Protein kinase RNA-regulated (PKR) is an established component of innate antiviral immunity. Recently, PKR has been shown to be essential for signal transduction in other situations of cellular stress. The relationship between PKR and the stress-activated protein kinases (SAPKs), such as p38 mitogen-activated protein kinase (MAPK), is not clear. Using embryonic ®broblasts from PKR wild-type and null mice, we established a requirement for PKR in the activation of SAPKs by double-stranded RNA, lipopolysaccharide (LPS) and proin¯ammatory cytokines. This does not re¯ect a global failure to activate SAPKs in the PKRnull background as these kinases are activated normally by anisomycin and other physicochemical stress. Activation of p38 MAPK was restored in immortalized PKR-null cells by reconstitution with human PKR. We also show that LPS induction of interleukin-6 and interleukin-12 mRNA is defective in PKR-null cells, and that production of these cytokines is impaired in PKR-null mice challenged with LPS. Our ®ndings indicate, for the ®rst time, that PKR is required for p38 MAPK signaling and plays a potentially important role in the innate response against bacterial endotoxin.
Cancer vaccines targeting 'self' antigens that are expressed at consistently high levels by tumor cells are potentially useful in immunotherapy, but immunological tolerance may block their function. Here, we describe a novel, naked DNA vaccine encoding an alphavirus replicon (self-replicating mRNA) and the self/tumor antigen tyrosinase-related protein-1. Unlike conventional DNA vaccines, this vaccine can break tolerance and provide immunity to melanoma. The vaccine mediates production of double-stranded RNA, as evidenced by the autophosphorylation of protein kinase R. Double-stranded RNA is critical to vaccine function because both the immunogenicity and the antitumor activity of the vaccine are blocked in mice deficient for the RNase L enzyme, a key component of the 2′,5′-linked oligoadenylate synthetase antiviral pathway involved in double-stranded RNA recognition. This study shows for the first time that alphaviral replicon-encoding DNA vaccines activate innate immune pathways known to drive antiviral immune responses, and points the way to strategies for improving the efficacy of immunization with naked DNA.Vaccine vectors based on recombinant viruses have been used for many years, but the delivery of target antigens can be accompanied by unwanted side effects. First, preexisting antibodies can neutralize the recombinant virus before it is able to deliver its payload. Second, structural proteins from the virus can dominate T-and B-cell-mediated immune responses, diverting immunity away from the target immunogen 1,2 . Hence, there is a critical need to develop vaccine vectors that are not only highly immunogenic, but also antigenically simple.The simplest of all recombinant vectors, naked plasmid DNA vaccines, have successfully been used in animal models to induce immune responses to many pathogens and model antigens. DNA vaccines are easy to produce, inexpensive and safe 3 , but for some applications insufficiently immunogenic. A variety of attempts have been made to improve DNA vaccines 4 , including the production of pro-apoptotic proteins 5 . Despite these advances, the poor immunogenicity of plasmid DNA remains apparent when attempting to elicit immunity to weak immunogens, such as non-mutated 'self' tumor-associated antigens that are recognized by anti-tumor T cells. One promising new strategy to improve naked DNA vaccines is to express the target antigen under the control of an alphaviral replicase 6,7 with the premise of using the ability of alphavirus to produce large amounts of viral mRNA (refs. 8 ,9 ). In alphavirus-derived DNA and RNA vaccines, the encoded alphaviral replicase-enzyme complex amplifies self-replicating RNA (replicon). In model systems, replicon containing nucleic acid vaccines display therapeutic efficacy at doses several logs lower than those required by conventional DNA vaccines 10-12 . In the current study, we examined whether a replicase-based DNA vaccine encoding a nonmutated self-antigen could be used to break tolerance and prevent B16 melanoma, a goal not previously ...
Beige adipocytes can interconvert between white and brown-like states and switch between energy storage versus expenditure. Here we report that beige adipocyte plasticity is important for feeding-associated changes in energy expenditure and is coordinated by the hypothalamus and the phosphatase TCPTP. A fasting-induced and glucocorticoid-mediated induction of TCPTP, inhibited insulin signaling in AgRP/NPY neurons, repressed the browning of white fat and decreased energy expenditure. Conversely feeding reduced hypothalamic TCPTP, to increase AgRP/NPY neuronal insulin signaling, white adipose tissue browning and energy expenditure. The feeding-induced repression of hypothalamic TCPTP was defective in obesity. Mice lacking TCPTP in AgRP/NPY neurons were resistant to diet-induced obesity and had increased beige fat activity and energy expenditure. The deletion of hypothalamic TCPTP in obesity restored feeding-induced browning and increased energy expenditure to promote weight loss. Our studies define a hypothalamic switch that coordinates energy expenditure with feeding for the maintenance of energy balance.
Agouti-related peptide (AgRP) neurons increase motivation for food, however whether metabolic sensing of homeostatic state in AgRP neurons potentiates motivation by interacting with dopamine reward systems is unexplored. As a model of impaired metabolic-sensing, we used the AgRP-specific deletion of carnitine acetyltransferase (Crat) in mice. We hypothesized that metabolic sensing in AgRP neurons is required to increase motivation for food reward by modulating accumbal or striatal dopamine release. Studies confirmed that Crat deletion in AgRP neurons (KO) impaired ex vivo glucose-sensing, as well as in vivo responses to peripheral glucose injection or repeated palatable food presentation and consumption. Impaired metabolic-sensing in AgPP neurons reduced acute dopamine release (seconds) to palatable food consumption and during operant responding, as assessed by GRAB-DA photometry in the nucleus accumbens, but not the dorsal striatum. Impaired metabolic-sensing in AgRP neurons suppressed radiolabelled 18F-fDOPA accumulation after ~30 minutes in the dorsal striatum but not the nucleus accumbens. Impaired metabolic sensing in AgRP neurons suppressed motivated operant responding for sucrose rewards during fasting. Thus, metabolic-sensing in AgRP neurons is required for the appropriate temporal integration and transmission of homeostatic hunger-sensing to dopamine signalling in the striatum.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.