Regulation of antioxidants in cancer.

Scientists in this field often joke, "If you don't have a mechanism, say it's ROS." Seemingly connected to every biological process ever described, reactive oxygen species (ROS) have numerous pleiotropic roles in physiology and disease. In some contexts, ROS act as secondary messengers, controlling a variety of signaling cascades. In other scenarios, they initiate damage to macromolecules. Finally, in their worst form, ROS are deadly to cells and surrounding tissues. A set of molecules with detoxifying abilities, termed antioxidants, is the direct counterpart to ROS. Notably, antioxidants exist in the public domain, touted as a "cure-all" for diseases. Research has disproved many of these claims and, in some cases, shown the opposite. Of all the diseases, cancer stands out in its paradoxical relationship with antioxidants. Although the field has made numerous strides in understanding the roles of antioxidants in cancer, many questions remain.

Proteome Birthdating Reveals Age-Selectivity of Protein Ubiquitination.

Within a cell, proteins have distinct and highly variable half-lives. As a result, the molecular ages of proteins can range from seconds to years. How the age of a protein influences its environmental interactions is a largely unexplored area of biology. To investigate the age-selectivity of cellular pathways, we developed a methodology termed "proteome birthdating" that barcodes proteins based on their time of synthesis. We demonstrate that this approach provides accurate measurements of protein turnover kinetics from a single biological sample encoding multiple labeling time-points. As a first application of the birthdated proteome, we investigated the age distribution of the human ubiquitinome. Our results indicate that the vast majority of ubiquitinated proteins in a cell consist of newly synthesized proteins and that these young proteins constitute the bulk of the degradative flux through the proteasome. Rapidly ubiquitinated nascent proteins are enriched in cytosolic subunits of large protein complexes. Conversely, proteins destined for the secretory pathway and vesicular transport have older ubiquitinated populations. Our data also identify a smaller subset of older ubiquitinated cellular proteins that do not appear to be targeted to the proteasome for rapid degradation. Together, our data provide an age census of the human ubiquitinome and establish proteome birthdating as a robust methodology for investigating the protein age-selectivity of diverse cellular pathways.

Deletion of dpy-19 like 2 (DPY19L2) gene is associated with total but not partial globozoospermia.

The dpy-19 like 2 (DPY19L2) gene is the most common genetic cause of globozoospermia characterised by the production of round-headed spermatozoa without an acrosome. The present study was performed on 63 men with globozoospermia and 41 normozoospermic individuals to evaluate the frequency of the DPY19L2 gene and exons; deletion and genetic changes in exons 1, 5, 7-11, 19, 21 and interval introns; and some epidemiological factors (e.g. varicocele, smoking, drug use, alcohol consumption and a family history of infertility). Homozygous deletion of DPY19L2 was identified in 35% of men with globozoospermia. Exon 7 was deleted in 4.8% of men with globozoospermia in which DPY19L2 was not deleted. No genetic variations were observed within the DPY19L2 exons examined, but five intronic polymorphisms were detected: 1054-77T>C in intron 9, 1131+65T>C and 1131+53A>G in intron 10 and 1218+22T>C and 1218+73T>C in intron 11. There were significant differences in the frequency of 1054-77T>C and 1218+22T>C polymorphisms between the globozoospermic and normozoospermic groups. In addition, there were significant differences between the two groups in sperm count, sperm motility, a history of infertility in the family and varicocele. Based on these findings, DPY19L2 deletion is the major cause of total globozoospermia and there is no association between exons 1, 5, 8-11, 19 and 21 polymorphisms of the DPY19L2 gene in the occurrence of this defect.

Corrigendum to: Deletion of dpy-19 like 2 (DPY19L2) gene is associated with total but not partial globozoospermia.

The dpy-19 like 2 (DPY19L2) gene is the most common genetic cause of globozoospermia characterised by the production of round-headed spermatozoa without an acrosome. The present study was performed on 63 men with globozoospermia and 41 normozoospermic individuals to evaluate the frequency of the DPY19L2 gene and exons; deletion and genetic changes in exons 1, 5, 7-11, 19, 21 and interval introns; and some epidemiological factors (e.g. varicocele, smoking, drug use, alcohol consumption and a family history of infertility). Homozygous deletion of DPY19L2 was identified in 35% of men with globozoospermia. Exon 7 was deleted in 4.8% of men with globozoospermia in which DPY19L2 was not deleted. No genetic variations were observed within the DPY19L2 exons examined, but five intronic polymorphisms were detected: 1054-77T>C in intron 9, 1131+65T>C and 1131+53A>G in intron 10 and 1218+22T>C and 1218+73T>C in intron 11. There were significant differences in the frequency of 1054-77T>C and 1218+22T>C polymorphisms between the globozoospermic and normozoospermic groups. In addition, there were significant differences between the two groups in sperm count, sperm motility, a history of infertility in the family and varicocele. Based on these findings, DPY19L2 deletion is the major cause of total globozoospermia and there is no association between exons 1, 5, 8-11, 19 and 21 polymorphisms of the DPY19L2 gene in the occurrence of this defect.

Catabolism of extracellular glutathione supplies amino acids to support tumor growth.

Restricting amino acids from tumors is an emerging therapeutic strategy with significant promise. While typically considered an intracellular antioxidant with tumor-promoting capabilities, glutathione (GSH) is a tripeptide of cysteine, glutamate, and glycine that can be catabolized, yielding amino acids. The extent to which GSH-derived amino acids are essential to cancers is unclear. Here, we find that GSH catabolism promotes tumor growth. We show that depletion of intracellular GSH does not perturb tumor growth, and extracellular GSH is highly abundant in the tumor microenvironment, highlighting the potential importance of GSH outside of tumors. We find supplementation with GSH can rescue cancer cell survival and growth in cystine-deficient conditions, and this rescue is dependent on the catabolic activity of γ-glutamyltransferases (GGTs). Finally, pharmacologic targeting of GGTs' activity prevents the breakdown of circulating GSH, lowers tumor cysteine levels, and slows tumor growth. Our findings indicate a non-canonical role for GSH in supporting tumors by acting as a reservoir of amino acids. Depriving tumors of extracellular GSH or inhibiting its breakdown is potentially a therapeutically tractable approach for patients with cancer. Further, these findings change our view of GSH and how amino acids, including cysteine, are supplied to cells.

Glutathione synthesis in the mouse liver supports lipid abundance through NRF2 repression.

Cells rely on antioxidants to survive. The most abundant antioxidant is glutathione (GSH). The synthesis of GSH is non-redundantly controlled by the glutamate-cysteine ligase catalytic subunit (GCLC). GSH imbalance is implicated in many diseases, but the requirement for GSH in adult tissues is unclear. To interrogate this, we have developed a series of in vivo models to induce Gclc deletion in adult animals. We find that GSH is essential to lipid abundance in vivo. GSH levels are highest in liver tissue, which is also a hub for lipid production. While the loss of GSH does not cause liver failure, it decreases lipogenic enzyme expression, circulating triglyceride levels, and fat stores. Mechanistically, we find that GSH promotes lipid abundance by repressing NRF2, a transcription factor induced by oxidative stress. These studies identify GSH as a fulcrum in the liver's balance of redox buffering and triglyceride production.

Glutathione supports lipid abundance in vivo.

Cells rely on antioxidants to survive. The most abundant antioxidant is glutathione (GSH). The synthesis of GSH is non-redundantly controlled by the glutamate-cysteine ligase catalytic subunit (GCLC). GSH imbalance is implicated in many diseases, but the requirement for GSH in adult tissues is unclear. To interrogate this, we developed a series of in vivo models to induce Gclc deletion in adult animals. We find that GSH is essential to lipid abundance in vivo. GSH levels are reported to be highest in liver tissue, which is also a hub for lipid production. While the loss of GSH did not cause liver failure, it decreased lipogenic enzyme expression, circulating triglyceride levels, and fat stores. Mechanistically, we found that GSH promotes lipid abundance by repressing NRF2, a transcription factor induced by oxidative stress. These studies identify GSH as a fulcrum in the liver's balance of redox buffering and triglyceride production.