Eva Szegezdi

Bio: Eva Szegezdi is an academic researcher from National University of Ireland, Galway. The author has contributed to research in topics: Apoptosis & Receptor. The author has an hindex of 33, co-authored 78 publications receiving 10554 citations. Previous affiliations of Eva Szegezdi include Hungarian Academy of Sciences & University College Hospital.

Guidelines for the use and interpretation of assays for monitoring autophagy (3rd edition)

Abstract: In 2008 we published the first set of guidelines for standardizing research in autophagy. Since then, research on this topic has continued to accelerate, and many new scientists have entered the field. Our knowledge base and relevant new technologies have also been expanding. Accordingly, it is important to update these guidelines for monitoring autophagy in different organisms. Various reviews have described the range of assays that have been used for this purpose. Nevertheless, there continues to be confusion regarding acceptable methods to measure autophagy, especially in multicellular eukaryotes. For example, a key point that needs to be emphasized is that there is a difference between measurements that monitor the numbers or volume of autophagic elements (e.g., autophagosomes or autolysosomes) at any stage of the autophagic process versus those that measure flux through the autophagy pathway (i.e., the complete process including the amount and rate of cargo sequestered and degraded). In particular, a block in macroautophagy that results in autophagosome accumulation must be differentiated from stimuli that increase autophagic activity, defined as increased autophagy induction coupled with increased delivery to, and degradation within, lysosomes (in most higher eukaryotes and some protists such as Dictyostelium) or the vacuole (in plants and fungi). In other words, it is especially important that investigators new to the field understand that the appearance of more autophagosomes does not necessarily equate with more autophagy. In fact, in many cases, autophagosomes accumulate because of a block in trafficking to lysosomes without a concomitant change in autophagosome biogenesis, whereas an increase in autolysosomes may reflect a reduction in degradative activity. It is worth emphasizing here that lysosomal digestion is a stage of autophagy and evaluating its competence is a crucial part of the evaluation of autophagic flux, or complete autophagy. Here, we present a set of guidelines for the selection and interpretation of methods for use by investigators who aim to examine macroautophagy and related processes, as well as for reviewers who need to provide realistic and reasonable critiques of papers that are focused on these processes. These guidelines are not meant to be a formulaic set of rules, because the appropriate assays depend in part on the question being asked and the system being used. In addition, we emphasize that no individual assay is guaranteed to be the most appropriate one in every situation, and we strongly recommend the use of multiple assays to monitor autophagy. Along these lines, because of the potential for pleiotropic effects due to blocking autophagy through genetic manipulation, it is imperative to target by gene knockout or RNA interference more than one autophagy-related protein. In addition, some individual Atg proteins, or groups of proteins, are involved in other cellular pathways implying that not all Atg proteins can be used as a specific marker for an autophagic process. In these guidelines, we consider these various methods of assessing autophagy and what information can, or cannot, be obtained from them. Finally, by discussing the merits and limits of particular assays, we hope to encourage technical innovation in the field.

Mediators of endoplasmic reticulum stress-induced apoptosis.

Abstract: The efficient functioning of the endoplasmic reticulum (ER) is essential for most cellular activities and survival. Conditions that interfere with ER function lead to the accumulation and aggregation of unfolded proteins. ER transmembrane receptors detect the onset of ER stress and initiate the unfolded protein response (UPR) to restore normal ER function. If the stress is prolonged, or the adaptive response fails, apoptotic cell death ensues. Many studies have focused on how this failure initiates apoptosis, as ER stress-induced apoptosis is implicated in the pathophysiology of several neurodegenerative and cardiovascular diseases. In this review, we examine the role of the molecules that are activated during the UPR in order to identify the molecular switch from the adaptive phase to apoptosis. We discuss how the activation of these molecules leads to the commitment of death and the mechanisms that are responsible for the final demise of the cell.

Caspase-12 and ER-stress-mediated apoptosis: the story so far.

Abstract: The labyrinth of the endoplasmic reticulum (ER) interweaves the cytosol and connects to the nucleus, mitochondria, and the plasma membrane. In the lumen of the ER, the essential function of lipid synthesis, Ca(2+) storage, folding, and maturation of proteins take place. Therefore, the tight regulation and maintenance of ER homeostasis is vital. Disturbance of the Ca(2+) homeostasis during hypoxia, or imbalance between the demand and capacity of the protein-folding apparatus, initiates an adaptive response of the cell, termed the unfolded protein response (UPR, ER stress response). As a result, ER-localized chaperones are induced, protein synthesis is slowed down, and a protein degrading system is initiated. However, if the ER stress cannot be alleviated, it culminates in apoptosis. This paper reviews the newly outlined signaling pathways of the unfolded protein response and describes the central role of caspase-12 in the initiation of cell death. The complex role of the ER and its signaling pathways provides a novel angle on apoptosis research and may offer a key to apoptosis-associated diseases.

Transglutaminase 2-/- mice reveal a phagocytosis-associated crosstalk between macrophages and apoptotic cells.

Abstract: Tissue transglutaminase (TGase2) is a protein-crosslinking enzyme known to be associated with the in vivo apoptosis program Here we report that apoptosis could be induced in TGase2-/- mice; however, the clearance of apoptotic cells was defective during the involution of thymus elicited by dexamethasone, anti-CD3 antibody, or I³-irradiation, and in the liver after induced hyperplasia The lack of TGase2 prevented the production of active transforming growth factor-I²1 in macrophages exposed to apoptotic cells, which is required for the up-regulation of TGase2 in the thymus in vivo, for accelerating deletion of CD4+CD8+ cells and for efficient phagocytosis of apoptotic bodies The deficiency is associated with the development of splenomegaly, autoantibodies, and immune complex glomerulonephritis in TGase2-/- mice These findings have broad implications not only for diseases linked to inflammation and autoimmunity but also for understanding the interrelationship between the apoptosis and phagocytosis process Transglutaminases (TGases) (1) are a family of thiol- and Ca2+-dependent acyl transferases that catalyze the formation of a covalent bond between the I³-carboxamide groups of peptide-bound glutamine residues and various primary amines, including the Iµ-amino group of lysine in certain proteins The reaction results in posttranslational modification of proteins by establishing Iµ-(I³-glutamyl)lysine crosslinkages and/or covalent incorporation of polyamines and histamine into proteins Eight distinct enzymatically active transglutaminases have so far been described (1, 2) One of them, TGase2, has additionally G protein signaling activity (3) TGase2 is ubiquitously expressed in mammalian tissues (4) found both extracellularly at the cell surface in association with the extracellular matrix (5) and intracellularly in membrane-associated as well as cytosolic form TGase2 has been implicated in a variety of cellular processes, including signaling (6), signal transduction (3), cell adhesion and spreading (7), wound healing (8), and tissue mineralization (9) Additionally, it has also been demonstrated that TGase2 is one of the few genes induced during the in vivo apoptotic program (10–12) Cells expressing TGase2 antisense RNA are less sensitive to apoptosis induced by various agents, whereas cells overexpressing TGase2 have increased sensitivity (13, 14) Because intracellularly GTP, Zn2+,and nitric oxide inhibit the crosslinking activity of TGase2, the accumulation of TGase2 inside the cell is not necessarily associated with the activation of its crosslinking activity (15) However, Ca2+-dependent activation of the enzyme leads to the formation of a detergentinsoluble crosslinked protein scaffold in cells undergoing programmed cell death (16) This insoluble protein scaffold may stabilize the integrity of the dying cells before their clearance by phagocytosis, thus preventing the nonspecific release of harmful intracellular components and consequently inflammatory responses and scar formation in bystander tissues (17) Although TGase2 seems to be strongly linked to the in vivo apoptosis program (10–12), the up-regulation of TGase2 cannot be detected during the induction of in vitro apoptosis in many cells, suggesting that factors present only in the tissue environment are required for its induction in vivo (12) To assess the role of TGase2 in programmed cell death, TGase2-/- mice have been generated (18) Because these mice did not show an overt apoptosis-related phenotype during fetal life, we decided to investigate the role of TGase2 in the in vivo apoptosis program in distinct biological contexts by using the thymus and liver as model systems Data presented in this study indicate that the lack of TGase2 affects both the killing and the clearance of dying cells The disturbance of these events results from a deficiency in transforming growth factor (TGF)-I² activation and is associated with the development of splenomegaly, autoantibodies, and glomerulonephritis in TGase2-/- mice These findings have implications for inflammation and autoimmune diseases such as systemic lupus erythematosus

Molecular mechanisms of cell death: recommendations of the Nomenclature Committee on Cell Death 2018.

Abstract: Over the past decade, the Nomenclature Committee on Cell Death (NCCD) has formulated guidelines for the definition and interpretation of cell death from morphological, biochemical, and functional perspectives. Since the field continues to expand and novel mechanisms that orchestrate multiple cell death pathways are unveiled, we propose an updated classification of cell death subroutines focusing on mechanistic and essential (as opposed to correlative and dispensable) aspects of the process. As we provide molecularly oriented definitions of terms including intrinsic apoptosis, extrinsic apoptosis, mitochondrial permeability transition (MPT)-driven necrosis, necroptosis, ferroptosis, pyroptosis, parthanatos, entotic cell death, NETotic cell death, lysosome-dependent cell death, autophagy-dependent cell death, immunogenic cell death, cellular senescence, and mitotic catastrophe, we discuss the utility of neologisms that refer to highly specialized instances of these processes. The mission of the NCCD is to provide a widely accepted nomenclature on cell death in support of the continued development of the field.

Molecular definitions of cell death subroutines: recommendations of the Nomenclature Committee on Cell Death 2012

Abstract: In 2009, the Nomenclature Committee on Cell Death (NCCD) proposed a set of recommendations for the definition of distinct cell death morphologies and for the appropriate use of cell death-related terminology, including 'apoptosis', 'necrosis' and 'mitotic catastrophe'. In view of the substantial progress in the biochemical and genetic exploration of cell death, time has come to switch from morphological to molecular definitions of cell death modalities. Here we propose a functional classification of cell death subroutines that applies to both in vitro and in vivo settings and includes extrinsic apoptosis, caspase-dependent or -independent intrinsic apoptosis, regulated necrosis, autophagic cell death and mitotic catastrophe. Moreover, we discuss the utility of expressions indicating additional cell death modalities. On the basis of the new, revised NCCD classification, cell death subroutines are defined by a series of precise, measurable biochemical features.

Integrating the mechanisms of apoptosis induced by endoplasmic reticulum stress.

Abstract: The ability to respond to perturbations in endoplasmic reticulum (ER) function is a fundamentally important property of all cells, but ER stress can also lead to apoptosis. In settings of chronic ER stress, the associated apoptosis may contribute to pathophysiological processes involved in a number of prevalent diseases, including neurodegenerative diseases, diabetes, atherosclerosis and renal disease. The molecular mechanisms linking ER stress to apoptosis are the topic of this review, with emphases on relevance to pathophysiology and integration and complementation among the various apoptotic pathways induced by ER stress.

Mediators of endoplasmic reticulum stress-induced apoptosis.

Abstract: The efficient functioning of the endoplasmic reticulum (ER) is essential for most cellular activities and survival. Conditions that interfere with ER function lead to the accumulation and aggregation of unfolded proteins. ER transmembrane receptors detect the onset of ER stress and initiate the unfolded protein response (UPR) to restore normal ER function. If the stress is prolonged, or the adaptive response fails, apoptotic cell death ensues. Many studies have focused on how this failure initiates apoptosis, as ER stress-induced apoptosis is implicated in the pathophysiology of several neurodegenerative and cardiovascular diseases. In this review, we examine the role of the molecules that are activated during the UPR in order to identify the molecular switch from the adaptive phase to apoptosis. We discuss how the activation of these molecules leads to the commitment of death and the mechanisms that are responsible for the final demise of the cell.

Apoptosis in cancer: from pathogenesis to treatment

Abstract: Apoptosis is an ordered and orchestrated cellular process that occurs in physiological and pathological conditions. It is also one of the most studied topics among cell biologists. An understanding of the underlying mechanism of apoptosis is important as it plays a pivotal role in the pathogenesis of many diseases. In some, the problem is due to too much apoptosis, such as in the case of degenerative diseases while in others, too little apoptosis is the culprit. Cancer is one of the scenarios where too little apoptosis occurs, resulting in malignant cells that will not die. The mechanism of apoptosis is complex and involves many pathways. Defects can occur at any point along these pathways, leading to malignant transformation of the affected cells, tumour metastasis and resistance to anticancer drugs. Despite being the cause of problem, apoptosis plays an important role in the treatment of cancer as it is a popular target of many treatment strategies. The abundance of literature suggests that targeting apoptosis in cancer is feasible. However, many troubling questions arise with the use of new drugs or treatment strategies that are designed to enhance apoptosis and critical tests must be passed before they can be used safely in human subjects.