Biomedical subjects

H M Johnson

Publications and source records attributed to H M Johnson.

At least 37 records · Page 2Linked to original sources

PubMed1998

IFNgamma induction of p21WAF1 in prostate cancer cells: role in cell cycle, alteration of phenotype and invasive potential.

Type I and type II interferons (IFNs) are known to exert antitumor effects on a variety of tissues and cell types. We have previously shown that the type I IFN IFN alpha induces the expression of the cyclin-dependent kinase inhibitor p21WAF1 and inhibits the cell cycle of the human prostate adenocarcinoma cell line, DU145, that carries mutations in the tumor suppressor gene products p53 and pRB. We now show that the type II IFN IFN gamma similarly induces the expression of p21WAF1 and inhibits the cell cycle of DU145 cells. In addition, we show that while both IFNs exert antiproliferative activity, only IFN gamma induced phenotypic changes in these cells that accompanied the antiproliferative effect. For example, IFN gamma, but not IFN alpha, caused a significant reduction in epidermal growth factor receptor expression as well as an increase in the adhesion molecules intercellular adhesion molecule-1 and integrin alpha3. These phenotypic changes in DU145 cells are suggestive of the acquisition of a non-tumorigenic state. Consistent with these findings, IFN gamma showed a significantly lower invasive ability in in vitro assays using invasion chambers. Thus, IFN gamma inhibits both the cell cycle and the metastatic potential of DU145 cells independent of the p53 and RB status, and our data describe a mechanism for mediating the antitumor capabilities of IFN gamma that bypasses tumor suppressor genes like p53.

Cell Cycle↗

PubMed1998

IFN-tau suppresses both the autoreactive humoral and cellular immune responses and induces stable remission in mice with chronic experimental allergic encephalomyelitis.

We have previously shown that interferon-tau (IFN-tau) pretreatment inhibits the development of both acute and chronic mouse experimental allergic encephalomyelitis (EAE), an animal model for the human demyelinating disease multiple sclerosis (MS). IFN-tau is a type I IFN that has pregnancy recognition hormone activity in ruminants. Here we show that IFN-tau induced remission in SJL/J mice that had ongoing chronic active EAE disease and protected mice against secondary relapses. IFN-tau treatment reversed lymphocyte infiltration and microglial activation in the central nervous system. Mice that were treated with IFN-tau had lower levels of anti-MBP antibodies than untreated mice in both chronic and acute forms of EAE. MBP induced proliferation in B cells from EAE mice, but treatment with IFN-tau either in vivo or in vitro blocked activation. Furthermore, IFN-tau inhibited MBP activation of T cells from EAE mice. Thus, IFN-tau inhibits the humoral arm as well as the cellular arm of the autoimmune disease EAE. The data presented here show that IFN-tau inhibits both B cell and T cell responses in EAE as well as active, chronic EAE, and this may help explain the effectiveness of type I IFNs in treatment of MS.

Animals↗

PubMed1998

Type I interferon induction of the Cdk-inhibitor p21WAF1 is accompanied by ordered G1 arrest, differentiation and apoptosis of the Daudi B-cell line.

We show, in this study, that type I IFN induction of the cyclin-dependent kinase (cdk) inhibitor p21WAF1 in the human Burkitt lymphoma B cell-line Daudi and ensuing cell cycle arrest correlate with the terminal differentiation of these cells, and is ultimately followed by apoptosis and cell death. The expression of p21WAF1 paralleled the onset of G1 arrest and the reduction of surface IgM expression which was used as a marker of the differentiation response, and the IFN treated cells acquired a typical plasma cell-like morphology. The type II IFN IFNgamma, which does not inhibit the growth of Daudi cells, did not induce the expression of p21WAF1, nor affect the expression of surface IgM. The induction of p21WAF1 which paralleled the inhibition of the phosphorylation of the retinoblastoma protein, pRB, was preceded by the strong reduction in c-myc levels. We propose that the coupled down-regulation of c-myc and induction of p21WAF1 may be crucial to the induction of differentiation and G1 arrest in Daudi cells by type I IFN. Growth arrest and differentiation was followed by apoptosis and cell death, and was accompanied by the induction of the activity of the apoptotic ICE-family protease CPP32. G1 arrest and differentiation followed by apoptotic cell death are characteristics of terminal differentiation. Thus, our data suggest that the induction of p21WAF1 and G1 arrest mediated by type I IFN in Daudi cells is part of terminal differentiation response in these cells, highlighting a role for type I IFN as B cell terminal differentiation factors.

Apoptosis↗

PubMed1998

Cytokine-receptor complexes as chaperones for nuclear translocation of signal transducers.

A variety of ligands that include interleukins, interferons, and growth hormones activate STAT transcriptions factors. When activated, STATs are translocated to the nucleus apparently through the well described importin/Ran system where they activate target genes. Molecules utilizing this nuclear import system require specific nuclear localization sequences (NLSs). Paradoxically, such NLSs are not identifiable on STATs, raising the question of how they are imported into the nucleus. Surprisingly, most ligands and/or receptors that signal through STATs contain putative NLSs, and where examined either ligand or receptor undergo nuclear translocation. We hypothesize that these ligands and/or their receptors serve as chaperones in the nuclear translocation of STATs, and that they may be directly involved in signal transduction. Using IFN gamma as a model system we provide a possible mechanism for how this direct role is fulfilled. A C-terminal domain of IFN gamma has been identified that contains a functional NLS. Besides the fact that this domain, and the NLS in particular, is crucial for the biological properties of IFN gamma, a peptide encompassing this domain is sufficient to induce an antiviral state. Moreover, this domain interacts exclusively with an internal cytoplasmic domain of a subunit of the receptor complex in a region that is directly involved in the recruitment and activation of the elements of the JAK/STAT pathway. We suggest that this novel mode of receptor recognition and activation may be a driving force for nuclear translocation of molecules like STATs that are associated with the ligand-receptor complex.

Amino Acid Sequence↗

PubMed1998

Human IFN gamma receptor cytoplasmic domain: expression and interaction with HuIFN gamma.

To investigate the structural basis for human interferon gamma (huIFN gamma) binding to intracellular regions of the human IFN gamma receptor (huIFN gamma R), we have subcloned and expressed the huIFN gamma R free of fusion proteins in the yeast strain Pichia pastoris. HuIFN gamma bound to the cytoplasmic domain of the receptor via the IFN gamma C-terminus. Binding was inhibited by both human and mouse C-terminus peptides. N-terminus peptides failed to inhibit cytoplasmic binding. Thus, while extracellular receptor domain binding is species specific, binding to the cytoplasmic domain of the receptor is species non-specific. In solid-phase binding assays, IFN gamma had a Kd of 3.7 x 10(-8) M for the newly expressed cytoplasmic domain. Peptide competitions showed that IFN gamma bound to a receptor site corresponding to the membrane proximal residues 253-287, which is adjacent to the site of binding of the tyrosine kinase JAK2. The cytoplasmic binding affinity and binding site specificity suggest that the huIFN gamma R cytoplasmic domain can function independent of the extracellular domain to bind huIFN gamma and induce the biological activity previously associated with internalized huIFN gamma.

Animals↗

PubMed1998

Modulation of disease by superantigens.

Increasing evidence suggests that bacterial and viral superantigens are involved in immune-mediated disease. Studies using an animal model for multiple sclerosis show that superantigens can induce relapses and bring into play autoreactive T cells with restricted usage of T cell receptor V beta families that may be indirectly involved in the initial episode of disease. This may also involve epitope spreading. Superantigens have also been implicated in other autoimmune diseases such as rheumatoid arthritis and psoriasis. Superantigens encoded by viruses such as mouse mammary tumor virus play an important role in disease progression.

Animals↗

PubMed1998

Updating accounts following a correction of misinformation.

The research examined whether corrected misinformation influences anaphoric inferences people make during subsequent reading. Participants read a set of corrected-misinformation and no-misinformation stories and made judgments about probe words that were either appropriate or inappropriate anaphoric referents. At a short delay, the results showed less activation for appropriate referents that were corrections of misinformation. At longer delays, the activation of appropriate referents showed no significant difference, but misinformation probes were more quickly recognized than were inappropriate referents that were incidentally mentioned in control story versions. In all conditions, appropriate referents showed more activation than inappropriate ones. The results suggest that corrected misinformation can continue to influence on-line reading processes.

Adult↗

PubMed1998

Mechanism of HIV pathogenesis: role of superantigens in disease.

Initial infection with human immunodeficiency virus (HIV) results in a burst of viremia and an ensuing spread of virus to secondary lymphoid organs, after which a "latency" period occurs with little or no virus detectable in the circulation. The term latent period has been shown to be a misnomer, because substantial viral replication occurs during this time in lymph nodes, although clinically there appears to be few symptoms of disease. However, a telling indicator of active infection during this period is the initiation of decline in CD4+ T-cell numbers. A number of hypotheses have been postulated for the mechanism(s), as of yet not fully elucidated, by which T cells are depleted. Although quiescent cells can be infected, it has been shown that replication of HIV in CD4+ T cells requires cellular activation. The levels of viremia early in infection indicate that a large number of cells are actively infected, further suggesting that a mechanism must exist by which HIV activates a large pool of cells and ultimately causes their depletion. One possible mechanism for activation would be the presence of an HIV-encoded superantigen. Superantigens are proteins that are polyclonal stimulators of CD4+ T lymphocytes. This occurs as a result of their ability to form a trimolecular complex with MHC class II molecules on antigen-presenting cells and the Vbeta-specific region on the T-cell receptor. Thus, superantigen activation of T cells is antigen-nonspecific. The prototype superantigens are the staphylococcal enterotoxins. Putative viral superantigens include a protein from mouse mammary tumor virus and related retroviruses, rabies nucleocapsid, and the Nef protein of HIV. Nef is required for optimal HIV pathogenesis, and this may be due to its superantigen properties, where CD4 cells are transformed to the activated state for virus replication.

Animals↗

PubMed1998

Immunomodulating functions of recombinant ovine interferon tau: potential for therapy in multiple sclerosis and autoimmune disorders.

The interferons (IFN) are a family of complex proteins possessing antiviral, antiproliferative, and immunomodulatory activities. Two type I recombinant human IFN have been recently approved for the treatment of multiple sclerosis (MS). However, use of high dose type I IFN treatment in MS patients has been limited by dose-related toxicity. Ovine IFN tau is a unique type I interferon discovered for its role in the animal reproductive cycle. It differs from other type I IFNs in that it is remarkably less toxic even at high concentrations, is able to cross species barriers, and is not inducible by viral infection. Ovine IFN tau has been shown to be very effective in the treatment of animal models of MS. In this study, we examined the toxicity of OvIFN tau on human T-cells at high doses and its immunregulatory properties at equivalent doses. Our experiments confirmed the remarkably non-toxic nature of OvIFN tau on human cells at high concentrations as well as immunomodulating properties consistent with other type I IFNs including an antilymphoproliferative effect and inhibition of IFN gamma-induced HLA class II expression. These results suggest that OvIFN tau could be developed into a potentially less toxic therapeutic option for immune-mediated disorders including MS.

Antigen Presentation↗

PubMed1998

Hypothesis: ligand/receptor-assisted nuclear translocation of STATs.

The STAT transcription factors are mediators of signal transduction of a variety of factors, including interferons (IFNs), interleukins, growth factors, and peptide hormones. Subsequent to activation, STATs are translocated to the nucleus apparently through the well-described importin/Ran system, where they activate target genes. Molecules utilizing this nuclear import system require specific nuclear localization sequences (NLSs). Paradoxically, such NLSs are not identifiable on STATs, thus raising the question of how they are imported into the nucleus. Of considerable interest is the observation that ligands and/or receptors that signal through STATs contain putative NLSs and, where examined, either ligand or receptor undergoes nuclear translocation. We hypothesize that ligands and/or their receptors serve as vehicles for the nuclear translocation of STATs, and that they may be directly involved in signal transduction. Using IFNgamma as a model system, we provide a possible mechanism for how this direct role is fulfilled. A functional NLS has been identified in a C-terminal domain of IFNgamma. This domain and the NLS contained within are crucial for the biological properties of IFNgamma in that a peptide encompassing this domain is sufficient to induce an antiviral state. Further, this domain binds specifically to a membrane-proximal region internal cytoplasmic domain of the alpha subunit of the receptor complex in a region that is directly involved in the recruitment and activation of the JAK/STAT pathway. We suggest that this novel mode of receptor recognition and activation may be a driving force for nuclear translocation of molecules like STATs that are associated with the ligand-receptor complex.

Amino Acid Sequence↗

PubMed1997

The solution structure of a class II major histocompatibility complex superantigen binding domain.

We have used 600 MHz 1H NMR spectroscopy data to determine the solution structure of a 31-residue domain of a murine class II major histocompatibility (MHC) protein. This domain, I-Ab(beta)-(60-90), binds to the superantigen staphylococcal enterotoxin A. Distance geometry and dynamical simulated annealing calculations were performed using NOESY- and COSY-deduced constraints. I-Ab(beta)-(60-90), which is mostly alpha-helical, is more similar to the corresponding region of the class II MHC protein HLA-DR1 than to the class I MHC protein HLA-A2. Arg-72 and Arg-80 lie on the same side of the helix and face away from the antigenic peptide binding groove. His-81, implicated in both superantigen and peptide binding, is located midway between the surface defined by Arg-72/Arg-80 and residues that define the inside of the peptide binding groove, allowing for its participation in both types of binding.

Amino Acid Sequence↗

PubMed1997

Potent anti-feline immunodeficiency virus and anti-human immunodeficiency virus effect of IFN-tau.

Ovine IFN-tau is a newly described protein related to IFN-alpha that is responsible for maternal recognition of pregnancy in sheep. It has been shown to exhibit potent antiviral and antiproliferative activity. To determine its antiviral activity against feline immunodeficiency virus (FIV) and HIV, the activity of the RNA-dependent DNA polymerase, reverse transcriptase, was assayed in FIV- and HIV-infected feline and human PBL treated with IFN-tau. Significant dose-dependent inhibition of reverse transcriptase activity by IFN-tau was detected by day 6 of culture and was maintained through the peak of virus replication. In addition, production of the FIV core protein, p25, was blocked by IFN-tau. Both the amino- and carboxyl-terminal regions of IFN-tau, as identified by synthetic peptides, appear to be involved in its antiretroviral activity. Comparison of the anti-HIV activities of IFN-tau and recombinant human IFN-alpha2 (rHuIFN-alpha2) indicated that while rHuIFN-alpha2 was toxic to cells at 10,000 U/ml, IFN-tau antiretroviral activity was not associated with a decrease in either cell viability or immunologic reactivity. Thus, IFN-tau displayed potent anti-FIV and anti-HIV activity without the cytotoxicity associated with high concentrations of rHuIFN-alpha2.

Animals↗

PubMed1997

IFNalpha induces the expression of the cyclin-dependent kinase inhibitor p21 in human prostate cancer cells.

Prostate cancer, like other types of cancer, is associated with the loss of cell cycle control, resulting in unregulated growth of cells. We report here on the inhibitory effects of interferon alpha (IFN alpha) on the cell cycle of prostate cancer cells, using the human prostate carcinoma cell line DU145 that has mutations in the tumor suppressor genes pRB, p53 and KAI1. IFN alpha inhibited growth and colony formation of DU145 cells and analysis by flow cytometry suggests that IFN alpha inhibited the progression of these cancer cells from the G1 through S phase of the cell cycle. IFN alpha treatment of DU145 cells reduced cyclin dependent kinase 2 (cdk2) activity. In particular, cyclin E dependent cdk2 activity was inhibited by IFN alpha treatment. IFN alpha treatment, however, did not affect the amount of cdk2 bound to cyclin E. Consistent with this data, IFN alpha was able to induce expression of the kinase inhibitor p21 in DU145 cells. Furthermore, IFN treatment increased the amounts of p21 complexed with cdk2 in these cells. These data support a role for p21 in mediating the antiproliferative action of IFN alpha. The induction of p21 and its growth inhibitory effects in DU145 cells appears independent of p53, pRB and KAI1 status.

Antineoplastic Agents↗

PubMed1997

V beta activation by HIV Nef protein: detection by a simple amplification procedure.

We previously reported that Nef protein from human immunodeficiency virus (HIV) has superantigen properties. However, we were unable to consistently demonstrate V beta-specific expansion by Nef using flow cytometry, possibly due to its lower mitogenic activity compared to prototypic superantigens. Therefore, we developed a simple amplification detection method using immobilized anti-V beta antibodies. Human peripheral blood mononuclear cells from adult donors were treated for 24 h with Nef and restimulated with immobilized anti-V beta antibodies for an additional 72 h. Significant expansion of V beta 5.3 and V beta 18 T-cells were detected in Nef-treated cultures, with expansion of V beta 18 occurring with all donors tested, and V beta 5.3 expansion occurring in 50% of the donors. Variable responses were obtained with V beta 2, V beta 3, and V beta 9. These results were confirmed using the more time-consuming method of reverse transcriptase-polymerase chain reaction (RT-PCR). Thus, this novel, reproducible, and relatively simple method can detect V beta-specific expansion by weak superantigens.

Adult↗

PubMed1997

CD4 T suppressor cells mediate interferon tau protection against experimental allergic encephalomyelitis.

Interferon tau is a type I IFN that was originally identified as a pregnancy recognition hormone produced by trophoblast cells. It is as potent an antiviral agent as IFN alpha and IFN beta, but lacks the toxicity associated with high concentrations of these IFNs in tissue culture and in animal studies. We recently showed that IFN tau, like IFN beta, can prevent the development of experimental allergic encephalomyelitis (EAE). We report here that IFN tau prevents EAE in mice by induction of suppressor cells and suppressor factors. Suppressor cells can be induced by IFN tau in tissue culture, and in vivo by either intraperitoneal injection or by oral administration to mice. Incubation of suppressor cells with myelin basic protein (MBP)-sensitized T cells blocked or delayed the MBP-induced proliferation. Further intraperitoneal injection of suppressor cells into mice blocked induction of EAE by MBP. Suppressor cells possessed the CD4 T cell phenotype, and produced soluble suppressor factors that inhibited MBP activation of T cells from EAE mice. The suppressor factors were found to be IL-10 and TGF beta, which acted synergistically to inhibit the MBP activation of T cells from EAE mice. These findings are important for understanding the mechanism(s) by which type I IFNs protect against autoimmune disease.

Animals↗

PubMed1997

Oral feeding of interferon tau can prevent the acute and chronic relapsing forms of experimental allergic encephalomyelitis.

IFN tau is a member of the type I IFN family but unlike IFN alpha and IFN beta, IFN tau lacks toxicity at high concentrations. Recently, ovine IFN tau was shown to prevent acute induction and superantigen reactivation of experimental allergic encephalomyelitis (EAE), an animal model for multiple sclerosis (MS). In this report, we examined the ability of IFN tau when administered by oral feeding to block development of EAE. Oral feeding of INF tau prevented paralysis in the acute form of EAE in NZW mice and chronic-relapsing EAE in SJL/J mice. In addition, oral feeding of IFN tau at 10(5) U/dose was as effective as intraperitoneal (i.p.) injection in preventing chronic-relapsing EAE, and both forms of IFN tau administration resulted in IL10 production. Histological examination revealed no inflammatory lymphocytic infiltration to the CNS in IFN tau treated animals as compared to controls. Prolonged treatment of IFN tau was shown to be necessary for chronic-relapsing EAE since removal of IFN tau treatment by either oral feeding or i.p. injection resulted in onset of disease. Lastly, sera from SJL/J mice which received prolonged IFN tau treatment by oral feeding exhibited little to no development of anti-IFN tau antibodies. Thus, oral feeding of ovine IFN tau may be a successful form of IFN tau administration for treatment of autoimmune diseases such as MS and may circumvent potentially debilitative antibody responses.

Acute Disease↗

PubMed1997

Superantigens as virulence factors in autoimmunity and immunodeficiency diseases.

Virulence factors are microbial products that are known to be harmful to the host and may assist in the pathogenesis of the micro-organism. Superantigens, including those produced by bacteria and viruses, clearly act as virulence factors. The clinical effects of superantigens can be not only acute but also chronic and complex. Recent evidence suggests that superantigens may play a central role in the pathogenesis of autoimmune and immunodeficiency disorders. It is our contention that superantigens, as environmental factors, can change a controllable disease into one that becomes relentless for susceptible individuals. To illustrate the detrimental effects of superantigens on disease outcome, modulation of experimental allergic encephalomyelitis by superantigen, as well as the potential role of superantigens in human immunodeficiency virus pathogenesis will be discussed. The information presented may provide valuable insight into the role of superantigens in autoimmunity and human immunodeficiency virus infection.

Animals↗

PubMed1997

A role for the cyclin-dependent kinase inhibitor p21 in the G1 cell cycle arrest mediated by the type I interferons.

Type I interferons (IFN), such as IFN-alpha, are potent antiproliferative and antitumor agents. IFN-tau, originally identified as a pregnancy recognition hormone, is a type I IFN that is related to IFN-alpha. We examine here the mechanism of the antiproliferative effects of IFN-alpha and IFN-tau in terms of their effects on intracellular events that regulate the cell cycle. Both IFN inhibited proliferation of the human Burkitt lymphoma cell line, Daudi, causing accumulation of cells in the G1 phase of the cell cycle. IFN-alpha was more effective than IFN-tau in this regard. Both IFN were found to inhibit the kinase activity of the cyclin-dependent kinase cdk2 in a manner that correlated with their relative abilities to cause cells to accumulate in the G1 phase of the cell cycle. Further, IFN treatment did not affect the expression of cdk2 protein, suggesting that the IFN modulated cdk2 activity through a cdk inhibitor. Consistent with this conclusion, both IFN induced the expression of the cyclin-dependent kinase inhibitor protein p21. The levels of p21 induced also correlated with the relative abilities of the IFN to inhibit cdk2 activity and to arrest cell growth in the G1 phase of the cell cycle. Moreover, following IFN treatment, increased levels of p21 were found complexed with cdk2, consistent with its role in the inhibition of cdk2 activity. These data suggest that p21-mediated inhibition of cdk2 activity plays an important role in the antiproliferative activity of type I IFN. The findings highlight interesting similarities between these cytokines and the products of tumor suppressor genes, such as p53, and may indicate a mechanism for the antitumor effects of the type I IFN.

Antineoplastic Agents↗