bluuebunny/crossref_metadata_2025_split huggingface dataset:
Distinct N-Terminal Regulatory Domains of Ca2+/H+ Antiporters
Authors: Pittman Jon K. , Sreevidya Coimbatore S. , Shigaki Toshiro , Ueoka-Nakanishi Hanayo , Hirschi Kendal D. 
Published: October 2002

AbstractThe regulation of intracellular Ca2+ levels is achieved in part by high-capacity vacuolar Ca2+/H+ antiporters. An N-terminal regulatory region (NRR) on the Arabidopsis Ca2+/H+antiporter CAX1 (cation exchanger 1) has been shown previously to regulate Ca2+ transport by a mechanism of N-terminal auto-inhibition. Here, we examine the regulation of other CAX transporters, both within Arabidopsis and from another plant, mung bean (Vigna radiata), to ascertain if this mechanism is commonly used among Ca2+/H+ antiporters. Biochemical analysis of mung bean VCAX1 expressed in yeast (Saccharomyces cerevisiae) showed that N-terminal truncated VCAX1 had approximately 70% greater antiport activity compared with full-length VCAX1. A synthetic peptide corresponding to the NRR of CAX1, which can strongly inhibit Ca2+ transport by CAX1, could not dramatically inhibit Ca2+ transport by truncated VCAX1. The N terminus of Arabidopsis CAX3 was also shown to contain an NRR. Additions of either the CAX3 or VCAX1 regulatory regions to the N terminus of an N-terminal truncated CAX1 failed to inhibit CAX1 activity. When fused to N-terminal truncated CAX1, both the CAX3 and VCAX1 regulatory regions could only auto-inhibit CAX1 after mutagenesis of specific amino acids within this NRR region. These findings demonstrate that N-terminal regulation is present in other plant CAX transporters, and suggest distinct regulatory features among these transporters.
Bundle Sheath Diffusive Resistance to CO2 and Effectiveness of C4 Photosynthesis and Refixation of Photorespired CO2 in a C4 Cycle Mutant and Wild-Type Amaranthus edulis
Authors: Kiirats Olavi , Lea Peter J. , Franceschi Vincent R. , Edwards Gerald E. 
Published: October 2002

Abstract
A mutant of the NAD-malic enzyme-type C4 plant,Amaranthus edulis, which lacks phosphoenolpyruvate carboxylase (PEPC) in the mesophyll cells was studied. Analysis of CO2 response curves of photosynthesis of the mutant, which has normal Kranz anatomy but lacks a functional C4 cycle, provided a direct means of determining the liquid phase-diffusive resistance of atmospheric CO2 to sites of ribulose 1,5-bisphosphate carboxylation inside bundle sheath (BS) chloroplasts (r bs) within intact plants. Comparisons were made with excised shoots of wild-type plants fed 3,3-dichloro-2-(dihydroxyphosphinoyl-methyl)-propenoate, an inhibitor of PEPC. Values of r bs in A. edulis were 70 to 180 m2 s−1mol−1, increasing as the leaf matured. This is about 70-fold higher than the liquid phase resistance for diffusion of CO2 to Rubisco in mesophyll cells of C3 plants. The values of r bs in A. edulis are sufficient for C4 photosynthesis to elevate CO2 in BS cells and to minimize photorespiration. The calculated CO2 concentration in BS cells, which is dependent on input of r bs, was about 2,000 μbar under maximum rates of CO2 fixation, which is about six times the ambient level of CO2. High re-assimilation of photorespired CO2 was demonstrated in both mutant and wild-type plants at limiting CO2 concentrations, which can be explained by high r bs. Increasing O2 from near zero up to ambient levels under low CO2, resulted in an increase in the gross rate of O2 evolution measured by chlorophyll fluorescence analysis in the PEPC mutant; this increase was simulated from a Rubisco kinetic model, which indicates effective refixation of photorespired CO2 in BS cells.
Expression Profiling of the Whole Arabidopsis Shaggy-Like Kinase Multigene Family by Real-Time Reverse Transcriptase-Polymerase Chain Reaction
Authors: Charrier Bénédicte , Champion Anthony , Henry Yves , Kreis Martin 
Published: October 2002

AbstractThe recent publication of the complete sequence of the Arabidopsis genome allowed us to identify and characterize the last two members of the SHAGGY-like kinase (AtSK) gene family. As a result, the study of the overall spatio-temporal organization of the whole AtSK family in Arabidopsis has become an achievable and necessary aim to understand the role of each SHAGGY-like kinase during plant development. An analysis of the transcript level of the 10 members of the family has been performed using the technique of real-time quantitative reverse transcriptase-polymerase chain reaction. Transcript levels in several organs, under different growth conditions, were analyzed. To calibrate the results obtained, a number of other genes, such as those coding for the two MAP3Kεs and the two MAP4Kαs, as well as the stress response marker RD29A; the small subunit of the Rubisco photosynthetic enzyme Ats1A; the MEDEA chromatin remodeling factor; and the SCARECROW, ASYMMETRIC LEAVES 1, and SUPERMAN transcription factors all involved in key steps of plant development were used. The analysis of our data revealed that eight of the 10 genes of the AtSK family displayed a pseudo-constitutive expression pattern at the organ level. Conversely,AtSK13 responded to osmotic changes and saline treatment, whereas AtSK31 was flower specific and responded to osmotic changes and darkness.
Risk factors for acute graft-versus-host disease in patients undergoing transplantation with CD34+ selected blood cells from HLA-identical siblings
Authors: Urbano-Ispizua Alvaro , Rozman Ciril , Pimentel Pedro , Solano Carlos , de la Rubia Javier , Brunet Salut , Pérez-Oteyza Jaime , Ferrá Christelle , Zuazu Javier , Caballero Dolores , Bargay Joan , Carvalhais Alzira , Dı́ez Jose Luis , Espigado Ildefonso , Alegre Adrián , Rovira Montserrat , Campilho Fernando , Odriozola Jesús , Sanz Miguel Angel , Sierra Jordi , Garcı́a-Conde Javier , Montserrat Emili 
Published: October 2002

Abstract
A study on 315 patients undergoing transplantation with CD34+ selected blood cells from HLA-identical siblings was performed to determine risk factors for acute GVHD (aGVHD). Recipients of a dose of CD34+ cells (× 106/kg) of 2 or less, more than 2 to 4, and more than 4 had a cumulative incidence of aGVHD grades I-IV of 21%, 35%, and 43%, respectively (log-rankP = .01); similarly, recipients of a dose of CD3+ cells (× 106/kg) of 0.05 or less, more than 0.05 to 0.1, and more than 0.1 had a cumulative incidence of aGVHD grades I-IV of 18%, 35%, and 44%, respectively (log-rankP = .007). Using a Cox regression model, 4 independent factors for aGVHD I-IV were identified: increased CD34+cell dose (P = .02), increased CD3+ cell dose (P = .02), female patients (P = .01), and higher patient age (&gt; 42 years) (P = .007). This study shows, for the first time in T-cell–depleted transplantations, a positive correlation between the number of CD34+ cells and aGVHD and, also, that the number of CD3+ cells necessary to initiate aGVHD is lower than previously reported.
Temporary increase in the risk for recurrence during pregnancy in women with a history of venous thromboembolism
Authors: Pabinger Ingrid , Grafenhofer Helga , Kyrle Paul A. , Quehenberger Peter , Mannhalter Christine , Lechner Klaus , Kaider Alexandra 
Published: October 2002

AbstractThere is strong evidence that the incidence of venous thromboembolism (VTE) is increased during pregnancy. However, it is unknown whether and to which extent pregnancy influences the risk for recurrent VTE in women with previous thrombosis. To investigate whether pregnancy temporarily increases the risk for recurrent thrombosis, we retrospectively evaluated the recurrence rate in 109 women who had at least one pregnancy after an episode of VTE by comparing the time period during pregnancy with the nonpregnant period. Forty-three women had a first recurrence during a total observation time of 1014 years. Eight events (73 observation years) occurred during pregnancy, and 35 events (941 observation years) occurred outside pregnancy. Recurrence rates per 100 patient-years were 10.9% during and 3.7% outside pregnancy. Relative risk during pregnancy was 3.5 (95% confidence interval, 1.6-7.8; P = .002). Our data suggest that pregnancy leads to a temporary increase in the risk for recurrent thrombotic events.
Decreased susceptibility of leukemic cells with PIG-Amutation to natural killer cells in vitro
Authors: Nagakura Shoichi , Ishihara Sonoko , Dunn Daniel E. , Nishimura Jun-ichi , Kawaguchi Tatsuya , Horikawa Kentaro , Hidaka Michihiro , Kagimoto Tadashi , Eto Nozomu , Mitsuya Hiroaki , Kinoshita Taroh , Young Neal S. , Nakakuma Hideki 
Published: October 2002

AbstractThe cloning of the PIG-A gene has facilitated the unraveling of the complex pathophysiology of paroxysmal nocturnal hemoglobinuria (PNH). Of current major concern is the mechanism by which a PNH clone expands. Many reports have suggested that an immune mechanism operates to cause bone marrow failure in some patients with PNH, aplastic anemia, and myelodysplastic syndromes. Because blood cells of PNH phenotype are often found in patients with these marrow diseases, one hypothesis is that the PNH clone escapes immune attack, producing a survival advantage by immunoselection. To test this hypothesis, we examined the sensitivity of blood cells, with or withoutPIG-A mutations, to killing by natural killer (NK) cells, using 51Cr-release assay in vitro. To both peripheral blood and cultured NK cells, PIG-A mutant cells prepared from myeloid and lymphoid leukemic cell lines were less susceptible than their control counterparts (reverted from the mutant cells by transfection with a PIG-A cDNA). NK activity was completely abolished with concanamycin A and by calcium chelation, indicating that killing was perforin-dependent. There were no differences in major histocompatibility (MHC) class I expression or sensitivity to either purified perforin or to interleukin-2–activated NK cells betweenPIG-A mutant and control cells. From these results, we infer that PIG-A mutant cells lack molecules needed for NK activation or to trigger perforin-mediated killing. Our experiments suggest that PIG-A mutations confer a relative survival advantage to a PNH clone, contributing to selective expansion of these cells in the setting of marrow injury by cytotoxic lymphocytes.
Nucleotides induce chemotaxis and actin polymerization in immature but not mature human dendritic cells via activation of pertussis toxin–sensitive P2y receptors
Authors: Idzko Marco , Dichmann Stefan , Ferrari Davide , Di Virgilio Francesco , la Sala Andrea , Girolomoni Giampiero , Panther Elisabeth , Norgauer Johannes 
Published: October 2002

AbstractDendritic cells (DCs) are considered the principal initiators of immune response because of their ability to migrate into peripheral tissues and lymphoid organs, process antigens, and activate naive T cells. There is evidence that extracellular nucleotides regulate certain functions of DCs via G-protein–coupled P2Y receptors (P2YR) and ion-channel–gated P2X receptors (P2XR). Here we investigated the chemotactic activity and analyzed the migration-associated intracellular signaling events such as actin reorganization and Ca++ transients induced by common P2R agonists such as adenosine 5′-triphosphate (ATP) and 2-methylthioadenosine triphosphate, the P2YR agonists UTP and adenosine 5′-diphosphate (ADP), or the P2XR agonists αβ-methylenadenosine-5′-triphosphate and 2′,3′-(4-benzoyl)benzoyl-ATP. The common P2R agonists and the selective P2YR agonists turned out to be potent chemotactic stimuli for immature DCs, but not for mature DCs. In contrast, P2XR agonists had only marginal chemotactic activity in both DC types. Chemotaxis was paralleled by a rise in the intracellular Ca++concentration and by actin polymerization. Studies with pertussis toxin implicated that intracellular signaling events such as actin polymerization, mobilization of intracellular Ca++, and migration induced by nucleotides was mediated via Gi/oprotein–coupled P2YR. Moreover, functional studies revealed selective down-regulation of this Gi/oprotein–coupled chemotactic P2YR responsiveness during maturation, although immature and mature DCs expressed similar amounts of mRNA for the P2R subtypes (P2Y2R, P2Y4R, P2Y5R, P2Y7R, P2Y11R and P2X1R, P2X4R, P2X7R), and no major differences in respect to the mRNA expression of these receptors could be observed by semiquantitative reverse transcription and polymerase chain reaction (RT-PCR). In summary, our data describe a differential chemotactic response of immature and mature DCs to nucleotides, and lend further support to the hypothesis that P2R are a novel class of immunomodulatory plasma membrane receptors suitable for pharmacological intervention.
Interactions of STAT5b-RARα, a novel acute promyelocytic leukemia fusion protein, with retinoic acid receptor and STAT3 signaling pathways
Authors: Dong Shuo , Tweardy David J. 
Published: October 2002

AbstractSignal transducer and activator of transcription (STAT) 5b-retinoic acid receptor (RAR) α is the fifth fusion protein identified in acute promyelocytic leukemia (APL). Initially described in a patient with all-trans retinoic acid (ATRA)–unresponsive disease, STAT5b-RARα resulted from an interstitial deletion on chromosome 17. To determine the molecular mechanisms of myeloid leukemogenesis and maturation arrest in STAT5b-RARα+ APL and its unresponsiveness to ATRA, we examined the effect of STAT5b-RARα on the activity of myeloid transcription factors including RARα/retinoid X receptor (RXR) α, STAT3, and STAT5 as well as its molecular interactions with the nuclear receptor corepressor, SMRT, and nuclear receptor coactivator, TRAM-1. STAT5b-RARα bound to retinoic acid response elements (RAREs) both as a homodimer and as a heterodimer with RXRα and inhibited wild-type RARα/RXRα transactivation. Although STAT5b-RARα had no effect on ligand-induced STAT5b activation, it enhanced interleukin 6–induced STAT3-dependent reporter activity, an effect shared by other APL fusion proteins including promyelocytic leukemia-RARα and promyelocytic leukemia zinc finger (PLZF)–RARα. SMRT was released from STAT5b-RARα/SMRT complexes by ATRA at 10−6 M, whereas TRAM-1 became associated with STAT5b-RARα at 10−7 M. The coiled-coil domain of STAT5b was required for formation of STAT5b-RARα homodimers, for the inhibition of RARα/RXRα transcriptional activity, and for stability of the STAT5b-RARα/SMRT complex. Thus, STAT5b-RARα contributes to myeloid maturation arrest by binding to RARE as either a homodimer or as a heterodimer with RXRα resulting in the recruitment of SMRT and inhibition of RARα/RXRα transcriptional activity. In addition, STAT5b-RARα and other APL fusion proteins may contribute to leukemogenesis by interaction with the STAT3 oncogene pathway.
Regulation of endothelial cell branching morphogenesis by endogenous chemokine stromal-derived factor-1
Authors: Salvucci Ombretta , Yao Lei , Villalba Sabrina , Sajewicz Agatha , Pittaluga Stefania , Tosato Giovanna 
Published: October 2002

AbstractThe chemokine stromal-derived factor-1 (SDF-1) and its unique receptor, CXCR4, are required for normal cardiovascular development, but a critical role for SDF-1 in postnatal vascular remodeling and the mechanisms underlying SDF-1/CXCR-4 vasculogenesis are unclear. Here we show that SDF-1 is expressed by the vascular endothelium from selected healthy and tumor tissues. In vitro, primary endothelial cells constitutively express SDF-1 that is detected in the cytoplasm, on the cell surface, and in the culture supernatant. Vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) increase SDF-1 expression in endothelial cells. In functional studies, pertussis toxin and antibodies to SDF-1 or CXCR-4 disrupt extracellular matrix-dependent endothelial cell tube formation in vitro. This morphogenic process is associated with time-dependent modulation of surface CXCR-4 expression that changes from being diffuse to being polarized and subsequently lost. In vivo, pertussis toxin and neutralizing antibodies directed at SDF-1 inhibit growth factor–dependent neovascularization. These results indicate that SDF-1/CXCR-4 identifies VEGF- and bFGF-regulated autocrine signaling systems that are essential regulators of endothelial cell morphogenesis and angiogenesis.
Hematopoietic cells expressing the peripheral cannabinoid receptor migrate in response to the endocannabinoid 2-arachidonoylglycerol
Authors: Alberich Jordà Meritxell , Verbakel Sandra E. , Valk Peter J. M. , Vankan-Berkhoudt Yolanda V. , Maccarrone Mauro , Finazzi-Agrò Allessandro , Löwenberg Bob , Delwel Ruud 
Published: October 2002

Abstract
Cb2 is a novel protooncogene encoding the peripheral cannabinoid receptor. Previous studies demonstrated that 2 distinct noncoding first exons exist: exon-1A and exon-1B, which both splice to protein-coding exon-2. We demonstrate that in retrovirally induced murine myeloid leukemia cells with proviral insertion inCb2, exon-1B/exon-2 Cb2 messenger RNA levels have been increased, resulting in high receptor numbers. In myeloid leukemia cells without virus insertion in this locus, low levels of only exon-1A/exon-2 Cb2 transcripts were present and receptors could not be detected. To elucidate the function of Cb2 in myeloid leukemia cells, a set of in vitro experiments was carried out using 32D/G-CSF-R (granulocyte colony-stimulating factor receptor) cells transfected with exon-1B/exon-2 Cb2 complementary DNA and a myeloid cell line carrying a virus insertion in Cb2(ie, NFS 78). We demonstrate that a major function of the Cb2 receptor is stimulation of migration as determined in a transwell assay. Exposure of Cb2-expressing cells to different cannabinoids showed that the true ligand for Cb2 is 2-arachidonoylglycerol (2-AG), which may act as chemoatractant and as a chemokinetic agent. Furthermore, we observed a significant synergistic activity between 2-AG and interleukin-3 or G-CSF, suggesting cross-talk between the different receptor systems. Radioactive-ligand binding studies revealed significant numbers of Cb2 receptors in normal spleen. Transwell experiments carried out with normal mouse spleen cells showed 2-AG–induced migration of B220-, CD19-, immunoglobulin M–, and immunoglobulin D–expressing B lymphocytes. Our study demonstrates that a major function of Cb2 receptor expressed on myeloid leukemia cells or normal splenocytes is stimulation of migration.
Role of protein kinase C in the phosphorylation of CD33 (Siglec-3) and its effect on lectin activity
Authors: Grobe Kay , Powell Leland D. 
Published: October 2002

AbstractCD33 (Siglec-3) is a marker of myeloid progenitor cells, mature myeloid cells, and most myeloid leukemias. Although its biologic role remains unknown, it has been demonstrated to function as a sialic acid–specific lectin and a cell adhesion molecule. Many of the Siglecs (including CD33) have been reported to be tyrosine phosphorylated in the cytosolic tails under specific stimulation conditions. Here we report that CD33 is also a serine/threonine phosphoprotein, containing at least 2 sites of serine phosphorylation in its cytoplasmic domain, catalyzed by protein kinase C (PKC). Phosphorylation could be augmented by exposure to the protein kinase–activating cytokines interleukin 3, erythropoietin, or granulocyte-macrophage colony-stimulating factor, in a cytokine-dependent cell line, TF-1. The CD33 cytoplasmic tail was phosphorylated by PKC in vitro, in a Ca++/lipid-dependent manner. CHOK1 cells stably expressing CD33 with cytoplasmic tails of various length also showed phorbol myristate acetate (PMA)-dependent phosphorylation of CD33. Inhibition of CD33 phosphorylation with pharmacologic agents resulted in an increase of sialic acid–dependent rosette formation. Furthermore, the occupancy of the lectin site affected its basal level of phosphorylation. Rosette formation by COS cells expressing a form of CD33 lacking its cytoplasmic domain was not affected by these same agents. These data indicate that CD33 is a phosphoprotein, that its phosphorylation may be controlled by PKC downstream of cytokine stimulation, and that its phosphorylation is cross-regulated with its lectin activity. Notably, although this is the first example of serine/threonine phosphorylation in the subfamily of CD33-like Siglecs, some of the other members also have putative target sites in their cytoplasmic tails.
A functional role of Stat3 in in vivo megakaryopoiesis
Authors: Kirito Keita , Osawa Masatake , Morita Haruhiko , Shimizu Ritsuko , Yamamoto Masayuki , Oda Atsushi , Fujita Hiroyoshi , Tanaka Masaru , Nakajima Koichi , Miura Yasusada , Ozawa Keiya , Komatsu Norio 
Published: October 2002

AbstractThe signal transducer and activator of transcription 3 (Stat3), a member of the Stat family of proteins, is commonly activated by thrombopoietic cytokines including thrombopoietin (TPO), interleukin (IL)-6, and interleukin-11. This finding strongly suggested that Stat3 has an important role in megakaryopoiesis and thrombopoiesis. To clarify the functional role of Stat3 in in vivo megakaryopoiesis and thrombopoiesis, we generated transgenic mice overexpressing a dominant-negative Stat3, Stat3F, to suppress the function of endogenous Stat3. To accomplish the selective expression of Stat3F in megakaryocytic lineage cells, we used the regulatory gene region of GATA-1 transcription factor selectively expressed in megakaryocytic and erythroid lineage cells. Two independent transgenic (Tg) mice lines were established. It was confirmed by Western blotting analysis that Stat3F proteins were highly expressed in the platelets from the Tg mice. In addition, it was found that Stat3 activation induced by TPO stimulation was drastically suppressed in these Tg mice compared with littermates. These findings indicate that Stat3F works well in the Tg mice. Platelet counts were within the normal range in steady-state conditions and were recovered normally from transient thrombocytopenia induced by antiplatelet serum injection. Interestingly, the platelet recovery from myelosuppression after 5-fluorouracil treatment was significantly delayed in the Tg mice. Collectively, our results strongly suggest that Stat3 plays an important role in the early stage of megakaryopoiesis, presumably through the expansion of megakaryocytic progenitor cells.
Type I interferons produced by dendritic cells promote their phenotypic and functional activation
Authors: Montoya Maria , Schiavoni Giovanna , Mattei Fabrizio , Gresser Ion , Belardelli Filippo , Borrow Persephone , Tough David F. 
Published: October 2002

AbstractResting dendritic cells (DCs) are resident in most tissues and can be activated by environmental stimuli to mature into potent antigen-presenting cells. One important stimulus for DC activation is infection; DCs can be triggered through receptors that recognize microbial components directly or by contact with infection-induced cytokines. We show here that murine DCs undergo phenotypic maturation upon exposure to type I interferons (type I IFNs) in vivo or in vitro. Moreover, DCs either derived from bone marrow cells in vitro or isolated from the spleens of normal animals express IFN-α and IFN-β, suggesting that type I IFNs can act in an autocrine manner to activate DCs. Consistent with this idea, the ability to respond to type I IFN was required for the generation of fully activated DCs from bone marrow precursors, as DCs derived from the bone marrow of mice lacking a functional receptor for type I IFN had reduced expression of costimulatory and adhesion molecules and a diminished ability to stimulate naive T-cell proliferation compared with DCs derived from control bone marrow. Furthermore, the addition of neutralizing anti–IFN-α/β antibody to purified splenic DCs in vitro partially blocked the “spontaneous” activation of these cells, inhibiting the up-regulation of costimulatory molecules, secretion of IFN-γ, and T-cell stimulatory activity. These results show that DCs both secrete and respond to type I IFN, identifying type I interferons as autocrine DC activators.