TAK1 kinase switches cell fate from apoptosis to necrosis following TNF stimulation

TNF activates three distinct intracellular signaling cascades leading to cell survival, caspase-8–mediated apoptosis, or receptor interacting protein kinase 3 (RIPK3)–dependent necrosis, also called necroptosis. Depending on the cellular context, one of these pathways is activated upon TNF challenge. When caspase-8 is activated, it drives the apoptosis cascade and blocks RIPK3-dependent necrosis. Here we report the biological event switching to activate necrosis over apoptosis. TAK1 kinase is normally transiently activated upon TNF stimulation. We found that prolonged and hyperactivation of TAK1 induced phosphorylation and activation of RIPK3, leading to necrosis without caspase activation. In addition, we also demonstrated that activation of RIPK1 and RIPK3 promoted TAK1 activation, suggesting a positive feedforward loop of RIPK1, RIPK3, and TAK1. Conversely, ablation of TAK1 caused caspase-dependent apoptosis, in which Ripk3 deletion did not block cell death either in vivo or in vitro. Our results reveal that TAK1 activation drives RIPK3-dependent necrosis and inhibits apoptosis. TAK1 acts as a switch between apoptosis and necrosis.     

Coexistence of FMRFamide, met-enkephalin and serotonin in molluscan neurons

1. Coexistence of FMRFamide, met-enkephalin and serotonin immunoreactivities was examined in Achatina fulica and Aplysia kurodai. 2. Coexistence of FMRFamide and serotonin was found in some neurons of the visceral, right parietal and pedal ganglia of Achatina fulica, and in the pedal ganglion of Aplysia kurodai. 3. In Achatina fulica, coexistence of FMRFamide and met-enkephalin was found in a neuron of the left parietal ganglion and that of met-enkephalin and serotonin was found in a giant neuron of the right parietal ganglion. 4. Based on these results, the biological significance of coexistence was discussed.     

In isolated DNA, formamidopyrimidine-DNA glycosylase-sensitive sites determined by electrophoresis correspond to the amount of 8-oxo-7,8-dihydro-2'-deoxyguanosine by HPLC-ECD.

Several methods have been developed for determining the amount of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) in DNA. In the present study, we compared an electrophoretic method that uses formamidopyrimidine-DNA glycosylase (FPG protein) with a HPLC-ECD method. Firstly, we produced 8-oxodG in lambda DNA with methylene blue and visible light and cleaved it in one-half of the modified DNA enzymatically with FPG protein. Then, we determined the number of FPG protein-sensitive sites by electrophoresis (Y) and the number of 8-oxodGs by HPLC-ECD (X) per 10(5)dG of isolated DNA. Simple regression analysis of the data showed Y=1.07X+1.52 to be the most likely relationship. The correlation coefficient was 0.97. The values obtained by the two methods were very similar. This result is noteworthy because the number of FPG protein-sensitive sites determined by other methods have not yet come close to the number obtained by HPLC-ECD. Thus, this method might be more quantitative than other methods that measure FPG protein-sensitive sites. Another reason this electrophoresis method might be more useful than HPLC-ECD is that we can determine some other types of oxidative DNA damage well, by changing the DNA glycosylase.     

Analysis for amide nitrogen in proteins

Existing procedures for amide analysis of soluble proteins have been studied. Use of the automatic amino acid analyser for the determination of released ammonia gave greatly increased sensitivity over the distillation procedure and more reliable blank values. For the insoluble fibrous proteins, wool and silk hydrolysis in vacuo was found to remove the need for an extrapolation procedure; prolonged hydrolysis was required with hydrochloric acid but not with hydriodic acid.     

Autoregulation of Osteocyte Sema3A Orchestrates Estrogen Action and Counteracts Bone Aging

1. Download high-res image (184KB)
2. Download full-size image