Induction of heat shock proteins (Hsps) following cellular damage can prevent apoptosis induced by both the intrinsic and the extrinsic pathways. The intrinsic pathway is characterized by mitochondrial outer membrane permeabilization (MOMP), cytochrome c release, apoptosome assembly, and caspase activation. Hsps promote cell survival by preventing MOMP or apoptosome formation as well as via regulation of Akt and JNK activities. Engagement of the TNF death receptors induces the extrinsic pathway that is characterized by Fas-associated death domain–dependent (FADD-dependent) caspase-8 activation or induction of NF-κB to promote cellular survival. Hsps can directly suppress proapoptotic signaling events or stabilizing elements of the NF-κB pathway to promote cellular survival.
Helen M. Beere
Cell death by apoptosis or necrosis is often important in the etiology and treatment of disease. Since mitochondria play important roles in cell death pathways, these organelles are potentially prime targets for therapeutic intervention. Here we discuss the mechanisms through which mitochondria participate in the cell death process and also survey some of the pharmacological approaches that target mitochondria in various ways.
Lisa Bouchier-Hayes, Lydia Lartigue, Donald D. Newmeyer
The commitment to programmed cell death involves complex interactions among pro- and antiapoptotic members of the Bcl-2 family of proteins. The physiological result of a decision by these proteins to undergo cell death is permeabilization of the mitochondrial outer membrane. Pharmacologic manipulation of proteins in this family appears both feasible and efficacious, whether the goal is decreased cell death, as in ischemia of the myocardium or brain, or increased cell death, as in cancer.
Anthony Letai
Disturbances in the normal functions of the ER lead to an evolutionarily conserved cell stress response, the unfolded protein response, which is aimed initially at compensating for damage but can eventually trigger cell death if ER dysfunction is severe or prolonged. The mechanisms by which ER stress leads to cell death remain enigmatic, with multiple potential participants described but little clarity about which specific death effectors dominate in particular cellular contexts. Important roles for ER-initiated cell death pathways have been recognized for several diseases, including hypoxia, ischemia/reperfusion injury, neurodegeneration, heart disease, and diabetes.
Chunyan Xu, Beatrice Bailly-Maitre, John C. Reed
Caspases, a family of cysteine proteases, play a central role in apoptosis. During the last decade, major progress has been made to further understand caspase structure and function, providing a unique basis for drug design. This Review gives an overview of caspases and their classification, structure, and substrate specificity. We also describe the current knowledge of how interference with caspase signaling can be used to pharmacologically manipulate cell death.
Inna N. Lavrik, Alexander Golks, Peter H. Krammer
Recent studies have shown that members of the inhibitor of apoptosis (IAP) protein family are highly expressed in several classes of cancer. The primary implication of these findings is that the elevated expression of IAPs is not coincidental but actually participates in oncogenesis by helping to allow the malignant cell to avoid apoptotic cell death. This concept, together with the discovery of several IAP-regulatory proteins that use a conserved mode of action, has stimulated a major effort by many research groups to devise IAP-targeting strategies as a means of developing novel antineoplastic drugs. In this Review, we consider the evidence both for and against the IAPs being valid therapeutic targets, and we describe the types of strategies being used to neutralize their functions.
Casey W. Wright, Colin S. Duckett
The visualization of autophagosomes in dying cells has led to the belief that autophagy is a nonapoptotic form of programmed cell death. This concept has now been evaluated using cells and organisms deficient in autophagy genes. Most evidence indicates that, at least in cells with intact apoptotic machinery, autophagy is primarily a pro-survival rather than a pro-death mechanism. This review summarizes the evidence linking autophagy to cell survival and cell death, the complex interplay between autophagy and apoptosis pathways, and the role of autophagy-dependent survival and death pathways in clinical diseases.
Beth Levine, Junying Yuan
This series of Reviews on cell death explores the creation of new therapies for correcting excessive or deficient cell death in human disease. Signal transduction pathways controlling cell death and the molecular core machinery responsible for cellular self-destruction have been elucidated with unprecedented celerity during the last decade, leading to the design of novel strategies for blocking pathological cell loss or for killing unwanted cells. Thus, an increasing number of compounds targeting a diverse range of apoptosis-related molecules are being explored at the preclinical and clinical levels. Beyond the agents that are already FDA approved, a range of molecules targeting apoptosis-regulatory transcription factors, regulators of mitochondrial membrane permeabilization, and inhibitors or activators of cell death–related proteases are under close scrutiny for drug development.
Douglas R. Green, Guido Kroemer
Despite recent advances in preventing sudden cardiac death (SCD) due to cardiac arrhythmia, its incidence in the population at large has remained unacceptably high. Better understanding of the interaction among various functional, structural, and genetic factors underlying the susceptibility to, and initiation of, fatal arrhythmias is a major goal and will provide new tools for the prediction, prevention, and therapy of SCD. Here, we review the role of aberrant intracellular Ca2+ handling, ionic imbalances associated with acute myocardial ischemia, neurohumoral changes, and genetic predisposition in the pathogenesis of SCD due to cardiac arrhythmia. Therapeutic measures to prevent SCD are also discussed.
Michael Rubart, Douglas P. Zipes
The thyroid-stimulating hormone receptor (TSHR) is a G protein–linked, 7–transmembrane domain (7-TMD) receptor that undergoes complex posttranslational processing unique to this glycoprotein receptor family. Due to its complex structure, TSHR appears to have unstable molecular integrity and a propensity toward over- or underactivity on the basis of point genetic mutations or antibody-induced structural changes. Hence, both germline and somatic mutations, commonly located in the transmembrane regions, may induce constitutive activation of the receptor, resulting in congenital hyperthyroidism or the development of actively secreting thyroid nodules. Similarly, mutations leading to structural alterations may induce constitutive inactivation and congenital hypothyroidism. The TSHR is also a primary antigen in autoimmune thyroid disease, and some TSHR antibodies may activate the receptor, while others inhibit its activation or have no influence on signal transduction at all, depending on how they influence the integrity of the structure. Clinical assays for such antibodies have improved significantly and are a useful addition to the investigative armamentarium. Furthermore, the relative instability of the receptor can result in shedding of the TSHR ectodomain, providing a source of antigen and activating the autoimmune response. However, it may also provide decoys for TSHR antibodies, thus influencing their biological action and clinical effects. This review discusses the role of the TSHR in the physiological and pathological stimulation of the thyroid.
Terry F. Davies, Takao Ando, Reigh-Yi Lin, Yaron Tomer, Rauf Latif
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