Sprouty, an inhibitor of receptor tyrosine kinase signaling, plays an important role in the regulation of a wide variety of biological processes. Although it is established that the Sprouty inhibitory activity is induced by tyrosine phosphorylation in response to stimuli, its action mechanisms have not been fully elucidated. Here, we report identification of a novel target of Sprouty. We find that Sprouty1 and Sprouty2 bind to the adaptor protein CrkL in a stimulus-dependent manner. Biochemical analyses show that the binding requires tyrosine phosphorylation of Sprouty and that both the SH2 domain and the N-terminal SH3 domain of CrkL are necessary for the binding. In fibroblast growth factor-stimulated NIH3T3 cells, CrkL binding to Sprouty2 occurs concomitantly with tyrosine phosphorylation of Sprouty2, which occurs slowly but is sustained. Importantly, our results show that tyrosine-phosphorylated Sprouty2 suppresses Rap1 activation. These results taken together indicate that Sprouty2 acts as an inhibitor of CrkL-Rap1 signaling.
Effector lymphocytes cytotoxic to autologous tumor cells consist of heterogeneous populations. In this communication, we have presented the results of experiments, in which these heterogeneous effector cells were classified based on their surface markers and modes of differentiation depending upon culture conditions. NK cells with a typical phenotype of CD2+ 3-16+ were one of major populations, which could respond to IL-2 and be differentiated into lymphokine activated killer (LAK) cells. LAK cells were also induced from a CD3+4-8- T cell subset by IL-2 stimulation. Effector cells with a phenotype of CD2+ 3-4-8-16-, which may belong to the T cells at early stages of differentiation, could also be induced by stimulation of immunoadjuvants. Finally, it was shown that the effector cells with a typical phenotype of cytotoxic T lymphocytes, CD3+4-8+16-, and a non-MHC-restricted cytotoxicity were induced by IL-2 in the tumor infiltrating lymphocytes.
Pre-mRNA in eukaryotes is subjected to mRNA processing, which includes capping, polyadenylation, and splicing. Transcription and mRNA processing are coupled, and this coupling stimulates mRNA processing; however, the effects of mRNA processing on transcription are not fully understood. In this study, we found that inhibition of U2 snRNP by a splicing inhibitor, spliceostatin A (SSA), or by an antisense oligonucleotide to U2 snRNA, caused gene-specific 3′-end down-regulation. Removal of SSA from the culture media restored expression of the 3′ ends of genes, suggesting that U2 snRNP is required for expression of the 3′ end of genes. Finally, we found that SSA treatment caused accumulation of Pol II near the 5′ end of 3′-end down regulated genes, such as CDK6, SMEK2 and EGFR, indicating that SSA treatment led to transcription elongation arrest on these genes. These findings suggest that U2 snRNP is important for production of full length mRNA probably through regulation of transcription elongation, and that a novel checkpoint mechanism prevents pre-mRNA from accumulating as a result of splicing deficiencies, and thereby prevents production of aberrant proteins that might be translated from pre-mRNAs through the arrest of transcription elongation.
The influence of intraperitoneal administration of disulfiram on the serotonin (5HT) turnover and the brain sensitivity to barbiturates were investigated in rats. Treatment of the animals with 200 mg/kg disulfiram resulted in the prolongation of duration of barbiturate-induced hypnosis. This indication and increment of the brain sensitivity to barbiturates after disulfiram treatment. Under the identical condition, disulfiram caused both the reduction of turnover of 5HT and the elevation of 5HT levels, although this effect was less potent than that of phenobarbital. Furthermore, simultaneous administration of disulfiram and phenobarbital resulted in the severe retardation of 5HT metabolism. These results strongly suggest that disulfiram potentiates the hypnotic action of barbiturates by altering 5HT metabolism in rat brain.
CD11b(+) Gr-1(+) immature myeloid cells (ImCs), which are abnormally increased in tumor-bearing mice, were classified into three different subsets according to their phenotypic and morphological characteristics: Gr-1(low) F4/80(+) macrophages (MΦ-ImCs), Gr-1(mid) stab neutrophils (Neut(stab)-ImCs), and Gr-1(high) segmented neutrophils (Neut(seg)-ImCs). In the spleen, only MΦ-ImCs but not Neut(stab)-ImCs and Neut(seg)-ImCs exhibited a significant immunosuppressive activity in MLR. In contrast, tumor-infiltrating leukocytes (TILs) contained only two ImC subsets, MΦ-ImCs and Neut(seg)-ImC, both of which exhibited stronger inhibitory activity against T cells compared with spleen-MΦ-ImCs. Thus, we concluded that tumor-infiltrating MΦ-ImCs and Neut(seg)-ImCs were fully differentiated myeloid-derived suppressor cells (MDSCs) with stronger T-cell inhibitory activity. Indeed, spleen MΦ-ImCs were converted into stronger MΦ-MDSCs by tumor-derived factor (TDF). Moreover, both spleen Neut(stab)-ImCs and Neut(seg)-ImCs differentiated into Neut(seg)-MDSCs with suppressive activity after culture with TDF. We first demonstrated that administration of anti-IL-6R mAb could downregulate the accumulation of MΦ-MDSCs and Neut(seg)-MDSCs in tumor-bearing mice. The elimination of those MDSCs caused subsequent enhancement of antitumor T-cell responses, including IFN-γ-production. The therapeutic effect of anti-IL-6R mAb was further enhanced by combination with gemcitabine (GEM). Thus, we propose that anti-IL-6R mAb could become a novel tool for the downmodulation of MDSCs to enhance antitumor T-cell responses in tumor-bearing hosts.
Using a novel self-calibration technique, a high-accuracy (16 b) and high-speed (6 mu s) successive approximation audio A/D converter has been developed on a small chip (3.8*4.8 mm/sup 2/). Small die size has been realized by reducing the number of capacitors. The high-speed conversion has been achieved by reducing the total capacitance of the capacitor array.< >
