Yuichi Sekine

Hokkaido University, Sapporo, Hokkaidō, Japan

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Publications (61)227.5 Total impact

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    ABSTRACT: Signal-transducing adaptor protein-2 (STAP-2) is a recently identified adaptor protein that regulates immune and inflammatory responses through interactions with a variety of signaling and transcriptional molecules. In the current study, we clarified the physiological role of STAP-2 in mast cell function, a key mediator of IgE-associated allergic responses. STAP-2 is constitutively expressed in mast cells. STAP-2 deficiency in mast cells greatly enhances FcεRI-mediated signals, resulting in the increased tyrosine phosphorylation of the phospholipase C-γ isoform, calcium mobilization, and degranulation. Of importance, STAP-2-deficient mice challenged with DNP-BSA after passive sensitization with anti-DNP IgE show more severe rectal temperature decrease than do wild-type mice. STAP-2-deficient mice also show increased vascular permeability and more severe cutaneous anaphylaxis after DNP-BSA injection. These regulatory functions performed by STAP-2 indicate that there is an interaction between STAP-2 and FcεRI. In addition, our previous data indicate that STAP-2 binds to the phospholipase C-γ isoform and IκB kinase-β. Therefore, our data described in this article strongly suggest that manipulation of STAP-2 expression in mast cells may control the pathogenesis of allergic diseases and have the potential for treating patients with allergy.
    The Journal of Immunology 03/2014; · 5.52 Impact Factor
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    ABSTRACT: Signal-transducing adaptor protein-2 (STAP-2) was cloned as a c-fms/M-CSF receptor-interacting protein. STAP-2 is an adaptor protein carrying pleckstrin homology- and Src homology 2-like domains, as well as a YXXQ motif. STAP-2 has been indicated to have an ability to bind and modulate a variety of signaling and transcriptional molecules. Especially, our previous in vitro studies showed that STAP-2 is crucial for immune and/or inflammatory responses.Here, we have investigated the role of STAP-2 in intestinal inflammation in vivo. The disruption of STAP-2 attenuates dextran sodium sulfate-induced colitis via inhibition of macrophage recruitment. To study whether hematopoietic or epithelial cell-derived STAP-2 is required to this phenomenon, we generated BM chimeric mice. STAP-2 deficient macrophages impair the ability of CXCL12-induced migration. Intriguingly, STAP-2 also regulates production of proinflammatory chemokines and cytokines such as CXCL1 and TNF-α from intestinal epithelial cells. Therefore, STAP-2 has a potential to regulate plural molecular events during pathological inflammatory responses. Furthermore, our findings not only indicate that STAP-2 is important in regulating intestinal inflammation, but also provide new insights toward the development of novel therapeutic approaches.This article is protected by copyright. All rights reserved
    European Journal of Immunology 03/2014; · 4.97 Impact Factor
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    ABSTRACT: Tyrosine kinase 2 (Tyk2), a member of the Jak kinase family, mediates signals triggered by various cytokines, which are related to the pathogenesis of psoriasis. In this study, we investigated the role of Tyk2 in IL-23-induced psoriasis-like skin inflammation. Tyk2(-/-) mice when injected with IL-23 showed significantly reduced ear skin swelling with epidermal hyperplasia and inflammatory cell infiltration compared with wild-type mice. In addition, Tyk2 deficiency reduced production of pro-inflammatory cytokines and psoriasis-relevant anti-microbial peptides. More noteworthy is that Tyk2 directly regulated IL-22-dependent inflammation and epidermal hyperplasia. Taken together with the inhibition of IL-23-induced inflammation by treatment with neutralizing antibodies against IL-17 or IL-22, Tyk2 participates in both IL-23 and IL-22 signal transduction to mediate psoriasis-like skin inflammation. On the basis of these findings, we demonstrated for the first time that a small-molecule Tyk2 inhibitor significantly inhibited IL-23-induced inflammation and cytokine production in the skin. These observations demonstrate the important role of Tyk2 in experimental skin inflammation and indicate the therapeutic potential of Tyk2 inhibition in human psoriasis.
    International Immunology 12/2013; · 3.14 Impact Factor
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    ABSTRACT: Although Y14 is known to be a component of the exon junction complex, we previously reported that Y14 regulates IL-6-induced STAT3 activation. In this study, we showed that endogenous Y14 positively regulated TNF-α-induced IL-6 expression in HeLa cells. Small interfering RNA-mediated Y14-knockdown reduced TNF-α-induced and NF-κB-mediated transcriptional activity, phosphorylation/degradation of IκBα, and nuclear localization of NF-κB/p65. As in the case of IL-6 stimuli, Y14 enhanced TNF-α-induced STAT3 phosphorylation, which is important for its nuclear retention. However, our manipulation of Y14 expression indicated that it is involved in TNF-α-induced IL-6 expression via both STAT3-dependent and -independent mechanisms. We screened signaling molecules in the TNF-α-NF-κB pathway and found that Y14 endogenously associated with receptor-interacting protein 1 (RIP1) and TNFR-associated death domain (TRADD). Overexpression of RIP1, but not TRADD, restored TNF-α-induced NF-κB activation in Y14-knockdown cells, and Y14 overexpression restored TNF-α-induced NF-κB activation in TRADD-knockdown cells, but not in RIP1-knockdown cells, indicating that Y14 lies downstream of TRADD and upstream of RIP1. Of importance, Y14 significantly enhanced the binding between RIP1 and TRADD, and this is a possible new mechanism for Y14-mediated modification of TNF-α signals. Although Y14 associates with MAGOH in the exon junction complex, Y14's actions in the TNF-α-NF-κB pathway are unlikely to require MAGOH. Therefore, Y14 positively regulates signals for TNF-α-induced IL-6 production at multiple steps beyond an exon junction complex protein.
    The Journal of Immunology 07/2013; · 5.52 Impact Factor
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    ABSTRACT: We found that an adaptor protein, signal-transducing adaptor protein (STAP)-2, is a new member of the Fas-death-inducing signaling complex and participates in activation-induced cell death in T cells. STAP-2 enhanced Fas-mediated apoptosis and caspase-8 aggregation and activation in Jurkat T cells. Importantly, STAP-2 directly interacted with caspase-8 and Fas, resulting in enhanced interactions between caspase-8 and FADD in the Fas-death-inducing signaling complex. Moreover, STAP-2 protein has a consensus caspase-8 cleavage sequence, VEAD, in its C-terminal domain, and processing of STAP-2 by caspase-8 was crucial for Fas-induced apoptosis. Physiologic roles of STAP-2 were confirmed by observations that STAP-2-deficient mice displayed impaired activation-induced cell death and superantigen-induced T cell depletion. Therefore, STAP-2 is a novel participant in the regulation of T cell apoptosis after stimulation.
    The Journal of Immunology 05/2012; 188(12):6194-204. · 5.52 Impact Factor
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    ABSTRACT: In chronic myeloid leukemia (CML), the BCR-ABL fusion oncoprotein activates multiple pathways involved in cell survival, growth promotion and disease progression. In this report, we show that the signal-transducing adaptor protein-2 (STAP-2) is involved in BCR-ABL activity. We demonstrate that STAP-2 bound to BCR-ABL, and BCR and ABL proteins, depending on the STAP-2 Src homology 2-like domain. BCR-ABL phosphorylates STAP-2 Tyr250 and the phosphorylated STAP-2 in turn upregulated BCR-ABL phosphorylation, leading to enhanced activation of downstream signaling molecules including ERK (extracellular-signal-regulated kinase), STAT5 (signal transducer and activator of transcription 5), BCL-xL (B-cell lymphoma-extra large) and BCL-2(B-cell lymphoma 2). In addition, STAP-2 interacts with BCR-ABL to alter chemokine receptor expression leading to downregulation of CXCR4 and upregulation of CCR7. The interaction between STAP-2 and BCR-ABL plays a crucial role in conferring a growth advantage and resistance to imatinib, a BCR-ABL inhibitor, as well as tumor progression. Notably, mice injected with BCR-ABL/STAP-2-expressing Ba/F3 cells developed lymph node enlargement and hepatosplenomegaly. Moreover, suppression of STAP-2 in K562 CML cells resulted in no tumor formation in mice. Our results demonstrate a critical contribution of STAP-2 in BCR-ABL activity, and suggest that STAP-2 might be an important candidate for drug development for patients with CML. Furthermore, the expression of STAP-2 provides useful information for estimating the characteristics of individual CML clones.
    Oncogene 01/2012; 31(40):4384-96. · 8.56 Impact Factor
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    Osamu Ikeda, Yuichi Sekine, Tadashi Matsuda
    Breast Cancer - Carcinogenesis, Cell Growth and Signalling Pathways, 11/2011; , ISBN: 978-953-307-714-7
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    ABSTRACT: Krüppel-associated box-associated protein 1 (KAP1) is thought to act mainly as a scaffold for protein complexes, which together silence transcription by triggering the formation of heterochromatin. Using small interfering RNA-mediated KAP1 knockdown, we found that endogenous KAP1 negatively regulated TNF-α-induced IL-6 production in HeLa cells. KAP1 is likely to modulate the binding of NF-κB to the IL-6 promoter because KAP1 knockdown enhanced TNF-α-induced NF-κB-luciferase activity, but not IκBα degradation. Of importance, we found negative regulatory effects of KAP1 on the serine phosphorylation of STAT3, the acetylation of NF-κB/p65 by p300, and the nuclear localization of NF-κB/p65. In addition, KAP1 associated with NF-κB/p65 and inhibited the binding between NF-κB/p65 and p300. Thus, KAP1 is likely to negatively control the acetylation of NF-κB/p65, which is critical for its nuclear retention. Taken together, KAP1 modulated the acetylation of NF-κB/p65 by interfering with the interactions among STAT3, p300, and NF-κB/p65, resulting in reduced IL-6 production after TNF-α stimulation. Our findings that KAP1 directly interacts with transcriptional factors are new, and will inform further research to elucidate KAP1 function.
    The Journal of Immunology 09/2011; 187(5):2476-83. · 5.52 Impact Factor
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    ABSTRACT: Tyrosine kinase-2 (Tyk2) participates in the signaling pathways of multiple cytokines in innate and acquired immunity. In the present study, we investigated the in vivo involvement of Tyk2 in anti-type II collagen antibody-induced arthritis (CAIA) using Tyk2-deficient mice. Hind paws of wild-type mice showed massive swelling and erythema by arthritogenic antibody injection, whereas Tyk2-deficient mice did not show any signs of arthritis. Indeed, neither the infiltration of inflammatory cells nor the fibrillation of articular cartilages was observed in Tyk2-deficient mice. Tyk2 deficiency also reduced the production of T(h)1/T(h)17-related cytokines, the other proinflammatory cytokines and matrix metalloproteases, which are induced in the CAIA paw. Our results demonstrate a critical contribution of Tyk2 in the development of arthritis, and we propose that Tyk2 might be an important candidate for drug development.
    International Immunology 09/2011; 23(9):575-82. · 3.14 Impact Factor
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    ABSTRACT: Tyrosine kinase-2 (Tyk2), a member of the Jak family of kinases, mediates the signals triggered by various cytokines, including type I IFNs, IL-12, and IL-23. In the current study, we investigated the in vivo involvement of Tyk2 in several IL-12/Th1- and IL-23/Th17-mediated models of experimental diseases, including methylated BSA injection-induced footpad thickness, imiquimod-induced psoriasis-like skin inflammation, and dextran sulfate sodium- or 2,4,6-trinitrobenzene sulfonic acid-induced colitis. In these disease models, Tyk2 deficiency influenced the phenotypes in immunity and/or inflammation. Our findings demonstrate a somewhat broader contribution of Tyk2 to immune systems than previously expected and suggest that Tyk2 may represent an important candidate for drug development by targeting both the IL-12/Th1 and IL-23/Th17 axes.
    The Journal of Immunology 07/2011; 187(1):181-9. · 5.52 Impact Factor
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    ABSTRACT: Zipper-interacting protein kinase (ZIPK) is a widely expressed serine/threonine kinase that has been implicated in apoptosis and transcriptional regulation. Here, we identified Nemo-like kinase (NLK) as a novel ZIPK-binding partner, and found that ZIPK regulates NLK-mediated repression of canonical Wnt/beta-catenin signaling. Indeed, siRNA-mediated reduction of endogenous ZIPK expression reduced Wnt/beta-catenin signaling. Furthermore, ZIPK affected complex formation of NLK-T-cell factor (TCF) 4. Importantly, ZIPK siRNA treatment in human colon carcinoma cells resulted in a reduction of beta-catenin/TCF-mediated gene expression and cell growth. These results indicate that ZIPK may serve as a transcriptional regulator of canonical Wnt/beta-catenin signaling through interaction with NLK/TCF4.
    Journal of Biological Chemistry 03/2011; · 4.65 Impact Factor
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    ABSTRACT: Zipper-interacting protein kinase (ZIPK) is a widely expressed serine/threonine kinase that has been implicated in apoptosis and transcriptional regulation. Here, we identified Nemo-like kinase (NLK) as a novel ZIPK-binding partner and found that ZIPK regulates NLK-mediated repression of canonical Wnt/β-catenin signaling. Indeed, siRNA-mediated reduction of endogenous ZIPK expression reduced Wnt/β-catenin signaling. Furthermore, ZIPK affected the formation of NLK-T-cell factor 4 (TCF4) complex. Importantly, ZIPK siRNA treatment in human colon carcinoma cells resulted in a reduction of β-catenin/TCF-mediated gene expression and cell growth. These results indicate that ZIPK may serve as a transcriptional regulator of canonical Wnt/β-catenin signaling through interaction with NLK/TCF4.
    Journal of Biological Chemistry 03/2011; 286(21):19170-7. · 4.65 Impact Factor
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    ABSTRACT: Granuloma formation is an important host defense mechanism against intracellular bacteria; however, uncontrolled granulomatous inflammation is pathologic. T helper 17 (TH17) cells are thought to have a pathogenic role in autoimmune and inflammatory diseases, including in granulomas. Here, we report that the PDZ-LIM domain protein PDLIM2 inhibited TH17 cell development and granulomatous responses by acting as a nuclear ubiquitin E3 ligase that targeted signal transducer and activator of transcription 3 (STAT3), a transcription factor critical for the commitment of naïve CD4+ T cells to the TH17 lineage. PDLIM2 promoted the polyubiquitination and proteasomal degradation of STAT3, thereby disrupting STAT3-mediated gene activation. Deficiency in PDLIM2 resulted in the accumulation of STAT3 in the nucleus, enhanced the extent of TH17 cell differentiation, and exacerbated granuloma formation. This study delineates an essential role for PDLIM2 in inhibiting TH17 cell-mediated inflammatory responses by suppressing STAT3 signaling and provides a potential therapeutic target for the treatment of autoimmune diseases.
    Science Signaling 01/2011; 4(202):ra85. · 7.65 Impact Factor
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    ABSTRACT: STAP-2 (signal transducing adaptor protein-2) is a recently identified adaptor protein that contains pleckstrin homology (PH) and Src homology 2-like domains, as well as a STAT3-binding motif in its C-terminal region. STAP-2 is also a substrate of breast tumor kinase (Brk). In breast cancers, Brk expression is deregulated and promotes STAT3-dependent cell proliferation. In the present study, manipulated STAP-2 expression demonstrated essential roles of STAP-2 in Brk-mediated STAT3 activation. STAP-2 interacts with both Brk and STAT3. In addition, small interfering RNA-mediated reduction of endogenous STAP-2 expression strongly decreased Brk-mediated STAT3 activation in T47D breast cancer cells. The PH domain of STAP-2 is involved in multiple steps: the binding between Brk and STAP-2, the activation and tyrosine phosphorylation of STAT3, and the activation of Brk. Notably, a STAP-2 PH-Brk fusion protein exhibited robust kinase activity and increased activation and tyrosine phosphorylation of STAT3. Finally, STAP-2 knockdown in T47D cells induced a significant decrease of proliferation, as strong as that of Brk or STAT3 knockdown. Taken together, our findings are likely to inform the development of a novel therapeutic strategy, as well as the determination of novel prognostic values, in breast carcinomas.
    Journal of Biological Chemistry 12/2010; 285(49):38093-38103. · 4.65 Impact Factor
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    ABSTRACT: Death domain-associated protein (Daxx) is a multifunctional protein that modulates both cell death and transcription. Several recent studies have indicated that Daxx is a mediator of lymphocyte death and/or growth suppression, although the detailed mechanism is unclear. Previously, we reported that Daxx suppresses IL-6 family cytokine-induced gene expression by interacting with STAT3. STAT3 is important for the growth and survival of lymphocytes; therefore, we here examined the role of Daxx in the gp130/STAT3-dependent cell growth/survival signals. We found that Daxx suppresses the gp130/STAT3-dependent cell growth and that Daxx endogenously interacts with STAT3 and inhibits the DNA-binding activity of STAT3. Moreover, small-interfering RNA-mediated knockdown of Daxx enhanced the expression of STAT3-target genes and accelerated the STAT3-mediated cell cycle progression. In addition, knockdown of Daxx-attenuated lactate dehydrogenase leakage from cells, indicating that Daxx positively regulates cell death during gp130/STAT3-mediated cell proliferation. Notably, Daxx specifically suppressed the levels of Bcl2 mRNA and protein, even in cytokine-unstimulated cells, indicating that Daxx regulates Bcl2 expression independently of activated STAT3. These results suggest that Daxx suppresses gp130-mediated cell growth and survival by two independent mechanisms: inhibition of STAT3-induced transcription and down-regulation of Bcl2 expression.
    European Journal of Immunology 12/2010; 40(12):3570-80. · 4.97 Impact Factor
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    ABSTRACT: Signal-transducing adaptor protein (STAP)-2 is a recently identified adaptor protein that contains Pleckstrin homology and Src homology 2-like domains, and is also known to be a substrate of breast tumor kinase (Brk). In a previous study, we found that STAP-2 upregulated Brk-mediated activation of signal transducer and activator of transcription (STAT) 3 in breast cancer cells. Here, we examined the involvement of STAP-2 in Brk-mediated STAT5 activation in breast cancer cells. Ectopic expression of STAP-2 induced Brk-mediated transcriptional activity of STAT5. Furthermore, STAP-2-knockdown in T47D breast cancer cells induced a marked decrease in proliferation that was as strong as that after Brk- or STAT5b-knockdown. Regarding the mechanism, the Pleckstrin homology domain of STAP-2 is likely to participate in the process by which Brk phosphorylates and activates STAT5. Taken together, our findings provide insights toward the development of novel therapeutic strategies as well as novel prognostic values in breast carcinomas.
    Cancer Science 12/2010; 102(4):756-61. · 3.48 Impact Factor
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    ABSTRACT: STAP-2 (signal transducing adaptor protein-2) is a recently identified adaptor protein that contains pleckstrin homology (PH) and Src homology 2-like domains, as well as a STAT3-binding motif in its C-terminal region. STAP-2 is also a substrate of breast tumor kinase (Brk). In breast cancers, Brk expression is deregulated and promotes STAT3-dependent cell proliferation. In the present study, manipulated STAP-2 expression demonstrated essential roles of STAP-2 in Brk-mediated STAT3 activation. STAP-2 interacts with both Brk and STAT3. In addition, small interfering RNA-mediated reduction of endogenous STAP-2 expression strongly decreased Brk-mediated STAT3 activation in T47D breast cancer cells. The PH domain of STAP-2 is involved in multiple steps: the binding between Brk and STAP-2, the activation and tyrosine phosphorylation of STAT3, and the activation of Brk. Notably, a STAP-2 PH-Brk fusion protein exhibited robust kinase activity and increased activation and tyrosine phosphorylation of STAT3. Finally, STAP-2 knockdown in T47D cells induced a significant decrease of proliferation, as strong as that of Brk or STAT3 knockdown. Taken together, our findings are likely to inform the development of a novel therapeutic strategy, as well as the determination of novel prognostic values, in breast carcinomas.
    Journal of Biological Chemistry 10/2010; 285(49):38093-103. · 4.65 Impact Factor
  • Yuichi Sekine
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    ABSTRACT: Signal-transducing adaptor protein-2 (STAP-2) was recently identified as a novel adaptor protein and is a family of STAP adaptor protein and has a variety of functions in cellular signal transductions. Especially STAP-2 has a crucial role in immune systems by controlling cytokine signal transduction. STAP-2 functionally interacts with STAT3 through its YXXQ motif and enhances STAT3 transcriptional activation. In contrast, STAP-2 interacts with STAT5 through its PH and SH2-like domains and decreases STAT5 activity. Importantly, STAP-2 also binds to MyD88 and IKK-alpha/beta and regulates LPS/TLR4 signaling. Moreover, STAP-2 interacts with Epstein-Barr virus-derived LMP1 and modulates LMP1-mediated NF-kappaB signaling. More importantly, experiments using STAP-2 deficient mice showed that STAP-2 modulated several T-cell functions. T-cells from STAP-2 deficient mice showed enhanced integrin-mediated cell adhesion to fibronectin. Furthermore STAP-2-deficient T-cells show reduced chemotaxis toward SDF-1alpha. These accumulated evidences indicate that novel adaptor protein STAP-2 plays an important modulator role in both of innate and adaptive immune systems.
    Yakugaku zasshi journal of the Pharmaceutical Society of Japan 06/2010; 130(6):769-75. · 0.46 Impact Factor
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    ABSTRACT: Epstein-Barr virus latent membrane protein 1 (LMP1) activates NF-kappaB signaling pathways through two C-terminal regions, CTAR1 and CTAR2. Previous studies have demonstrated that BS69, a multidomain cellular protein, regulates LMP1/CTAR2-mediated NF-kappaB activation by interfering with the complex formation between TRADD and LMP1/CTAR2. Here, we found that BS69 directly interacted with the LMP1/CTAR1 domain and regulated LMP1/CTAR1-mediated NF-kappaB activation and subsequent IL-6 production. Regarding the mechanisms involved, we found that BS69 directly interacted with TRAF3, a negative regulator of NF-kappaB activation. Furthermore, small-interfering RNA-mediated knockdown experiments revealed that TRAF3 was involved in the BS69-mediated suppression of LMP1/CTAR1-induced NF-kappaB activation.
    FEBS letters 02/2010; 584(5):865-72. · 3.54 Impact Factor
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    ABSTRACT: Signal-transducing adaptor protein-2 (STAP-2) is a recently identified adaptor protein that contains pleckstrin and Src homology 2-like domains, as well as a YXXQ motif in its C-terminal region. Our previous studies revealed that STAP-2 regulates integrin-mediated T cell adhesion. In the present study, we find that STAP-2 expression affects Jurkat T cell migration after stromal cell-derived factor-1alpha (SDF-1alpha)-treatment. Furthermore, STAP-2-deficient T cells exhibit reduced cell migration after SDF-1alpha-treatment. Importantly, overexpression of STAP-2 in Jurkat T cells induces activation of small guanine triphosphatases, such as Rac1 and Cdc42. Regarding the mechanism for this effect, we found that STAP-2 associates with Vav1, the guanine-nucleotide exchanging factor for Rac1, and enhances downstream Vav1/Rac1 signaling. These results reveal a novel STAP-2-mediated mechanism for the regulation of SDF-1alpha-induced chemotaxis of T cells via activation of Vav1/Rac1 signaling.
    The Journal of Immunology 11/2009; 183(12):7966-74. · 5.52 Impact Factor

Publication Stats

707 Citations
227.50 Total Impact Points

Institutions

  • 2002–2014
    • Hokkaido University
      • Graduate School of Pharmaceutical Sciences
      Sapporo, Hokkaidō, Japan
  • 2011
    • RIKEN
      • Laboratory for Inflammatory Regulation
      Wako, Saitama-ken, Japan
  • 2008
    • Osaka University
      • Department of Molecular Immunology
      Suika, Ōsaka, Japan
  • 2003
    • Toyama Medical and Pharmaceutical University
      Тояма, Toyama, Japan