Apoptosis: Programmed cell death at a molecular level*,*,**

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Abstract

Objectives: To characterize cell surface receptors, their ligands, and their proteins in the 2 major pathways of apoptosis; the components that promote/suppress these interactions; the noninflammatory removal of apoptotic bodies by dendritic cells; and methods of assay in studies of cell death. To describe: how deregulation of apoptosis may contribute to autoimmunity, cancer, and neurodegenerative disorders and strategies some viruses have evolved that interfere with the host's apoptotic pathways. Methods: The authors reviewed and compiled literature on the extrinsic (tumor necrosis factor [TNF] receptor superfamily and ligands) and intrinsic (mitochondria-associated) apoptotic pathways, the pro- and antiapoptotic proteins of the B-cell follicular lymphoma (Bcl)-2 family, the nuclear factor (NF)-κB family of proteins, commonly used laboratory methods to distinguish apoptosis from necrosis, the recognition and removal by phagocytosis of apoptotic cells by dendritic cells, and viral strategies to avoid a host's apoptotic response. Results: The 2 major pathways of apoptosis are (1) FasL and other TNF superfamily ligands induce trimerization of cell-surface death receptors and (2) perturbated mitochondria release cytochrome c, the flavoprotein apoptosis-inducing factor, and second mitochondria-derived activator of caspases/DIABLO (a protein that directly neutralizes inhibitors of apoptotic proteins and activates proteases). Catalytically inactive cysteine proteases, called caspases, and other proteases are activated, ultimately leading to cell death with characteristic cellular chromatin condensation and DNA cleavage to fragments of approximately 180 bp. The inhibitory/promoting action of Bcl-2 family members is involved in the release of cytochrome c, an essential factor for the mitochondrial-associated pathway. A balance between inhibition/promotion determines a cell's fate. The NF-κB family in the cytoplasm of cells activates various genes carrying the NF-κB response element, such as members of the inhibitor of apoptotic proteins family. A few of the more common methods to detect apoptotic cell death are described, which use immunochemical, morphologic and flow cytometric methods, and genetic markers. Exposed phosphatidylserine at the outer leaflet of the plasma membrane of the apoptotic cell serves as a possible receptor for phagocytosis by immature dendritic cells. These cells phagocytize both apoptotic and necrotic cells, but only the latter induce maturation to become fully functional antigen-presenting cells. Viral inhibitors of apoptosis allow increased virus replication in cells, possibly resulting in their oncogenicity. Conclusions: Balanced apoptosis is crucial in development and homeostasis, and all multicellular organisms have a physiologically programmed continuum of pathways to apoptotic cell death. Further studies of the control at the molecular level of key components and promoters/suppressors of apoptosis may provide better approaches to treatment of autoimmune diseases, malignancies, and neurodegenerative disorders. Many important questions remain regarding the advantages of modifying apoptotic programs in clinical situations. Semin Arthritis Rheum 32:345-369. © 2003 Elsevier Inc. All rights reserved.

Section snippets

The extrinsic pathway

Activation of apoptotic pathways and programmed cell death are initiated by the binding of a specific protein ligand to a cell surface transmembrane receptor (Fig 1).

. The 2 major pathways of apoptosis—the extrinsic (Fas and other TNFR superfamily members and ligands) and the intrinsic (mitochondria-associated) pathways. Both pathways lead to activation of caspase-3, giving rise to apoptotic cell death. Only a few examples of proteins that directly affect cell death and the resulting DNA

The Bcl-2 family: Pro- and antiapoptotic proteins

Human bcl-2 was the first protooncogene identified to function by protecting cells from programmed cell death (50, 51, 52, 53, 54, 55). It was recognized early that Bcl-2 was a mammalian homologue of the antideath protein cell death abnormal (ced)-9 of the nematode C elegans, and was mainly located on the outer membrane of mitochondria, but was also on the endoplasmic reticular membrane and outer nuclear envelope (50, 51, 52, 53, 54, 55). Mutations of ced-9 that decreased or eliminated its

Regulation of apoptosis by transcription factor NF-κB

NF-κB is a collective term that refers to a family of proteins involved in inflammatory reactions, lymphoid organ development, and innate and adaptive immunity. For purposes of this review, the action of NF-κB in pro- and antiapoptotic cellular responses is the focus. NF-κBs are dimeric transcription factors in the Rel family that are regulated by shuttling within cells from the cytoplasm to the nucleus in response to various stimuli (90). Maintained as an inactive form in the cytoplasm, on

Methods for detection of apoptotic cell death

Table 2 tabulates, briefly describes, and references some of the more commonly used methods to detect apoptotic cell death.

. Some Published Methods for Detection of Apoptotic Cells

Method*DescriptionDistinguishes Apoptosis From NecrosisReference
Gel electrophoresis to detect DNA fragmentation in apoptotic cells†DNA ladders (200-5000 bp fragments): visualized after staining gels with fluorescent or chromogenic reagentsYes98-100
TUNEL methodsIn situ—end labeling of free 3′ ends of DNA fragments by

Recognition and removal of apoptotic cells

Of the phospholipids distributed in membranes of viable cells, anionic phosphatidylserine is totally located in the inner leaflet (cytoplasmic side), and is not normally in contact with blood components. After the death pathways described previously have been activated in these cells, a specific sequence of highly regulated events takes place in which phosphatidylserine is translocated from the inner to the outer leaflet of the plasma membrane (ie, the cell surface) and is exposed to the

Regulation of apoptosis by viruses

Many viruses have evolved molecules that regulate apoptosis in cells of the host. For example, crmA is expressed by the cowpox virus, and is an antiapoptotic protein that potently blocks Fas- and TNF-induced apoptosis by inhibiting caspase activation (194). The inhibitory action by the cowpox factor prolongs replication in host cells. Another protein (p35) encoded by baculoviruses also inhibits caspases (195). The IAP family of proteins, of which there are several cellular homologues, blocks

References (221)

  • CG Tepper et al.

    Modulation of caspase-8 and FLICE-inhibitor inhibitor protein expression as a potential mechanism of Epstein-Barr virus tumorigenesis in Burkitt's lymphoma

    Blood

    (1999)
  • H Li et al.

    Cleavage of BID by caspase 8 mediates the mitochondrial damage in the Fas pathway of apoptosis

    Cell

    (1998)
  • P Ghafourifar et al.

    Ceramide induces cytochrome c release from isolated mitochondria

    J Biol Chem

    (1999)
  • X Liu et al.

    Induction of apoptotic program in cell-free extracts: requirement for dATP and cytochrome c

    Cell

    (1996)
  • P Li et al.

    Cytochrome c and dATP-dependent formation of Apaf-1/caspase 9 complex initiates an apoptotic protease cascade

    Cell

    (1997)
  • ML Cleary et al.

    Cloning and structural analysis of cDNAs for bcl-2 and a hybrid bcl-2/immunoglobulin transcript resulting from the t(14;18) translocation

    Cell

    (1986)
  • M. Jäättelä

    Escaping cell death: survival proteins in cancer

    Exp Cell Res

    (1999)
  • DA Moulding et al.

    Mcl-1 expression in human neutrophils: regulation by cytokines and correlation with cell survival

    Blood

    (1998)
  • PI Chuang et al.

    A1 is a constitutive and inducible Bcl-2 homologue in mature human neutrophils

    Biochem Biophys Res Commun

    (1998)
  • P Li et al.

    Cytochrome c and dATP-dependent formation of Apaf-1/caspase 9 complex initiates an apoptotic protease cascade

    Cell

    (1997)
  • J Cai et al.

    Mitochondrial control of apoptosis: the role of cytochrome c

    Biochim Biophys Acta

    (1998)
  • B Antonsson et al.

    The Bcl-2 protein family

    Exp Cell Res

    (2000)
  • A Kelekar et al.

    Bcl-2 family proteins: the role of the BH3 domain in apoptosis

    Trends Cell Biol

    (1998)
  • SN Farrow et al.

    New members of the Bcl-2 family and their protein partners

    Curr Opin Genet Dev

    (1996)
  • JM McDonnell et al.

    Solution structure of the pro-apoptotic molecule Bid: A structural basis for apoptotic agonists and antagonists

    Cell

    (1999)
  • E Yang et al.

    Molecular thanatopsis: a discourse on the BCL2 family and cell death

    Blood

    (1996)
  • Y Tsujimoto et al.

    Bcl-2 family: life or death switch

    FEBS Lett

    (2000)
  • S Ghosh et al.

    Missing pieces in the NF-κB puzzle

    Cell

    (2002)
  • JF Kerr et al.

    Apoptosis: a basic biological phenomenon with wide-ranging implications in tissue kinetics

    Br J Cancer

    (1972)
  • KR Aupperle et al.

    Regulation of synoviocytes proliferation, apoptosis, and invasion by the p53 tumor suppressor gene

    Am J Pathol

    (1998)
  • ML Fields et al.

    Fas/Fas ligand deficiency results in altered localization of anti-double-stranded DNA B cells and dendritic cells

    J Immunol

    (2001)
  • DG Green et al.

    Killers or clean-up crew. How central are the central mechanisms of apoptosis

  • J Banchereau et al.

    Dendritic cells and the control of immunity

    Nature

    (1998)
  • C Reis e Sousa

    Dendritic cells as sensors of infection

    Immunity

    (2001)
  • TS Griffith et al.

    Fas ligand-induced apoptosis as a mechanism of immune privilege

    Science

    (1995)
  • D Bellgrau et al.

    A role for CD95 ligand in preventing graft rejection

    Nature

    (1995)
  • NP. Restifo

    Not so Fas: re-evaluating the mechanisms of immune privilege and tumor escape

    Nature Med

    (2000)
  • A Ashkenazi et al.

    Death receptors: signaling and modulation

    Science

    (1998)
  • NU Waterhouse et al.

    Calpain activation is upstream of caspases in radiation-induced apoptosis

    Cell Death Differ

    (1998)
  • ME Guicciardi et al.

    Cathepsin B contributes to TNF-α-mediated hepatocyte apoptosis by promoting mitochondrial release of cytochrome c

    J Clin Invest

    (2000)
  • DE. Johnson

    Noncaspase proteases in apoptosis

    Leukemia

    (2000)
  • KA Jellinger et al.

    The enigma of cell death in neurodenerative disorders

    J Neural Transm

    (2000)
  • PC Rath et al.

    TNF-induced signaling in apoptosis

    J Clin Immunol

    (1999)
  • JP Sheridan et al.

    Control of TRAIL-induced apoptosis by a family of signaling and decoy receptors

    Science

    (1997)
  • N Itoh et al.

    The polypeptide encoded by the cDNA for human cell surface antigen Fas can mediate apoptosis

    Cell

    (1991)
  • M Tanaka et al.

    Expression of the functional soluble form of human fas ligand in activated lymphocytes

    EMBO J

    (1995)
  • D Wallach et al.

    Tumor necrosis factor receptor and Fas signaling mechanisms

    Annu Rev Immunol

    (1999)
  • WC Yeh et al.

    FADD: essential for embryo development and signaling from some, but not all, inducers of apoptosis

    Science

    (1998)
  • JD Lünemann et al.

    Death ligand TRAIL induces no apoptosis but inhibits activation of human (auto) antigen-specific T cells

    J Immunol

    (2002)
  • M Enari et al.

    A caspase-activated DNAase that degrades DNA during apoptosis, and its inhibitor ICAD

    Nature

    (1998)
  • Cited by (311)

    View all citing articles on Scopus
    *

    Duane R. Schultz, PhD: Professor of Medicine, Division of Rheumatology & Immunology, Department of Medicine, University of Miami School of Medicine, Miami, FL; William J. Harrington, Jr., MD: Professor of Medicine, Division of Hematology/Oncology, Department of Medicine, University of Miami School of Medicine, Miami, FL.

    *

    Address reprint requests to Duane R. Schultz, PhD, Division of Rheumatology & Immunology (R-102), Department of Medicine, University of Miami School of Medicine, PO Box 016960, Miami, FL 33101.

    **

    0049-0172/03/3206-0001$30.00/0

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