Biomedical subjects

Masakazu Hattori

Publications and source records attributed to Masakazu Hattori.

At least 19 recordsLinked to original sources

PubMed2006

Role of SPA-1 in phenotypes of chronic myelogenous leukemia induced by BCR-ABL-expressing hematopoietic progenitors in a mouse model.

SPA-1 is a negative regulator of Rap1 signal in hematopoietic cells, and SPA-1-deficient mice develop myeloproliferative disorders (MPD) of long latency. In the present study, we showed that the MPDs in SPA-1(-/-) mice were associated with the increased hematopoietic stem cells expressing LFA-1 in bone marrow and their premature mobilization to spleen with extensive extramedullary hematopoiesis, resembling human chronic myelogenous leukemia (CML). We further showed that human BCR-ABL oncogene caused a partial down-regulation of endogenous SPA-1 gene expression in mouse hematopoietic progenitor cells (HPC) and immature hematopoietic cell lines. Although both BCR-ABL-transduced wild-type (wt) and SPA-1(-/-) HPC rapidly developed CML-like MPD when transferred to severe combined immunodeficient mice, the latter recipients showed significantly increased proportions of BCR-ABL(+) Lin(-) c-Kit(+) cells compared with the former ones. Serial transfer experiments revealed that spleen cells of secondary recipients of BCR-ABL(+) wt HPC failed to transfer MPD to tertiary recipients due to a progressive reduction of BCR-ABL(+) Lin(-) c-Kit(+) cells. In contrast, SPA-1(-/-) BCR-ABL(+) Lin(-) c-Kit(+) cells were sustained at high level in secondary recipients, and their spleen cells could transfer MPD to tertiary recipients, a part of which rapidly developed blast crisis. Present results suggest that endogenous SPA-1 plays a significant role in regulating expansion and/or survival of BCR-ABL(+) leukemic progenitors albeit partial repression by BCR-ABL and that Rap1 signal may represent a new molecular target for controlling leukemic progenitors in CML.

Animals↗

PubMed2006

Enhancement of insulin signaling pathway in adipocytes by oxovanadium(IV) complexes.

Recently, we have found that some oxovanadium(IV) complexes are potent insulin-mimetic compounds for treating both type I and type II diabetic animals. However, the functional mechanism of oxovanadium(IV) complexes is not fully understood. In this report, we have shown that oxovanadium(IV)-picolinate complexes such as VO(pa)(2), VO(3mpa)(2), and VO(6mpa)(2) act on the insulin signaling pathway in 3T3-L1 adipocytes. Among them, VO(3mpa)(2) was found to be the highest potent activator in inducing not only the phosphotyrosine levels of both IRbeta and IRS but also the activation of downstream kinases in the insulin receptor, such as Akt and GSK3beta, which in turn translocated the insulin-dependent GLUT4 to the plasma membrane. Then, we examined whether or not oxovanadium(IV)-picolinates exhibit the hypoglycemic activity in STZ-induced diabetic mice, and found that VO(3mpa)(2) is more effective than the others in improving the hyperglycemia of the animals. Our present data indicate that both activation of insulin signaling pathway, which follows the GLUT4 translocation to the plasma membrane, and enhancement of glucose utilization by oxovanadium(IV) complexes cause the hypoglycemic effect in diabetic animals.

3T3-L1 Cells↗

PubMed2006

Rap1 signal controls B cell receptor repertoire and generation of self-reactive B1a cells.

We previously reported that the mice deficient for SPA-1, a Rap1 GTPase-activating protein, developed hematopoietic stem cell disorders. Here, we demonstrate that SPA-1(-/-) mice show an age-dependent increase in B220(high) B1a cells producing anti-dsDNA antibody and lupus-like nephritis. SPA-1(-/-) peritoneal B1 cells revealed the altered Vkappa gene repertoire, including skewed Vkappa4 usage and the significant Igkappa/Iglambda isotype inclusion indicative of extensive receptor editing. Rap1GTP induced OcaB gene activation via p38MAPK-dependent Creb phosphorylation, and consistently, SPA-1(-/-) immature BM B cells showing high Rap1GTP exhibited the augmented expression of OcaB and Vkappa4 genes. SPA-1(-/-) BM cells could transfer the autoimmunity in association with the generation of peritoneal B220(high) B1a cells in Rag-2(-/-) recipients. Finally, a portion of SPA-1(-/-) mice developed B1 cell leukemia with hemolytic autoantibody. Present results suggest that the regulated Rap1 signal in the immature B cells plays a role in modifying the B cell receptor repertoire and in maintaining the self-tolerance.

Animals↗

PubMed2006

[Clinical examination of safety and effectiveness of primary chemotherapy with CEF followed by docetaxel in preoperative breast cancer].

SUBJECTS: The subjects were patients with resectable breast cancer who visited our department between August 2003 and November 2004, did not have any other risk factors defined in the St. Gallen Consensus Conference,and were receptor-negative or had axillary lymph node metastasis. METHODS: The histological type, ER, PgR, HER2, and histological grade were evaluated by needle biopsy. Four courses of CEF (5-FU: 500 mg/m(2)+EPI: 75 mg/m(2)+CPA: 500 mg/m(2)) were performed at 3-week intervals, followed by 4 courses of Docetaxel (70 mg/m(2)). RESULTS: Treatment was performed in 14 patients including a male. Their age ranged from 37 to 69 years (mean, 55.3 years). Stage IIA was observed in 5 patients, IIB in 4, IIIA in 1, and IIIB in 4. In patients with Grade 3 or more, leukocytopenia was observed in 7 patients and diarrhea in 1 as adverse events. CR was obtained in 6 patients, PR in 5, and NC in 3 (response rate, 78.5%). Pathological examination showed pCR in 1 patient and pPR in 10 (response rate, 78.5%). Of the 10 patients with pPR, 2 showed a state near pCR. DISCUSSION: Our results showed the safety and effectiveness of preoperative chemotherapy with CEF followed by Docetaxel.

Adult↗

PubMed2005

Prethymic T-cell development defined by the expression of paired immunoglobulin-like receptors.

T cells are produced in the thymus from progenitors of extrathymic origin. As no specific markers are available, the developmental pathway of progenitors preceding thymic colonization remains unclear. Here we show that progenitors in murine fetal liver and blood, which are capable of giving rise to T cells, NK cells and dendritic cells, but not B cells, can be isolated by their surface expression of paired immunoglobulin-like receptors (PIR). PIR expression is maintained until the earliest intrathymic stage, then downregulated before the onset of CD25 expression. Unlike intrathymic progenitors, generation of prethymic PIR(+) progenitors does not require Hes1-mediated Notch signaling. These findings disclose a prethymic stage of T-cell development programmed for immigration of the thymus, which is genetically separable from intrathymic stages.

Animals↗

PubMed2005

Long-term follow up of patients with multiple gastric carcinoids associated with type A gastritis.

Little is known about the natural course of multiple gastric carcinoids associated with type A gastritis. Between 1993 and 2003, we enrolled eight patients, diagnosed as having multiple gastric carcinoids associated with type A gastritis, in a follow-up program without surgical resection. In these patients, endoscopy showed multiple small polyps on the gastric body, with nonantral atrophic gastritis. Histologically, biopsy specimens obtained from the polyps revealed carcinoid tumors. The serum gastrin level was found to be very high in all patients, and testing for anti-parietal cell antibody was positive in seven. The mean follow-up was 5.8 years (range, 1.5-10.8 years). The levels of serum gastrin increased in all patients, but, endoscopically, the carcinoid tumors did not change in size. Neither hepatic nor lymphatic metastasis was detected on abdominal computed tomography (CT). These patients were free of the development or metastasis of carcinoids, in spite of their continuous hypergastrinemia. It was concluded that multiple gastric carcinoids associated with type A gastritis may be indolent.

Aged↗

PubMed2005

Hes1 directly controls cell proliferation through the transcriptional repression of p27Kip1.

A transcriptional regulator, Hes1, plays crucial roles in the control of differentiation and proliferation of neuronal, endocrine, and T-lymphocyte progenitors during development. Mechanisms for the regulation of cell proliferation by Hes1, however, remain to be verified. In embryonic carcinoma cells, endogenous Hes1 expression was repressed by retinoic acid in concord with enhanced p27(Kip1) expression and cell cycle arrest. Conversely, conditional expression of a moderate but not maximal level of Hes1 in HeLa cells by a tetracycline-inducible system resulted in reduced p27(Kip1) expression, which was attributed to decreased basal transcript rather than enhanced proteasomal degradation, with concomitant increases in the growth rate and saturation density. Hes1 induction repressed the promoter activity of a 5' flanking basal enhancer region of p27(Kip1) gene in a manner dependent on Hes1 expression levels, and this was mediated by its binding to class C sites in the promoter region. Finally, hypoplastic fetal thymi, as well as livers and brains of Hes1-deficient mice, showed significantly increased p27(Kip1) transcripts compared with those of control littermates. These results have suggested that Hes1 directly contributes to the promotion of progenitor cell proliferation through transcriptional repression of a cyclin-dependent kinase inhibitor, p27(Kip1).

5' Flanking Region↗

PubMed2004

Regression of rectal mucosa-associated lymphoid tissue lymphoma but persistence of Helicobacter pylori infection of gastric mucosa after administration of levofloxacin: report of a case.

PURPOSE: Several articles have reported regression of rectal lymphoma of mucosa-associated lymphoid tissue after anti- Helicobacter pylori therapy. It remains unclear, however, whether lymphoma of rectal mucosa-associated lymphoid tissue is related to Helicobacter pylori infection. METHODS: A 60-year-old woman visited our hospital with a complaint of hematochezia. On colonoscopy a pale, ulcerated protrusion approximately 3.5 cm in diameter was found in the rectum. Pathologic diagnosis of a biopsy specimen was low-grade mucosa-associated lymphoid tissue lymphoma. The patient received a ten-day course of levofloxacin, and the cycle was repeated three times over seven months. RESULTS: Although persistence of Helicobacter pylori infection was confirmed, the tumor regressed completely. CONCLUSION: Our findings in this case suggest that rectal lymphoma of mucosa-associated lymphoid tissue may be related to unknown microorganisms other than Helicobacter pylori. Levofloxacin may be effective for treatment of rectal lymphoma of mucosa-associated lymphoid tissue regardless of Helicobacter pylori infection.

Anti-Infective Agents↗

PubMed2004

Aquaporin-2 trafficking is regulated by PDZ-domain containing protein SPA-1.

Targeted positioning of water channel aquaporin-2 (AQP2) strictly regulates body water homeostasis. Trafficking of AQP2 to the apical membrane is critical to the reabsorption of water in renal collecting ducts. Controlled apical positioning of AQP2 suggests the existence of proteins that interact with AQP2. A biochemical search for AQP2-interacting proteins led to the identification of PDZ-domain containing protein, signal-induced proliferation-associated gene-1 (SPA-1) which is a GTPase-activating protein (GAP) for Rap1. The distribution of SPA-1 coincided with that of AQP2 in renal collecting ducts. The site of colocalization was concomitantly relocated by hydration status. AQP2 trafficking to the apical membrane was inhibited by the SPA-1 mutant lacking Rap1GAP activity and by the constitutively active mutant of Rap1. AQP2 trafficking was impaired in SPA-1-deficient mice. Our results show that SPA-1 directly binds to AQP2 and regulates at least in part AQP2 trafficking.

Animals↗

PubMed2004

Specific recruitment of SPA-1 to the immunological synapse: involvement of actin-bundling protein actinin.

SPA-1 is involved in the regulation of T cell activation in response to antigens through the control of Rap1 GTPase signaling. In this study, the subcellular localization of SPA-1 in the T cells was examined by using anti-SPA-1 antibody and GFP-SPA-1. While SPA-1 was detected diffusely at the surface cortical region in the floating unpolarized T cells, it was concentrated at the matrix-adhesion region with dense actin-cytoskeleton. Upon interaction with specific antigen-presenting cells, SPA-1 was highly concentrated at the immunological synapse closely co-localizing with actin. By yeast two-hybrid system, SPA-1 was shown to interact with an actin-bundling protein alpha-actinin, and it was indicated that SPA-1 co-localized with alpha-actinin at the immunological synapse. The results have suggested that SPA-1 in the T cells is selectively recruited to the immunological synapse with dense actin-cytoskeletal reorganization and keeps restraining the levels of Rap1GTP at the local TCR-signaling complex for the T cell activation.

Actinin↗

PubMed2004

Rap1 and SPA-1 in hematologic malignancy.

Rap1 is a member of the Ras family of GTPases and, depending on the cellular context, has an important role in the regulation of proliferation or cell adhesion. In lymphohematopoietic tissues, SPA-1 is a principal Rap1 GTPase-activating protein. Mice that are deficient for the SPA-1 gene develop age-dependent progression of T-cell immunodeficiency followed by a spectrum of late onset myeloproliferative disorders, mimicking human chronic myeloid leukemia. Recent studies reveal that deregulated Rap1 activation in SPA-1-deficient mice causes enhanced expansion of the bone marrow hematopoietic progenitors, but induces progressive unresponsiveness or anergy in T cells. Rap1 and its regulator, SPA-1, could, therefore, provide unique molecular targets for the control of human hematologic malignancy.

Animals↗

PubMed2004

Bromodomain protein Brd4 binds to GTPase-activating SPA-1, modulating its activity and subcellular localization.

Brd4 is a mammalian protein that contains a double bromodomain. It binds to chromatin and regulates cell cycle progression at multiple stages. By immunopurification and mass spectrometry, we identified a Rap GTPase-activating protein (GAP), signal-induced proliferation-associated protein 1 (SPA-1), as a factor that interacts with Brd4. SPA-1 localizes to the cytoplasm and to a lesser degree in the nucleus, while Brd4 resides in the nucleus. Bifluorescence complementation revealed that Brd4 and SPA-1 interact with each other in the nucleus of living cells. Supporting the functional importance of the interaction, Brd4 enhanced Rap GAP activity of SPA-1. Furthermore ectopic expression of SPA-1 and Brd4 redirected subcellular localization of the partner and disrupted normal cell cycle progression. These effects were, however, reversed by coexpression of the two proteins, indicating that a proper balance between Brd4 and SPA-1 in G2 is required for cell division. This work reveals a novel link between Brd4 and a GTPase-dependent mitogenic signaling pathway.

Animals↗

PubMed2003

Physiological beta cell death triggers priming of self-reactive T cells by dendritic cells in a type-1 diabetes model.

The prelude to type-1 diabetes is leukocyte infiltration into the pancreatic islets, or insulitis. This process begins in pancreatic lymph nodes when T lymphocytes reactive to islet beta cells encounter antigen-presenting cells (APCs) displaying peptides derived from beta cell proteins. We show here that a ripple of physiological beta cell death, which occurs at 2 wk of age in all mouse strains, precipitates the arrival of such APCs, and that the relevant APC is a dendritic cell of CD11c+CD11b+CD8alpha- phenotype. These findings have significant implications concerning the nature of the diabetes-provoking deficits in NOD mice, the identity of the primordial diabetogenic antigens, and our understanding of the balance between immunity and tolerance in a pathological context.

Animals↗

PubMed2003

Activation of CEA-CAM-1-mediated cell adhesion via CD98: involvement of PKCdelta.

CD98 is a multifunctional protein involved in amino acid transport and regulation of integrin-mediated cell adhesion. Herein, we demonstrated that CD98 stimulation by anti-CD98 antibodies induced CEA-CAM-1-mediated cell adhesion in BaF3 cells expressing CEA-CAM-1, and suggest that this might be responsible for compact clumping of F9 embryonic carcinoma cells by CD98 stimulation. CEA-CAM-1 was co-immunoprecipitated by anti-CD98 antibody. CD98 stimulation induced the translocation of cytoplasmic protein kinase Cdelta (PKCdelta) to the cell adhesion sites, and rottlerin that inhibited the PKCdelta translocation abolished the cell aggregation without affecting integrin activation. The results suggested that CD98 stimulation could activate CEA-CAM-1-mediated cell adhesion independently of integrins.

Adenosine Triphosphatases↗

PubMed2003

Antigen-driven T cell anergy and defective memory T cell response via deregulated Rap1 activation in SPA-1-deficient mice.

SPA-1 is a principal Rap1 GTPase-activating protein in the hematopoietic progenitors and peripheral T cells, and SPA-1-deficient mice develop a spectrum of myeloproliferative stem cell disorders of late onset. In the present study, we show that SPA-1-deficient mice develop age-dependent T cell unresponsiveness preceding the myeloid disorders, whereas the T cell numbers remained unchanged. Progression of the T cell dysfunction was attributed to the age-dependent increase in CD44high T cell population that was unresponsive to T cell receptor stimulation. Younger SPA-1-deficient mice exhibited selectively impaired recall T cell responses against a T-dependent antigen with normal primary antibody response. These results suggested that the unresponsiveness of CD44high T cells was antigen-driven in vivo. T cells from younger SPA-1-/- mice showed much greater and more persisted Rap1 activation by anti-CD3 stimulation than control T cells. Furthermore, freshly isolated T cells from SPA-1-/- mice exhibited progressive accumulation of Rap1GTP as mice aged. T cells from aged SPA-1-/- mice with high amounts of Rap1GTP showed normal or even enhanced Ras activation with little extracellular signal-regulated kinase activation in response to anti-CD3 stimulation, indicating that excess Rap1GTP induced the uncoupling of Ras-mediated extracellular signal-regulated kinase activation. These results suggested that antigenic activation of naïve T cells in SPA-1-/- mice was followed by anergic rather than memory state due to the defective down-regulation of Rap1 activation, resulting in the age-dependent progression of overall T cell immunodeficiency.

Animals↗

PubMed2003

AF-6 controls integrin-mediated cell adhesion by regulating Rap1 activation through the specific recruitment of Rap1GTP and SPA-1.

In the present study, we showed that SPA-1, a Rap1 GTPase-activating protein (GAP), was bound to a cytoskeleton-anchoring protein AF-6. SPA-1 and AF-6 were co-immunoprecipitated in the 293T cells transfected with both cDNAs as well as in normal thymocytes. In vitro binding studies using truncated fragments and their mutants suggested that SPA-1 was bound to the PDZ domain of AF-6 via probable internal PDZ ligand motif within the GAP-related domain. The motif was conserved among Rap1 GAPs, and it was shown that rapGAP I was bound to AF-6 comparably with SPA-1. RapV12 was also bound to AF-6 via the N-terminal domain, and SPA-1 and RapV12 were co-immunoprecipitated only in the presence of AF-6, indicating that they could be brought into close proximity via AF-6 in cells. Immunostaining analysis revealed that SPA-1 and RapV12 were co-localized with AF-6 at the cell attachment sites. In HeLa cells expressing SPA-1 in a tetracycline-regulatory manner, expression of AF-6 inhibited endogenous Rap1GTP and beta(1) integrin-mediated cell adhesion to fibronectin in SPA-1-induced conditions, whereas it affected neither of them in SPA-1-repressed conditions. These results suggested that AF-6 could control integrin-mediated cell adhesion by regulating Rap1 activation through the recruitment of both SPA-1 and Rap1GTP via distinct domains.

Animals↗

PubMed2003

Myeloproliferative stem cell disorders by deregulated Rap1 activation in SPA-1-deficient mice.

SPA-1 (signal-induced proliferation-associated gene-1) is a principal Rap1 GTPase-activating protein in hematopoietic progenitors. SPA-1-deficient mice developed a spectrum of myeloid disorders that resembled human chronic myelogenous leukemia (CML) in chronic phase, CML in blast crisis, and myelodysplastic syndrome as well as anemia. Preleukemic SPA-1-deficient mice revealed selective expansion of marrow pluripotential hematopoietic progenitors, which showed abnormal Rap1GTP accumulation. Overexpression of an active form of Rap1 promoted the proliferation of normal hematopoietic progenitors, while SPA-1 overexpression markedly suppressed it. Furthermore, restoring SPA-1 gene in a SPA-1-deficient leukemic blast cell line resulted in the dissolution of Rap1GTP accumulation and concomitant loss of the leukemogenicity in vivo. These results unveiled a role of Rap1 in myeloproliferative stem cell disorders and a tumor suppressor function of SPA-1.

Animals↗

PubMed2003

Rap1 GTPase: functions, regulation, and malignancy.

Rap1 is a member of the Ras family of small GTPases that is activated by diverse extracellular stimuli in many cell types. It is activated by distinct types of Rap1 guanine nucleotide exchange factors coupled with various receptors or second messengers, while activated Rap1 is down-regulated by Rap1 GTPase-activating proteins, through which Rap1 activation is controlled spatio-temporally. Functionally, Rap1 either interferes with Ras-mediated ERK activation or activates ERK independently of Ras in a cell-context dependent manner. Accumulating evidence also indicates that Rap1 is a major activator of integrins, playing important roles in the regulation of a variety of integrin-dependent cellular functions. Most recently, significant evidence has emerged that dysregulation of Rap1 activation is responsible for the development of malignancy. Recent extensive research has begun to unveil the roles of this controversial small G protein in physiology and diseases.

Animals↗