled as a function of magnitude, frequency, and application time of the applied electric field. The degree of SWNT alignment was assessed using optical microscopy and polarized Raman spectroscopy, and the morphology of the aligned nanocomposites was investigated by high-resolution scanning electron microscopy. The structure of the field induced aligned SWNTs was intrinsically different from that of shear aligned SWNTs. In the present work, SWNTs are not only aligned along the field, but also migrate laterally to form thick, aligned SWNT percolative columns between the electrodes. The actively aligned SWNTs amplify the electrical and dielectric properties of the composite. All of these properties of the aligned nanocomposites exhibited anisotropic characteristics, which were controllable by tuning the applied field parameters.