| 1. |
- Wein, Marc N., et al.
(författare)
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SIKs control osteocyte responses to parathyroid hormone
- 2016
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 7
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Tidskriftsartikel (refereegranskat)abstract
- Parathyroid hormone (PTH) activates receptors on osteocytes to orchestrate bone formation and resorption. Here we show that PTH inhibition of SOST (sclerostin), a WNT antagonist, requires HDAC4 and HDAC5, whereas PTH stimulation of RANKL, a stimulator of bone resorption, requires CRTC2. Salt inducible kinases (SIKs) control subcellular localization of HDAC4/5 and CRTC2. PTH regulates both HDAC4/5 and CRTC2 localization via phosphorylation and inhibition of SIK2. Like PTH, new small molecule SIK inhibitors cause decreased phosphorylation and increased nuclear translocation of HDAC4/5 and CRTC2. SIK inhibition mimics many of the effects of PTH in osteocytes as assessed by RNA-seq in cultured osteocytes and following in vivo administration. Once daily treatment with the small molecule SIK inhibitor YKL-05-099 increases bone formation and bone mass. Therefore, a major arm of PTH signalling in osteocytes involves SIK inhibition, and small molecule SIK inhibitors may be applied therapeutically to mimic skeletal effects of PTH.
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| 2. |
- Ducommun, Serge, et al.
(författare)
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Chemical genetic screen identifies Gapex-5/GAPVD1 and STBD1 as novel AMPK substrates
- 2019
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Ingår i: Cellular Signalling. - : Elsevier BV. - 0898-6568 .- 1873-3913. ; 57, s. 45-57
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Tidskriftsartikel (refereegranskat)abstract
- AMP-activated protein kinase (AMPK) is a key regulator of cellular energy homeostasis, acting as a sensor of energy and nutrient status. As such, AMPK is considered a promising drug target for treatment of medical conditions particularly associated with metabolic dysfunctions. To better understand the downstream effectors and physiological consequences of AMPK activation, we have employed a chemical genetic screen in mouse primary hepatocytes in an attempt to identify novel AMPK targets. Treatment of hepatocytes with a potent and specific AMPK activator 991 resulted in identification of 65 proteins phosphorylated upon AMPK activation, which are involved in a variety of cellular processes such as lipid/glycogen metabolism, vesicle trafficking, and cytoskeleton organisation. Further characterisation and validation using mass spectrometry followed by immunoblotting analysis with phosphorylation site-specific antibodies identified AMPK-dependent phosphorylation of Gapex-5 (also known as GTPase-activating protein and VPS9 domain-containing protein 1 (GAPVD1)) on Ser902 in hepatocytes and starch-binding domain 1 (STBD1) on Ser175 in multiple cells/tissues. As new promising roles of AMPK as a key metabolic regulator continue to emerge, the substrates we identified could provide new mechanistic and therapeutic insights into AMPK-activating drugs in the liver.
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| 3. |
- Göransson, Olga, et al.
(författare)
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Mechanism of action of A-769662, a valuable tool for activation of AMP-activated protein kinase
- 2007
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Ingår i: Journal of Biological Chemistry. - 1083-351X. ; 282:45, s. 32549-32560
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Tidskriftsartikel (refereegranskat)abstract
- We have studied the mechanism of A- 769662, a new activator of AMP- activated protein kinase ( AMPK). Unlike other pharmacological activators, it directly activates native rat AMPK by mimicking both effects of AMP, i. e. allosteric activation and inhibition of dephosphorylation. We found that it has no effect on the isolated alpha subunit kinase domain, with or without the associated autoinhibitory domain, or on interaction of glycogen with the beta subunit glycogen- binding domain. Although it mimics actions of AMP, it has no effect on binding of AMP to the isolated Bateman domains of the gamma subunit. The addition of A- 769662 to mouse embryonic fibroblasts or primary mouse hepatocytes stimulates phosphorylation of acetyl- CoA carboxylase ( ACC), effects that are completely abolished in AMPK- alpha 1(-/-) alpha 2(-/-) cells but not in TAK1(-/-) mouse embryonic fibroblasts. Phosphorylation of AMPK and ACC in response to A- 769662 is also abolished in isolated mouse skeletal muscle lacking LKB1, a major upstream kinase for AMPK in this tissue. However, in HeLa cells, which lack LKB1 but express the alternate upstream kinase calmodulin- dependent protein kinase kinase-beta, phosphorylation of AMPK and ACC in response to A- 769662 still occurs. These results show that in intact cells, the effects of A- 769662 are independent of the upstream kinase utilized. We propose that this direct and specific AMPK activator will be a valuable experimental tool to understand the physiological roles of AMPK.
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| 4. |
- Henriksson, Emma, et al.
(författare)
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SIK2 regulates CRTCs, HDAC4 and glucose uptake in adipocytes
- 2015
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Ingår i: Journal of Cell Science. - : The Company of Biologists. - 0021-9533 .- 1477-9137. ; 128:3, s. 472-486
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Tidskriftsartikel (refereegranskat)abstract
- Salt-inducible kinase 2 (SIK2) is an AMP-activated protein kinase (AMPK) related kinase abundantly expressed in adipose tissue. Our aim was to identify molecular targets and functions of SIK2 in adipocytes, and to address the role of PKA-mediated phosphorylation of SIK2 on Ser358. Modulation of SIK2 in adipocytes resulted in altered phosphorylation of CREB-regulated transcription co-activator 2 (CRTC2), CRTC3 and class IIa histone deacetylase 4 (HDAC4). Furthermore, CRTC2, CRTC3, HDAC4 and protein phosphatase 2A (PP2A) interacted with SIK2, and the binding of CRTCs and PP2A to wild-type but not Ser358Ala SIK2, was reduced by cAMP elevation. Silencing of SIK2 resulted in reduced GLUT4 (also known as SLC2A4) protein levels, whereas cells treated with CRTC2 or HDAC4 siRNA displayed increased levels of GLUT4. Overexpression or pharmacological inhibition of SIK2 resulted in increased and decreased glucose uptake, respectively. We also describe a SIK2-CRTC2-HDAC4 pathway and its regulation in human adipocytes, strengthening the physiological relevance of our findings. Collectively, we demonstrate that SIK2 acts directly on CRTC2, CRTC3 and HDAC4, and that the cAMP-PKA pathway reduces the interaction of SIK2 with CRTCs and PP2A. Downstream, SIK2 increases GLUT4 levels and glucose uptake in adipocytes.
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| 5. |
- Mogilenko, Denis A., et al.
(författare)
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Metabolic and Innate Immune Cues Merge into a Specific Inflammatory Response via the UPR
- 2019
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Ingår i: Cell. - : CELL PRESS. - 0092-8674 .- 1097-4172. ; 177:5, s. 1201-
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Tidskriftsartikel (refereegranskat)abstract
- Innate immune responses are intricately linked with intracellular metabolism of myeloid cells. Toll-like receptor (TLR) stimulation shifts intracellular metabolism toward glycolysis, while anti-inflammatory signals depend on enhanced mitochondrial respiration. How exogenous metabolic signals affect the immune response is unknown. We demonstrate that TLR-dependent responses of dendritic cells (DCs) are exacerbated by a high-fatty-acid (FA) metabolic environment. FAs suppress the TLR-induced hexokinase activity and perturb tricarboxylic acid cycle metabolism. These metabolic changes enhance mitochondria! reactive oxygen species (mtROS) production and, in turn, the unfolded protein response (UPR), leading to a distinct transcriptomic signature with IL-23 as hallmark. Interestingly, chemical or genetic suppression of glycolysis was sufficient to induce this specific immune response. Conversely, reducing mtROS production or DC-specific deficiency in XBP1 attenuated IL-23 expression and skin inflammation in an IL-23-dependent model of psoriasis. Thus, fine-tuning of innate immunity depends on optimization of metabolic demands and minimization of mtROS-induced UPR.
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| 6. |
- Mounier, Remi, et al.
(författare)
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AMPK alpha 1 Regulates Macrophage Skewing at the Time of Resolution of Inflammation during Skeletal Muscle Regeneration
- 2013
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Ingår i: Cell Metabolism. - : Elsevier BV. - 1550-4131. ; 18:2, s. 251-264
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Tidskriftsartikel (refereegranskat)abstract
- Macrophages control the resolution of inflammation through the transition from a proinflammatory (M1) to an anti-inflammatory (M2) phenotype. Here, we present evidence for a role of AMPK alpha 1, a master regulator of energy homeostasis, in macrophage skewing that occurs during skeletal muscle regeneration. Muscle regeneration was impaired in AMPK alpha 1(-/-) mice. In vivo loss-of-function (LysM-Cre;AMPK alpha 1(fl/fl) mouse) and rescue (bone marrow transplantation) experiments showed that macrophagic AMPK alpha 1 was required for muscle regeneration. Cell-based experiments revealed that AMPK alpha 1(-/-) macrophages did not fully acquire the phenotype or the functions of M2 cells. In vivo, AMPK alpha 1(-/-) leukocytes did not acquire the expression of M2 markers during muscle regeneration. Skewing from M1 toward M2 phenotype upon phagocytosis of necrotic and apoptotic cells was impaired in AMPK alpha 1(-/-) macrophages and when AMPK activation was prevented by the inhibition of its upstream activator, CaMKK beta. In conclusion, AMPK alpha 1 is crucial for phagocytosis-induced macrophage skewing from a pro-to anti-inflammatory phenotype at the time of resolution of inflammation.
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| 7. |
- Patel, Kashyap, et al.
(författare)
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The LKB1-salt-inducible kinase pathway functions as a key gluconeogenic suppressor in the liver.
- 2014
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Ingår i: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 5:Aug 4
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Tidskriftsartikel (refereegranskat)abstract
- LKB1 is a master kinase that regulates metabolism and growth through adenosine monophosphate-activated protein kinase (AMPK) and 12 other closely related kinases. Liver-specific ablation of LKB1 causes increased glucose production in hepatocytes in vitro and hyperglycaemia in fasting mice in vivo. Here we report that the salt-inducible kinases (SIK1, 2 and 3), members of the AMPK-related kinase family, play a key role as gluconeogenic suppressors downstream of LKB1 in the liver. The selective SIK inhibitor HG-9-91-01 promotes dephosphorylation of transcriptional co-activators CRTC2/3 resulting in enhanced gluconeogenic gene expression and glucose production in hepatocytes, an effect that is abolished when an HG-9-91-01-insensitive mutant SIK is introduced or LKB1 is ablated. Although SIK2 was proposed as a key regulator of insulin-mediated suppression of gluconeogenesis, we provide genetic evidence that liver-specific ablation of SIK2 alone has no effect on gluconeogenesis and insulin does not modulate SIK2 phosphorylation or activity. Collectively, we demonstrate that the LKB1-SIK pathway functions as a key gluconeogenic gatekeeper in the liver.
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| 8. |
- Säll, Johanna, et al.
(författare)
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Salt-inducible kinases are required for glucose uptake and insulin signaling in human adipocytes
- 2023
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Ingår i: Obesity. - 1930-739X. ; 31:10, s. 2515-2529
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVE: Salt-inducible kinase 2 (SIK2) is abundantly expressed in adipocytes and downregulated in adipose tissue from individuals with obesity or insulin resistance. The main aims of this work were to investigate the involvement of SIKs in the regulation of glucose uptake in primary mature human adipocytes and to identify mechanisms underlying this regulation.METHODS: Primary mature adipocytes were isolated from human, rat, or mouse adipose tissue and treated with pan-SIK inhibitors. Adipocytes isolated from wild type, ob/ob, and SIK2 knockout mice were also used. Glucose uptake was examined by glucose tracer assay. The insulin signaling pathway was monitored by Western blotting, co-immunoprecipitation, and total internal reflection fluorescence microscopy.RESULTS: This study demonstrates that SIK2 is downregulated in obese ob/ob mice and that SIK activity is required for intact glucose uptake in primary human and mouse adipocytes. The underlying mechanism involves direct effects on the insulin signaling pathway, likely at the level of phosphatidylinositol (3,4,5)-trisphosphate (PIP3) generation or breakdown. Moreover, lack of SIK2 alone is sufficient to attenuate glucose uptake in mouse adipocytes.CONCLUSIONS: SIK2 is required for insulin action in human adipocytes, and the mechanism includes direct effects on the insulin signaling pathway.
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