Reciprocal Regulation of Shh Trafficking and H2O2 Levels via a Noncanonical BOC-Rac1 Pathway

Awakening adult neural stem cells: NOX signalling as a positive regulator of the quiescence-to-proliferation transition in the Xenopus retina

A growing wealth of data suggest that reactive oxygen species (ROS) signalling might be crucial in conferring embryonic or adult stem cells their specific properties. However, how stem cells control ROS production and scavenging, and how ROS in turn contribute to stemness, remain poorly understood. Using the Xenopus retina as a model system, we first investigated the redox status of retinal stem cells (RSCs). We discovered that they exhibit higher ROS levels compared with progenitors and retinal neurons, and express a set of specific redox genes. We next addressed the question of ROS functional involvement in these cells. Using pharmacological or genetic tools, we demonstrate that inhibition of NADPH oxidase-dependent ROS production increases the proportion of quiescent RSCs. Surprisingly, this is accompanied by an apparent acceleration of the mean division speed within the remaining proliferating pool. Our data further unveil that such impact on RSC cell cycling is achieved by modulation of the Wnt/Hedgehog signalling balance. Altogether, we highlight that RSCs exhibit distinctive redox characteristics and exploit NADPH oxidase signalling to limit quiescence and fine-tune their proliferation rate.

Redox Biology and Liver Fibrosis

Hepatic fibrosis is a complex process that develops in chronic liver diseases. Even though the initiation and progression of fibrosis rely on the underlying etiology, mutual mechanisms can be recognized and targeted for therapeutic purposes. Irrespective of the primary cause of liver disease, persistent damage to parenchymal cells triggers the overproduction of reactive species, with the consequent disruption of redox balance. Reactive species are important mediators for the homeostasis of both hepatocytes and non-parenchymal liver cells. Indeed, other than acting as cytotoxic agents, reactive species are able to modulate specific signaling pathways that may be relevant to hepatic fibrogenesis. After a brief introduction to redox biology and the mechanisms of fibrogenesis, this review aims to summarize the current evidence of the involvement of redox-dependent pathways in liver fibrosis and focuses on possible therapeutic targets.

TMED10 mediates the loading of neosynthesised Sonic Hedgehog in COPII vesicles for efficient secretion and signalling

The morphogen Sonic Hedgehog (SHH) plays an important role in coordinating embryonic development. Short- and long-range SHH signalling occurs through a variety of membrane-associated and membrane-free forms. However, the molecular mechanisms that govern the early events of the trafficking of neosynthesised SHH in mammalian cells are still poorly understood. Here, we employed the retention using selective hooks (RUSH) system to show that newly-synthesised SHH is trafficked through the classical biosynthetic secretory pathway, using TMED10 as an endoplasmic reticulum (ER) cargo receptor for efficient ER-to-Golgi transport and Rab6 vesicles for Golgi-to-cell surface trafficking. TMED10 and SHH colocalized at ER exit sites (ERES), and TMED10 depletion significantly delays SHH loading onto ERES and subsequent exit leading to significant SHH release defects. Finally, we utilised the Drosophila wing imaginal disc model to demonstrate that the homologue of TMED10, Baiser (Bai), participates in Hedgehog (Hh) secretion and signalling in vivo. In conclusion, our work highlights the role of TMED10 in cargo-specific egress from the ER and sheds light on novel important partners of neosynthesised SHH secretion with potential impact on embryonic development.

Hydrogen Peroxide Signaling in Physiology and Pathology

Reactive oxygen species (ROS) were originally described as toxic by-products of aerobic cellular energy metabolism associated with the development of several diseases, such as cancer, neurodegenerative diseases, and diabetes [...]