Differential involvement of caspase-6 in amyloid-β-induced fragmentation of lamin A and B

An expeditious and facile method of amyloid beta (1-42) purification

For the study of amyloid beta (Aβ) associated toxicity which is supposed to be the main pathological agent in Alzheimer's disease (AD), it is important to secure Aβ peptide with appropriate biological activity. However, commercial and synthetic Aβ often have some pitfalls like less cell toxicity, prompt aggregation and excess price, using recombinant technology, these issues can be resolved though the method also suffered from some problems such as low yield, aggregation and prolong time to purify. Thus, we previously developed an easy, economic and convenient method for Aβ42 purification using highly expressed GroES-Ubiquitin-Aβ42 fusion protein. The method was efficient, but further development was performed to improve the procedure and increase the yield. Focus was on the isolation of the fusion protein (GroES-Ubiquitin) from Aβ42 peptide. After a series of systematic testing with several chemicals, we found that methanol could precipitate efficiently the fusion protein, while the Aβ peptide was recovered in the supernatant. By this method, Aβ peptide was easily purified without tedious chromatographic steps which are main obstacles to purify the peptide in the previous method. This method yielded ~20 mg highly pure Aβ42 peptide from 1-liter bacterial culture. Different biophysical characterizations and bioactivity assays indicate that the peptide purified using this method was competitive with others which have been previously reported whereas considering the simplicity, final yield and time of purification, this method is the optimal solution.

Involvement of calcium ions in amyloid-β-induced lamin fragmentation

Amyloid-β (Aβ) peptide, the main pathogenic peptide in Alzheimer's disease, has been shown to induce an increase in cytoplasmic calcium concentration (CCC). In the current study, we explored the cytotoxic signal transduction pathway in 42-amino-acid Aβ (Aβ42)-treated HeLa cells in relation to the increase in CCC. The increase in CCC was prominent in cells treated twice with oligomeric Aβ42. We previously showed that double treatment also promoted Aβ-induced lamin fragmentation (AILF), which appears to be mediated by cathepsin L. Apoptotic caspase activation was a downstream event of AILF. The Ca²⁺ chelator BAPTA-AM suppressed cell death, cathepsin L activation, AILF, and caspase activation in Aβ-treated cells. These results indicate that Aβ42 induces an increase in CCC, which is an event upstream of the cytotoxic processes. The products of AILF are different from those produced by other cell death-inducing agents, such as staurosporine, which induces caspase-6-mediated lamin fragmentation (CMLF). CMLF was unaffected by BAPTA-AM and was not detected in cells treated with Aβ42, indicating that Aβ42 peptide induced a specific cytotoxic pathway involving AILF via increased CCC. We confirmed that the same processes (except caspase activation) operated in Aβ42-treated neuroblastoma SH-SY5Y cells.

Radiotherapy modulates tumor cell fate decisions: a review

Cancer has always been a worldwide problem, and the application of radiotherapy has greatly improved the survival rate of cancer patients. Radiotherapy can modulate multiple cell fate decisions to kill tumor cells and achieve its therapeutic effect. With the development of radiotherapy technology, how to increase the killing effect of tumor cells and reduce the side effects on normal cells has become a new problem. In this review, we summarize the mechanisms by which radiotherapy induces tumor cell apoptosis, necrosis, necroptosis, pyroptosis, ferroptosis, autophagy, senescence, mitotic catastrophe, and cuproptosis. An in-depth understanding of these radiotherapy-related cell fate decisions can greatly improve the efficiency of radiotherapy for cancer.

Evidence for a Strong Relationship between the Cytotoxicity and Intracellular Location of β-Amyloid

β-Amyloid (Aβ) is a hallmark peptide of Alzheimer’s disease (AD). Herein, we explored the mechanism underlying the cytotoxicity of this peptide. Double treatment with oligomeric 42-amino-acid Aβ (Aβ42) species, which are more cytotoxic than other conformers such as monomers and fibrils, resulted in increased cytotoxicity. Under this treatment condition, an increase in intracellular localization of the peptide was observed, which indicated that the peptide administered extracellularly entered the cells. The cell-permeable peptide TAT-tagged Aβ42 (tAβ42), which was newly prepared for the study and found to be highly cell-permeable and soluble, induced Aβ-specific lamin protein cleavage, caspase-3/7-like DEVDase activation, and high cytotoxicity (5–10-fold higher than that induced by the wild-type oligomeric preparations). Oligomeric species enrichment and double treatment were not necessary for enhancing the cytotoxicity and intracellular location of the fusion peptide. Taiwaniaflavone, an inhibitor of the cytotoxicity of wild-type Aβ42 and tAβ42, strongly blocked the internalization of the peptides into the cells. These data imply a strong relationship between the cytotoxicity and intracellular location of the Aβ peptide. Based on these results, we suggest that agents that can reduce the cell permeability of Aβ42 are potential AD therapeutics.