Biomedical subjects

Takeshi Senga

Publications and source records attributed to Takeshi Senga.

14 recordsLinked to original sources

PubMed2004

A dimerized coiled-coil domain and an adjoining part of geminin interact with two sites on Cdt1 for replication inhibition.

Geminin is a cellular protein that associates with Cdt1 and inhibits Mcm2-7 loading during S phase. It prevents multiple cycles of replication per cell cycle and prevents episome replication. It also directly inhibits the HoxA11 transcription factor. Here we report that geminin forms a parallel coiled-coil homodimer with atypical residues in the dimer interface. Point mutations that disrupt the dimerization abolish interaction with Cdt1 and inhibition of replication. An array of glutamic acid residues on the coiled-coil domain surface interacts with positive charges in the middle of Cdt1. An adjoining region interacts independently with the N-terminal 100 residues of Cdt1. Both interactions are essential for replication inhibition. The negative residues on the coiled-coil domain and a different part of geminin are also required for interaction with HoxA11. Therefore a rigid cylinder with negative surface charges is a critical component of a bipartite interaction interface between geminin and its cellular targets.

Amino Acid Sequence↗

PubMed2004

Stat3-dependent induction of interleukin-3 receptor expression in leukemia inhibitory factor-stimulated M1 mouse leukemia cells.

M1 mouse leukemia cells differentiate to macrophages/monocytes by the stimulation of interleukin-6 (IL-6)/leukemia inhibitory factor (LIF). To identify new LIF-induced genes, we have performed representational difference analysis using M1 cells and cloned mouse interleukin-3 (IL-3) receptor beta subunit gene. The mRNA expression of both IL-3 receptor (IL-3R) alpha and beta subunits is upregulated after 1 h stimulation of LIF and remains to be elevated along the differentiation of M1 cells. This induction is almost completely suppressed in M1 cells expressing a dominant negative form of Stat3. Furthermore, we show that IL-3-induced Stat5 phosphorylation increases in LIF-stimulated M1 cells. These results suggest that Stat3 may play a role in the differentiation of myeloid cells by regulating IL-3R expression.

Amino Acid Substitution↗

PubMed2004

Tyrosine phosphorylation of NOS3 in a breast cancer cell line and Src-transformed cells.

We investigated the tyrosine phosphorylation of NOS3 by active Src. In a cell line derived from human breast cancer, BT474, we found activation of c-Src and tyrosine phosphorylation of NOS3. Phosphorylation of NOS3 was suppressed by treatment of BT474 with PP1, an Src kinase inhibitor, in a dose-dependent manner, suggesting that phosphorylation of NOS3 is catalyzed by active c-Src. Phosphorylation of NOS3 was further examined by a series of Src mutants. In cells expressing v-Src, substantial phosphorylation of NOS3 was observed, whereas NOS3 phosphorylation was not evident in cells expressing c-Src. Similarly, NOS1 was also phosphorylated in cells expressing v-Src. Consistently, in cells expressing a temperature-sensitive mutant of v-Src, NOS3 phosphorylation was temperature-dependent. Moreover, transforming mutant of c-Src, Y527Fc-Src, could activate NOS3 phosphorylation. In contrast, non-myristoylated form of v-Src, G2Av-Src and a kinase-inactive mutant of v-Src, K295Mv-Src, could not activate NOS3 phosphorylation. Taken together, our results suggest that active, membrane-bound form of Src can induce constitutive phosphorylation of NOS3.

Animals↗

PubMed2003

SH2 domain containing protein tyrosine phosphatase 2 regulates concanavalin A-dependent secretion and activation of matrix metalloproteinase 2 via the extracellular signal-regulated kinase and p38 pathways.

We investigated the role of SH2 domain containing protein tyrosine phosphatase (SHP) 2 in Concanavalin A (Con A) -dependent signaling that leads to the augmented secretion and activation of matrix metalloproteinase (MMP) 2. In cells expressing mutant SHP-2 in which 65 amino acids in the SH2-N domain were deleted, we found that production, secretion, and proteolytic activation of MMP-2 in response to Con A treatment was severely impaired. Under Con A stimulation, complex formation of SHP-2 with SOS-1 and Grb-2 together with the activation of Ras signaling was clearly observed in wild-type cells, but not in SHP-2 mutant cells. In wild-type cells, Con A-treatment activated dual signaling pathways, extracellular signal-regulated kinase (Erk) and p38, in a Ras-dependent manner, whereas Con A-dependent activation of these signaling pathways was absent in SHP-2 mutant cells. In addition, pretreatment of wild-type cells with U0126, a potent inhibitor for mitogen-activated protein/ERK kinase 1, or with SB203580, a specific inhibitor for p38, significantly inhibited the Con A-dependent secretion and activation of MMP-2. However, overexpression of active mitogen-activated protein/ERK kinase 1 in SHP-2 mutant cells could not induce clear activation of MMP-2 secretion, although these cells responded well to the Con A treatment in a p38-dependent manner. Finally, reintroduction of wild-type SHP-2 into SHP-2 mutant cells rescued Erk and p38 activation, and also MMP-2 secretion, whereas dominant-negative SHP-2 could block the Con A-dependent activation of Erk and p38. Taken together, our results strongly suggest that SHP-2 plays a critical role as a positive mediator for Con A-dependent activation of MMP-2 secretion via Ras-Erk and Ras-p38 signalings.

Animals↗

PubMed2003

Cysteine residues in the C-terminal lobe of Src: their role in the suppression of the Src kinase.

To evaluate the function of cysteine residues of the Src kinase, we constructed a series of Src mutants in which some of cysteines were replaced to alanines. With these mutants, we studied the effect of SH-alkylating agents, N-[p-(2-benzimidazolyl)phenyl] maleimide (BIPM) and N-(9-acridinyl) maleimide (NAM), on their kinase activity. Of 10 cysteine residues scattered over v-Src, either a single mutation at Cys520 or multiple mutations at the four clustered cyteines, Cys483, Cys487, Cys496 and Cys498, yielded clear resistance to the treatment with 10 microM BIPM or 1 microM NAM. In contrast, other cysteines including those in the SH2 domain and those in the catalytic cleft of the kinase domain were dispensable for the inactivation by BIPM and NAM. Similarly, deletion of SH2 and SH3 did not confer the resistance to v-Src, suggesting the inactivation by the SH-alkylating agents is SH2/SH3-independent. Although Cys520-mutated v-Src was resistant to 1 microM NAM, it was inactivated by 5 microM NAM. However, combined mutation including all of Cys483, Cys487, Cys496, Cys498 and Cys520 yielded clear resistance to 5 microM NAM. Among these mutants, those with double mutations in the four clustered cysteines yielded a temperature sensitive phenotype in the transfected cells, whereas Cys520 did not, suggesting that Cys520 has, at least in part, a discrete function. In contrast to v-Src, c-Src, which lacks cysteine at position 520, was resistant to 1 microM NAM but sensitive to 5 microM NAM. While replacement of Phe520 of c-Src to cysteine made it sensitive to 1 microM NAM, double mutation in clustered cysteines again yielded resistance to 5 microM NAM. Taken together, our results strongly suggest that the multiple cysteine residues clustered at the end of the C-terminal lobe are critical for the inhibition by the SH-alkylating agents and, thereby, have an allosteric repressor effect on the catalytic activity of Src in a SH2-phosphoTyr527 independent manner.

Alkylating Agents↗

PubMed2003

Secretion of matrix metalloproteinase-9 by the proinflammatory cytokine, IL-1beta: a role for the dual signalling pathways, Akt and Erk.

BACKGROUND: Matrix metalloproteinases including MMP-9 mediate matrix destruction during chronic inflammatory diseases such as arthritis and atherosclerosis. MMP-9 up-regulation by inflammatory cytokines involve interactions between several transcription factors including activator protein-1 and NFkappaB. The upstream regulatory pathways are less well understood. RESULTS: To search for the mechanism of tissue destruction in the process of inflammatory disorders, we investigated the signalling pathway critical for the activation of MMP-9 expression and secretion by IL-1beta. Treatment of Balb 3T3 cells with IL-1beta activated MMP-9 transcription and subsequent secretion in a time- and dose-dependent manner. Concomitantly, IL-1beta treatment of cells activated phosphorylation of Akt, Erk and p38. Treatment of cells with either LY294002, a PI3K inhibitor, or expression of a dominant negative form of Akt drastically suppressed the IL-1beta-dependent secretion of MMP-9. Pretreatment of cells with a MEK1 inhibitor, U0126, also strongly inhibited IL-1beta-dependent secretion of MMP-9. In contrast, pre-treatment with a specific p38 kinase inhibitor, SB203580, had no effect on IL-1beta-dependent secretion of MMP-9. In addition, cells expressing constitutively active form of Akt or MEK1 showed no clear activation of MMP-9 secretion, whereas these cells responded well to IL-1beta treatment. However, co-transfection of cells with both active Akt and MEK1 was sufficient to induce MMP-9 secretion without stimulation with IL-1beta. CONCLUSION: Taken together, our results suggest that IL-1beta stimulation of cells activates MMP-9 secretion by the activation of the dual signalling pathways, the PI3K-Akt and MEK1-Erk and constitutive activation of these pathways were sufficient to induce MMP-9 secretion.

Animals↗

PubMed2003

Profiling of gene expression associated with hepatolithiasis by complementary DNA expression array.

By use of cDNA expression array method, we compared the expression profiles of genes in hepatolithiasis tissues with those of paired normal tissues. Expression of 1176 cancer related genes that include 33 tumor suppressor genes, 100 proto-oncogenes and 37 DNA damage repair genes were examined in this study. We found that expression of tumor suppressor genes and proto-oncogenes was systemically activated in hepatholithiasis tissues, suggesting that expression of genes controlling cell growth becomes unstable in liver lobe of hepatolithiasis. In contrast, expression of DNA damage repair genes were not activated but rather remained unchanged in hepatholithiasis tissues, suggesting that repair process is not strongly activated but rather impaired in hepatholithiasis tissues.

Calculi↗

PubMed2002

A role for SHPS-1/SIRPalpha1 in IL-1beta- and TNFalpha-dependent signaling.

We investigated the role of SHPS-1/SIRPalpha1 in IL-1beta- and TNFalpha-dependent signaling that leads to the activation of Erk 1/2 and Akt. Treatment of Balb3T3 cells with IL-1beta or TNFalpha activated tyrosine phosphorylation of SHPS-1, its association with SHP-2 and the phosphorylation of Erk 1/2 and Akt. PP1, a specific inhibitor for the Src family protein tyrosine kinases, strongly inhibited tyrosine phosphorylation of SHPS-1 and complex formation of SHPS-1 with SHP-2 by IL-1beta. In addition, PP1 substantially inhibited the IL-2beta- and TNFalpha-dependent activation of Erk 1/2 and Akt. Exogenous expression of either SHPS-1 mutants that lack SHP-2 binding function or a dominant negative mutant of SHP-2 markedly inhibited the activation of Erk 1/2 and Akt by IL-1beta, whereas wild type SHPS-1 did not. Moreover, IL-1beta-stimulation induced association of SHPS-1 with IL-1RAcP, a second subunit of IL-1 receptor, whereas expression of SHPS-1 mutant that lack SHP-2 binding function clearly blocked the association and tyrosine phosphorylation of endogenous SHPS-1. Taken together, our results strongly suggest that activation of Erk 1/2 and Akt by proinflammatory cytokines requires tyrosine phosphorylation of SHPS-1 and subsequent association of SHPS-1 with SHP-2.

3T3 Cells↗

PubMed2002

Stat3-dependent induction of BATF in M1 mouse myeloid leukemia cells.

Stat3 mediates cellular responses associated with proliferation, survival and differentiation, but the mechanisms underlying the diverse effects of this signaling molecule remain unknown. M1 mouse myeloid leukemia cells arrest growth and differentiate into macrophages following treatment with interleukin 6 (IL-6) or leukemia inhibitory factor (LIF), and recent studies have shown that Stat3 plays a central role in this process. Utilizing representational difference analysis, we demonstrate that expression of the mouse BATF gene is upregulated as an early response to IL-6/LIF stimulation and Stat3 activation in this cell system. Immunoblots using antibodies to BATF detected an increase in BATF protein in response to LIF/IL-6 stimulation. BATF is a member of the AP-1 family of basic leucine zipper transcription factors and functions to inhibit the transcriptional and biological functions of AP-1 activity in mammalian cells. BATF forms complexes with c-Jun in M1 cells and forced expression of BATF in the absence of Stat3 signaling results in a reduced rate of cellular growth. These results indicate that Stat3 mediates cellular growth by modulating AP-1 activity through the induction of BATF.

Animals↗

PubMed2002

LSSIG is a novel murine leukocyte-specific GPCR that is induced by the activation of STAT3.

G-protein-coupled receptors (GPCRs) transduce the signal of a wide variety of chemokines, cytokines, neurotransmitters, hormones, odorants, and others to regulate the biologic homeostasis, including hematopoiesis and immunity. Here we report the molecular cloning of leukocyte-specific STAT-induced GPCR (LSSIG), which is a novel murine orphan GPCR with the highest homology to human GPR43. The mRNA expression of LSSIG was clearly induced in M1 leukemia cells during the leukemia inhibitory factor (LIF)-induced differentiation to macrophages, and the induction was evidently signal transducers and activators of transcription 3 (STAT3)-dependent. GPR43 expression was also strongly induced in HL-60 and U937 leukemia cells during the differentiation to monocytes. Further analysis showed that the expression of both LSSIG and GPR43 is highly restricted in hematopoietic tissues. Cytokine-stimulation induced LSSIG and GPR43 in bone marrow cells, and monocytes and neutrophils, respectively. These results suggest that LSSIG and GPR43 might play pivotal roles in differentiation and immune response of monocytes and granulocytes.

Animals↗

PubMed2002

Hyaluronan-CD44s signaling regulates matrix metalloproteinase-2 secretion in a human lung carcinoma cell line QG90.

We investigated the production of matrix metalloproteinase (MMP) by hyaluronan(HA) stimulation in a human cancer cell line, QG90, that expresses a large amount of CD44s, a HA receptor. Treatment of QG90 with HA strongly activated MMP-2 secretion in a time- and dose-dependent manner. We found that expression of antisense CD44s in QG90 cells substantially inhibited the HA-dependent secretion of MMP-2, whereas overexpression of full-length CD44s augmented the HA-dependent secretion of MMP-2. In addition, pretreatment of cells with the neutralizing anti-CD44 antibody significantly inhibited both the HA-dependent MMP-2 secretion and the HA-dependent activation of mitogen-activated protein kinase in a dose-dependent manner. Similarly, treatment of cells with a Ras farnesyltransferase inhibitor, manumycin A, strongly inhibited the HA-dependent MMP-2 secretion. Moreover, in vitro invasiveness of QG90 and its activation by HA were clearly suppressed by the expression of antisense CD44s. In addition, treatment of cells with anti-CD44, a mitogen-activated protein/extracellular signal-regulated kinase kinase 1 inhibitor, PD98059, or phosphatidylinositol 3'-kinase inhibitors, wortmannin and LY294002, effectively blocked the HA-dependent activation of the invasiveness. In contrast, overexpression of full-length CD44 substantially activated the invasiveness of QG90. Taken together, HA-CD44s signaling plays a key role in the HA-dependent secretion of MMP-2 and, hence, in the invasiveness of QG90 cells.

Carcinoma, Small Cell↗

PubMed2002

Repair by Src kinase of function-impaired RET with multiple endocrine neoplasia type 2A mutation with substitutions of tyrosines in the COOH-terminal kinase domain for phenylalanine.

An oncogenic mutant of c-RET as a receptor-type tyrosine kinase, termed RET-MEN2A, displays both cell-transforming activity in vivo and strong catalytic activity in vitro. In this study, we compared the activities of mutant RET-MEN2A with substitutions of each of nine tyrosines for phenylalanine (Y1062F, Y1015F, Y981F, Y952F, Y928F, Y905F, Y900F, Y864F, and Y826F), which had been transfected into NIH 3T3 cells. In RET-MEN2A with the Y905F mutation, the cell-transforming activity was drastically reduced with a great reduction in the in vitro catalytic activity. Unexpectedly, we found that in vitro kinase activity was severely impaired in RET-MEN2A with Y981F, Y952F, or Y928F mutation, which displayed near-normal cell-transforming activity and only a partially impaired tyrosine phosphorylation level in vivo. Phosphoamino acid analysis actually demonstrated some increase in phosphotyrosine in the Y905F mutant but no or barely detectable increase in the Y981F, Y952F, or Y928F mutant after incubation for in vitro kinase assay. This suggested a crucial role of the Y981/Y952/Y928-linked structural integrity of the COOH end of the catalytic domain of RET in starting Y905 autophosphorylation. Interestingly, the apparent defect in intrinsic kinase activity in vitro in the Y981F, Y952F, or Y928F mutant, but not the reduction in activity in the Y905F mutant, could be partially repaired or restored by c-Src or, more extensively, by v-Src, which promoted Y905 phosphorylation in trans. A complex was shown to be formed between v-Src and RET-MEN2A through association of both with a cholesterol-rich membrane microdomain known as "a raft," possibly for efficient contact of submembranous domains of Src and RET to promote phosphorylation of Y905 of the latter. Finally, endogenous c-Src was shown to promote Y905 phosphorylation of the Y981F mutant in vivo. These results reveal a novel Src kinase-mediated repair mechanism of otherwise function-impaired mutant RET kinases.

3T3 Cells↗

PubMed2002

Abnormal accumulation of hyaluronan matrix diminishes contact inhibition of cell growth and promotes cell migration.

Elevated hyaluronan biosynthesis and matrix deposition correlates with cell proliferation and migration. We ectopically expressed three isoforms of hyaluronan synthase (HAS1, HAS2, or HAS3) in nontransformed rat 3Y1 cells and observed a de novo, massive formation of a hyaluronan matrix that resulted in a partial loss of contact-mediated inhibition of cell growth and migration. All three HAS transfectants showed an enhanced motility in scratch wound assays, and a significant increase in their confluent cell densities. In high-density cultures, the HAS transfectants had a fibroblastic cell shape and markedly formed overlapping cell layers. This phenotype was more pronounced in the HAS2 transfectants than HAS1 or HAS3 transfectants, and occurred with significant alterations in the microfilament organization and N-cadherin distribution at the cell-cell border. Inhibition of a phosphatidylinositol 3-kinase (PI3-kinase) pathway resulted in reacquisition of the normal phenotype of HAS2 transfectants, suggesting that the intracellular PI3-kinase signaling regulates diminution of contact inhibition induced by formation of the massive hyaluronan matrix. Our observations suggest that hyaluronan and its matrix can modulate contact inhibition of cell growth and migration, and provide evidence for functional differences between hyaluronan synthesized by the different HAS proteins.

Agar↗

PubMed2002

Possible activation of the renin-angiotensin system in the feto-placental unit in preeclampsia.

The purpose of this study was to elucidate the mechanisms underlying the regulation of feto-placental circulation mediated by the renin-angiotensin system under preeclamptic conditions. We measured angiotensin-converting enzyme (ACE) activity, protein expression, and mRNA expression in uncomplicated and preeclamptic placentas and examined the localization of ACE. In addition, ACE activity and mRNA expression in human umbilical venous endothelial cells (HUVECs) under hypoxic conditions were analyzed. ACE activity, protein expression, and mRNA expression in placental tissues from preeclampsia were all significantly higher than those from uncomplicated pregnancies. ACE activity in vessel fractions was extensively higher than that in trophoblast-rich or macrophage-rich fractions. Additionally, ACE activity in HUVECs was significantly higher than that in human arterial endothelial cells, and ACE mRNA was primarily localized to venous endothelial cells of stem villous in placentas. Furthermore, hypoxic condition induced both ACE activity and mRNA expression in HUVECs. These results suggested that venous endothelial cells within placental stem villous tissues and umbilicus play an important role in the regulation of the feto-placental renin-angiotensin system, and in response to hypoxic conditions the feto-placental unit seemed to induce ACE activity in the placenta; such an effect would be likely to lead to regulation of the fetal circulation.

Adult↗