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R Weil

Publications and source records attributed to R Weil.

At least 37 records · Page 2Linked to original sources
PubMed1997

Control of NF-kappa B activity by the I kappa B beta inhibitor.

The transcription factor NF-kappa B is maintained in an inactive cytoplasmic state by I kappa B inhibitors. In mammalian cells, I kappa B alpha and I kappa B beta proteins have been purified and shown to be the inhibitors of NF-kappa B through their association with the p65 or c-Rel subunits. In addition, we have isolated a third NF-kappa B inhibitor, I kappa B epsilon (1). Upon treatment with a large variety of inducers, I kappa B alpha, I kappa B beta are proteolytically degraded, resulting in NF-kappa B translocation into the nucleus. Here we show that in E29.1 T cell hybridoma I kappa B alpha and I kappa B beta are equally associated with p65 and that I kappa B beta is degraded in response to TNF alpha in contrast to what has been originally published. Our data also suggest that, unlike I kappa B alpha, I kappa B beta is constitutively phosphorylated and resynthesized as a hypophosphorylated form. The absence of slow migrating forms of I kappa B beta following stimulation suggests that the phosphorylation does not necessarily constitute the signal-induced event which targets the molecule for proteolysis.

Animals↗
PubMed1996

Association of tyrosine protein kinase Zap-70 with the protooncogene product p120c-cbl in T lymphocytes.

Accumulating data show that the tyrosine protein kinase Zap-70 plays an essential role in T cell receptor-mediated signal transduction. However, the model of action, as well as the physiologically relevant substrates of Zap-70, have not been determined. We have attempted to identify a 120-kD tyrosine-phosphorylated protein (p120) that associates with Zap-70 in activated T lymphocytes. The results of our analyses showed that p120 is largely encoded by the c-cbl protooncogene. Furthermore, the association of Zap-70 with c-Cbl was shown to be induced by T cell receptor stimulation, implying that it required posttranslational modification of one or both of these products. FynT, but not Lck, also associated with c-Cbl in activated T cells. Finally, using a heterologous system, it was demonstrated that the ability of Zap-70 to cause tyrosine phosphorylation of p120c-cbl was dependent on Lck- or FynT-mediated signals. As c-Cbl can associate with several other signaling molecules, it may couple Zap-70 to downstream effectors during T cell activation.

Animals↗
PubMed1995

Regulation of Zap-70 by Src family tyrosine protein kinases in an antigen-specific T-cell line.

To further understand the interactions between Zap-70, Src family kinases, and other T-cell proteins, we have examined the regulation of Zap-70 in the antigen-specific T-cell line BI-141. By analyzing derivatives containing an activated version of either p56lck or p59fynT, it was observed that the two Src-related enzymes augmented T-cell receptor (TCR)-mediated tyrosine phosphorylation of Zap-70, as well as its association with components of the antigen receptor complex. Importantly, the accumulation of TCR.Zap-70 complexes quantitatively and temporally correlated with the induction of tyrosine phosphorylation of the CD3 and zeta chains of TCR. Using a CD4-positive variant of BI-141, we also found that the ability of Zap-70 to undergo tyrosine phosphorylation and associate with TCR was enhanced by aggregation of TCR with the CD4 co-receptor. Further studies allowed the identification of two distinct pools of tyrosine-phosphorylated Zap-70 in activated T-cells. While one population was associated with TCR, the other was co-immunoprecipitated with a 120-kDa tyrosine-phosphorylated protein of unknown identity. In addition to supporting the notion that Src-related enzymes regulate the recruitment of Zap-70 in TCR signaling, these data added further complexity to previous models of regulation of Zap-70. Furthermore, they suggested that p120 may be an effector and/or a regulator of Zap-70 in activated T-lymphocytes.

Animals↗
PubMed1994

Intramolecular and extramolecular mechanisms repress the catalytic function of p56lck in resting T-lymphocytes.

Accumulating data show that the catalytic function of the Src-related tyrosine protein kinase p56lck is repressed by phosphorylation of a conserved carboxyl-terminal tyrosine residue (tyrosine 505). However, previous findings (Abraham, N., Miceli M.C., Parnes, J.R., and Veillette, A. (1991) Nature 350, 62-66) suggest that mechanisms unrelated to tyrosine 505 phosphorylation repress the catalytic function of p56lck in resting T-cells. In keeping with this view, we report herein that the Src homology 3 (SH3) and SH2 domains negatively regulate the catalytic activity of p56lck, by a process independent of carboxyl-terminal tyrosine phosphorylation. While the exact mechanism of this inhibition are not established, its structural requirements in the SH2 domain are distinct from those allowing recruitment of Lck in T-cell receptor signaling. In addition, we obtained evidence that the elevated tyrosine protein phosphatase activity present in T-cells also contributes to inhibit the enzymatic function of p56lck. Such an effect is seemingly mediated by dephosphorylation of tyrosine 394, the site of positive regulation of p56lck. Collectively, these results indicate that the catalytic function of p56lck in resting T-cells is repressed by a complex set of processes, which involves both intramolecular and extramolecular mechanisms.

3T3 Cells↗
PubMed1993

Ig CDR3-like region of the CD4 molecule is involved in HIV-induced syncytia formation but not in viral entry.

The HIV1 envelope glycoprotein gp120 binding site has been previously mapped by genetic studies to the CDR2-like region of the first domain of the CD4 molecule. mAb reactive with epitopes linked to this region (e.g., OKT4A) inhibit both HIV entry into CD4-positive cells and syncytia formation. A second area of this domain, the CDR3-like region, has been shown to be involved in gp120-CD4 interactions, but its role remained so far unclear. We show here that a mAb specific for the CDR3-like region of the CD4 receptor, 13B8-2, actually blocks soluble gp120 binding to CD4, inhibits HIV-induced cell-cell fusion, and prevents viral production by infected cells. However, this mAb fails to inhibit the binding of viral particles to cell-surface CD4 and their entry into CD4-positive cells. These results strongly suggest i) that soluble gp120 and virion-anchored gp120 bind CD4 in distinct manners, ii) that gp120-CD4 interactions required for viral entry and syncytia formation are different, and iii) that mAb binding to the CDR3-like region of the first domain of CD4 affects a post-entry step of the HIV replicative cycle.

Antibodies, Monoclonal↗
PubMed1993

Interactions of the SH2 domain of lymphocyte-specific tyrosine protein kinase p56lck with phosphotyrosine-containing proteins.

We have previously demonstrated that the non-catalytic Src homology 2 (SH2) domain is required for both positive and negative regulation of the catalytic function of the lymphocyte-specific tyrosine protein kinase p56lck. Indeed, the ability of activated p56lck molecules (tyrosine 505 to phenylalanine 505 mutants) to enhance T-cell receptor (TCR)-induced tyrosine protein phosphorylation is dramatically reduced by deletion of the SH2 domain. Paradoxically, removal of the SH2 sequence also results in constitutive elevation of the catalytic function of wild-type Lck polypeptides, rendering them capable of oncogenic transformation of rodent fibroblasts. As SH2 sequences can mediate binding to phosphotyrosine-containing peptides, the ability of the Lck SH2 domain to interact with tyrosine-phosphorylated proteins was tested. We found that the SH2 sequence of p56lck can bind several of the TCR-regulated tyrosine phosphorylation substrates in vitro. One of the substrates, an 80-kilodalton (kDa) phosphoprotein (p80) showed the tightest binding to the SH2 domain of Lck. Additionally, it was observed that the SH2 domain of Lck can bind a synthetic peptide containing the phosphorylated carboxy-terminal tyrosine 505 of p56lck. Indirect evidence indicating that the SH2 region interacts with the tyrosine-phosphorylated carboxy terminus of Lck in vivo was also obtained. As deletion of the SH2 domain or mutation of tyrosine 505 results in p56lck activation in vivo, it is conceivable that interactions between these two regions impose a conformation that is unfavorable to phosphorylation of intracellular substrates. Collectively, these findings suggest that the SH2 domain modulates the catalytic function of Lck through complex interactions with phosphotyrosine-containing proteins.

Animals↗
PubMed1992

Parathyroid anatomy in hyperplasia.

Pathologically enlarged parathyroid glands offer the surgeon a vital medium for studying parathyroid anatomy. The advantages include gland magnification, rapid-section diagnosis to aid dissections, and postoperative clinical and laboratory responses to check for "missed" or supernumerary glands. In this series, each of 71 patients had at least four hyperplastic glands. Both mediastinal and intrathyroidal glands occurred in nine instances (13%), supernumerary glands in eight (11%), and ectopic neck glands in seven (10%). In total, anomalous parathyroid glands occurred in almost half (46%) of these patients with parathyroid hyperplasia.

Humans↗
PubMed1992

Cyclosporin A and FK506 prevent the derepression of the IL-2 gene in mitogen-induced primary T lymphocytes.

In resting primary T lymphocytes the interleukin 2 (IL-2) gene is silenced by a repressor binding to the Pud element spanning positions -292 to -264 upstream of the cap site. Upon T-cell activation, this silencer is displaced by a positive transcription factor (TF) and the gene is derepressed and transcribed. Cyclosporin A (CsA) and FK506 interfere with normal derepression of the IL-2 gene. Both drugs exert no direct effect on basal transcription of the IL-2 or control viral genes. Direct addition does not abolish the active state of positive TFs present in proteins from activated T cells. However, if T cells are activated in the presence of either drug, their proteins not only fail to derepress, but efficiently and irreversibly silence IL-2 transcription. DNA-protein binding data show that proteins present in drug-treated cells form retarded complexes corresponding in size to the silencer and positive TF. Thus, in drug-treated cells a functional silencer persists, and a positive TF-like factor appears which is functionally abnormal. Moreover, drug-treated T cells appear to form a component that prevents functioning of normal positive TF.

Animals↗
PubMed1992

Clinical, epidemiologic, and virologic studies in four clusters of the chronic fatigue syndrome.

BACKGROUND: The purpose of this study is to provide a case definition of chronic fatigue syndrome in an outbreak occurring in the Nevada-California region to evaluate candidate etiologic agents and observe the natural history of the illness. METHODS: Patients diagnosed as having chronic fatigue syndrome were studied by repeated interviews, questionnaires, and blood collection over a 3-year period. Serum samples were tested for antibodies to Epstein-Barr virus, human herpesvirus-6, and human T-lymphotropic viruses I and II. Leukocytes from typical cases were also assayed for human T-lymphotropic viruses I and II. RESULTS: Cases were defined as persons who had: (1) severe persistent fatigue following an acute illness appearing in an individual with no previous physical or psychological symptoms; (2) presenting signs and symptoms of an acute infection; (3) severe and persistent headache and/or myalgias; and (4) abrupt change in cognitive function or the appearance of a new mood disorder. After 3 years of follow-up, almost all study subjects were able to return to pre-illness activity. None of the viruses evaluated--human T-lymphotropic viruses I and II, Epstein-Barr virus, or human herpesvirus-6--could be etiologically linked to these outbreaks. CONCLUSION: Clinical features of outbreaks of chronic fatigue syndrome differ sufficiently to suggest different etiologic agents. Giardiasis appears to have precipitated one of the four clusters in this study but the cause(s) of the other three outbreaks is as yet uncertain. The overall prognosis of chronic fatigue syndrome is usually favorable.

Antibodies, Viral↗
PubMed1991

Silencing and trans-activation of the mouse IL-2 gene in Xenopus oocytes by proteins from resting and mitogen-induced primary T-lymphocytes.

The Xenopus oocyte system was used to test functionally, putative trans-active elements involved in the transcriptional control of the mouse interleukin-2 (IL-2) gene in resting and mitogen-induced primary T-lymphocytes. The IL-2 gene injected into the oocyte is active over a wide range of DNA concentrations. This basal activity is silenced by the addition of protein extracts from G0-arrested spleen cells. Extracts from 8 h-stimulated spleen cells do not silence but moderately increase transcription over basal level. When IL-2 transcription is silenced first by an injection of extract from resting spleen cells, the addition of proteins from stimulated cells results in a strong increase in transcription (derepression). Use of proteins from purified splenic T-lymphocytes shows that both silencer(s) and activator(s) are contributed by these cells. Extracts from control tissues have neither a silencing nor stimulatory effect. None of the proteins tested affects the activities of co-injected control genes. Injections with IL-2 promoter mutants indicate that the main target sequence of the silencing and activating factors is a purine region (Pu-box) lying between positions -261 and -292 upstream of the IL-2 gene. Bandshift assays show differential binding of the Pu-box with proteins from resting or activated T-cells.

Animals↗
PubMed1991

[Laparoscopic cholecystectomy].

The standard treatment for cholelithiasis is cholecystectomy at open operation, which requires relatively long hospitalization and long absence from work. These socio-economic factors and a desire to avoid operative trauma and its complications led to the development of noninvasive therapy. The methods used so far, stone dissolution and extracorporeal shock wave lithotripsy, have proven unsatisfactory. The first takes a long time and has a high recurrence rate, the second has relatively frequent complications. Furthermore, both methods leave the diseased gallbladder in place. During the past year laparoscopic cholecystectomy has been developed in various centers and has been adopted in our department. We describe our initial experience with the technique in 70 cases aged 18-79 years.

Adult↗