Ricin is a plant toxin with high bioterrorism potential due to its natural abundance and potency in inducing cell death. Early detection of the active toxin is essential for developing appropriate countermeasures. Here we review concepts for designing ricin detection methods, including mechanism of action of the toxin, advantages and disadvantages of current detection assays, and perspectives on the future development of rapid and reliable methods for detecting ricin in environmental samples.

The COVID-19 pandemic, caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), represents an unprecedented challenge to global public health. At the time of this review, COVID-19 has been diagnosed in over 40 million cases and associated with 1.1 million deaths worldwide. Current management strategies for COVID-19 are largely supportive, and while there are more than 2000 interventional clinical trials registered with the U.S. National Library of Medicine (clinicaltrials.gov), results that can clarify benefits and risks of candidate therapies are only gradually becoming available. We herein describe recent advances in understanding SARS-COV-2 pathobiology and potential therapeutic targets that are involved in viral entry into host cells, viral spread in the body, and the subsequent COVID-19 progression. We highlight two major lines of therapeutic strategies for COVID-19 treatment: 1) repurposing the existing drugs for use in COVID-19 patients, such as antiviral medications (e.g., remdesivir) and immunomodulators (e.g., dexamethasone) which were previously approved for other disease conditions, and 2) novel biological products that are designed to target specific molecules that are involved in SARS-COV-2 viral entry, including neutralizing antibodies against the spike protein of SARS-COV-2, such as REGN-COV2 (an antibody cocktail) and LY-COV555, as well as recombinant human soluble ACE2 protein to counteract SARS-COV-2 binding to the transmembrane ACE2 receptor in target cells. Finally, we discuss potential drug resistance mechanisms and provide thoughts regarding clinical trial design to address the diversity in COVID-19 clinical manifestation. Of note, preventive vaccines, cell and gene therapies are not within the scope of the current review.

TNF-related apoptosis inducing ligand (TRAIL) selectively induces apoptosis in cancer cells without harming most normal cells. Currently, multiple clinical trials are underway to evaluate the antitumor activity of recombinant human TRAIL (rhTRAIL) and agonistic antibodies that target death receptors (DRs) 4 or 5. It is encouraging that these products have shown a tolerated safety profile in early phase studies. However, their therapeutic potential is likely limited by the emergence of tumor drug resistance phenomena. Increasing evidence indicates that TRAIL DRs are deficient on the plasma membrane of some cancer cells despite their total protein expression. Notably, the lack of surface DR4/DR5 is sufficient to render cancers resistant to TRAIL-induced apoptosis, regardless of the status of other apoptosis signaling components. The current review highlights recent findings on the dynamic expression of TRAIL death receptors, including the regulatory roles of endocytosis, autophagy, and Ras GTPase-mediated signaling events. This information could aid in the identification of novel predictive biomarkers of tumor response as well as the development of combinational drugs to overcome or bypass tumor drug resistance to TRAIL receptor-targeted therapies.

Doxorubicin is an important anticancer drug in the clinic. Unfortunately, it causes cumulative and dose-dependent cardiotoxic side effects. As the population of cancer survivors who have been exposed to treatment continues to grow, there is increased interest in assessing the long-term cardiac effects of doxorubicin and understanding the underlying mechanisms at play. In this study, we investigated doxorubicin-induced transcriptomic changes using RNA-sequencing (RNAseq) and a cellular model comprised of human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs). Analyses of predicted upstream regulators identified the p53 protein as a key regulator of transcriptomic changes induced by doxorubicin. Clustering and pathway analyses showed that increased death receptor (DR) expression and enrichment of the extrinsic apoptotic pathway are significantly associated with doxorubicin-induced cardiotoxicity. Increased expression of p53 and DRs were confirmed via immunoblotting. Our data pinpoints increased DR expression as an early transcriptomic indicator of cardiotoxicity, suggesting that DR expression might function as a predictive biomarker for cardiac damage.

Ubiquitin and ubiquitin-like proteins (Ubls) are now at the center stage of molecular and cell biology because of their diverse functions in many fundamentally important cellular processes. Besides the celebrated role of ubiquitin in the 26S proteasome-mediated protein degradation pathway, the non-proteolytic functions of ubiquitin are being uncovered at a fast pace. The prominent examples include membrane trafficking, innate immunity, kinase signaling, chromatin dynamics and DNA damage response. Researchers in the area of DNA damage response have witnessed rapid progress within the past decade, largely stimulated by the seminal findings that ubiquitination and SUMOylation of a key DNA replication/repair protein, proliferating cell nuclear antigen (PCNA), controls precisely how eukaryotic cells respond to different types of DNA damage, and how cellular DNA damage repair or tolerance pathways are selected to cope with damage in the DNA genome. Here, we will review the recent findings on translesion synthesis (TLS) and its regulation by PCNA ubiquitination in eukaryotes. We will discuss two prevalent models, i.e., the postreplicative gap-filling and the polymerase switch, which have been invoked to account for eukaryotic cells' ability to overcome DNA damage associated replication blockade through TLS. Results from both in vitro reconstitution and from genetic systems will be discussed. We will also summarize the recent findings revealing the crosstalk between two major human DNA damage response pathways (the TLS and the Fanconi anemia pathways), and the ATR and ATM-independent regulation of PCNA ubiquitination. Lastly, new methods of preparing ubiquitinated PCNA will be reviewed. The availability of milligram levels of ubiquitinated PCNA will help our understanding of the molecular details in eukaryotic TLS.