Respiratory (oxidative) burst of neutrophils is explosive formation of reactive oxygen species controlled by a complex intracellular signaling network. If activation of the respiratory burst is sufficiently prolonged and intense, it could initiate regulated cell death through various mechanisms, the best known of which is NETosis, a specific form of lytic regulated cell death involving release of extracellular DNA networks. We investigated dynamics, concentration dependence, and activation parameters of the respiratory burst and regulated death of human neutrophils upon stimulation of protein kinase C with the diacylglycerol mimetic, phorbol 12-myristate 13-acetate (PMA), using flow cytometry and fluorescence microscopy. When isolated neutrophils were activated with PMA, the fastest and most sensitive response was granule secretion, assessed by CD63 expression using flow cytometry. Reactive oxygen species (ROS) generation followed next in the temporal and concentration hierarchy of responses. Lytic death of neutrophils observed by flow cytometry followed the ROS generation and occurred at the same activator concentrations. Yet, as the PMA concentration increased, the number of neutrophils recorded by the cytometer decreased substantially, indicating complete cell destruction. To determine the extent of this destruction, we examined response of the neutrophils in the leukocyte-rich blood plasma by fluorescence microscopy in a flow chamber, where the dynamics of the process was considerably slower. Pronounced cell lysis occurred in response to PMA activation via both the NETosis and necrosis pathways. ROS generation became concentrated in the individual neutrophil vacuoles within several tens of minutes after activation. Overall, in response to activation, neutrophils display a classic sequence of signaling events, which could culminate in a respiratory burst accompanying phagocytosis, necrosis, NETosis, or secondary necrosis.
Ribosome hibernation is a key bacterial survival strategy under stress conditions. While most eubacteria utilize ribosome silencing factor (RsfS) and hibernation promoting factor (HPF), the functional interplay of ribosome-associated factors, including ribosome modulation factor (RMF), short HPF, and YfiA in γ-proteobacteria remains poorly understood. Here, we systematically investigated the role of these four ribosome-associated factors in Pseudomonas putida PCL1760 by examining their gene expression patterns, effects of overexpression, and contribution to long-term survival. Transcriptional analysis revealed that rmf, hpf, and yfiA are strongly induced upon entry into stationary phase with distinct temporal expression patterns, whereas rsfS expression remained constitutive. Overexpression of RMF, YfiA, and RsfS caused strong growth inhibition, while HPF overexpression resulted only in moderate growth suppression. Long-term survival assays of knockout mutants revealed HPF as the most critical factor, with the Δhpf mutant showing a 75
This review is devoted to molecular mechanisms of ferroptosis, a type of programmed cell death dependent on lipid peroxidation and limited by iron influx, mediated by the transferrin receptor (TfR1 or CD71). In addition to the iron-saturated transferrin, ligands of transferrin receptor also include its homologues lactoferrin and melanotransferrin, as well as heavy-chain ferritin and heme complex with human serum albumin. Activation of ferroptosis, including by increasing the labile pool of iron in tumor cells, is considered a promising strategy for combating cancer. However, a number of pathogenic human viruses, including influenza virus, SARS-CoV-2 coronavirus, and rabies virus, use binding with TfR1 to infect cells and affect ferroptosis. The review summarizes information on natural and synthetic TfR1 regulators, including the mechanisms of their influence on the development of ferroptosis and the prospects for their use as antiviral agents.
Programmed cell death (PCD) is a set of tightly controlled biological pathways that eliminate obsolete or damaged cells to preserve tissue homeostasis and support development. Despite their mechanistic variations, all PCD pathways share three fundamental characteristics: a genetic basis, stringent regulation, and an active requirement for energy to drive cellular self-destruction. While PCD signaling pathways are heavily studied, their precise spatial and temporal organization remains elusive. Intrinsically disordered proteins (IDPs), liquid–liquid phase separation (LLPS), and membraneless organelles (MLOs) have emerged as fundamental principles for cellular organization, enabling rapid stress adaptation and signal integration. This review provides a brief overview of the complexity of PCD pathways and summarizes the roles of IDPs, LLPS, and MLOs in PCD regulation and execution. This biophysical perspective challenges the view of cell death as a fatalistic, binary outcome, reimagining cellular suicide not as something ‘written in stone’, but as a highly regulated continuum of decreasing vitality.
Phytaspases are plant proteases involved in stress-induced plant cell death. They share substrate specificity with animal apoptotic proteases (caspases) and exhibit high selectivity toward their protein substrates. Rice phytaspase has previously been shown to hydrolyze, and thereby inactivate, the heterologous protein human gastrin, a peptide hormone. Because reducing gastrin levels may be beneficial in several human pathological conditions, we compared phytaspase activity across a wide range of edible plants. Phytaspase activity varied by one to two orders of magnitude, even among closely related plant species. We isolated and identified phytaspase from pepper fruits (Capsicum annuum), one of the plant materials with the highest activity, produced the recombinant enzyme, and characterized some of its biochemical properties, including substrate specificity. We further demonstrated that pepper phytaspase efficiently hydrolyzes human gastrin in vitro. These findings support further experimental investigation of the hypothesis that consuming pepper may reduce gastrin levels in the human body.
