Upregulated expression of ubiquitin ligase TRIM21 promotes PKM2 nuclear translocation and astrocyte activation in experimental autoimmune encephalomyelitis
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ABSTRACT: Reactive astrocytes play critical roles in the occurrence of various neurological diseases such as multiple sclerosis. Activation of astrocytes is often accompanied by a glycolysis-dominant metabolic switch. We found that PKM2 displayed nuclear translocation in astrocytes of EAE mice, an animal model of multiple sclerosis. And we identified the ubiquitination-mediated regulation of PKM2 nuclear import by ubiquitin ligase TRIM21. To detect the expression of TRM21 in EAE mice, We used single-cell sequencing to analyze the expression of TRM21 in EAE mice.
Project description:Alternative splicing of the Pkm gene product generates the PKM1 and PKM2 isoforms of pyruvate kinase, and PKM2 expression is closely linked to embryogenesis, tissue regeneration, and cancer. To interrogate the functional requirement for PKM2 during development and tissue homeostasis, we generated germline PKM2 null mice (Pkm2-/-). Unexpectedly, despite being the primary isoform expressed in most wild-type adult tissues, we found that Pkm2-/- mice are viable and fertile. Thus, PKM2 is not required for embryonic or postnatal development. Loss of PKM2 leads to compensatory expression of PKM1 in the tissues that normally express PKM2. Strikingly, PKM2 loss leads to spontaneous development of hepatocellular carcinoma (HCC) with high penetrance that is accompanied by progressive changes in systemic metabolism characterized by altered systemic glucose homeostasis, inflammation, and hepatic steatosis. Therefore, in addition to its role in cancer metabolism, PKM2 plays a role in controlling systemic metabolic homeostasis and inflammation, thereby preventing HCC by a non-cell-autonomous mechanism. RNA was isolated from flash frozen ground whole liver tissue of 35 week old PKM2 KO and WT mice. Three independent mice from each condition were used as biological replicates.
Project description:Macrophage polarization followed by acute myocardial infarction (MI) is essential for the regulation of inflammation and scar formation. Tripartite motif-containing protein 21 (TRIM21), a member of E3 ubiquitin ligases, is a crucial mediator in the process of inflammation and heart failure. However, the potential roles of TRIM21 in modulating post-MI inflammation and macrophage polarization remain elusive. We detected that the levels of TRIM21 were significantly reduced in macrophages of WT mice after MI. In contrast, MI was ameliorated in TRIM21 knockout (TRIM21-/-) mice with improved cardiac remodeling, characterized by a marked decrease in mortality, increased wall thickness, and improved cardiac function in comparison with wild-type (WT) MI mice. Importantly, TRIM21 deficiency decreased the post-MI apoptosis and DNA damage in the hearts of mice, and the accumulation of M1 phenotype macrophages in infarcted hearts significantly decreased in TRIM21-/- mice compared with WT controls. Mechanistically, depletion of TRIM21 orchestrated the process of M1 macrophage polarization via a PI3K/Akt signaling pathway. Overall, these data reveal that TRIM21 drives the inflammatory response and cardiac remodeling after MI via stimulating M1 macrophage polarization through a PI3K/Akt signaling pathway.
Project description:Experimental autoimmune encephalomyelitis (EAE) is a murine model of multiple sclerosis, a chronic neurodegenerative and inflammatory autoimmune condition of the central nervous system (CNS). Pathology is driven by the infiltration of autoreactive CD4+ lymphocytes into the CNS where they attack neuronal sheaths causing ascending paralysis. We used an isotope-coded protein labelling approach to investigate the proteome of CD4+ cells isolated from the spinal cord and brain of mice at various stages of EAE progression in two EAE disease models; PLP139-151-induced relapsing-remitting EAE and MOG35-55-induced chronic EAE, which emulate the two forms of human multiple sclerosis. A total of 1120 proteins were quantified across disease onset, peak-disease and remission phases of disease and of these, 13 up-regulated proteins of interest were identified with functions relating to the regulation of inflammation, leukocyte adhesion and migration, tissue repair and the regulation of transcription/translation. Proteins implicated in processes such as inflammation (S100A4 and S100A9) and tissue repair (Annexin A1), which represent key events during EAE progression were validated by quantitative PCR. This is the first targeted analysis of autoreactive cells purified from the CNS during EAE, highlighting fundamental CD4+ cell-driven processes that occur during the initiation of relapse and remission stages of disease.
Project description:Multiple sclerosis (MS) is an autoimmune disease of the central nervous system (CNS); its cause is unknown. To understand the pathogenesis of MS, researchers often use the experimental autoimmune encephalomyelitis (EAE) mouse model. Here, our aim was to build a proteome map of the biological changes that occur during MS at the major onset sites—the brain and the spinal cord. We performed quantitative proteome profiling in five specific brain regions and the spinal cord of EAE and healthy mice with high-resolution mass spectrometry based on tandem mass tags.
Project description:In the central nervous system (CNS) the transcription factor NF-kappaB is a key regulator of inflammation and secondary injury processes. Following trauma or disease, the expression of NF-kappaB-dependent genes is activated, leading to both protective and detrimental effects on CNS recovery. Here we show that transgenic inactivation of astroglial NF-kappaB in mice (GFAP-IkappaBalpha-dn mice) resulted in dramatic reduction of disease severity and improvement in functional recovery following EAE. This coincided with a higher presence of leukocytes in the cord and brain of transgenic mice at the chronic phase of the disease, when the functional recovery over WT mice was the most significant. We observed that expression of proinflammatory genes in both spinal cord and cerebellum was delayed and reduced, while the loss of neuronal-specific molecules essential for synaptic transmission was limited compared to WT mice. Furthermore, death of retinal ganglion cells in affected retinas was almost abolished, suggesting the activation of neuroprotective mechanisms. Our data indicate that inhibiting NF-kappaB in astrocytes results in neuroprotective effects following EAE, directly implicating astrocytes in the pathophysiology of this disease. Keywords: time course, EAE, transgenic mice, astrocytes, inflammation, cytokines, chemokines
Project description:Nuclear translocation of the key metabolic enzyme Pyruvate Kinase Isoform 2 (PKM2) is widely observed in cancer, but its contribution to gene regulation and pathogenesis remains unclear. Here we find that PKM2 specifically recognized folded RNA G-quadruplex (rG4) structures in vitro with high affinity. In human cells, nuclear PKM2 bound thousands of precursor mRNAs at potential rG4 sites and translocation of PKM2 to the nucleus resulted in increased expression of rG4-containing mRNAs.
Project description:Vascular endothelial cells (ECs) senescence correlates with the increase of cardiovascular diseases in ageing population. Although ECs rely glycolysis for energy production, little is known about the role of glycolysis in ECs senescence. Here, we report a critical role for glycolysis-derived serine biosynthesis in preventing ECs senescence. During senescence, the expression of serine biosynthetic enzyme PHGDH is significantly reduced due to decreased transcription of the activating transcription factor ATF4, which leads to decreased intracellular serine. PHGDH prevents premature senescence primarily by enhancing the stability and activity of pyruvate kinase M2 (PKM2). Mechanistically, PHGDH interacts with PKM2, which prevents PCAF-catalyzed PKM2 K305 acetylation and subsequent degradation by autophagy. In addition, PHGDH facilitates p300-catalyzed PKM2 K433 acetylation, which promotes PKM2 nuclear translocation and stimulates its activity to phosphorylate H3T11 and regulate the transcription of senescence-associated genes. Vascular endothelium-targeted expression of PHGDH and PKM2 ameliorates the mice ageing phenotype. Our findings reveal that enhancing serine biosynthesis could become a novel therapy to promote healthy ageing.
Project description:Alternative splicing of the Pkm gene product generates the PKM1 and PKM2 isoforms of pyruvate kinase, and PKM2 expression is closely linked to embryogenesis, tissue regeneration, and cancer. To interrogate the functional requirement for PKM2 during development and tissue homeostasis, we generated germline PKM2 null mice (Pkm2-/-). Unexpectedly, despite being the primary isoform expressed in most wild-type adult tissues, we found that Pkm2-/- mice are viable and fertile. Thus, PKM2 is not required for embryonic or postnatal development. Loss of PKM2 leads to compensatory expression of PKM1 in the tissues that normally express PKM2. Strikingly, PKM2 loss leads to spontaneous development of hepatocellular carcinoma (HCC) with high penetrance that is accompanied by progressive changes in systemic metabolism characterized by altered systemic glucose homeostasis, inflammation, and hepatic steatosis. Therefore, in addition to its role in cancer metabolism, PKM2 plays a role in controlling systemic metabolic homeostasis and inflammation, thereby preventing HCC by a non-cell-autonomous mechanism.
Project description:Experimental autoimmune encephalomyelitis (EAE) is a mouse model for multiple sclerosis (MS) a chronic autoimmune disease of the central nervous system. We have observed dysfunction of the RNA binding protein hnRNP A1 in neurons from the brains of patients with MS, and the spinal cords of mice with EAE. Here, we sought to characterize the consequences of EAE-induced dysfunction of hnRNP A1 on the RNAs it binds by using CLIPseq to establish both the normal central nervous system RNA binding profile of hnRNP A1 in the spinal cords of naive mice, and any alterations to the binding profile of hnRNP A1 in the spinal cords of mice with EAE.