Alpha4 is Critical for Adipocyte Maintenance and Mitochondrial Homeostasis through Regulation of Insulin Signaling
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ABSTRACT:
PROVIDER: PRJNA865656 | ENA |
REPOSITORIES: ENA
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Project description: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.
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Project description:Insulin resistance is a major risk factor for human metabolic diseases including type 2 diabetes, cardiovascular diseases and some cancers. We analysed the proteome analyses across in vitro and in vivo models of insulin resistance to find common features of insulin resistance and identified lower expression of enzymes within the mevalonate pathway. mitochondrial CoQ was lower in all models of insulin resistance. Specifically, the coenzyme Q (CoQ) biosynthetic proteins Coq 7 and 9 were decreased in adipose tissue from a mouse model of diet-induced obesity, and mitochondrial CoQ was lower in all models of insulin resistance. Moreover, the mitochondrial content of CoQ in adipose tissue correlated positively with insulin sensitivity in obese humans. Inhibition of CoQ biosynthesis induced insulin resistance, while replenishment of CoQ restored insulin sensitivity in cell culture models and in animals, demonstrating that loss of CoQ is both necessary and sufficient for adipocyte insulin resistance. Mechanistically, loss of CoQ increased mitochondrial peroxides. These findings place defective mitochondrial CoQ homeostasis upstream of increased mitochondrial oxidants in the induction of insulin resistance in adipocytes and highlight the CoQ biosynthetic pathway as an appealing therapeutic target to combat insulin resistance.
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Project description: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 investigate the role of phosphatase binding protein Alpha4 (α4) that is essential for the serine/threonine protein phosphatase 2A (PP2A) in insulin action/resistance in adipocytes. Unexpectedly, adipocyte-specific inactivation of α4 impairs insulin-induced Akt-mediated serine/threonine phosphorylation despite a decrease in the protein phosphatase 2A (PP2A) levels. Interestingly, loss of α4 also reduces insulin-induced insulin receptor tyrosine phosphorylation. This occurs through decreased association of α4 with Y-box protein 1, resulting in the enhancement of the tyrosine phosphatase protein tyrosine phosphatase 1B (PTP1B) expression. Moreover, adipocyte-specific knockout of α4 in male mice results in impaired adipogenesis and altered mitochondrial oxidation leading to increased inflammation, systemic insulin resistance, hepatosteatosis, islet hyperplasia, and impaired thermogenesis. Thus, the α4 /Y-box protein 1(YBX1)-mediated pathway of insulin receptor signaling is involved in maintaining insulin sensitivity, normal adipose tissue homeostasis and systemic metabolism.
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Project description:Extracellular vesicles are membranous nanoparticles that convey signaling between cells, tissues and organs. By applying fluorescence tracing and SILAC-labeling paired with (phospho)proteomics, we identified the transfer of functional insulinotropic protein cargo via adipocyte-derived extracellular vesicles (AdEVs) from adipose tissue to pancreatic ß-cells in vivo and in vitro. AdEV-derived proteins were targets for phosphorylation, increased the overall abundances and phosphosite dynamics of insulinotropic GPCR/cAMP/PKA pathways and amplified 1st-phase glucose-stimulated insulin secretion (GSIS) in murine islets. Notably, insulinotropic effects were restricted to AdEVs from obese and insulin resistant, but not lean mice, which was consistent with differential protein loads and AdEV luminal morphologies. Pre-treatment with AdEVs from obese mice amplified insulin secretion and glucose tolerance in mice independent from hyperglycemia. These data suggest that secreted AdEVs can inform pancreatic ß-cells about adipose tissue insulin resistance in order to amplify GSIS in times of increased insulin demand.
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