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The gluconeogenic enzyme PCK1 phosphorylates INSIG1/2 for lipogenesis 期刊论文
NATURE, 2020, 580 (7804) : 530-+
作者:  Erler, Janine T.;  Bennewith, Kevin L.;  Nicolau, Monica;  Dornhofer, Nadja;  Kong, Christina;  Le, Quynh-Thu;  Chi, Jen-Tsan Ashley;  Jeffrey, Stefanie S.;  Giaccia, Amato J.
收藏  |  浏览/下载:46/0  |  提交时间:2020/07/03

Phosphorylation of INSIG1 and INSIG2 by PCK1 leads to a reduction in the binding of sterols, the activation of SREBP1 and SREBP2 and the downstream transcription of lipogenesis-associated genes that promote tumour growth.


Cancer cells increase lipogenesis for their proliferation and the activation of sterol regulatory element-binding proteins (SREBPs) has a central role in this process. SREBPs are inhibited by a complex composed of INSIG proteins, SREBP cleavage-activating protein (SCAP) and sterols in the endoplasmic reticulum. Regulation of the interaction between INSIG proteins and SCAP by sterol levels is critical for the dissociation of the SCAP-SREBP complex from the endoplasmic reticulum and the activation of SREBPs(1,2). However, whether this protein interaction is regulated by a mechanism other than the abundance of sterol-and in particular, whether oncogenic signalling has a role-is unclear. Here we show that activated AKT in human hepatocellular carcinoma (HCC) cells phosphorylates cytosolic phosphoenolpyruvate carboxykinase 1 (PCK1), the rate-limiting enzyme in gluconeogenesis, at Ser90. Phosphorylated PCK1 translocates to the endoplasmic reticulum, where it uses GTP as a phosphate donor to phosphorylate INSIG1 at Ser207 and INSIG2 at Ser151. This phosphorylation reduces the binding of sterols to INSIG1 and INSIG2 and disrupts the interaction between INSIG proteins and SCAP, leading to the translocation of the SCAP-SREBP complex to the Golgi apparatus, the activation of SREBP proteins (SREBP1 or SREBP2) and the transcription of downstream lipogenesis-related genes, proliferation of tumour cells, and tumorigenesis in mice. In addition, phosphorylation of PCK1 at Ser90, INSIG1 at Ser207 and INSIG2 at Ser151 is not only positively correlated with the nuclear accumulation of SREBP1 in samples from patients with HCC, but also associated with poor HCC prognosis. Our findings highlight the importance of the protein kinase activity of PCK1 in the activation of SREBPs, lipogenesis and the development of HCC.


  
Spontaneous gyrotropic electronic order in a transition-metal dichalcogenide 期刊论文
NATURE, 2020, 578 (7796) : 545-+
作者:  Kum, Hyun S.;  Lee, Hyungwoo;  Kim, Sungkyu;  Lindemann, Shane;  Kong, Wei;  Qiao, Kuan;  Chen, Peng;  Irwin, Julian;  Lee, June Hyuk;  Xie, Saien;  Subramanian, Shruti;  Shim, Jaewoo;  Bae, Sang-Hoon;  Choi, Chanyeol;  Ranno, Luigi;  Seo, Seungju;  Lee, Sangho;  Bauer, Jackson;  Li, Huashan;  Lee, Kyusang;  Robinson, Joshua A.;  Ross, Caroline A.;  Schlom, Darrell G.;  Rzchowski, Mark S.;  Eom, Chang-Beom;  Kim, Jeehwan
收藏  |  浏览/下载:21/0  |  提交时间:2020/07/03

Chirality is ubiquitous in nature, and populations of opposite chiralities are surprisingly asymmetric at fundamental levels(1,2). Examples range from parity violation in the subatomic weak force to homochirality in biomolecules. The ability to achieve chirality-selective synthesis (chiral induction) is of great importance in stereochemistry, molecular biology and pharmacology(2). In condensed matter physics, a crystalline electronic system is geometrically chiral when it lacks mirror planes, space-inversion centres or rotoinversion axes(1). Typically, geometrical chirality is predefined by the chiral lattice structure of a material, which is fixed on formation of the crystal. By contrast, in materials with gyrotropic order(3-6), electrons spontaneously organize themselves to exhibit macroscopic chirality in an originally achiral lattice. Although such order-which has been proposed as the quantum analogue of cholesteric liquid crystals-has attracted considerable interest(3-15), no clear observation or manipulation of gyrotropic order has been achieved so far. Here we report the realization of optical chiral induction and the observation of a gyrotropically ordered phase in the transition-metal dichalcogenide semimetal 1T-TiSe2. We show that shining mid-infrared circularly polarized light on 1T-TiSe2 while cooling it below the critical temperature leads to the preferential formation of one chiral domain. The chirality of this state is confirmed by the measurement of an out-of-plane circular photogalvanic current, the direction of which depends on the optical induction. Although the role of domain walls requires further investigation with local probes, the methodology demonstrated here can be applied to realize and control chiral electronic phases in other quantum materials(4,16).


Optical chiral induction and spontaneous gyrotropic electronic order are realized in the transition-metal chalcogenide 1T-TiSe2 by using illumination with mid-infrared circularly polarized light and simultaneous cooling below the critical temperature.


  
Bringing the concept of ammonia critical levels into managing cork-oak woodland for conservation 期刊论文
FOREST ECOLOGY AND MANAGEMENT, 2019, 453
作者:  Rocha, Bernardo;  Pinho, Pedro;  Branquinho, Cristina;  Boieiro, Mario;  Matos, Paula
收藏  |  浏览/下载:21/0  |  提交时间:2020/02/17
Montado  Ecological indicators  Lichens  Critical levels  Environmental management