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  • 1
    Publication Date: 2015-06-23
    Description: Stearoyl-CoA desaturase (SCD) is conserved in all eukaryotes and introduces the first double bond into saturated fatty acyl-CoAs. Because the monounsaturated products of SCD are key precursors of membrane phospholipids, cholesterol esters and triglycerides, SCD is pivotal in fatty acid metabolism. Humans have two SCD homologues (SCD1 and SCD5), while mice have four (SCD1-SCD4). SCD1-deficient mice do not become obese or diabetic when fed a high-fat diet because of improved lipid metabolic profiles and insulin sensitivity. Thus, SCD1 is a pharmacological target in the treatment of obesity, diabetes and other metabolic diseases. SCD1 is an integral membrane protein located in the endoplasmic reticulum, and catalyses the formation of a cis-double bond between the ninth and tenth carbons of stearoyl- or palmitoyl-CoA. The reaction requires molecular oxygen, which is activated by a di-iron centre, and cytochrome b5, which regenerates the di-iron centre. To understand better the structural basis of these characteristics of SCD function, here we crystallize and solve the structure of mouse SCD1 bound to stearoyl-CoA at 2.6 A resolution. The structure shows a novel fold comprising four transmembrane helices capped by a cytosolic domain, and a plausible pathway for lateral substrate access and product egress. The acyl chain of the bound stearoyl-CoA is enclosed in a tunnel buried in the cytosolic domain, and the geometry of the tunnel and the conformation of the bound acyl chain provide a structural basis for the regioselectivity and stereospecificity of the desaturation reaction. The dimetal centre is coordinated by a unique spacial arrangement of nine conserved histidine residues that implies a potentially novel mechanism for oxygen activation. The structure also illustrates a possible route for electron transfer from cytochrome b5 to the di-iron centre.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4689147/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉   〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4689147/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Bai, Yonghong -- McCoy, Jason G -- Levin, Elena J -- Sobrado, Pablo -- Rajashankar, Kanagalaghatta R -- Fox, Brian G -- Zhou, Ming -- P41 GM103403/GM/NIGMS NIH HHS/ -- P41GM103403/GM/NIGMS NIH HHS/ -- R01 DK088057/DK/NIDDK NIH HHS/ -- R01 GM098878/GM/NIGMS NIH HHS/ -- R01 HL086392/HL/NHLBI NIH HHS/ -- R01DK088057/DK/NIDDK NIH HHS/ -- R01GM050853/GM/NIGMS NIH HHS/ -- R01GM098878/GM/NIGMS NIH HHS/ -- R01HL086392/HL/NHLBI NIH HHS/ -- U54 GM094584/GM/NIGMS NIH HHS/ -- U54GM094584/GM/NIGMS NIH HHS/ -- U54GM095315/GM/NIGMS NIH HHS/ -- England -- Nature. 2015 Aug 13;524(7564):252-6. doi: 10.1038/nature14549. Epub 2015 Jun 22.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉Verna and Marrs McLean Department of Biochemistry and Molecular Biology, Baylor College of Medicine, Houston, Texas 77030, USA. ; Department of Biochemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA. ; NE-CAT and Department of Chemistry and Chemical Biology, Cornell University, Argonne National Laboratory, Argonne, Illinois 60439, USA.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26098370" target="_blank"〉PubMed〈/a〉
    Keywords: Acyl Coenzyme A/chemistry/metabolism ; Animals ; Binding Sites ; Crystallography, X-Ray ; Cytochromes b5/chemistry/metabolism ; Electron Transport ; Histidine/chemistry/metabolism ; Iron/metabolism ; Mice ; Models, Molecular ; Oxygen/metabolism ; Protein Structure, Tertiary ; Static Electricity ; Stearoyl-CoA Desaturase/*chemistry/metabolism ; Structure-Activity Relationship
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 2
    Publication Date: 2012-12-04
    Description: Ionic protein-lipid interactions are critical for the structure and function of membrane receptors, ion channels, integrins and many other proteins. However, the regulatory mechanism of these interactions is largely unknown. Here we show that Ca(2+) can bind directly to anionic phospholipids and thus modulate membrane protein function. The activation of T-cell antigen receptor-CD3 complex (TCR), a key membrane receptor for adaptive immunity, is regulated by ionic interactions between positively charged CD3epsilon/zeta cytoplasmic domains (CD3(CD)) and negatively charged phospholipids in the plasma membrane. Crucial tyrosines are buried in the membrane and are largely protected from phosphorylation in resting T cells. It is not clear how CD3(CD) dissociates from the membrane in antigen-stimulated T cells. The antigen engagement of even a single TCR triggers a Ca(2+) influx and TCR-proximal Ca(2+) concentration is higher than the average cytosolic Ca(2+) concentration. Our biochemical, live-cell fluorescence resonance energy transfer and NMR experiments showed that an increase in Ca(2+) concentration induced the dissociation of CD3(CD) from the membrane and the solvent exposure of tyrosine residues. As a consequence, CD3 tyrosine phosphorylation was significantly enhanced by Ca(2+) influx. Moreover, when compared with wild-type cells, Ca(2+) channel-deficient T cells had substantially lower levels of CD3 phosphorylation after stimulation. The effect of Ca(2+) on facilitating CD3 phosphorylation is primarily due to the charge of this ion, as demonstrated by the fact that replacing Ca(2+) with the non-physiological ion Sr(2+) resulted in the same feedback effect. Finally, (31)P NMR spectroscopy showed that Ca(2+) bound to the phosphate group in anionic phospholipids at physiological concentrations, thus neutralizing the negative charge of phospholipids. Rather than initiating CD3 phosphorylation, this regulatory pathway of Ca(2+) has a positive feedback effect on amplifying and sustaining CD3 phosphorylation and should enhance T-cell sensitivity to foreign antigens. Our study thus provides a new regulatory mechanism of Ca(2+) to T-cell activation involving direct lipid manipulation.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Shi, Xiaoshan -- Bi, Yunchen -- Yang, Wei -- Guo, Xingdong -- Jiang, Yan -- Wan, Chanjuan -- Li, Lunyi -- Bai, Yibing -- Guo, Jun -- Wang, Yujuan -- Chen, Xiangjun -- Wu, Bo -- Sun, Hongbin -- Liu, Wanli -- Wang, Junfeng -- Xu, Chenqi -- England -- Nature. 2013 Jan 3;493(7430):111-5. doi: 10.1038/nature11699. Epub 2012 Dec 2.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉State Key Laboratory of Molecular Biology, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/23201688" target="_blank"〉PubMed〈/a〉
    Keywords: Animals ; Calcium/*metabolism/pharmacology ; Cell Membrane/metabolism ; Cytoplasm/metabolism ; Feedback, Physiological/drug effects ; Humans ; Jurkat Cells ; Lipid Bilayers/chemistry/metabolism ; *Lymphocyte Activation/drug effects ; Mice ; Phospholipids/*chemistry/*metabolism ; Phosphorylation/drug effects ; Receptor-CD3 Complex, Antigen, T-Cell/drug effects/immunology/*metabolism ; *Signal Transduction/drug effects ; Solvents/chemistry/metabolism ; Static Electricity ; T-Lymphocytes/drug effects/immunology/*metabolism ; Tyrosine/metabolism
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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  • 3
    Publication Date: 2016-03-17
    Description: CD8(+) T cells have a central role in antitumour immunity, but their activity is suppressed in the tumour microenvironment. Reactivating the cytotoxicity of CD8(+) T cells is of great clinical interest in cancer immunotherapy. Here we report a new mechanism by which the antitumour response of mouse CD8(+) T cells can be potentiated by modulating cholesterol metabolism. Inhibiting cholesterol esterification in T cells by genetic ablation or pharmacological inhibition of ACAT1, a key cholesterol esterification enzyme, led to potentiated effector function and enhanced proliferation of CD8(+) but not CD4(+) T cells. This is due to the increase in the plasma membrane cholesterol level of CD8(+) T cells, which causes enhanced T-cell receptor clustering and signalling as well as more efficient formation of the immunological synapse. ACAT1-deficient CD8(+) T cells were better than wild-type CD8(+) T cells at controlling melanoma growth and metastasis in mice. We used the ACAT inhibitor avasimibe, which was previously tested in clinical trials for treating atherosclerosis and showed a good human safety profile, to treat melanoma in mice and observed a good antitumour effect. A combined therapy of avasimibe plus an anti-PD-1 antibody showed better efficacy than monotherapies in controlling tumour progression. ACAT1, an established target for atherosclerosis, is therefore also a potential target for cancer immunotherapy.〈br /〉〈br /〉〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4851431/" target="_blank"〉〈img src="https://static.pubmed.gov/portal/portal3rc.fcgi/4089621/img/3977009" border="0"〉〈/a〉   〈a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4851431/" target="_blank"〉This paper as free author manuscript - peer-reviewed and accepted for publication〈/a〉〈br /〉〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Yang, Wei -- Bai, Yibing -- Xiong, Ying -- Zhang, Jin -- Chen, Shuokai -- Zheng, Xiaojun -- Meng, Xiangbo -- Li, Lunyi -- Wang, Jing -- Xu, Chenguang -- Yan, Chengsong -- Wang, Lijuan -- Chang, Catharine C Y -- Chang, Ta-Yuan -- Zhang, Ti -- Zhou, Penghui -- Song, Bao-Liang -- Liu, Wanli -- Sun, Shao-cong -- Liu, Xiaolong -- Li, Bo-liang -- Xu, Chenqi -- HL 60306./HL/NHLBI NIH HHS/ -- R01 HL060306/HL/NHLBI NIH HHS/ -- England -- Nature. 2016 Mar 31;531(7596):651-5. doi: 10.1038/nature17412. Epub 2016 Mar 16.〈br /〉〈span class="detail_caption"〉Author address: 〈/span〉State Key Laboratory of Molecular Biology, National Center for Protein Science Shanghai, Shanghai Science Research Center, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China. ; State Key Laboratory of Molecular Biology, CAS Center for Excellence in Molecular Cell Science, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China. ; Institute for Nutritional Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China. ; MOE Key Laboratory of Protein Science, School of Life Sciences, Collaborative Innovation Center for Infectious Diseases, Tsinghua University, Beijing 100084, China. ; Department of Biochemistry, Geisel School of Medicine at Dartmouth, Hanover, New Haven 03755, USA. ; Rheumatology and Immunology Department of ChangZheng Hospital, Second Military Medical University, Shanghai 200433, China. ; Sun Yat-sen University Cancer Center, State Key Laboratory of Oncology in South China, Collaborative Innovation Center for Cancer Medicine, Guangzhou 510060, China. ; College of Life Sciences, Wuhan University, Wuhan, Hubei Province 430072, China. ; Department of Immunology, The University of Texas MD Anderson Cancer Center, Houston, Texas 77054, USA. ; State Key Laboratory of Cell Biology, CAS Center for Excellence in Molecular Cell Science, Institute of Biochemistry and Cell Biology, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences, Shanghai 200031, China. ; School of Life Science and Technology, ShanghaiTech University, 100 Haike Road, Shanghai 201210, China.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/26982734" target="_blank"〉PubMed〈/a〉
    Keywords: Acetates/*pharmacology/therapeutic use ; Acetyl-CoA C-Acetyltransferase/antagonists & ; inhibitors/deficiency/genetics/metabolism ; Animals ; Atherosclerosis/drug therapy ; CD8-Positive T-Lymphocytes/*drug effects/*immunology/metabolism ; Cell Membrane/drug effects/metabolism ; Cholesterol/*metabolism ; Esterification/drug effects ; Female ; Immunological Synapses/drug effects/immunology/metabolism ; Immunotherapy/*methods ; Male ; Melanoma/*drug therapy/*immunology/metabolism/pathology ; Mice ; Programmed Cell Death 1 Receptor/antagonists & inhibitors/immunology ; Receptors, Antigen, T-Cell/immunology/metabolism ; Signal Transduction/drug effects ; Sulfonic Acids/*pharmacology/therapeutic use
    Print ISSN: 0028-0836
    Electronic ISSN: 1476-4687
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
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