[Show abstract][Hide abstract] ABSTRACT: Oxidative stress has been implicated in cardiac remodeling (cardiac fibrosis and hypertrophy), which impairs cardiac function and metabolism; therefore, it is anticipated antioxidative compounds will have protective properties against cardiac remodeling. Luteolin (3',4',5,7-tetrahydroxyflavone), a widely distributed flavonoid found in many herbal extracts including celery, green pepper, perilla leaves and seeds, and chamomile, is a known to be a potent antioxidant and was previously demonstrated to exert an antifibrotic effect in the lungs and the liver. In this study, we clearly demonstrate that oral pretreatment with the higher-luteolin diet (0.035% (wt/wt)) protected against cardiac fibrosis and hypertrophy as well as a hyperoxidative state in Ang II-infused rats. In cardiac tissue, increased gene expression levels of TGFβ1, CTGF, Nox2, Nox4, ANP, and BNP induced by Ang II were restored by oral pretreatment of this high-luteolin diet. In cultured rat cardiac fibroblasts, H2O2-induced TGFβ1 expression and the phosphorylation of JNK were suppressed by luteolin pretreatment. In conclusion, food-derived luteolin has protective actions against Ang II-induced cardiac remodeling, which could be mediated through attenuation of oxidative stress.
PLoS ONE 09/2015; 10(9):e0137106. DOI:10.1371/journal.pone.0137106 · 3.23 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Angiotensin II (AngII) type I receptor (AT1R) recognizes AngII, a cardiovascular peptide hormone that acts as a terminal effector of the renin-angiotensin system (RAS). AT1R belongs to the rhodopsin-like peptidergic family of G protein-coupled receptors (GPCRs) and serves as a therapeutic target for the treatment of cardiovascular diseases, such as hypertension, cardiac hypertrophy and heart failure. Classically, AT1R was considered to signal only through G proteins. However, recent studies have revealed that AT1R is capable of activating G protein-independent signaling that is mediated by β-arrestins. β-arrestin is a cytosolic scaffold that is recruited to the activated GPCRs. In vitro and ex vivo studies have demonstrated that the activation of the AT1R-β-arrestin pathway stimulates contractility and exerts prosurvival effects in cardiomyocytes. TRV027, a potent synthetic β-arrestin-biased ligand for AT1R, specifically activates AT1R-β-arrestin signaling without stimulating G proteins. In preclinical studies, TRV027 not only produced vasodilation by antagonizing the AT1R-Gαq pathway but also enhanced cardiac performance by activating AT1R-β-arrestin signaling. Because of this unique pharmacological profile, TRV027 is now being evaluated in a phase II clinical trial as a novel therapeutic for acute heart failure (AHF).
International Heart Journal 07/2015; DOI:10.1536/ihj.15-256 · 1.07 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Coronary arterial complications associated with Kawasaki disease (KD), such as a giant coronary aneurysm, determine the relative risk of future cardiac events and require lifelong medical treatment. Here, we describe a 24-year-old man who developed myocardial infarction due to poor adherence to medical treatment for a giant coronary aneurysm in the chronic phase of KD. He was hospitalized two hours after the onset of chest pain. The presence of the giant coronary aneurysm made primary percutaneous coronary intervention (PCI) difficult. However, we were able to perform primary PCI successfully utilizing previous coronary computed tomography (CT) angiographic pictures as a reference. This case provides valuable insight for the management of coronary arterial complications associated with KD. Patients in the chronic phase of KD are usually asymptomatic, even in the presence of giant coronary aneurysms which have been reported to have a high risk of morbidity and mortality. Therefore, patient education is critical for preventing poor adherence to medical treatment for coronary arterial complications. In preparation for potential coronary intervention in the future, it is also useful to perform coronary CT angiography, coronary magnetic resonance (MR) angiography, and/or coronary angiography on a regular basis while patients remain free from serious cardiac events.
International Heart Journal 07/2015; DOI:10.1536/ihj.15-155 · 1.07 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Identification of cognate ligands for G protein-coupled receptors (GPCRs) provides a starting point for understanding novel regulatory mechanisms. Although GPCR ligands have typically been evaluated through the activation of heterotrimeric G proteins, recent studies have shown that GPCRs signal not only through G proteins but also through β-arrestins. As such, monitoring β-arrestin signaling instead of G protein signaling will increase the likelihood of identifying currently unknown ligands, including β-arrestin-biased agonists. Here, we developed a cell-based assay for monitoring ligand-dependent GPCR-β-arrestin interaction via β-lactamase enzyme fragment complementation. Inter alia, β-lactamase is a superior reporter enzyme because of its cell-permeable fluorescent substrate. This substrate makes the assay non-destructive and compatible with fluorescence-activated cell sorting (FACS). In a reporter cell, complementary fragments of β-lactamase (α and ω) were fused to β-arrestin 2 and GPCR, respectively. Ligand stimulation initiated the interaction of these chimeric proteins (β-arrestin-α and GPCR-ω), and this inducible interaction was measured through reconstituted β-lactamase activity. Utilizing this system, we screened various mammalian tissue extracts for agonistic activities on human bombesin receptor subtype 3 (hBRS3). We purified peptide E as a low-affinity ligand for hBRS3, which was also found to be an agonist for the other two mammalian bombesin receptors such as gastrin-releasing peptide receptor (GRPR) and neuromedin B receptor (NMBR). Successful purification of peptide E has validated the robustness of this assay. We conclude that our newly developed system will facilitate the discovery of GPCR ligands.
PLoS ONE 06/2015; 10(6):e0127445. DOI:10.1371/journal.pone.0127445 · 3.23 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: G protein-coupled receptors (GPCRs) play a critical role in many physiological systems and represent one of the largest families of signal-transducing receptors. The number of GPCRs at the cell surface regulates cellular responsiveness to their cognate ligands, and the number of GPCRs, in turn, is dynamically controlled by receptor endocytosis. Recent studies have demonstrated that GPCR endocytosis, in addition to affecting receptor desensitization and resensitization, contributes to acute G protein-mediated signaling. Thus, endocytic GPCR behavior has a significant impact on various aspects of physiology. In this study, we developed a novel GPCR internalization assay to facilitate characterization of endocytic GPCR behavior. We genetically engineered chimeric GPCRs by fusing HaloTag (a catalytically inactive derivative of a bacterial hydrolase) to the N-terminal end of the receptor (HT-GPCR). HaloTag has the ability to form a stable covalent bond with synthetic HaloTag ligands that contain fluorophores or a high-affinity handle (such as biotin) and the HaloTag reactive linker. We selectively labeled HT-GPCRs at the cell surface with a HaloTag PEG ligand, and this pulse-chase covalent labeling allowed us to directly monitor the relative number of internalized GPCRs after agonist stimulation. Because the endocytic activities of GPCR ligands are not necessarily correlated with their agonistic activities, applying this novel methodology to orphan GPCRs, or even to already characterized GPCRs, will increase the likelihood of identifying currently unknown ligands that have been missed by conventional pharmacological assays.
PLoS ONE 05/2015; 10(5):e0129394. DOI:10.1371/journal.pone.0129394 · 3.23 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Circulating glucocorticoid levels oscillate with a robust circadian rhythm, yet the physiological relevance of this rhythmicity remains unclear. Here, we show that modulation of circadian glucocorticoid oscillation by enhancing its amplitude leads to anxiolytic-like behavior. We observed that mice with adrenal subcapsular cell hyperplasia (SCH), a common histological change in the adrenals, are less anxious than mice without SCH. This behavioral change was found to be dependent on the higher amplitude of glucocorticoid oscillation, although the total glucocorticoid secretion is not increased in these mice. Genetic and pharmacologic experiments demonstrated that intermediate opioid peptides secreted from SCH activate CXCR7, a β-arrestin-biased G-protein-coupled receptor (GPCR), to augment circadian oscillation of glucocorticoid levels in a paracrine manner. Furthermore, recapitulating this paracrine axis by subcutaneous administration of a synthetic CXCR7 ligand is sufficient to induce anxiolytic-like behavior. Adrenocortical β-arrestin-biased GPCR signaling is a potential target for modulating circadian glucocorticoid oscillation and emotional behavior.
[Show abstract][Hide abstract] ABSTRACT: Mixed-lineage-leukemia (MLL) fusion oncogenes are closely involved in infant acute leukemia, which is frequently accompanied by mutations or overexpression of FMS-like receptor tyrosine kinase 3 (FLT3). Earlier studies have shown that MLL fusion proteins induced acute leukemia together with another mutation, such as an FLT3 mutant, in mouse models. However, little has hitherto been elucidated regarding the molecular mechanism of the cooperativity in leukemogenesis. Using murine model systems of the MLL-fusion-mediated leukemogenesis leading to oncogenic transformation in vitro and acute leukemia in vivo, this study characterized the molecular network in the cooperative leukemogenesis. This research revealed that MLL fusion proteins cooperated with activation of Ras in vivo, which was substitutable for Raf in vitro, synergistically, but not with activation of signal transducer and activator of transcription 5 (STAT5), to induce acute leukemia in vivo as well as oncogenic transformation in vitro. Furthermore, Hoxa9, one of the MLL-targeted critical molecules, and activation of Ras in vivo, which was replaceable with Raf in vitro, were identified as fundamental components sufficient for mimicking MLL-fusion-mediated leukemogenesis. These findings suggest that the molecular crosstalk between aberrant expression of Hox molecule(s) and activated Raf may have a key role in the MLL-fusion-mediated-leukemogenesis, and may thus help develop the novel molecularly targeted therapy against MLL-related leukemia.
Leukemia: official journal of the Leukemia Society of America, Leukemia Research Fund, U.K 09/2009; 23(12):2197-209. DOI:10.1038/leu.2009.177 · 10.43 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We have analyzed leukocyte mono-Ig-like receptor 5 (LMIR5) as an activating receptor among paired LMIRs. Mouse LMIR5 (mLMIR5) is expressed in myeloid cells such as mast cells, granulocytes, macrophages, and dendritic cells. Cross-linking of transduced mLMIR5 in bone marrow-derived mast cells (BMMCs) caused activation events, including cytokine production, cell survival, degranulation, and adhesion to the extracellular matrix. mLMIR5 associated with DAP12 and to a lesser extent with DAP10, and mLMIR5-mediated functions of BMMCs were strongly inhibited by DAP12 deficiency. Importantly, cross-linking of endogenous mLMIR5 induced Syk-dependent activation of fetal liver-derived mast cells. Unlike mLMIR5, cross-linking of human LMIR5 (hLMIR5) induced cytokine production of BMMCs even in the absence of both DAP12 and DAP10, suggesting the existence of unidentified adaptors. Interestingly, hLMIR5 possessed a tyrosine residue (Y188) in the cytoplasmic region. Signaling via Y188 phosphorylation played a predominant role in hLMIR5-mediated cytokine production in DAP12-deficient, but not wild-type BMMCs. In addition, experiments using DAP10/DAP12 double-deficient BMMCs suggested the existence of Y188 phoshorylation-dependent and -independent signals from unidentified adaptors. Collectively, although both mouse and human LMIR5 play activatory roles in innate immunity cells, the functions of LMIR5 were differentially regulated in mouse versus human cells.
[Show abstract][Hide abstract] ABSTRACT: Transforming growth factor-beta (TGF-beta)-stimulated clone-22 (TSC-22) was originally isolated as a TGF-beta-inducible gene. In this study, we identified TSC-22 as a potential leukemia suppressor. Two types of FMS-like tyrosine kinase-3 (Flt3) mutations are frequently found in acute myeloid leukemia: Flt3-ITD harboring an internal tandem duplication in the juxtamembrane domain associated with poor prognosis and Flt3-TKD harboring a point mutation in the kinase domain. Comparison of gene expression profiles between Flt3-ITD- and Flt3-TKD-transduced Ba/F3 cells revealed that constitutive activation of Flt3 by Flt3-TKD, but not Flt3-ITD, upregulated the expression of TSC-22. Importantly, treatment with an Flt3 inhibitor PKC412 or an Flt3 small interfering RNA decreased the expression level of TSC-22 in Flt3-TKD-transduced cells. Forced expression of TSC-22 suppressed the growth and accelerated the differentiation of several leukemia cell lines into monocytes, in particular, in combination with differentiation-inducing reagents. On the other hand, a dominant-negative form of TSC-22 accelerated the growth of Flt3-TKD-transduced 32Dcl.3 cells. Collectively, these results suggest that TSC-22 is a possible target of leukemia therapy.
[Show abstract][Hide abstract] ABSTRACT: The leukocyte mono-Ig-like receptor (LMIR) belongs to a new family of paired immunoreceptors. In this study, we analyzed activating receptor LMIR4/CLM-5 as a counterpart of inhibitory receptor LMIR3/CLM-1. LMIR4 is expressed in myeloid cells, including granulocytes, macrophages, and mast cells, whereas LMIR3 is more broadly expressed. The association of LMIR4 with Fc receptor-gamma among immunoreceptor tyrosine-based activation motif-bearing molecules was indispensable for LMIR4-mediated functions of bone marrow-derived mast cells, but dispensable for its surface expression. Cross-linking of LMIR4 led to Lyn- and Syk-dependent activation of bone marrow-derived mast cells, resulting in cytokine production and degranulation, whereas that of LMIR3 did not. The triggering of LMIR4 and TLR4 synergistically caused robust cytokine production in accordance with enhanced activation of ERK, whereas the co-ligation of LMIR4 and LMIR3 dramatically abrogated cytokine production. Notably, intraperitoneal administration of lipopolysaccharide strikingly up-regulated LMIR3 and down-regulated LMIR4, whereas that of granulocyte colony-stimulating factor up-regulated both LMIR3 and LMIR4 in granulocytes. Cross-linking of LMIR4 in bone marrow granulocytes also resulted in their activation, which was enhanced by lipopolysaccharide. Collectively, these results suggest that the innate immune system is at least in part regulated by the qualitative and quantitative balance of the paired receptors LMIR3 and LMIR4.
[Show abstract][Hide abstract] ABSTRACT: Internal tandem duplication of FLT3 tyrosine kinase (FLT3-ITD) is the most prevalent mutation found in acute myelogenous leukemia (AML), having been identified in 20% to 30% of all AML patients. We have previously shown that FLT3-ITD signals mainly through the signal transducer and activator of transcription 5 (STAT5) pathway and have suggested the possible involvement of Tyk2 in STAT5 activation by FLT3-ITD. The present study addressed the role of Tyk2 in FLT3-ITD signaling in a murine bone marrow transplantation (BMT) model. Transplantation of wild-type bone marrow cells transduced with the FLT3-ITD gene induced lethal myeloproliferative disease (MPD) in the recipient mice at a median latency of 89 days. Interestingly, some mice presented the proliferation of B- or T-lymphoid blasts in various organs, a presentation that resembled acute lymphoblastic leukemia (ALL). Mice that received Tyk2-deficient bone marrow cells transduced with FLT3-ITD developed lethal MPD with a disease latency (median, 100 days) and pathologic picture similar to those of mice that received wild-type bone marrow cells. These results indicate that (1) Tyk2 is not essential for MPD induction by FLT3-ITD and (2) FLT3-ITD by itself can induce ALL in a murine BMT model.
International Journal of Hematology 08/2006; 84(1):54-9. DOI:10.1532/IJH97.06016 · 1.92 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Integrin αIIb, a well-known marker of megakaryocyte-platelet lineage, has been recently recognized on hemopoietic progenitors. We now demonstrate that integrin αIIbβ3 is highly expressed on mouse and human mast cells including mouse bone marrow-derived mast cells, peritoneal mast cells, and human cord blood-derived mast cells, and that its binding to extracellular matrix proteins leads to enhancement of biological functions of mast cells in concert with various stimuli. With exposure to various stimuli, including cross-linking of FcεRI and stem cell factor, mast cells adhered to extracellular matrix proteins such as fibrinogen and von Willebrand factor in an integrin αIIbβ3-dependent manner. In addition, the binding of mast cells to fibrinogen enhanced proliferation, cytokine production, and migration and induced uptake of soluble fibrinogen in response to stem cell factor stimulation, implicating integrin αIIbβ3 in a variety of mast cell functions. In conclusion, mouse and human mast cells express functional integrin αIIbβ3.
The Journal of Immunology 03/2006; 176(1). DOI:10.4049/jimmunol.176.1.52 · 4.92 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Integrin alphaIIb, a well-known marker of megakaryocyte-platelet lineage, has been recently recognized on hemopoietic progenitors. We now demonstrate that integrin alphaIIbbeta3 is highly expressed on mouse and human mast cells including mouse bone marrow-derived mast cells, peritoneal mast cells, and human cord blood-derived mast cells, and that its binding to extracellular matrix proteins leads to enhancement of biological functions of mast cells in concert with various stimuli. With exposure to various stimuli, including cross-linking of FcepsilonRI and stem cell factor, mast cells adhered to extracellular matrix proteins such as fibrinogen and von Willebrand factor in an integrin alphaIIbbeta3-dependent manner. In addition, the binding of mast cells to fibrinogen enhanced proliferation, cytokine production, and migration and induced uptake of soluble fibrinogen in response to stem cell factor stimulation, implicating integrin alphaIIbbeta3 in a variety of mast cell functions. In conclusion, mouse and human mast cells express functional integrin alphaIIbbeta3.
The Journal of Immunology 02/2006; 176(1):52-60. · 4.92 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: The mechanisms by which mixed-lineage leukemia (MLL) fusion products resulting from in utero translocations in 11q23 contribute to leukemogenesis and infant acute leukemia remain elusive. It is still controversial whether the MLL fusion protein is sufficient to induce acute leukemia without additional genetic alterations, although carcinogenesis in general is known to result from more than 1 genetic disorder accumulating during a lifetime. Here we demonstrate that the fusion partner-mediated homo-oligomerization of MLL-SEPT6 is essential to immortalize hematopoietic progenitors in vitro. MLL-SEPT6 induced myeloproliferative disease with long latency in mice, but not acute leukemia, implying that secondary genotoxic events are required to develop leukemia. We developed in vitro and in vivo model systems of leukemogenesis by MLL fusion proteins, where activated FMS-like receptor tyrosine kinase 3 (FLT3) together with MLL-SEPT6 not only transformed hematopoietic progenitors in vitro but also induced acute biphenotypic or myeloid leukemia with short latency in vivo. In these systems, MLL-ENL, another type of the fusion product that seems to act as a monomer, also induced the transformation in vitro and leukemogenesis in vivo in concert with activated FLT3. These findings show direct evidence for a multistep leukemogenesis mediated by MLL fusion proteins and may be applicable to development of direct MLL fusion-targeted therapy.
[Show abstract][Hide abstract] ABSTRACT: Growth factors, cell-surface receptors, adhesion molecules, and extracellular matrix proteins play critical roles in vascular pathophysiology by affecting growth, migration, differentiation, and survival of vascular cells. In a search for secreted and cell-surface molecules expressed in the cardiovascular system, by using a retrovirus-mediated signal sequence trap method, we isolated a cell-surface protein named vasorin. Vasorin is a typical type I membrane protein, containing tandem arrays of a characteristic leucine-rich repeat motif, an epidermal growth factor-like motif, and a fibronectin type III-like motif at the extracellular domain. Expression analyses demonstrated that vasorin is predominantly expressed in vascular smooth muscle cells, and that its expression is developmentally regulated. To clarify biological functions of vasorin, we searched for its binding partners and found that vasorin directly binds to transforming growth factor (TGF)-beta and attenuates TGF-beta signaling in vitro. Vasorin expression was down-regulated during vessel repair after arterial injury, and reversal of vasorin down-regulation, by using adenovirus-mediated in vivo gene transfer, significantly diminished injury-induced vascular lesion formation, at least in part, by inhibiting TGF-beta signaling in vivo. These results suggest that down-regulation of vasorin expression contributes to neointimal formation after vascular injury and that vasorin modulates cellular responses to pathological stimuli in the vessel wall. Thus, vasorin is a potential therapeutic target for vascular fibroproliferative disorders.
Proceedings of the National Academy of Sciences 08/2004; 101(29):10732-7. DOI:10.1073/pnas.0404117101 · 9.67 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: Most of the human genome has now been sequenced and about 30,000 potential open reading frames have been identified, indicating that we use these 30,000 genes to functionally organize our biologic activities. However, functions of many genes are still unknown despite intensive efforts using bioinformatics as well as transgenic and knockout mice. Retrovirus-mediated gene transfer is a powerful tool that can be used to understand gene functions. We have developed a variety of retrovirus vectors and efficient packaging cell lines that have facilitated the development of efficient functional expression cloning methods. In this review, we describe retrovirus-mediated strategies used for investigation of gene functions and function-based screening strategies.
[Show abstract][Hide abstract] ABSTRACT: The receptor tyrosine kinase FLT3 is constitutively activated by an internal tandem duplication (ITD) mutation within the juxtamembrane domain in 20-30% of patients with acute myeloid leukemia. In this study, we identified GTP-14564 as a specific kinase inhibitor for ITD-FLT3 and investigated the molecular basis of its specificity. GTP-14564 inhibited the growth of interleukin-3-independent Ba/F3 expressing ITD-FLT3 at 1 microM, whereas a 30-fold higher concentration of GTP-14564 was required to inhibit FLT3 ligand-dependent growth of Ba/F3 expressing wild type FLT3 (wt-FLT3). However, this inhibitor suppressed the kinase activities of wt-FLT3 and ITD-FLT3 equally, suggesting that the signaling pathways for proliferation differ between wt-FLT3 and ITD-FLT3. Analysis of downstream targets of FLT3 using GTP-14564 revealed STAT5 activation to be essential for growth signaling of ITD-FLT3. In contrast, wt-FLT3 appeared to mainly use the MAPK pathway rather than the STAT5 pathway to transmit a proliferative signal. Further analysis demonstrated that the first two tyrosines in an ITD were critical for STAT5 activation and growth induction but that all of the tyrosines in the juxtamembrane region were dispensable in terms of the proliferation signals of wt-FLT3. These results indicate that an ITD mutation in FLT3 elicits an aberrant STAT5 activation that results in increased sensitivity to GTP-14564. Thus, FLT3-targeted inhibition is an attractive approach, with the potential for selective cytotoxicity, to the treatment of ITD-FLT3-positive acute myeloid leukemia.
[Show abstract][Hide abstract] ABSTRACT: We have identified and characterized two mouse cDNAs in a mouse antigen-stimulated bone marrow-derived mast cell cDNA library, both of which encode type I transmembrane proteins. The genes were closely mapped in the distal region of mouse chromosome 11 and expressed not only in mast cells but also widely in leukocytes. The extracellular domains of their encoded proteins contain a single variable immunoglobulin (Ig) motif sharing about 90% identity with amino acids, showing that they comprise a pair of molecules and belong to the Ig superfamily. We named these molecules leukocyte mono-Ig-like receptor1 and 2 (LMIR1 and 2). The intracellular domain of LMIR1 contains several immunoreceptor tyrosine-based inhibition motifs (ITIMs). When cross-linked, the intracellular domain was tyrosine phosphorylated and capable of recruiting tyrosine phosphatases, SHP-1 and SHP-2 and inositol polyphosphate 5-phosphatase, SHIP. LMIR2, on the other hand, contains a short cytoplasmic tail and a characteristic transmembrane domain carrying two positively charged amino acids associated with three kinds of immunoreceptor tyrosine-based activation motif (ITAM)-bearing molecules, DAP10, DAP12, and FcRgamma. These findings suggest that a new pair of ITIM/ITAM-bearing receptors, LMIR1 and 2, regulate mast cell-mediated inflammatory responses through yet to be defined ligand(s).
Biochemical and Biophysical Research Communications 09/2003; 307(3):719-29. DOI:10.1016/S0006-291X(03)01245-2 · 2.30 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We report the cloning and characterization of a human cDNA predicted to encode a novel hydrophobic protein containing four transmembrane domains and a zinc metalloprotease motif, HEXXH, between the third and fourth transmembrane domains, and have named the molecule metalloprotease-related protein-1 (MPRP-1). The MPRP-1 gene was localized to chromosome 1-p32.3 by radiation hybrid mapping, and Northern blot analysis revealed expression in many organs, with strong expression in the heart, skeletal muscle, kidney and liver. Immunohistochemical analyisis showed that MPRP-1 was localized in the endoplasmic reticulum (ER), and not in the Golgi compartment. Fragments of DNA encoding a segment homologous to the HEXXH motif of MPRP-1 are widely found in bacteria, yeast, plants, and animals. These results suggest that the MPRP-1 may have highly conserved functions, such as in intracellular proteolytic processing in the ER.
DNA Research 07/2003; 10(3):123-8. DOI:10.1093/dnares/10.3.123 · 5.48 Impact Factor
[Show abstract][Hide abstract] ABSTRACT: We recently demonstrated that STAT5 can induce a variety of biological functions in mouse IL-3-dependent Ba/F3 cells; STAT5-induced expression of pim-1, p21(WAF/Cip1), and suppressor of cytokine signaling-1/STAT-induced STAT inhibitor-1/Janus kinase binding protein is responsible for induction of proliferation, differentiation, and apoptosis, respectively. In the present study, using a constitutively active STAT5A (STAT5A1*6), we show that STAT5 induces macrophage differentiation of mouse leukemic M1 cells through a distinct mechanism, autocrine production of IL-6. The supernatant of STAT5A1*6-transduced cells contained sufficient concentrations of IL-6 to induce macrophage differentiation of parental M1 cells, and STAT3 was phosphorylated on their tyrosine residues in these cells. Treatment of the cells with anti-IL-6 blocking Abs profoundly inhibited the differentiation. We also found that the STAT5A1*6 transactivated the IL-6 promoter, which was mediated by the enhanced binding of NF-kappaB p65 (RelA) to the promoter region of IL-6. These findings indicate that STAT5A cooperates with Rel/NF-kappaB to induce production of IL-6, thereby inducing macrophage differentiation of M1 cells in an autocrine manner. In summary, we have shown a novel mechanism by which STAT5 induces its pleiotropic functions. Cytokines
The Journal of Immunology 11/2001; 167(7):3652-60. DOI:10.4049/jimmunol.167.7.3652 · 4.92 Impact Factor