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C Morimoto

Publications and source records attributed to C Morimoto.

At least 73 records · Page 4Linked to original sources
PubMed1998

Correlation of the epitopes defined by anti-CD26 mAbs and CD26 function.

To clarify the different anti-CD26 mAbs corresponding different functions of CD26, the correlation of the epitopes defined by anti-CD26 mAbs and the functions of CD26 have been studied. Using truncated, human-rat CD26 swap mutants and cross-blocking studies, 13 anti-CD26 mAbs were divided into 5 separate groups. These 5 epitopes were localized between the 1-247th, 248-358th, 359-449th (closer to the 359th amino acid), 450-577th and 359 653th amino acid regions. MAbs against two of these five epitopes, the 248-358th and 359-449th amino acid regions, were associated with inducing modulation of CD26 and T-cell costimulation through the CD3 pathway. Furthermore, mAbs against one of these epitopes, the 359-449th amino acid region, appeared to encompass the ADA binding domain. Analysing the avidity of each mAb to the CD26 molecule using DPPIV enzymatic activity as an indicator, we found that the function of CD26 had little correlation with the avidity of anti-CD26 mAbs, suggesting that distinct epitopes defined by anti-CD26 mAbs appeared to be associated with different functions of CD26. These results will be very useful in the further definition of the functional domains of CD26.

Animals↗
PubMed1998

Surrogate thrombopoietin.

The extracellular domain of human c-Mpl, the receptor for thrombopoietin (TPO), was expressed as a chimeric protein with the interleukin-2 receptor alpha chain on the surface of murine B cell-line B300-19. BALB/c mice were immunized with cells expressing the chimeric protein. The IgG purified from the resulting immune serum immunoprecipitated human c-Mpl. The immune IgG supported proliferation of both stable transfectant Ba/F3 cells expressing whole c-Mpl molecules (c-Mpl-Ba/F3 No. 9) and UT7/TPO cells bearing naturally occurring c-Mpl, whereas it did not support the growth of the untransfected parental Ba/F3 cells. Cell growth was induced using 3 to 100 microg/ml of immune IgG in a dose-dependent manner, but this induction was decreased at doses higher than 100 microg/ml. Non-immune IgG did not affect cell growth of c-Mpl-Ba/F3 No. 9 cells. Although the Fab fragment of immune IgG also immunoprecipitated c-Mpl, it did not support cell growth at concentrations as high as 180 microg/ml, implying that the bivalent binding of receptors by antibodies is essential for cell proliferation. These results suggest that antibodies against human c-Mpl stimulate the proliferation and differentiation of megakaryocytes by their bivalent binding to receptors like TPO.

Animals↗
PubMed1998

The structure and function of CD26 in the T-cell immune response.

CD26 is a widely distributed 110 kD cell-surface glycoprotein with known dipeptidyl-peptidase IV (DPP-IV) activity in its extracellular domain. This ecto-enzyme is capable of cleaving amino terminal dipeptides from polypeptides with either L-proline or L-alanine in the penultimate position. On human T cells, CD26 expression appears late in thymic differentiation and is preferentially restricted to the CD4+ helper/memory population, and CD26 can deliver a potent co-stimulatory T-cell activation signal. The cDNA sequence of CD26 predicts a type II membrane protein with only 6 amino acids in its cytoplasmic region, suggesting that, in addition to DPP-IV enzyme activity, other signal-inducing molecules may be associated with CD26. Considerable evidence exists that CD26 interacts, presumably in its extracellular domain, with both CD45, a protein tyrosine phosphatase, and adenosine deaminase (ADA), each of which is capable of functioning in a signal transduction pathway. In addition, CD26 is the receptor for ADA, and ADA on the cell surface is involved in an important immunoregulatory mechanism by which released ADA binds to the cell-surface ADA. This multifunctional molecule may be involved in cell migration and the HIV-1-associated loss of CD4+ cells through the process of programmed cell death. Thus, CD26 appears to play a key role in a number of aspects of lymphocyte function.

Adenosine Deaminase↗
PubMed1998

Antilipolytic actions of insulin on basal and hormone-induced lipolysis in rat adipocytes.

The levels of insulin, free fatty acids (FFA), and triglycerides in rat sera increase with age. The increase in serum FFA levels accompanied the stimulation of basal lipolysis (i.e., lipolysis in the absence of lipolytic agents) in fat cells and enlargement of the diameter of the cells. An overnight fast resulted in a significant increase in basal lipolysis in fat cells from 6- and 8-week-old rats. Although insulin inhibited lipolysis induced by norepinephrine and ACTH at a concentration of 10(-10) M, it failed to inhibit basal lipolysis even at a concentration of 10(-6) M. Propranolol, another antilipolytic agent like insulin, also did not affect basal lipolysis. Insulin did not inhibit the accelerated basal lipolysis in enlarged fat cells, fasted fat cells, and sonicated cells. These results indicate that insulin inhibits only the lipolysis induced by lipolytic agents such as norepinephrine and ACTH but not the basal lipolysis found in the absence of lipolytic agents. The possibility that free fatty acids produced by enlarged fat cells initiate insulin resistance and diabetes mellitus, is discussed.

Adipocytes↗
PubMed1997

Determination of adenosine deaminase binding domain on CD26 and its immunoregulatory effect on T cell activation.

CD26, a 110-kDa cell surface glycoprotein, exhibits dipeptidyl peptidase IV enzyme activity and plays an important role in T cell costimulation. In the present study, we examined both the exact adenosine deaminase (ADA) binding domain on CD26 and the functional consequences of mutated CD26 transfectants that were deficient for cell surface ADA. Using CD26 deletion, human-rat swap, and point mutations, we found that the residues of L340, V341, A342, and R343 on the CD26 molecule were essential amino acids for ADA binding. When these amino acids were mutated and transfected into Jurkat cells, the resultant CD26 transfectants expressed only CD26, not ADA, on the cell surface. The amount of IL-2 produced by wild-type and mutated CD26 transfectants was almost the same following stimulation with anti-CD3 plus PMA. However, the mutated CD26 transfectants were much more sensitive to the inhibitory effect of adenosine on IL-2 production than were the wild CD26 transfectants. These data suggest that ADA on the cell surface does not directly involve T cell activation. Conversely, CD26 alone does not result in modulating the inhibitory effect of adenosine. Only the ADA bound to CD26 on the cell surface was functional and could counteract the inhibitory effect of elevated extracellular adenosine.

Adenosine Deaminase↗
PubMed1997

Cytomegalovirus (CMV) retinitis and CMV antigenemia as a clue to impaired adrenocortical function in patients with AIDS.

OBJECTIVE: To elucidate the relationship between the activity of CMV disease and adrenocortical function in patients with AIDS. DESIGN AND PATIENTS: CMV retinitis and CMV antigenemia assay (CMV-Ag: numbers of polymorphonuclear leukocytes positive for CMV pp65 antigen per 1.5 x 10(5) cells) are the least invasive and easily accessible examinations to assess the CMV disease activity. All HIV-infected patients with CD4+ lymphocyte counts < 50 x 10(6)/l who were admitted to the Research Hospital of the Institute of the Medical Science (University of Tokyo) between May 1995 to April 1996 were included in this study. METHODS: Fundoscopic examination on CMV retinitis and CMV-Ag were chosen as methods to assess CMV activity because of their simplicity. Adrenocortical function was evaluated by basal plasma adrenocorticotropin, plasma cortisol, plasma aldosterone, plasma renin activity, and responses of plasma cortisol and plasma aldosterone to 250 micrograms intravenous cosyntropin [rapid adrenocorticotropin test (RAT)]. RESULTS: Thirty patients were enrolled in this study with a maximum CD4+ lymphocyte count of 32 x 10(6)/l. Eleven out of 30 patients showed impaired RAT response (37%). Fourteen out of 30 patients had CMV retinitis. A significant correlation was found between the presence of CMV retinitis and subnormal cortisol response (P < 0.005). Sixteen out of the 30 patients were CMV-Ag-positive. A significant correlation was found between CMV-Ag positivity and subnormal cortisol response to RAT (P < 0.005). CMV-Ag levels in the patients with subnormal cortisol response to RAT were significantly higher than those with normal response (P < 0.001). Importantly, five patients with subnormal cortisol response but not overt adrenal insufficiency at the time of RAT developed overt disease shortly afterwards. Autopsy was performed in six patients with subnormal cortisol response and showed multiple inclusion bodies indicative of CMV adrenitis. CONCLUSION: The adrenal gland is most frequently affected by CMV in AIDS patients. Our result suggests that CMV retinitis or CMV-Ag positivity independently serve as an indication of possible adrenal dysfunction.

AIDS-Related Opportunistic Infections↗
PubMed1997

Altered tyrosine phosphorylation via the very late antigen (VLA)/beta1 integrin stimulation is associated with impaired T-cell signaling through VLA-4 after allogeneic bone marrow transplantation.

Our previous study showed that the cross-linking of very late antigen (VLA)/beta1 with anti-CD29 monoclonal antibody (MoAb), or interactions with extracellular matrix (ECM) proteins through VLA/beta1, failed to induce T-cell costimulation via the CD3/T cell receptor (TCR) pathway for over 1 year after allogeneic bone marrow transplantation (allo-BMT), although normal CD29 and CD3 expression was observed after 3 months following allo-BMT. Molecular analysis revealed altered tyrosine phosphorylation of cellular proteins by the solid-phase cross-linking of VLA/beta1 molecules in T cells from patients after allo-BMT. In T cells from early allo-BMT patients (<4 months), various sizes of highly tyrosine phosphorylated proteins were observed as high background even without the stimulation through VLA/beta1 integrin. The high tyrosine phosphorylation pattern gradually disappeared and it was finally returned to normal tyrosine phosphorylation patterns by 2 years after BMT. Interestingly, poor expression of focal adhesion kinase (pp125FAK), a VLA/beta1-mediated signaling molecule, was observed within 1 year after BMT. These results suggest that these molecular defects appear to be implicated in the impaired VLA/beta1-mediated signaling in T cells from patients after allo-BMT, and it could explain, in part, the persistent immunoincompetent state after allo-BMT at least 1 year.

Adolescent↗
PubMed1997

Tyrosine phosphorylation of Crk-associated substrates by focal adhesion kinase. A putative mechanism for the integrin-mediated tyrosine phosphorylation of Crk-associated substrates.

Integrin-ligand binding induces the tyrosine phosphorylation of various proteins including focal adhesion kinase (pp125(FAK)) and Crk-associated substrate (Cas). FAK is activated and autophosphorylated by the ligation of integrins, although the substrate of FAK has not been revealed. We show here that p130(Cas) and Cas-L are FAK substrates. FAK directly phosphorylates Cas proteins primarily at the YDYVHL sequence that is conserved among all Cas proteins. Furthermore, the phosphorylated YDYVHL sequence is a binding site for Src family protein-tyrosine kinases, and the recruited Src family kinase phosphorylates the other tyrosine residues within Cas. The Cas-L YDYVHL sequence is phosphorylated upon integrin-ligand binding, and this integrin-mediated tyrosine phosphorylation is inhibited by the cotransfection of the FAK COOH-terminal domain that does not contain a kinase domain. These findings strongly suggest that FAK initiates integrin-mediated tyrosine phosphorylation of Cas proteins; then, Src family tyrosine kinases, which are recruited to phosphorylated Cas and FAK, further phosphorylate Cas proteins.

Adaptor Proteins, Signal Transducing↗
PubMed1997

CD154/CD40 and CD70/CD27 interactions have different and sequential functions in T cell-dependent B cell responses: enhancement of plasma cell differentiation by CD27 signaling.

CD40, a TNF receptor family member, plays a central role in T cell-mediated B cell activation. We have recently demonstrated that CD27, another TNF receptor family member, was also involved in B cell regulation and enhanced Ig production. In this report we compare CD27 and CD40 signals in B cell function. We selectively mimicked the effect of T cell help by addition to peripheral blood B cells activated with Staphylococcus aureus Cowan I strain and IL-2 of irradiated 300-19 cells transfected with either the CD70 (CD27 ligand) gene or the CD154 (CD40 ligand) gene, the vector alone, or both CD70 and CD154 genes. CD27 ligation induced only a slight increase in B cell proliferation compared with the dramatic enhancement induced by CD40 ligation; double ligation proved to be less efficient than CD40 ligation alone. In contrast, IgG production was increased only by CD27 ligation alone. Moreover, the CD27 signal was more efficient when it was given on day 2 of the culture rather than on day 0. Phenotypic analysis of the activated cells showed that CD27 ligation increased the percentage of cells showing a plasma cell profile (CD19-, CD38+), whereas upon CD40 ligation most of the cells still had a germinal center-like phenotype (CD19+, CD38+). Our results suggest that the CD27 and CD40 signals are not synergistic but, rather, are complementary and involve distinct steps of T cell-dependent B cell activation. CD27 may be more important in the induction of plasma cell differentiation at a time when the expansion phase has already occurred.

B-Lymphocytes↗
PubMed1997

CD27/CD70 interaction contributes to the activation and the function of human autoreactive CD27+ regulatory T cells.

CD27, a tumor necrosis factor receptor family member, is a constimulatory molecule for T and B cell activation. We demonstrate here that CD27 signaling is critical for T cell activation in the autologous mixed lymphocyte reaction (aMLR) and for aMLR-induced generation of regulatory T cells that suppress pokeweed mitogen-driven immunoglobulin G synthesis by B cells. Moreover, CD27, expressed on CD45RA+ CD4+ T cells, is directly involved in the suppressor function of aMLR-activated CD4+ T cells, probably by interfering with the interaction between CD70, the CD27 ligand, expressed on CD45RO+ CD4+ helper T cells, and CD27, expressed on B cells. CD8+ T cells, which are required in this system to obtain suppression, on the other hand, do not need CD27 engagement to exert their suppressor function.

Antigens, CD↗
PubMed1997

B cell subpopulations separated by CD27 and crucial collaboration of CD27+ B cells and helper T cells in immunoglobulin production.

B cell immunoglobulin production is regulated by helper T cells through direct interaction and secreted cytokines. In the present study, we functionally analyzed CD27 in cord and peripheral blood B cells. Adult peripheral blood B cells were separated into CD27+ and CD27- cells, which differed in their morphology. Cord blood B cells did not express CD27, and CD27 expression on peripheral blood B cells increased with age. Only CD27+ B cells had the ability to produce immunoglobulin, which was increased by contact with a tumor necrosis factor-related transmembrane ligand, CD70. Adult peripheral blood CD27+ B cells can be further subdivided into two discrete subtypes: IgD- CD27+ and IgD+ CD27+ B cells. IgD- CD27+ B cells produce IgG, IgM and IgA, whereas IgD+ CD27+ B cells predominantly produce IgM. The addition of activated CD4+ CD45RO T cells expressing CD70 caused down-regulation of CD27 expression on activated B cells, and this down-modulation was completely blocked by anti-CD70 monoclonal antibody, indicating direct T-B cell contact via CD27/CD70. The triggering via CD27 and CD40 additively increased the immunoglobulin production under Staphylococcus aureus Cowan strain plus interleukin-2 stimulation. Taken together, our findings demonstrate that peripheral blood B cells are separated into subpopulations by CD27 and IgD expression and that CD27+ B cells produce large amounts of immunoglobulin by interaction with the CD70 molecule.

Adult↗
PubMed1997

Ligation of the T cell antigen receptor induces tyrosine phosphorylation of p105CasL, a member of the p130Cas-related docking protein family, and its subsequent binding to the Src homology 2 domain of c-Crk.

p105CasL (CasL) is a recently identified signaling molecule closely related to the p130Cas (Crk-associated substrate) docking protein. CasL has a single Src homology (SH) 3 domain in its N-terminal portion followed by multiple consensus motifs for binding to SH2 domains. Like original p130Cas, CasL undergoes tyrosine phosphorylation upon integrin-mediated cell adhesion. In the present report, we provide direct evidence that CasL is also involved in T cell antigen receptor (TcR)-mediated signal transduction. In binding studies in vitro using glutathione-S-transferase fusion proteins, we have identified 105- and 120-kDa phosphotyrosyl proteins (pp105 and pp120, respectively) tightly bound to the SH2 domain of the Crk adapter protein in the H9 human T cell line after stimulation through the CD3/TcR complex. pp120, but not pp105, also bound to the SH3 of another adapter protein, Ash/Grb2. Immunoblotting with specific antibodies revealed that pp120 and pp105 were identical to the c-cbl proto-oncogene product (p120cbl) and CasL, respectively. Association between Crk and tyrosine-phosphorylated CasL after TcR stimulation was also confirmed in vivo. CasL phosphorylation induced by TcR ligation reached maximal levels within 2 min and rapidly declined thereafter, whereas the integrin-dependent response occurred slowly and was more prolonged. Finally, we demonstrated that Crk/CasL association occurred in peripheral blood T lymphocytes in response to TcR engagement. Our findings suggest that CasL is involved in T cell activation signals and resides at a point where two distinct receptor-mediated signaling pathways converge. This provides one mechanism by which integrins may mediate T cell co-stimulation.

Adaptor Proteins, Signal Transducing↗
PubMed1997

Different regulatory effects of pentoxifylline on human T cell activation pathways.

Pentoxifylline (PTX), a methylxanthine derivative, was examined for its effects on T cell proliferation and cytokine production stimulated by cross-linking anti-CD3 alone, anti-CD3 with PMA, anti-CD3 with anti-CD26, or anti-CD3 with anti-CD28 mAb, respectively. PTX at a 3.5 x 10(-5) M concentration significantly inhibited T cell proliferation and the production of tumor necrosis factor-alpha, interleukin-2, and interleukin-4. Moreover, this effect was selective for stimulation by cross-linking anti-CD3 with PMA, or anti-CD3 with anti-CD26, but not by cross-linking anti-CD3 with anti-CD28. These results suggest that the inhibitory effect of PTX on T cell activation involves the CD3 and CD26, but not the CD28 signal pathway.

Cell Survival↗
PubMed1997

Activation of human monocytes for enhanced production of interleukin 8 during transendothelial migration in vitro.

Interleukin-8 (IL-8) is a chemokine for polymorphonuclear leukocytes (PMNs) and lymphocytes, which promotes the extravasation of these inflammatory cells. In this study, we investigated IL-8 synthesis induced by the adhesive interaction between monocytes and endothelial cells during transmigration and the capacity of transmigrated monocytes to produce IL-8. Cocultured human monocytes and human umbilical vein endothelial cell (HUVEC) monolayers induced the synergistic production of IL-8, compared with cultures of either monocytes or HUVEC monolayers alone. Coculture-induced IL-8 production almost doubled after HUVECs were stimulated with IL-1 beta. The induced IL-8 mRNA expression was consistent with the protein data, indicating the de novo synthesis of IL-8 by the coculture. Monoclonal antibodies (mAbs) against IL-8 inhibited the transendothelial chemotactic activity of the supernatants for PMNs by 55%. Immunohistochemistry revealed that both adherent and transmigrated monocytes and unstimulated HUVECs expressed IL-8 protein, whereas nonadherent monocytes did little. Transmigrated monocytes spontaneously secreted a 3.8-fold greater amount of IL-8 than the initial monocytes. Coculture-induced IL-8 production was inhibited about 30% by polyclonal Abs against IL-alpha, IL-1 beta, or tumor necrosis factor alpha, while it was not affected by mAbs against intercellular adhesion molecule 1 or vascular cell adhesion molecule 1. The results suggested that adhesive interaction during the transmigration of monocytes through HUVEC monolayers activates both cell types to produce IL-8 and that transmigrated monocytes are capable of producing ample IL-8.

Antibodies, Monoclonal↗
PubMed1997

Cross-linking of CD26 by antibody induces tyrosine phosphorylation and activation of mitogen-activated protein kinase.

CD26, a T-cell activation antigen that has dipeptidyl peptidase IV activity in its extracellular domain and has also been shown to play an important role in T-cell activation. The earliest biochemical events seen in stimulated T lymphocytes activated through the engagement of the T-cell receptor (TCR) is the tyrosine phosphorylation of a panel of cellular proteins. In this study we demonstrate that antibody-induced cross-linking of CD26-in CD26-transfected Jurkat cells induced tyrosine phosphorylation of several intracellular proteins with a similar pattern to that seen after TCR/CD3 stimulation. Herbimycin A, an inhibitor of the src family protein tyrosine kinases dramatically inhibited this CD26-mediated effect on tyrosine phosphorylation. Major tyrosine phosphorylated proteins were identified by immunoblotting, and included p56lck, p59fyn, zeta associated protein-tyrosine kinase of 70,000 MW (ZAP-70), mitogen-activated protein (MAP) kinase, c-Cb1, and phospholipase C gamma. CD26-induced tyrosine phosphorylation of MAP kinase correlated with increased MAP kinase activity. In addition, CD26 was costimulatory to CD3 signal transduction since co-cross-linking of CD26 and CD3 antigens induced prolonged and increased tyrosine phosphorylation in comparison with CD3 activation alone. We therefore conclude that CD26 is a true costimulatory entity that can up-regulate the signal transducing properties of the TCR.

Antibodies, Monoclonal↗
PubMed1997

Tyrosine phosphorylation of the product of the c-cbl protooncogene is [corrected] induced after integrin stimulation.

Integrin crosslinking on human B cells induces tyrosine phosphorylation of a set of proteins ranging from 105 to 130 kDa, among which is the focal adhesion kinase p125FAK. Here we show that the c-CBL protooncogene product p120c-CBL is a component of these substrates. beta 1 integrin stimulation of p120c-CBL phosphorylation was observed in both transformed and normal human B cells, and was inhibited by prior treatment of cells with cytochalasin B, which disrupts the actin network. In contrast, tyrosine phosphorylation of p120c-CBL following crosslinking of the B cell antigen receptor (BCR) was not affected by cytochalasin B. Integrin stimulation of the promegakaryocytic cell line MO7e also led to a cytoskeleton-dependent tyrosine phosphorylation of p120c-CBL. In MO7e cells, this stimulation was induced by ligation of either beta 1 or beta 2 integrin, whereas only by ligation of beta 1 integrin in B cells. Tyrosine phosphorylation of p120c-CBL links phosphatidylinositol-3 kinase (PI-3K) with the BCR signaling machinery. Although the p85 subunit of PI-3K was increased in p120c-CBL immunoprecipitates from BCR-stimulated B cells, this association was only minimally increased by beta 1 integrin ligation. The function of p120c-CBL remains unknown; however, its interactions in vitro and in vivo with Src homology 2 and 3 (SH2 and SH3) domain-containing proteins suggest that p120c-CBL has a significant function in signal transduction pathways, and therefore may play a role in integrin signaling in lymphoid and hematopoietic cells.

B-Lymphocytes↗
PubMed1997

Norepinephrine-induced lipolysis in rat fat cells from visceral and subcutaneous sites: role of hormone-sensitive lipase and lipid droplets.

Norepinephrine-induced lipolysis was examined in visceral (epididymal and omental) and subcutaneous (abdominal and femoral) fat cells in rats. Hormone-induced lipolysis was considerably higher in the visceral fat cells than in the subcutaneous cells. A higher hormone-sensitive lipase (HSL) activity was present in the visceral than in the subcutaneous fat cells. Endogenous lipid droplets were prepared from rat visceral (epididymal and omental) and subcutaneous (abdominal and femoral) fat cells and norepinephrine-induced lipolysis was examined in a cell-free system consisting of the lipid droplets prepared from fat cells from each site and a fixed amount of HSL from rat epididymal adipose tissue. In this cell-free system, norepinephrine induced a higher rate of lipolysis with lipid droplets from the visceral than from the subcutaneous fat cells. These findings suggest that the difference in norepinephrine-induced lipolysis between visceral and subcutaneous fat cells may be due to the differences in HSL activity and lipid droplet character at each site.

Abdomen↗