Cell Stress最新文献

When a host cell is infected by a virus, it activates the innate immune response, setting off a cascade of signalling events leading to the production of an antiviral response. This immune response is typically robust and in general works well to clear viral infections, however, viruses have evolved evasion strategies to combat this, and therefore, a better understanding of how this response works in more detail is needed for the development of novel and effective therapeutics. Lipid droplets (LDs) are intracellular organelles and have historically been thought of simply as cellular energy sources, however, have more recently been recognised as critical organelles in signalling events. Importantly, many viruses are known to take over host cellular production of LDs, and it has traditionally been assumed the sole purpose of this is to supply energy for viral life cycle events. However, our recent work positions LDs as important organelles during the first few hours of an antiviral response, showing that they underpin the production of important antiviral cytokines following viral infection. Following infection of cells with either RNA viruses (Zika, Dengue, Influenza A) or a DNA (Herpes Simplex Virus-1) virus, LDs were rapidly upregulated, and this response was also replicated following stimulation with viral mimic agonists. This upregulation of LDs following infection was transient, and interestingly, did not follow the well described homeostatic mechanism of LD upregulation, instead being controlled by EGFR. The cell's ability to mount an effective immune response was greatly diminished when inhibiting EGFR, thus inhibiting LD upregulation during infection, also leading to an increase in viral replication. In this microreview, we extrapolate our recent findings and discuss LDs as an important organelle in the innate immune response.

The yeast Atg8 protein and its paralogs in mammals, mammalian Atg8s (mAtg8s), have been primarily appreciated for their participation in autophagy. However, lipidated mAtg8s, including the most frequently used autophagosomal membrane marker LC3B, are found on cellular membranes other than autophagosomes. Here we put forward a hypothesis that the lipidation of mAtg8s, termed 'Atg8ylation', is a general membrane stress and remodeling response analogous to the role that ubiquitylation plays in tagging proteins. Ubiquitin and mAtg8s are related in sequence and structure, and the lipidation of mAtg8s occurs on its C-terminal glycine, akin to the C-terminal glycine of ubiquitin. Conceptually, we propose that mAtg8s and Atg8ylation are to membranes what ubiquitin and ubiquitylation are to proteins, and that, like ubiquitylation, Atg8ylation has a multitude of downstream effector outputs, one of which is autophagy.

PDLIM1, a member of the PDZ-LIM family, is a cytoskeletal protein and functions as a platform to form distinct protein complexes, thus participating in multiple physiological processes such as cytoskeleton regulation and synapse formation. Emerging evidence demonstrates that PDLIM1 is dysregualted in a variety of tumors and plays essential roles in tumor initiation and progression. In this review, we summarize the structure and function of PDLIM1, as well as its important roles in human cancers.

Autophagy is a critical cellular process by which biomolecules and cellular organelles are degraded in an orderly manner inside lysosomes. This process is particularly important in neurons: these post-mitotic cells cannot divide or be easily replaced and are therefore especially sensitive to the accumulation of toxic proteins and damaged organelles. Dysregulation of neuronal autophagy is well documented in a range of neurodegenerative diseases. However, growing evidence indicates that autophagy also critically contributes to neurodevelopmental cellular processes, including neurogenesis, maintenance of neural stem cell homeostasis, differentiation, metabolic reprogramming, and synaptic remodelling. These findings implicate autophagy in neurodevelopmental disorders. In this review we discuss the current understanding of the role of autophagy in neurodevelopment and neurodevelopmental disorders, as well as currently available tools and techniques that can be used to further investigate this association.

Eukaryotic cells release the phylogenetically ancient protein acyl coenzyme A binding protein (ACBP, which in humans is encoded by the gene DBI, diazepam binding inhibitor) upon nutrient deprivation. Accordingly, mice that are starved for one to two days and humans that undergo voluntary fasting for one to three weeks manifest an increase in the plasma concentration of ACBP/DBI. Paradoxically, ACBP/DBI levels also increase in obese mice and humans. Since ACBP/DBI stimulates appetite, this latter finding may explain why obesity constitutes a self-perpetuating state. Here, we present a theoretical framework to embed these findings in the mechanisms of weight control, as well as a bioinformatics analysis showing that, irrespective of the human cell or tissue type, one single isoform of ACBP/DBI (ACBP1) is preponderant (~90% of all DBI transcripts, with the sole exception of the testis, where it is ~70%). Based on our knowledge, we conclude that ACBP1 is subjected to a biphasic transcriptional and post-transcriptional regulation, explaining why obesity and fasting both are associated with increased circulating ACBP1 protein levels.

A ribosome typically moves at a particular rate on a given mRNA transcript to decode the nucleic acid information required to synthesize proteins. The speed and directionality of the ribosome movements during mRNA translation are determined by the mRNA sequence and structure and by various decoding factors. However, the molecular mechanisms of this remarkable movement during protein synthesis, or its relevance in brain disorders, remain unknown. Recent studies have indicated that defects in protein synthesis occur in various neurodegenerative diseases, but the mechanistic details are unclear. This is a major problem because identifying the factors that determine protein synthesis defects may offer new avenues for developing therapeutic remedies for currently incurable diseases like neurodegenerative disorders. Based on our recent study (Eshraghi et al., Nat Commun 12(1):1461; doi: 10.1038/s41467-021-21637-y), this short commentary will review the mechanistic understanding of Huntingtin (HTT)-mediated ribosome stalling indicating that central defects in protein synthesis in Huntington disease (HD) are orchestrated by jamming of ribosomes on mRNA transcripts.

Stress is a central concept in biology and has now been widely used in psychological, physiological, social, and even environmental fields. However, the concept of stress was cross-utilized to refer to different elements of the stress system including stressful stimulus, stressor, stress response, and stress effect. Here, we summarized the evolution of the concept of stress and the framework of the stress system. We find although the concept of stress is developed from Selye's "general adaptation syndrome", it has now expanded and evolved significantly. Stress is now defined as a state of homeostasis being challenged, including both system stress and local stress. A specific stressor may potentially bring about specific local stress, while the intensity of stress beyond a threshold may commonly activate the hypothalamic-pituitary-adrenal axis and result in a systematic stress response. The framework of the stress system indicates that stress includes three types: sustress (inadequate stress), eustress (good stress), and distress (bad stress). Both sustress and distress might impair normal physiological functions and even lead to pathological conditions, while eustress might benefit health through hormesis-induced optimization of homeostasis. Therefore, an optimal stress level is essential for building biological shields to guarantee normal life processes.

Cells maintain their cytosolic calcium (Ca²⁺) in nanomolar range and use controlled increase in Ca²⁺ for intracellular signaling. With the extracellular Ca²⁺ in the millimolar range, there is a steep Ca²⁺ gradient across the plasma membrane (PM). Thus, injury that damages PM, leads to a cytosolic Ca²⁺ overload, which helps activate PM repair (PMR) response. However, in order to survive, the cells must cope with the Ca²⁺ overload. In a recent study (Chandra et al. J Cell Biol, doi: 10.1083/jcb.202006035) we have examined how cells cope with injury-induced cytosolic Ca²⁺ overload. By monitoring Ca²⁺ dynamics in the cytosol and endoplasmic reticulum (ER), we found that PM injury-triggered increase in cytosolic Ca²⁺ is taken up by the ER. Pharmacological inhibition of ER Ca²⁺ uptake interferes with this process and compromises the repair ability of the injured cells. Muscle cells from patients and mouse model for the muscular dystrophy showed that lack of Anoctamin 5 (ANO5)/Transmembrane protein 16E (TMEM16E), an ER-resident putative Ca²⁺-activated chloride channel (CaCC), are poor at coping with cytosolic Ca²⁺ overload. Pharmacological inhibition of CaCC and lack of ANO5, both prevent Ca²⁺ uptake into ER. These studies identify a requirement of Cl^- uptake by the ER in sequestering injury-triggered cytosolic Ca²⁺ increase in the ER. Further, these studies show that ER helps injured cells cope with Ca²⁺ overload during PMR, lack of which contributes to muscular dystrophy due to mutations in the ANO5 protein.

Obesity is epidemiologically linked to 13 forms of cancer. The local and systemic obese environment is complex and likely affect tumors through multiple avenues. This includes modulation of cancer cell phenotypes and the composition of the tumor microenvironment. A molecular understanding of how obesity links to cancer holds promise for identifying candidate genes for targeted therapy for obese cancer patient. Herein, we review both the cell-autonomous and non-cell-autonomous mechanisms linking obesity and cancer as well as provide an overview of the mouse model systems applied to study this.

Dying (or dead) cells are increasingly recognized to impose significant biological influence within their tissues of residence-exerting paracrine effects through proteins and metabolites that are expressed or secreted during cellular demise. For example, certain molecules function as potent mitogens, promoting the repopulation of neighboring epithelial cells. And other myriad of factors-classified as damage-associated molecular patterns (DAMPs)-function as "find me" (attractant), "eat me" (engulfment), or "danger" (activation) signals for recruiting and activating effector immune cells (e.g., dendritic cells) to initiate inflammation. Since the discovery of immunogenic cell death (ICD), the current dogma posits DAMPs as immunological adjuvants for innate immune cell mobilization and activation, which ultimately leads to the antitumoral cross-priming of CD8⁺ T cells. However, what is currently unknown is how these immunostimulatory DAMPs are counteracted to avoid immune-overactivation. Our recent work builds on these fundamentals and introduces prostaglandin E₂ (PGE₂) as an 'inhibitory' DAMP-a new variable to the ICD equation. Prostaglandin E₂ functions as an immunosuppressive counterpoise of adjuvant DAMPs; and thus, mechanistically precludes ICD. Furthermore, the long-debated immunogenicity of gemcitabine chemotherapy was revealed to be contingent on inhibitory DAMP blockade and not due to its inability to promote DAMP expression (i.e., calreticulin) as previously reported. These findings were intriguing. First, despite the presence of gemcitabine-induced hallmark DAMPs, the inhibitory DAMP (i.e., PGE₂) was sufficient to hinder the ICD-induced antitumoral immune response (Fig. 1a). And second, rather than pharmacologically substantiating immunostimulatory DAMPs as conventionally approached, the mitigation of the inhibitory DAMP-tipping the immunostimulatory and inhibitory DAMP balance in favor of immunostimulatory DAMPs-was sufficient to render the cell death immunogenic and converted gemcitabine into an ICD-inducing therapy (Fig. 1b). In this microreview, we extrapolate our findings and implicate the value of inhibitory DAMP(s) in drug discovery, its use for clinical prognosis, and as target(s) for therapeutic intervention.