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Alpha4 is Critical for Adipocyte Maintenance and Mitochondrial Homeostasis through Regulation of Insulin Signaling

ABSTRACT: Insulin signaling is mediated via a network of protein phosphorylation. Dysregulation of this network is central to obesity, type 2 diabetes and metabolic syndrome. Here we have investigated the role of phosphatase binding protein Alpha4 (α4) that is essential for the Ser/Thr protein phosphatase PP2A in insulin action/resistance in adipocytes. Unexpectedly, adipocyte-specific inactivation of α4 impairs insulin-induced Akt-mediated Ser/Thr phosphorylation despite a decrease in the PP2A levels. Interestingly, loss of α4 also reduces insulin-induced insulin receptor Tyr phosphorylation. This occurs through decreased association of α4 with Y-box protein 1 (YBX1), resulting in the enhancement of the Tyr phosphatase PTP1B expression. Moreover, adipocyte-specific knockout of α4 results in impaired adipogenesis and altered mitochondrial oxidation leading to increased inflammation, systemic insulin resistance, hepatosteatosis, islet hyperplasia, and impaired thermogenesis. Thus, the α4 /YBX1-mediated pathway of insulin receptor signaling is essential for maintaining insulin sensitivity, normal adipose tissue homeostasis and systemic metabolism.

ORGANISM(S): Mus musculus

PROVIDER: GSE210407 | GEO | 2022/09/21

REPOSITORIES: GEO

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Project description:Different transcriptome, metabolome, and phosphoproteome studies have already indicated a regulatory role of Ser/Thr phosphorylation in the central metabolism of S. aureus. However, it remains still unknown how this exactly tunes its metabolism. For that reason, Extreme Pathway Analysis was used to understand metabolic flux regulation by Ser/Thr phosphorylation. YANAsquare software and YANAvergence routine were chosen to calculate pathway activities of WT, ΔpknB, Δstp, and double mutant S. aureus NewmanHG strains. Gene expression data of S. aureus NewmanHG were collected taking the wild type and mutations of kinase (pknB), phosphatase (stp) or both (pknB/stp) phenotypes. The resulting flux changes were modelled with YANAvergence taking the different gene expression data and an established genome scale model of S. aureus metabolic modes as basis. The fluxes of the different strains were next calculated, taking the gene expression data into account. A concerted metabolic change of fluxes was observed. In particular the pathways for peptidoglycan, nucleotide, and aromatic amino acid synthesis as well as catabolism involving aspartate transaminase (GOT) changed significantly compared to the wild type. Single mutations of pknB and stp were compared to illustrate their different contribution to the phenotype, e.g. pyrimidine synthesis is dramatically impaired by pknB deletion but much less by loss of stp. In the double knock out strain, there is higher activity of peptidoglycan, purine, and aromatic amino acids synthesis from glucose, but lower activity of pyrimidine synthesis from glucose compared to WT. The results suggest a probable regulatory role of Ser/Thr phosphorylation in amino acid catabolism and the glycolysis/gluconeogenesis switch to provide the cell with sufficient cell wall components, nucleotides, and aromatic amino acids. Yvck is suggested to serve as regulatory protein linking Ser/Thr phosphorylation to the previous results of S. aureus metabolism. Moreover, Yvck seems in particular to be involved in the switch between glycolysis and gluconeogenesis. However, further studies based on experimental approaches are needed to demonstrate that Ser/Thr phosphorylation and Yvck are necessary for a correct cell growth under gluconeogenic conditions. The metabolic model allows not only a comprehensive representation of these changes for all involved pathways in the four strains, it further points out the function of the previously unannotated ycvk operon.. The relevance of these specific metabolic pathway adaptations regarding the pathogenicity of S.aureus and their contributions to the infection process will be analyzed and discussed.

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Alpha4 is Critical for Adipocyte Maintenance and Mitochondrial Homeostasis through Regulation of Insulin Signaling

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