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GGPP depletion initiates metaflammation through disequilibrating CYB5R3-dependent eicosanoid metabolism.

ABSTRACT: Metaflammation is a primary inflammatory complication of metabolic disorders characterized by altered production of many inflammatory cytokines, adipokines, and lipid mediators. Whereas multiple inflammation networks have been identified, the mechanisms by which metaflammation is initiated have long been controversial. As the mevalonate pathway (MVA) produces abundant bioactive isoprenoids and abnormal MVA has a phenotypic association with inflammation/immunity, we speculate that isoprenoids from the MVA may provide a causal link between metaflammation and metabolic disorders. Using a line with the MVA isoprenoid producer geranylgeranyl diphosphate synthase (GGPPS) deleted, we find that geranylgeranyl pyrophosphate (GGPP) depletion causes an apparent metaflammation as evidenced by abnormal accumulation of fatty acids, eicosanoid intermediates, and proinflammatory cytokines. We also find that GGPP prenylate cytochrome b ₅ reductase 3 (CYB5R3) and the prenylated CYB5R3 then translocate from the mitochondrial to the endoplasmic reticulum (ER) pool. As CYB5R3 is a critical NADH-dependent reductase necessary for eicosanoid metabolism in ER, we thus suggest that GGPP-mediated CYB5R3 prenylation is necessary for metabolism. In addition, we observe that pharmacological inhibition of the MVA pathway by simvastatin is sufficient to inhibit CYB5R3 translocation and induces smooth muscle death. Therefore, we conclude that the dysregulation of MVA intermediates is an essential mechanism for metaflammation initiation, in which the imbalanced production of eicosanoid intermediates in the ER serve as an important pathogenic factor. Moreover, the interplay of MVA and eicosanoid metabolism as we reported here illustrates a model for the coordinating regulation among metabolite pathways.

SUBMITTER: Wei L

PROVIDER: S-EPMC7681012 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:Aging is the most important risk factor for neurodegenerative diseases associated with pathological protein aggregation such as Alzheimer's disease. Although aging is an important player, it remains unknown which molecular changes are relevant for disease initiation. Recently, it has become apparent that widespread protein aggregation is a common feature of aging. Indeed, several studies demonstrate that 100s of proteins become highly insoluble with age, in the absence of obvious disease processes. Yet it remains unclear how these misfolded proteins aggregating with age affect neurodegenerative diseases. Importantly, several of these aggregation-prone proteins are found as minor components in disease-associated hallmark aggregates such as amyloid-? plaques or neurofibrillary tangles. This co-localization raises the possibility that age-dependent protein aggregation directly contributes to pathological aggregation. Here, we show for the first time that highly insoluble proteins from aged Caenorhabditis elegans or aged mouse brains, but not from young individuals, can initiate amyloid-? aggregation in vitro. We tested the seeding potential at four different ages across the adult lifespan of C. elegans. Significantly, protein aggregates formed during the early stages of aging did not act as seeds for amyloid-? aggregation. Instead, we found that changes in protein aggregation occurring during middle-age initiated amyloid-? aggregation. Mass spectrometry analysis revealed several late-aggregating proteins that were previously identified as minor components of amyloid-? plaques and neurofibrillary tangles such as 14-3-3, Ubiquitin-like modifier-activating enzyme 1 and Lamin A/C, highlighting these as strong candidates for cross-seeding. Overall, we demonstrate that widespread protein misfolding and aggregation with age could be critical for the initiation of pathogenesis, and thus should be targeted by therapeutic strategies to alleviate neurodegenerative diseases.

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GGPP depletion initiates metaflammation through disequilibrating CYB5R3-dependent eicosanoid metabolism.

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