Cellular survival hinges on a delicate balance between accumulating damages and repair mechanisms. In this intricate equilibrium, oxidants, currently considered physiological molecules, can compromise vital cellular components, ultimately triggering cell death. On the other hand, cells possess countermeasures, such as autophagy, which degrades and recycles damaged molecules and organelles, restoring homeostasis. Lysosomes and their enzymatic arsenal, including cathepsins, play critical roles in this balance, influencing the cell’s fate toward either apoptosis and other mechanisms of regulated cell death or autophagy. However, the interplay between reactive oxygen species (ROS) and cathepsins in these life-or-death pathways transcends a simple cause-and-effect relationship. These elements directly and indirectly influence each other’s activities, creating a complex web of interactions. This review delves into the inner workings of regulated cell death and autophagy, highlighting the pivotal role of ROS and cathepsins in these pathways and their intricate interplay.

Vitamin B₁₂ (cobalamin) is an essential nutrient for humans and animals. Metabolically active forms of B₁₂-methylcobalamin and 5-deoxyadenosylcobalamin are cofactors for the enzymes methionine synthase and mitochondrial methylmalonyl-CoA mutase. Malfunction of these enzymes due to a scarcity of vitamin B₁₂ leads to disturbance of one-carbon metabolism and impaired mitochondrial function. A significant fraction of the population (up to 20%) is deficient in vitamin B₁₂, with a higher rate of deficiency among elderly people. B₁₂ deficiency is associated with numerous hallmarks of aging at the cellular and organismal levels. Cellular senescence is characterized by high levels of DNA damage by metabolic abnormalities, increased mitochondrial dysfunction, and disturbance of epigenetic regulation. B₁₂ deficiency could be responsible for or play a crucial part in these disorders. In this review, we focus on a comprehensive analysis of molecular mechanisms through which vitamin B₁₂ influences aging. We review new data about how deficiency in vitamin B₁₂ may accelerate cellular aging. Despite indications that vitamin B₁₂ has an important role in health and healthy aging, knowledge of the influence of vitamin B₁₂ on aging is still limited and requires further research.

Vitamin B12 (B12), a crucial water-soluble vitamin, plays an essential role in various cellular functions, including DNA synthesis and cellular metabolism. This review explores recent advancements in B12 delivery systems and their potential applications in drug delivery. The unique absorption pathways of B12, which involve specific binding proteins and receptors, are highlighted, emphasizing the vitamin’s protective mechanisms that enhance its bioavailability. The review discusses the intricate multi-protein network involved in B12 metabolism and the implications of B12 deficiency, which can lead to significant health issues, including neurological and hematological disorders. Additionally, the potential of B12 as a drug carrier to improve the pharmacokinetic properties of poorly bioavailable medications is examined. The findings suggest that optimizing B12 delivery could enhance therapeutic outcomes in nanomedicine and other clinical applications.

Methionine oxidation is a reversible post-translational protein modification, affecting protein function, and implicated in aging and degenerative diseases. The detection of accumulating methionine oxidation in living cells or organisms, however, has not been achieved. Here we introduce a genetically encoded probe for methionine oxidation (GEPMO), based on the super-folder green fluorescent protein (sfGFP), as a specific, versatile, and integrating sensor for methionine oxidation. Placed at amino acid position 147 in an otherwise methionine-less sfGFP, the oxidation of this specific methionine to methionine sulfoxide results in a ratiometric fluorescence change when excited with ~400 and ~470 nm light. The strength and homogeneity of the sensor expression is suited for live-cell imaging as well as fluorescence-activated cell sorting (FACS) experiments using standard laser wavelengths (405/488 nm). Expressed in mammalian cells and also in S. cerevisiae, the sensor protein faithfully reports on the status of methionine oxidation in an integrating manner. Variants targeted to membranes and the mitochondria provide subcellular resolution of methionine oxidation, e.g. reporting on site-specific oxidation by illumination of endogenous protoporphyrin IX.

Scorpion α‐toxins are polypeptides that inhibit voltage‐gated sodium channel inactivation. They are divided into mammal, insect and α‐like toxins based on their relative activity toward different phyla. Several factors are currently known to influence the selectivity, which are not just particular amino acid residues but also general physical, chemical, and topological properties of toxin structural modules. The objective of this study was to change the selectivity profile of a chosen broadly active α‐like toxin, BeM9 from Mesobuthus eupeus, toward mammal‐selective. Based on the available information on what determines scorpion α‐toxin selectivity, we designed and produced msBeM9, a BeM9 derivative, which was verified to be exclusively active toward mammalian sodium channels and, most importantly, toward the Na_v1.2 isoform expressed in the brain.