Showing papers by "Hiroyuki Mano published in 1999"

Repression of IL-4-induced gene expression by IFN-gamma requires Stat1 activation

Abstract: IFN-gamma antagonizes many physiological responses mediated by IL-4, including the inhibition of IL-4-induced IgE production. This event is largely mediated at the level of transcription. We observed that the IL-4 response element of the germline epsilon promoter is sufficient to confer IFN-gamma-mediated repression onto a reporter construct. The inhibitory effects were observed in both lymphoid and nonlymphoid cell lines. Stat1, which is activated by IFN-gamma, cannot recognize the Stat6-specific IL-4 response element in the epsilon promoter. Hence, competitive DNA binding does not seem to be the underlying mechanism for the inhibitory effect. This is supported by the observation that inhibition is not seen at early time points, but requires prolonged IFN-gamma treatment. IFN-gamma stimulation results in a loss of IL-4-induced Stat6 tyrosine phosphorylation, nuclear translocation, and DNA binding. Using the fibrosarcoma cell line U3A, which lacks Stat1, we demonstrated that the transcription activation function of Stat1 is required for the IFN-gamma-mediated repression. Repression was restored by overexpression of Stat1alpha, but not Stat1beta, in U3A cells. Treatment with IFN-gamma, but not IL-4, specifically up-regulates the expression of SOCS-1 (silencer of cytokine signaling), a recently characterized inhibitor of cytokine signaling pathways, such as IL-6 and IFN-gamma. Overexpression of SOCS-1 effectively blocks IL-4-induced Stat6 phosphorylation and transcription. This suggests that IFN-gamma-mediated repression of IL-4-induced transcription is at least in part mediated by SOCS-1.

Molecular cloning of a docking protein, BRDG1, that acts downstream of the Tec tyrosine kinase

Abstract: Tec, Btk, Itk, Bmx, and Txk constitute the Tec family of protein tyrosine kinases (PTKs), a family with the distinct feature of containing a pleckstrin homology (PH) domain. Tec acts in signaling pathways triggered by the B cell antigen receptor (BCR), cytokine receptors, integrins, and receptor-type PTKs. Although upstream regulators of Tec family kinases are relatively well characterized, little is known of the downstream effectors of these enzymes. The yeast two-hybrid system has identified several proteins that interact with the kinase domain of Tec, one of which is now revealed to be a previously unknown docking protein termed BRDG1 (BCR downstream signaling 1). BRDG1 contains a proline-rich motif, a PH domain, and multiple tyrosine residues that are potential target sites for Src homology 2 domains. In 293 cells expressing recombinant BRDG1 and various PTKs, Tec and Pyk2, but not Btk, Bmx, Lyn, Syk, or c-Abl, induced marked phosphorylation of BRDG1 on tyrosine residues. BRDG1 was also phosphorylated by Tec directly in vitro. Efficient phosphorylation of BRDG1 by Tec required the PH and SH2 domains as well as the kinase domain of the latter. Furthermore, BRDG1 was shown to participate in a positive feedback loop by increasing the activity of Tec. BRDG1 transcripts are abundant in the human B cell line Ramos, and the endogenous protein underwent tyrosine phosphorylation in response to BCR stimulation. BRDG1 thus appears to function as a docking protein acting downstream of Tec in BCR signaling.

The Tec family protein-tyrosine kinases: a subset of kinases for a subset of signalings.

Abstract: The Tec family has emerged recently as a subfamily among nonreceptor type protein-tyrosine kinases, consisting of Tec, Btk, Itk/Tsk/Emt, Bmx, and Txk/Rlk Because many members of this family have been shown to be activated in response to growth and differentiation stimuli in hematopoietic tissues, they are presumed to function in vivo as important signaling mediators Although that hypothesis was further strengthened by the knowledge that mutations in Btk cause agammaglobulinemia in humans, we have only limited information concerning the molecular interaction through which Tec kinases exert their effects One characteristic feature of Tec family members is the presence of a pleckstrin homology domain in their protein structure, suggesting a physical and functional interaction with the phospholipid-dependent signaling pathways Recent data have revealed that Tec kinases regulate phospholipase C isoforms This review summarizes current knowledge concerning the in vivo roles of the Tec family proteins

Tec tyrosine kinase promoter

Abstract: of EP0894866The present invention provides a DNA having promoter activity of Tec tyrosine kinase and a vector having incorporated within it the promoter to thereby enable a high level expression of an exogenous gene in hematopoietic stem cells and hepatic cells.