A Quantitative Map of the Liver Mitochondrial Phosphoproteome Reveals Posttranslational Control of Ketogenesis

Insulin resistance plays a major role in the development of type 2 diabetes and obesity and affects a number of biological processes such as mitochondrial biogenesis. Though mitochondrial dysfunction has been linked to the development of insulin resistance and pathogenesis of type 2 diabetes, the precise mechanism linking the two is not well understood. We used high fat diet (HFD)-induced obesity dependent diabetes mouse models to gain insight into the potential pathways altered with metabolic disease, and carried out quantitative proteomic analysis of liver mitochondria. As previously reported, proteins involved in fatty acid oxidation, branched chain amino acid degradation, tricarboxylic acid cycle, and oxidative phosphorylation were uniformly up-regulated in the liver of HFD fed mice compared with that of normal diet. Further, our studies revealed that retinol metabolism is distinctly down-regulated and the mitochondrial structural proteins-components of mitochondrial intermembrane space bridging (MIB) complex (Mitofilin, Sam50, and ChChd3), and Tim proteins-essential for protein import, are significantly up-regulated in HFD fed mice. Structural and functional studies on HFD and normal diet liver mitochondria revealed remodeling of HFD mitochondria to a more condensed form with increased respiratory capacity and higher ATP levels compared with normal diet mitochondria. Thus, it is likely that the structural remodeling is essential to accommodate the increased protein content in presence of HFD: the mechanism could be through the MIB complex promoting contact site and crista junction formation and in turn facilitating the lipid and protein uptake. Obesity has become a global epidemic and in the United States alone more than one third of adults (34%) are obese and over 11% of the population over the age of 20 are diabetic (1, 2). Even though the precise mechanisms causing obesity are still being determined, it is well established that obesity induces insulin resistance leading to the pathogenesis of type 2 diabetes (T2D) 1 (3, 4). Insulin resistance has been implicated in multiple organ damage such as liver, skeletal muscle, and adipose tissues (5). This is in view of the fact that cellular glucose homeostasis is tightly regulated by insulin secretion from the pancreatic ␤-cells and glucose uptake by muscle and output by liver. Thus, failure of insulin secretion by pancreatic ␤-cells to compensate for insulin resistance results in hyperglycemia (6, 7) and uncontrolled hyperglycemia has the potential to negatively impact a number of organ systems.Mitochondrial dysfunction has been thought to play a critical role in insulin resistance and T2D (8 -11), and the role of mitochondria in insulin resistance is highly tissue specific. Despite this the mechanisms of action is controversial: in skeletal muscle, oxidative metabolism of lipids is reduced in T2D patients (11,12). However, it has been reported that carnitine palmitoyl transferase (CPT) activity is decreased or long-chain acyl-CoA dehydrogenase (LACD) is defic...

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“…This is consistent with up-regulation of fatty acid beta-oxidation protein level in liver with obesity (34). supplemental Fig.…”

Section: Proteomic Profiling Of Hfd/nd Mice Liver Mitochondria-supporting

confidence: 76%

Quantitative Proteomic and Functional Analysis of Liver Mitochondria from High Fat Diet (HFD) Diabetic Mice

Guo

Darshi

et al. 2013

Molecular & Cellular Proteomics

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“…The present data suggesting mitochondrial intermembrane space localization of the Syk pathway also raise the question of whether Syk and Lyn might directly tyrosine-phosphorylate and modulate respiratory chain function. Indeed, there is precedence for a Src family kinase to modulate complex II activity, consistent with the observation that the respiratory chain is extensively posttranslationally modified (79,80). …”

Section: Discussionmentioning

confidence: 56%

A respiratory chain controlled signal transduction cascade in the mitochondrial intermembrane space mediates hydrogen peroxide signaling

Patterson

Gerbeth

Thiru

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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Reactive oxygen species (ROS) such as hydrogen peroxide (H2O2) govern cellular homeostasis by inducing signaling. H2O2 modulates the activity of phosphatases and many other signaling molecules through oxidation of critical cysteine residues, which led to the notion that initiation of ROS signaling is broad and nonspecific, and thus fundamentally distinct from other signaling pathways. Here, we report that H2O2 signaling bears hallmarks of a regular signal transduction cascade. It is controlled by hierarchical signaling events resulting in a focused response as the results place the mitochondrial respiratory chain upstream of tyrosine-protein kinase Lyn, Lyn upstream of tyrosine-protein kinase SYK (Syk), and Syk upstream of numerous targets involved in signaling, transcription, translation, metabolism, and cell cycle regulation. The active mediators of H2O2 signaling colocalize as H2O2 induces mitochondria-associated Lyn and Syk phosphorylation, and a pool of Lyn and Syk reside in the mitochondrial intermembrane space. Finally, the same intermediaries control the signaling response in tissues and species responsive to H2O2 as the respiratory chain, Lyn, and Syk were similarly required for H2O2 signaling in mouse B cells, fibroblasts, and chicken DT40 B cells. Consistent with a broad role, the Syk pathway is coexpressed across tissues, is of early metazoan origin, and displays evidence of evolutionary constraint in the human. These results suggest that H2O2 signaling is under control of a signal transduction pathway that links the respiratory chain to the mitochondrial intermembrane space-localized, ubiquitous, and ancient Syk pathway in hematopoietic and nonhematopoietic cells.

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“…Given the relatively high expression levels of RALDHs in the brain (4,30), it is likely that the enzymatic activity of RALDHs is acutely regulated by posttranslational modifications, such as phosphorylation. Indeed, phosphorylation sites on RALDHs have been reported by recent quantitative phosphoproteomics studies (32)(33)(34)(35)(36)(37)(38). Further work is needed to elucidate how CaN may directly or indirectly modulate RALDH activity in neurons through regulation of various phosphorylation sites.…”

Section: Discussionmentioning

confidence: 99%

Calcineurin mediates homeostatic synaptic plasticity by regulating retinoic acid synthesis

Arendt

Zhang

Ganesan

et al. 2015

Proc. Natl. Acad. Sci. U.S.A.

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Homeostatic synaptic plasticity is a form of non-Hebbian plasticity that maintains stability of the network and fidelity for information processing in response to prolonged perturbation of network and synaptic activity. Prolonged blockade of synaptic activity decreases resting Ca2+ levels in neurons, thereby inducing retinoic acid (RA) synthesis and RA-dependent homeostatic synaptic plasticity; however, the signal transduction pathway that links reduced Ca2+-levels to RA synthesis remains unknown. Here we identify the Ca2+-dependent protein phosphatase calcineurin (CaN) as a key regulator for RA synthesis and homeostatic synaptic plasticity. Prolonged inhibition of CaN activity promotes RA synthesis in neurons, and leads to increased excitatory and decreased inhibitory synaptic transmission. These effects of CaN inhibitors on synaptic transmission are blocked by pharmacological inhibitors of RA synthesis or acute genetic deletion of the RA receptor RARα. Thus, CaN, acting upstream of RA, plays a critical role in gating RA signaling pathway in response to synaptic activity. Moreover, activity blockade-induced homeostatic synaptic plasticity is absent in CaN knockout neurons, demonstrating the essential role of CaN in RA-dependent homeostatic synaptic plasticity. Interestingly, in GluA1 S831A and S845A knockin mice, CaN inhibitor- and RA-induced regulation of synaptic transmission is intact, suggesting that phosphorylation of GluA1 C-terminal serine residues S831 and S845 is not required for CaN inhibitor- or RA-induced homeostatic synaptic plasticity. Thus, our study uncovers an unforeseen role of CaN in postsynaptic signaling, and defines CaN as the Ca2+-sensing signaling molecule that mediates RA-dependent homeostatic synaptic plasticity.

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A Quantitative Map of the Liver Mitochondrial Phosphoproteome Reveals Posttranslational Control of Ketogenesis

Cited by 143 publications

References 48 publications

Quantitative Proteomic and Functional Analysis of Liver Mitochondria from High Fat Diet (HFD) Diabetic Mice

Quantitative Proteomic and Functional Analysis of Liver Mitochondria from High Fat Diet (HFD) Diabetic Mice

A respiratory chain controlled signal transduction cascade in the mitochondrial intermembrane space mediates hydrogen peroxide signaling

Calcineurin mediates homeostatic synaptic plasticity by regulating retinoic acid synthesis

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