The Carcinogen Cadmium Activates Lysine 63 (K63)-Linked Ubiquitin-Dependent Signaling and Inhibits Selective Autophagy

An ultrasensitive Cd2+ detection biosensor based on DNAzyme and CRISPR/Cas12a coupled with hybridization chain reaction

The detection of cadmium is essential because it poses a significant threat to human health and the environment. Recent advancements in biosensors that detect nonnucleic-acid targets using CRISPR/Cas12a in combination with aptamers or DNAzymes show promising performance. Herein, we integrated DNAzyme, hybridization chain reaction (HCR) and CRISPR/Cas12a into a single biosensor for the first time and realized the ultrasensitive detection of Cd2+. A single phosphorothioate ribonucleobase (rA)-containing oligonucleotide (PS substrate) and a Cd2+-specific DNAzyme (Cdzyme) are used for Cd2+ recognition, releasing short single-stranded DNA. Then, the HCR is triggered by the cleavage products for signal transduction and amplification. Next, the trans-cleavage activity of Cas12a is activated due to the presence of crRNA complementary strands and PAM sites in the HCR products. As a result, FQ-reporters are cleaved, and the fluorescence values can be easily read using a fluorometer, allowing Cd2+ quantification by measuring the fluorescent signal. The Cd2+ detection biosensor is ultrasensitive with a detection limit of 1.25 pM. Moreover, the biosensor shows great stability under different pH and various anion conditions. The proposed sensor was utilized for environmental water sample detection, demonstrating the dependability of the detection system. Considering the high sensitivity and reliable performance of the assay, it could be further used in environmental monitoring. In addition, the design strategy reported in this study could extend the application of CRISPR/Cas12a in heavy metal detection.

Role of K63-linked ubiquitination in cancer

Ubiquitination is a critical type of post-translational modifications, of which K63-linked ubiquitination regulates interaction, translocation, and activation of proteins. In recent years, emerging evidence suggest involvement of K63-linked ubiquitination in multiple signaling pathways and various human diseases including cancer. Increasing number of studies indicated that K63-linked ubiquitination controls initiation, development, invasion, metastasis, and therapy of diverse cancers. Here, we summarized molecular mechanisms of K63-linked ubiquitination dictating different biological activities of tumor and highlighted novel opportunities for future therapy targeting certain regulation of K63-linked ubiquitination in tumor.

Apoptosis, rather than neurogenesis, induces significant hippocampal-dependent learning and memory impairment in chronic low Cd2+ exposure

Cadmium (Cd), a ubiquitous toxic heavy metal, with the intractable trait of low degradation, can induce multiple organ damage. Whereas, far less is known about its neurotoxicity and the specific mechanism in the chronic low Cd exposure. To investigate the chronic neurotoxicity of Cd²⁺ , we traced its effects for up to 30 months in mice which were exposed to Cd²⁺ by drinking the mimicking Cd-polluted water. We found the toxicity of chronic Cd exposure was a process associated with the transition from autophagy to apoptosis, and the switch of autophagy-apoptosis was Cd dose-dependent with the threshold of [Cd²⁺ ] 0.04 mg/L. Furthermore, JNK was found to be a hub molecule orchestrated the switch of autophagy-apoptosis by interacting with Sirt1 and p53. At last, the hippocampus-dependent learning and memory was damaged by continuous neuron apoptosis rather than deficit of neurogenesis. Therefore, elucidation of the effect, process, and potential molecular mechanism of the chronic low Cd²⁺ exposure is important for controlling of the environmental-pollutant Cd.

TRIM14 inhibits OPTN-mediated autophagic degradation of KDM4D to epigenetically regulate inflammation

Histone methylation regulates gene transcription through a variety of methylases and demethylases. The regulatory role of autophagy, an important process of protein degradation and recycling, in these histone modifiers is still unclear. We report that TRIM14 stabilized the histone demethylase KDM4D to facilitate the transcription of interleukin 12 (Il12) and Il23 by inhibiting histone H3K9 trimethylation in vitro and in vivo. Mechanistically, TRIM14 recruited the deubiquitinases USP14 and BRCC3 to remove the K63-linked ubiquitin chains of KDM4D and prevented it from undergoing optineurin-mediated autophagic degradation. This study is valuable not only for increasing our understanding of the cross-talk between autophagy and epigenetic regulation, but also for demonstrating the potential of TRIM14 as a target for therapeutic interventions for inflammation-related diseases.

Autophagy is a fundamental cellular process of protein degradation and recycling that regulates immune signaling pathways via multiple mechanisms. However, it remains unclear how autophagy epigenetically regulates the immune response. Here, we identified TRIM14 as an epigenetic regulator that reduces histone H3K9 trimethylation by inhibiting the autophagic degradation of the histone demethylase KDM4D. TRIM14 recruited the deubiquitinases USP14 and BRCC3 to cleave the K63-linked ubiquitin chains of KDM4D, which prevented KDM4D from undergoing optineurin (OPTN)-mediated selective autophagy. Tripartite motif-containing 14 (TRIM14) deficiency in dendritic cells significantly impaired the expression of the KDM4D-directed proinflammatory cytokines interleukin 12 (Il12) and Il23 and protected mice from autoimmune inflammation. Taken together, these findings highlight the cross-talk between epigenetic regulation and autophagy and suggest TRIM14 is a potential target of therapeutic intervention for inflammation-related diseases.

Cardiac physiology and metabolic gene expression during late organogenesis among F. heteroclitus embryo families from crosses between pollution-sensitive and -resistant parents

BACKGROUND

The teleost fish Fundulus heteroclitus inhabit estuaries heavily polluted with persistent and bioaccumulative chemicals. While embryos of parents from polluted sites are remarkably resistant to toxic sediment and develop normally, embryos of parents from relatively clean estuaries, when treated with polluted sediment extracts, are developmentally delayed, displaying deformities characteristic of pollution-induced embryotoxicity. To gain insight into parental effects on sensitive and resistant phenotypes during late organogenesis, we established sensitive, resistant, and crossed embryo families using five female and five male parents from relatively clean and predominantly PAH-polluted estuaries each, measured heart rates, and quantified individual embryo expression of 179 metabolic genes.

RESULTS

Pollution-induced embryotoxicity manifested as morphological deformities, significant developmental delays, and altered cardiac physiology was evident among sensitive embryos resulting from crosses between females and males from relatively clean estuaries. Significantly different heart rates among several geographically unrelated populations of sensitive, resistant, and crossed embryo families during late organogenesis and pre-hatching suggest site-specific adaptive cardiac physiology phenotypes relative to pollution exposure. Metabolic gene expression patterns (32 genes, 17.9%, at p < 0.05; 11 genes, 6.1%, at p < 0.01) among the embryo families indicate maternal pollutant deposition in the eggs and parental effects on gene expression and metabolic alterations.

CONCLUSION

Heart rate differences among sensitive, resistant, and crossed embryos is a reliable phenotype for further explorations of adaptive mechanisms. While metabolic gene expression patterns among embryo families are suggestive of parental effects on several differentially expressed genes, a definitive adaptive signature and metabolic cost of resistant phenotypes is unclear and shows unexpected sensitive-resistant crossed embryo expression profiles. Our study highlights physiological and metabolic gene expression differences during a critical embryonic stage among pollution sensitive, resistant, and crossed embryo families, which may contribute to underlying resistance mechanisms observed in natural F. heteroclitus populations living in heavily contaminated estuaries.