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Biomedical subjects

B Lee

Publications and source records attributed to B Lee.

At least 163 records · Page 9Linked to original sources
PubMed1999

Unique morphological aspects of the rat ventral prostate gland revealed by vascular corrosion casting.

BACKGROUND: There is growing interest as to the potential role of the prostatic vascular system in mediating the effects of androgenic steroids on growth control of the prostate. Here we describe the use of a vascular corrosion casting technique that enables the visual characterization of the vascular system of the rat ventral prostate and the description of some unique morphological features of the mature rat prostate gland that were never previously observed. METHODS: Anesthetized adult male Sprague-Dawley rats were vascularly perfused with a fixative solution and then with a catalyzed methacrylate-based casting solution that was allowed to polymerize in situ. Ventral prostate glands were dissected from these rats and the tissues were subsequently dissolved in a corrosive solution, leaving residual vascular casts. The casts were then examined by scanning electron microscopy for pertinent morphological features. RESULTS: Vascular corrosion casts of individual lobes of the mature rat ventral prostate revealed a complex vascular structure that entered into the prostate near the base of the bladder. The morphological correspondence of the prostatic vasculature to the previously described ductal organization of the prostate was readily apparent. Examination of the entire vascular complex (under low-power scanning electron microscopy) revealed three differing surface features of the tissue and suggested that the glandular elements of the ventral prostate were directionally oriented towards a single surface (the anterior-lateral surface). An opposing face (posterior-medial) of the tissue demonstrated some unique spiral vessels, suggesting the need for a potential stretch-compensation mechanism at the prostate surface immediately adjacent to the bladder. CONCLUSIONS: Vascular casts of the rat ventral prostate gland reveal the obvious ductal organization of the prostatic parenchyma and demonstrate that these ducts are directionally oriented so that the glands of the prostate (at the distal tips of the ducts) uniformly lie near the anterior-lateral surface of the tissue. Unusual spiral arterioles found proximal to the bladder surface suggest that the rat ventral prostate gland has acquired the means to adapt to an anatomical position adjacent to a tissue (bladder) that acutely varies in size during the micturition cycle.

Animals↗
PubMed1999

Ryanodine and inositol trisphosphate receptors are differentially distributed and expressed in rat parotid gland.

The present study examines the cellular distribution of the ryanodine receptor/channel (RyR) and inositol 1,4,5-trisphosphate receptor (InsP3R) subtypes in parotid acini. Using fluorescently labelled 4,4-difluoro-4-bora-3a,4a-diaza-s-indacene-3-propionic acid glycyl-ryanodine (BODIPYtrade mark-ryanodine) and confocal microscopy, RyRs were localized primarily to the perinuclear region (basal pole) of the acinar cell. Ryanodine, Ruthenium Red, cAMP and cADP ribose (cADPR) competed with BODIPY-ryanodine, resulting in a reduction in the fluorescence signal. However, inositol 1,4, 5-trisphosphate [Ins(1,4,5)P3] did not alter the binding of BODIPY-ryanodine. Using receptor-subtype-specific antisera, InsP3Rs (types I, II and III) were located predominantly in the apical pole of the parotid cell. The presence of these three subtypes was confirmed using reverse transcriptase PCR with RNA-specific oligonucleotide probes. Binding studies using a parotid cell-membrane fraction identified and characterized RyRs and InsP3Rs in terms of binding affinity (Kd) and maximum binding capacity (Bmax) and confirmed that cADPR displaces ryanodine from its binding sites. Ruthenium Red and 8-Br-cADP-ribose blocked Ca2+ release in permeabilized acinar cells in response to cADPR and cAMP or forskolin, whereas Ins(1,4,5)P3-induced Ca2+ release was unaffected. The localization of the RyRs and InsP3Rs in discrete regions endow broad areas of the parotid cell with ligand-activated Ca2+ channels. The consequences of the dual activation of the RyRs and InsP3Rs by physiologically relevant stimuli such as noradrenaline (norepinephrine) are considered in relation to Ca2+ signalling in the parotid gland.

Animals↗
PubMed1999

Nitric oxide synthase inhibitors have antidepressant-like properties in mice. 2. Chronic treatment results in downregulation of cortical beta-adrenoceptors.

Down-regulation of cortical beta-adrenoceptors is observed in rodents following chronic treatment with many clinically effective antidepressant therapies. [3H]dihydroalprenolol binding to cortical beta-adrenoceptors was examined in mice treated with the nitric oxide (NO) synthase antagonist N(G)-nitro-L-arginine (L-NNA). Administration of L-NNA (0.1, 0.3 mg/kg) for 21 days produced a significant reduction (28%, 31%, respectively, P<0.05) in [3H]dihydroalprenolol binding to cortical membranes without affecting Kd. Dose 1 mg/kg of L-NNA given chronically also produced a 20% decrease in beta-adrenoceptor density, but this effect was not statistically significant. While chronic treatment with imipramine (15 and 30 mg/kg) produced respectively a 30% and 25% (P<0.05) reduction in the density of [3H]dihydroalpenolol, single injection of either imipramine (15 and 30 mg/kg) or L-NNA (0.1, 0.3, and 1 mg/kg) had no effect on [3H]dihydroalprenolol binding. These findings are consistent with the hypothesis that drugs which can affect the Ca2+ -calmodulin/nitric oxide synthase/guanylyl cyclase signaling pathway may represent a novel approach to the treatment of depression and are congruent with our previous observation, which has demonstrated the antidepressant-like properties of NO synthase inhibitors in the forced swim test.

Adrenergic Uptake Inhibitors↗
PubMed1999

A follower load increases the load-carrying capacity of the lumbar spine in compression.

STUDY DESIGN: An experimental approach was used to test human cadaveric spine specimens. OBJECTIVE: To assess the response of the whole lumbar spine to a compressive follower load whose path approximates the tangent to the curve of the lumbar spine. SUMMARY OF BACKGROUND DATA: Compression on the lumbar spine is 1000 N for standing and walking and is higher during lifting. Ex vivo experiments show it buckles at 80-100 N. Differences between maximum ex vivo and in vivo loads have not been satisfactorily explained. METHODS: A new experimental technique was developed for applying a compressive follower load of physiologic magnitudes up to 1200 N. The experimental technique applied loads that minimized the internal shear forces and bending moments, made the resultant internal force compressive, and caused the load path to approximate the tangent to the curve of the lumbar spine. RESULTS: A compressive vertical load applied in the neutral lordotic and forward-flexed postures caused large changes in lumbar lordosis at small load magnitudes. The specimen approached its extension or flexion limits at a vertical load of 100 N. In sharp contrast, the lumbar spine supported a load of up to 1200 N without damage or instability when the load path was tangent to the spinal curve. CONCLUSIONS: Until this study, an experimental technique for applying compressive loads of in vivo magnitudes to the whole lumbar spine was unavailable. The load-carrying capacity of the lumbar spine sharply increased under a compressive follower load, as long as the load path remained within a small range around the centers of rotation of the lumbar segments. The follower load path provides an explanation of how the whole lumbar spine can be lordotic and yet resist large compressive loads. This study may have implications for determining the role of trunk muscles in stabilizing the lumbar spine.

Adult↗
PubMed1999

GalR mutants defective in repressosome formation.

Transcription repression of the galactose operon of Escherichia coli requires (1) the binding of the GalR repressor to tandem operators flanking the promoters, (2) the binding of histone-like protein, HU, to a site between the GalR-binding sites, and (3) negatively supercoiled DNA. Under these conditions, protein-protein interactions mediate the formation of a nucleoprotein complex in the form of a DNA loop, which we have termed a repressosome. To analyze the structure of the repressosome, we have screened and isolated galR mutants in which single amino acid substitutions in GalR lead to defects in loop formation while the protein's operator-binding activity is retained. The mutant proteins were purified and their properties confirmed in vitro. We verified that in the case of the two stronger mutations, the proteins had secondary structures that were identical to that of wild-type GalR as reflected by circular dichroism spectroscopy. Homology-based modeling of GalR by use of the crystal structures of PurR and LacI has enabled us to place the three sites of mutation in a structural context. They occur in the carboxy-terminal subdomain of the GalR core, are surface exposed, and, therefore, may be involved in protein-protein interactions. On the basis of our model of GalR and its structural alignment with LacI and PurR, we have identified additional residues, the substitution of which leads to a specific defect in repression by looping. The effects of the mutations are the same in the presence of HMG-17, a eukaryotic protein unrelated to HU, which can also mediate GalR-dependent repression of the gal promoter. This observation suggests that the mutations define sites of GalR-GalR interaction rather than HU-GalR interaction in the repressosome.

Bacteriophages↗
PubMed1999

Quantification of CD4, CCR5, and CXCR4 levels on lymphocyte subsets, dendritic cells, and differentially conditioned monocyte-derived macrophages.

CCR5 and CXCR4 are the major HIV-1 coreceptors for R5 and X4 HIV-1 strains, respectively, and a threshold number of CD4 and chemokine receptor molecules is required to support virus infection. Therefore, we used a quantitative fluorescence-activated cell sorting assay to determine the number of CD4, CCR5, and CXCR4 antibody-binding sites (ABS) on various T cell lines, T cell subsets, peripheral blood dendritic cells (PBDC), and monocyte-derived macrophages by using four-color fluorescence-activated cell sorting analysis on fresh whole blood. Receptor levels varied dramatically among the various subsets examined and typically varied from 2- to 5-fold between individuals. CCR5 was expressed at much higher levels in CD4+/CD45RO+/CD62L-true memory cells compared with CD4+/CD45RO+/CD62L+ cells. Fresh PBDC had the highest number of CCR5 ABS among the leukocyte subsets examined but had few CXCR4 ABS, affording a strategy for sort-purifying PBDC. In vitro maturation of PBDC resulted in median 3- and 41-fold increases in CCR5 and CXCR4 ABS, respectively. We found that macrophage colony-stimulating factor caused the greatest up-regulation of both CCR5 and CXCR4 on macrophage maturation (from approximately 5,000 to approximately 50, 000 ABS) whereas granulocyte-macrophage colony-stimulating factor caused a marked decrease of CXCR4 (from approximately 5,000 ABS to <500) while up-regulating CCR5 expression (from approximately 5,000 to approximately 20,000 ABS). Absolute ABS for CD4 and the major HIV-1 coreceptors serve as a more quantitative measure of cell surface expression, and we propose that this be used for future studies looking at the modulation of CD4 or chemokine receptor expression by cytokines, HIV-1 infection, or receptor polymorphisms.

CD4 Antigens↗
PubMed1999

Epitope mapping of CCR5 reveals multiple conformational states and distinct but overlapping structures involved in chemokine and coreceptor function.

The chemokine receptor CCR5 is the major coreceptor for R5 human immunodeficiency virus type-1 strains. We mapped the epitope specificities of 18 CCR5 monoclonal antibodies (mAbs) to identify domains of CCR5 required for chemokine binding, gp120 binding, and for inducing conformational changes in Env that lead to membrane fusion. We identified mAbs that bound to N-terminal epitopes, extracellular loop 2 (ECL2) epitopes, and multidomain (MD) epitopes composed of more than one single extracellular domain. N-terminal mAbs recognized specific residues that span the first 13 amino acids of CCR5, while nearly all ECL2 mAbs recognized residues Tyr-184 to Phe-189. In addition, all MD epitopes involved ECL2, including at least residues Lys-171 and Glu-172. We found that ECL2-specific mAbs were more efficient than NH2- or MD-antibodies in blocking RANTES or MIP-1beta binding. By contrast, N-terminal mAbs blocked gp120-CCR5 binding more effectively than ECL2 mAbs. Surprisingly, ECL2 mAbs were more potent inhibitors of viral infection than N-terminal mAbs. Thus, the ability to block virus infection did not correlate with the ability to block gp120 binding. Together, these results imply that chemokines and Env bind to distinct but overlapping sites in CCR5, and suggest that the N-terminal domain of CCR5 is more important for gp120 binding while the extracellular loops are more important for inducing conformational changes in Env that lead to membrane fusion and virus infection. Measurements of individual antibody affinities coupled with kinetic analysis of equilibrium binding states also suggested that there are multiple conformational states of CCR5. A previously described mAb, 2D7, was unique in its ability to effectively block both chemokine and Env binding as well as coreceptor activity. 2D7 bound to a unique antigenic determinant in the first half of ECL2 and recognized a far greater proportion of cell surface CCR5 molecules than the other mAbs examined. Thus, the epitope recognized by 2D7 may represent a particularly attractive target for CCR5 antagonists.

Amino Acid Sequence↗
PubMed1999

Novel genes in the PAGE and GAGE family of tumor antigens found by homology walking in the dbEST database.

We have developed a computer-based screening strategy to search the dbEST database to find differentiation antigens that are expressed by cancers arising in nonessential normal tissues such as prostate, breast, and ovary (G. Vasmatzis et al., Proc. Natl. Acad. Sci. USA, 95: 300-304, 1998). Here, we report the identification of three new members of the GAGE/ PAGE family, termed XAGEs. XAGE-1 and XAGE-2 are expressed in Ewing's sarcoma, rhabdomyosarcoma, a breast cancer, and a germ cell tumor. We also describe the relationship of the XAGEs to the GAGE/ PAGE family. XAGE-1 and XAGE-2 should be evaluated as possible targets for vaccine-based therapies of cancer.

Amino Acid Sequence↗
PubMed1999

Hepatocyte gene therapy in a large animal: a neonatal bovine model of citrullinemia.

The development of gene-replacement therapy for inborn errors of metabolism has been hindered by the limited number of suitable large-animal models of these diseases and by inadequate methods of assessing the efficacy of treatment. Such methods should provide sensitive detection of expression in vivo and should be unaffected by concurrent pharmacologic and dietary regimens. We present the results of studies in a neonatal bovine model of citrullinemia, an inborn error of urea-cycle metabolism characterized by deficiency of argininosuccinate synthetase and consequent life-threatening hyperammonemia. Measurements of the flux of nitrogen from orally administered 15NH4 to [15N]urea were used to determine urea-cycle activity in vivo. In control animals, these isotopic measurements proved to be unaffected by pharmacologic treatments. Systemic administration of a first-generation E1-deleted adenoviral vector expressing human argininosuccinate synthetase resulted in transduction of hepatocytes and partial correction of the enzyme defect. The isotopic method showed significant restoration of urea synthesis. Moreover, the calves showed clinical improvement and normalization of plasma glutamine levels after treatment. The results show the clinical efficacy of treating a large-animal model of an inborn error of hepatocyte metabolism in conjunction with a method for sensitively measuring correction in vivo. These studies will be applicable to human trials of the treatment of this disorder and other related urea-cycle disorders.

Adenoviridae↗
PubMed1999

Incorporating qualitative knowledge in enzyme kinetic models using fuzzy logic.

Modeling of metabolic pathway dynamics requires detailed kinetic equations at the enzyme level. In particular, the kinetic equations must account for metabolite effectors that contribute significantly to the pathway regulation in vivo. Unfortunately, most kinetic rate laws available in the literature do not consider all the effectors simultaneously, and much kinetic information exists in a qualitative or semiquantitative form. In this article, we present a strategy to incorporate such information into the kinetic equation. This strategy uses fuzzy logic-based factors to modify algebraic rate laws that account for partial kinetic characteristics. The parameters introduced by the fuzzy factors are then optimized by use of a hybrid of simplex and genetic algorithms. The resulting model provides a flexible form that can simulate various kinetic behaviors. Such kinetic models are suitable for pathway modeling without complete enzyme mechanisms. Three enzymes in Escherichia coli central metabolism are used as examples: phosphoenolpyruvate carboxylase; phosphoenolpyruvate carboxykinase; and pyruvate kinase I. Results show that, with fuzzy logic-augmented models, the kinetic data can be much better described. In particular, complex behavior, such as allosteric inhibition, can be captured using fuzzy rules. The resulting models, even though they do not provide additional physical meaning in enzyme mechanisms, allow the model to incorporate semiquantitative information in metabolic pathway models.

Bacterial Proteins↗
PubMed1999

Interferon-gamma upregulates CCR5 expression in cord and adult blood mononuclear phagocytes.

The C-C chemokine receptors CCR5 and CCR3 are fusion coreceptors for human immunodeficiency virus (HIV) entry into macrophages. The regulation of their expression influences infectivity by HIV. We report here that interferon-gamma (IFN-gamma) a cytokine that has bidirectional effects on HIV infection of macrophages, significantly upregulated CCR5 and CCR3 cell surface expression in human mononuclear phagocytes isolated from placental cord blood and adult peripheral blood. Monocytes treated with IFN-gamma showed increased chemotaxis to the CCR5 ligands macrophage inflammatory protein-1alpha (MIP-1alpha) and MIP-1beta, confirming the functional relevance of IFN-gamma-induced CCR5 expression. However, IFN-gamma suppressed HIV entry into macrophages. Interestingly, we demonstrated that IFN-gamma inhibited cell surface expression of CD4, the major receptor for HIV. This finding may explain the suppressive effect of IFN-gamma on HIV entry into macrophages, despite its enhancing effect on the expression of CCR5 and CCR3 by these cells. In addition, IFN-gamma-induced secretion of C-C chemokines (RANTES, MIP-1alpha, and MIP-1beta) by mononuclear phagocytes may also suppress HIV entry into macrophages. These data provide further evidence for cytokine-mediated regulation of CCR5 expression and are consistent with a novel paradigm in which cytokines regulate HIV infection and leukocyte migration by reciprocal and opposing effects on the expression of CD4 and chemokine receptors.

Adult↗
PubMed1999

Coreceptor/chemokine receptor expression on human hematopoietic cells: biological implications for human immunodeficiency virus-type 1 infection.

The recent discovery of chemokine receptors as coreceptors for human immunodeficiency virus-type 1 (HIV-1) entry offers new avenues for investigating the pathogenesis of acquired immunodeficiency syndrome (AIDS)-related cytopenias. To this end, we sought to (1) phenotype human hematopoietic cells for CD4 and the HIV-1 coreceptors CXCR4, CCR5, CCR3, and CCR2b; (2) correlate CD4 and chemokine receptor expression with their susceptibility to HIV-1 infection; and (3) examine any potential interplay between inflammatory cytokines released during HIV-1 infection and regulation of chemokine receptor expression. Fluorescence-activated cell sorting (FACS) analysis of bone marrow mononuclear cells (BMMNC), cells derived from serum-free expanded hematopoietic lineages (colony-forming unit-granulocyte-macrophage [CFU-GM], colony-forming unit-megakaryocyte [CFU-Meg], and burst-forming unit-erythroid [BFU-E]), and CD34(+) cells showed differential expression of chemokine receptors and CD4 with some lineage specificity. Significantly, FACS-sorted CXCR4(+)/CD34(+) cells had the same clonogeneic potential as CXCR4(-)/CD34(+) cells. Reverse transcriptase-polymerase chain reaction (RT-PCR) analysis of FACS-sorted human candidate stem cells (HSC; CD34(+), c-kit+, Rho123(low)) showed the presence of CXCR4 mRNA but not CD4 mRNA. Infection studies with HIV-1 Env-pseudotyped luciferase reporter viruses indicated that X4 Env (CXCR4-using) pseudotypes infected megakaryocytic cells, whereas R5 Env (CCR5-using) pseudotypes did not. Similarly, R5 but not X4 Env-pseudotyped viruses infected granulocyte-macrophage cells in a CD4/CCR5-dependent manner. Erythroid cells were resistant to R5 or X4 viral infection. Finally, we found that gamma-interferon treatment upregulated CXCR4 expression on primary hematopoietic cells. In summary, the delineation of chemokine receptor expression on primary hematopoietic cells is a first step towards dissecting the chemokine-chemokine receptor axes that may play a role in hematopoietic cell proliferation and homing. Furthermore, susceptibility of hematopoietic cells to HIV-1 infection is likely to be more complicated than the mere physical presence of CD4 and the cognate chemokine receptor. Lastly, our results suggest a potential interplay between gamma-interferon secretion and CXCR4 expression.

Chemokines↗
PubMed1999

Trisomy 16q in a female newborn with a de novo X;16 translocation and hypoplastic left heart.

We report a case of a newborn female with minor dysmorphic features and hypoplastic left heart. Chromosome studies showed that she was the carrier of an unbalanced translocation between the X-chromosome and chromosome 16, resulting in monosomy for Xp and trisomy for 16q. Only a handful of partial trisomy 16q cases have been reported in the literature among liveborns. The great majority of these cases have had significant anomalies in contrast to what has been seen in our patient. The absence of dysmorphic features and other significant abnormalities in this case (with the exception to the hypoplastic left heart), suggested that the inactivation of the derivative X chromosome might have played a role in the mild phenotype of this patient. Conventional cytogenetic studies were conducted in this patient in conjunction with fluorescent in situ hybridization studies, which were used to characterize the X inactivation pattern. The studies revealed that the X chromosome material in the derivative chromosome was inactive while the chromosome 16 derived material in the derivative chromosome was early replicating and active in all cells studied.

Chromosome Banding↗
PubMed1999

Improving high-resolution MR bold venographic imaging using a T1 reducing contrast agent.

Recently, a new imaging method was proposed by Reichenbach et al (Radiology 1997;204:272-277) to image small cerebral venous vessels specifically. This method, referred to as high-resolution blood oxygen level-dependent venography (HRBV), relies on the susceptibility difference between the veins and the brain parenchyma. The resulting phase difference between the vessels and the brain parenchyma leads to signal losses over and above the usual T2* effect. At 1.5 T, a rather long TE (roughly 40 msec) is required for this cancellation to become significant, leading to enhanced susceptibility artifacts and a long data acquisition time. In this study, we examine the utility of incorporating a clinically available T1 reducing contrast agent, Omniscan (Sanofi Winthrop Pharmaceuticals, NY, NY), with the HRBV imaging approach to reduce susceptibility artifacts and imaging time while maintaining the visibility of cerebral veins. Using a double-dose injection of Omniscan, we were able to reduce TE from 40 to 25 msec. This led to a decrease in TR from 57 to 42 msec, allowing a 26% reduction in data acquisition time while maintaining the visibility of cerebral venous vessels and reducing susceptibility artifacts. J. Magn. Reson. Imaging 1999;10:118-123, 1999.

Artifacts↗
PubMed1999

Chemokine immunobiology in HIV-1 pathogenesis.

The discovery of HIV-1-suppressive chemokines and the subsequent discovery of their cognate receptors as coreceptors for HIV-1 entry herald a paradigmatic shift in the study of HIV-1 pathogenesis. The presence of polymorphisms in chemokine receptor and chemokine genes associated with altered progression and susceptibility to the HIV-1 disease further underscores the potential importance that chemokines and their cognate receptors play in HIV-1 pathogenesis. It has become increasingly apparent that the immune system maintains a delicate balance between the positive and negative regulators that govern the chemokine and cytokine networks. Here we review the most recent developments in chemokine biology and relate how research into their structure, regulation, and the mechanism of their actions can shed light on the immnunopathogenesis of HIV-1 disease.

Animals↗
PubMed1999

Systemically administered capsazepine prevents the capsaicin-induced functional desensitization and loss of substance P-like immunoreactivity (SP-LI) in guinea-pig bronchi.

In this study, we investigated whether the systemically administered capsazepine can prevent the capsaicin-induced desensitization ex vivo in guinea-pig bronchi. Pretreatment with capsaicin (2.5, 5 and 10 mg/kg, s.c.) induced the functional desensitization and the loss of substance P-like immunoreactivity (SP-LI) with a similar potency (ED50: 3.31 +/- 0.57 and 4.81 +/- 0.89 mg/kg, respectively) in isolated guinea-pig bronchi. Capsazepine (30 mg/kg, s.c.) co-administered with capsaicin (5 mg/kg, s.c.) prevented the capsaicin (5 mg/kg, s.c.)-induced functional desensitization and loss of SP-LI. These results suggest that capsazepine can antagonize systemically the desensitizing action of capsaicin at the level of receptor, preventing the loss of SP-LI and the establishment of functional desensitization in guinea-pig bronchi.

Animals↗
PubMed1999

Differences in phosphorylation of the IL-2R associated JAK/STAT proteins between HTLV-I(+), IL-2-independent and IL-2-dependent cell lines and uncultured leukemic cells from patients with adult T-cell lymphoma/leukemia.

To determine activation status of the IL-2R-associated (Jak/STAT) pathway in the HTLV-I infected cells, we examined tyrosine phosphorylation of Jak3, STAT3, and STAT5 in several HTLV-I(+) T-cell lines and in uncultured leukemic T cells isolated from patients with adult T-cell lymphoma/leukemia (ATLL). Constitutive basal phosphorylation of Jak3 and, usually, STAT3 and STAT5 was detected in all four IL-2-independent cell lines tested, but in none of the three IL-2-dependent cell lines. Similarly, there was no detectable basal phosphorylation of Jak3 and STAT5 in the leukemic cells from ATLL patients (0/8 and 0/3, respectively). However, stimulation with IL-2 resulted in Jak3 and STAT5 phosphorylation in both leukemic ATLL cells and IL-2-dependent lines. Furthermore, expression of SHP-1 phosphatase which is a negative regulator of cytokine receptor signaling, was lost in most IL-2 independent cell lines (3/4) but not in the leukemic ATLL cells (0/3). Finally, the HTLV-I(+) T-cell lines (313) but not the control, HTLV-I(-) T-cell lines were resistant to rapamycin and its novel analog RAD. We conclude that (1) HTLV-I infection per se does not result in a constitutive phosphorylation of the Jak3, STAT3, and STAT5 proteins; (2) malignant transformation in at least some cases of ATLL does not require the constitutive, but may require IL-2-induced, activation of the IL-2R Jak/STAT pathway; and (3) there are major differences in T-cell immortalization mechanism(s) which appear to involve SHP-1 and target molecules for rapamycin and RAD.

DNA-Binding Proteins↗