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Anthony J. Sadler

Other affiliations: Monash University, Hudson Institute, Cleveland Clinic  ...read more
Bio: Anthony J. Sadler is an academic researcher from Monash University, Clayton campus. The author has contributed to research in topics: Protein kinase R & Innate immune system. The author has an hindex of 19, co-authored 31 publications receiving 2987 citations. Previous affiliations of Anthony J. Sadler include Monash University & Hudson Institute.

Papers
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Journal ArticleDOI
TL;DR: This Review discusses four main effector pathways of the IFN-mediated antiviral response: the Mx GTPase pathway, the 2′,5′-oligoadenylate-synthetase-directed ribonuclease L pathways, the protein kinase R pathway and the ISG15 ubiquitin-like pathway.
Abstract: Since the discovery of interferons (IFNs), considerable progress has been made in describing the nature of the cytokines themselves, the signalling components that direct the cell response and their antiviral activities. Gene targeting studies have distinguished four main effector pathways of the IFN-mediated antiviral response: the Mx GTPase pathway, the 2',5'-oligoadenylate-synthetase-directed ribonuclease L pathway, the protein kinase R pathway and the ISG15 ubiquitin-like pathway. As discussed in this Review, these effector pathways individually block viral transcription, degrade viral RNA, inhibit translation and modify protein function to control all steps of viral replication. Ongoing research continues to expose additional activities for these effector proteins and has revealed unanticipated functions of the antiviral response.

1,927 citations

Book ChapterDOI
TL;DR: Responsibility for PKR in the regulation of transcription and signal transduction in infected cells, as well as uninfected but diseased tissues, such as in tumorigenesis and neurodegenerative diseases is advocated.
Abstract: The protein kinase R (PKR) is an intracellular sensor of stress, exemplified by viral infection. Double-stranded (ds) RNA produced during viral replication activates PKR, which in turn arrests protein synthesis by phosphorylating the α subunit of the translation initiation factor eIF2. As well as dsRNA, two additional ligands, PACT and heparin, directly activate the kinase. These mediate the response of PKR to additional indirect stimuli, including bacterial lipopolysaccharides, ceramide and polyanionic molecules. This responsiveness to multiple stimuli advocates a broader role for PKR as a signalling molecule for diverse physiological stresses. Appropriately, a number of other protein substrates have been reported for PKR. These substrates support additional roles for PKR in the regulation of transcription and signal transduction in infected cells, as well as uninfected but diseased tissues, such as in tumorigenesis and neurodegenerative diseases. Finally, PKR plays a role in normal cell differentiation in platelet-derived growth factor signalling and in osteoblast-mediated calcification.

187 citations

Journal ArticleDOI
TL;DR: R mediates responses via phosphorylation of protein substrates and promotes signal transduction pathways to maintain homeostasis, mediate immune responses, and, upon sustained activation, promote apoptosis.
Abstract: The effects of interferons (IFNs) are mediated through the induction of around 2,000 IFN-stimulated gene (ISG) products. However, the majority of these ISGs do not directly instigate IFN-mediated states, such as the defining resistance to viral infection. Rather, most ISGs encode cell signaling molecules that enhance the responsiveness to pathogens, and systemically disseminate signals from localized sites of infection. Relatively few IFN effector proteins have been well characterized. The protein kinase R (PKR) is one of the first and best characterized of these effector molecules. PKR mediates responses via phosphorylation of protein substrates and promotes signal transduction pathways to maintain homeostasis, mediate immune responses, and, upon sustained activation, promote apoptosis. As a number of reviews have dealt with PKR-dependent resistance to virus, this review will cover broader roles ascribed to PKR and the mechanism(s) by which PKR exerts its effects.

170 citations

Journal ArticleDOI
TL;DR: It is shown that STAT1 is serine phosphorylated in macrophages subjected to type A scavenger receptor ligands and endoplasmic reticulum stress in a manner requiring cytosolic calcium, calcium/calmodulin-dependent protein kinase II, and toll-like receptor-4.
Abstract: Background— Macrophage apoptosis is a critical process in the formation of necrotic cores in vulnerable atherosclerotic plaques. In vitro and in vivo data suggest that macrophage apoptosis in advanced atheromata may be triggered by a combination of endoplasmic reticulum stress and engagement of the type A scavenger receptor, which together induce death through a rise in cytosolic calcium and activation of toll-like receptor-4. Methods and Results— Using both primary peritoneal macrophages and studies in advanced atheromata in vivo, we introduce signal transducer and activator of transcription-1 (STAT1) as a critical and necessary component of endoplasmic reticulum stress/type A scavenger receptor–induced macrophage apoptosis. We show that STAT1 is serine phosphorylated in macrophages subjected to type A scavenger receptor ligands and endoplasmic reticulum stress in a manner requiring cytosolic calcium, calcium/calmodulin-dependent protein kinase II, and toll-like receptor-4. Remarkably, apoptosis was inhi...

138 citations

Journal ArticleDOI
TL;DR: An overview of what is currently known of the involvement of miRNA and RNA interference components in the fine‐tuning of innate immune responses is presented.
Abstract: MicroRNAs (miRNAs) are emerging as potent regulators of many biological processes, including cellular differentiation and disease. Recently, miRNA has been directly involved in innate immunity and transduction signalling by Toll-like receptors and the ensuing cytokine response. In this review, we present an overview of what is currently known of the involvement of miRNA and RNA interference components in the fine-tuning of innate immune responses.

116 citations


Cited by
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Journal ArticleDOI
TL;DR: This review presents current knowledge on pathogen recognition through different families of PRRs and the increasingly complex signaling pathways responsible for activation of an inflammatory and antimicrobial response and medical implications are discussed.
Abstract: Summary: The innate immune system constitutes the first line of defense against invading microbial pathogens and relies on a large family of pattern recognition receptors (PRRs), which detect distinct evolutionarily conserved structures on pathogens, termed pathogen-associated molecular patterns (PAMPs). Among the PRRs, the Toll-like receptors have been studied most extensively. Upon PAMP engagement, PRRs trigger intracellular signaling cascades ultimately culminating in the expression of a variety of proinflammatory molecules, which together orchestrate the early host response to infection, and also is a prerequisite for the subsequent activation and shaping of adaptive immunity. In order to avoid immunopathology, this system is tightly regulated by a number of endogenous molecules that limit the magnitude and duration of the inflammatory response. Moreover, pathogenic microbes have developed sophisticated molecular strategies to subvert host defenses by interfering with molecules involved in inflammatory signaling. This review presents current knowledge on pathogen recognition through different families of PRRs and the increasingly complex signaling pathways responsible for activation of an inflammatory and antimicrobial response. Moreover, medical implications are discussed, including the role of PRRs in primary immunodeficiencies and in the pathogenesis of infectious and autoimmune diseases, as well as the possibilities for translation into clinical and therapeutic applications.

2,565 citations

Journal ArticleDOI
TL;DR: Understanding the specific molecular events that regulate the production of IL-10 will help to answer the remaining questions that are important for the design of new strategies of immune intervention.
Abstract: Interleukin-10 (IL-10), a cytokine with anti-inflammatory properties, has a central role in infection by limiting the immune response to pathogens and thereby preventing damage to the host. Recently, an increasing interest in how IL10 expression is regulated in different immune cells has revealed some of the molecular mechanisms involved at the levels of signal transduction, epigenetics, transcription factor binding and gene activation. Understanding the specific molecular events that regulate the production of IL-10 will help to answer the remaining questions that are important for the design of new strategies of immune intervention.

2,491 citations

Journal ArticleDOI
TL;DR: In this paper, the authors summarize the signalling and epigenetic mechanisms that regulate type I IFN-induced STAT activation and ISG transcription and translation and conclude that these regulatory mechanisms determine the biological outcomes of type I ILN responses and whether pathogens are cleared effectively or chronic infection or autoimmune disease ensues.
Abstract: Type I interferons (IFNs) activate intracellular antimicrobial programmes and influence the development of innate and adaptive immune responses. Canonical type I IFN signalling activates the Janus kinase (JAK)-signal transducer and activator of transcription (STAT) pathway, leading to transcription of IFN-stimulated genes (ISGs). Host, pathogen and environmental factors regulate the responses of cells to this signalling pathway and thus calibrate host defences while limiting tissue damage and preventing autoimmunity. Here, we summarize the signalling and epigenetic mechanisms that regulate type I IFN-induced STAT activation and ISG transcription and translation. These regulatory mechanisms determine the biological outcomes of type I IFN responses and whether pathogens are cleared effectively or chronic infection or autoimmune disease ensues.

2,273 citations

Journal ArticleDOI
TL;DR: This review begins by introducing interferon (IFN) and the JAK-STAT signaling pathway to highlight features that impact ISG production and describes ways in which ISGs both enhance innate pathogen-sensing capabilities and negatively regulate signaling through the Jak-STAT pathway.
Abstract: Interferon-stimulated gene (ISG) products take on a number of diverse roles. Collectively, they are highly effective at resisting and controlling pathogens. In this review, we begin by introducing interferon (IFN) and the JAK-STAT signaling pathway to highlight features that impact ISG production. Next, we describe ways in which ISGs both enhance innate pathogen-sensing capabilities and negatively regulate signaling through the JAK-STAT pathway. Several ISGs that directly inhibit virus infection are described with an emphasis on those that impact early and late stages of the virus life cycle. Finally, we describe ongoing efforts to identify and characterize antiviral ISGs, and we provide a forward-looking perspective on the ISG landscape.

2,207 citations

Journal ArticleDOI
TL;DR: In this paper, the effects of miRNA dysregulation in the cellular pathways that lead to the progressive conversion of normal cells into cancer cells and the potential to develop new molecular miRNA-targeted therapies are discussed.
Abstract: MicroRNAs (miRNAs) are small noncoding RNAs that typically inhibit the translation and stability of messenger RNAs (mRNAs), controlling genes involved in cellular processes such as inflammation, cell-cycle regulation, stress response, differentiation, apoptosis, and migration. Thus, miRNAs have been implicated in the regulation of virtually all signaling circuits within a cell, and their dysregulation has been shown to play an essential role in the development and progression of cancer. Here, after a brief description of miRNA genomics, biogenesis, and function, we discuss the effects of miRNA dysregulation in the cellular pathways that lead to the progressive conversion of normal cells into cancer cells and the potential to develop new molecular miRNA-targeted therapies.

1,899 citations