1
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Zhang Y, Jiang Y, Wang Y, Wang L, Han W, Cheng X, Deng X, Qin C, Liu Y. An UPLC-MS/MS Method for Routine Quantification of Insulin Degludec in Plasma. CURR PHARM ANAL 2020. [DOI: 10.2174/1573412915666190304145149] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Background:
Chromatographic methods for determination of insulin degludec in rabbit
plasma by Ultra Performance Liquid Chromatography-Tandem Mass Spectrometry were developed.
Methods:
Analytes were eluted from Waters ACQUITY UPLC® Peptide BEH C18 (2.1×50mm, 300Å)
column with a mobile phase of water containing 0.1% formic acid (A) and acetonitrile containing 0.1%
formic acid (B). Quantitation of insulin degludec was performed using 1222.06 > 641.24 m/z on Multiple-
Reaction Monitoring (MRM) mode.
Results:
Good linearity was observed in the concentration range of 500-50000 ng/mL (r >0.99), and the
lower limit of quantification was 500ng/mL. The within-run and between-run precision (expressed as
relative standard deviation, RSD) of insulin degludec were ≤ 14.16% and ≤ 13.64% respectively, and
the accuracy was within 94.37-96.35%. The recovery and matrix effects were both within acceptable
limits.
Conclusion:
This method was successfully applied for the pharmacokinetic study of insulin degludec
in rabbit after subcutaneous administration.
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Affiliation(s)
- Yudong Zhang
- Pharmacy School, Chongqing Medical University, Chongqing, 400016, China
| | - Yue Jiang
- Pharmacy School, Chongqing Medical University, Chongqing, 400016, China
| | - Ya Wang
- Chongqing Medleader BioPharm Co., Ltd. Science and Technology Incubative Building, Chongqing, Maliu Riverside Development Zone, Chongqing, 404100, China
| | - Ling Wang
- Chongqing Medleader BioPharm Co., Ltd. Science and Technology Incubative Building, Chongqing, Maliu Riverside Development Zone, Chongqing, 404100, China
| | - Weijie Han
- Pharmacy School, Chongqing Medical University, Chongqing, 400016, China
| | - Xiaoyi Cheng
- Pharmacy School, Chongqing Medical University, Chongqing, 400016, China
| | - Xue Deng
- Pharmacy School, Chongqing Medical University, Chongqing, 400016, China
| | - Chunmeng Qin
- Pharmacy School, Chongqing Medical University, Chongqing, 400016, China
| | - Yan Liu
- Pharmacy School, Chongqing Medical University, Chongqing, 400016, China
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2
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Jang SH, Jun CD, Park ZY. Label-free quantitative phosphorylation analysis of human transgelin2 in Jurkat T cells reveals distinct phosphorylation patterns under PKA and PKC activation conditions. Proteome Sci 2015; 13:14. [PMID: 25844069 PMCID: PMC4384351 DOI: 10.1186/s12953-015-0070-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2014] [Accepted: 02/27/2015] [Indexed: 12/31/2022] Open
Abstract
Background Transgelin2, one of cytoskeletal actin binding proteins has recently been suggested to be involved in the formation of immune synapses. Although detailed function of transgelin2 is largely unknown, interactions between transgelin2 and actin appear to be important in regulating cellular functions of transgelin2. Because protein phosphorylation can change ability to interact with other proteins, comprehensive phosphorylation analysis of transgelin2 will be helpful in understanding its functional mechanisms. Results Here, a specific protein label-free quantitative phosphorylation analysis method combining immuno-precipitation, IMAC phosphopeptide enrichment technique and label-free relative quantification analysis was used to monitor the phosphorylation changes of transgelin2 overexpressed in Jurkat T cells under protein kinase C (PKC) and protein kinase A (PKA) activation conditions, two representative intracellular signalling pathways of immune cell activation and homeostasis. A total of six serine/threonine phosphorylation sites were identified including threonine-84, a novel phosphorylation site. Notably, distinct phosphorylation patterns of transgelin2 under the two kinase activation conditions were observed. Most phosphorylation sites showing specific kinase-dependent phosphorylation changes were discretely located in two previously characterized actin-binding regions: actin-binding site (ABS) and calponin repeat domain (CNR). PKC activation increased phosphorylation of threonine-180 and serine-185 in the CNR, and PKA activation increased phosphorylation of serine-163 in the ABS. Conclusions Multiple actin-binding regions of transgelin2 participate to accomplish its full actin-binding capability, and the actin-binding affinity of each actin-binding region appears to be modulated by specific kinase-dependent phosphorylation changes. Accordingly, different actin-binding properties or cellular functions of transgelin2 may result from distinct intracellular signalling events under immune response activation or homeostasis conditions. Electronic supplementary material The online version of this article (doi:10.1186/s12953-015-0070-9) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Se Hwan Jang
- School of Life Sciences, Gwangju Institute of Science & Technology, 123, Cheomdangwagi-Ro, Buk-Gu, 500-712 Gwangju Republic of Korea
| | - Chang-Duk Jun
- School of Life Sciences, Gwangju Institute of Science & Technology, 123, Cheomdangwagi-Ro, Buk-Gu, 500-712 Gwangju Republic of Korea
| | - Zee-Yong Park
- School of Life Sciences, Gwangju Institute of Science & Technology, 123, Cheomdangwagi-Ro, Buk-Gu, 500-712 Gwangju Republic of Korea
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3
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Mielke C, Lefort N, McLean C, Cordova JM, Langlais PR, Bordner AJ, Te JA, Ozkan SB, Willis WT, Mandarino LJ. Adenine nucleotide translocase is acetylated in vivo in human muscle: Modeling predicts a decreased ADP affinity and altered control of oxidative phosphorylation. Biochemistry 2014; 53:3817-29. [PMID: 24884163 PMCID: PMC4067143 DOI: 10.1021/bi401651e] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
Proteomics techniques have revealed that lysine acetylation is abundant in mitochondrial proteins. This study was undertaken (1) to determine the relationship between mitochondrial protein acetylation and insulin sensitivity in human skeletal muscle, identifying key acetylated proteins, and (2) to use molecular modeling techniques to understand the functional consequences of acetylation of adenine nucleotide translocase 1 (ANT1), which we found to be abundantly acetylated. Eight lean and eight obese nondiabetic subjects had euglycemic clamps and muscle biopsies for isolation of mitochondrial proteins and proteomics analysis. A number of acetylated mitochondrial proteins were identified in muscle biopsies. Overall, acetylation of mitochondrial proteins was correlated with insulin action (r = 0.60; P < 0.05). Of the acetylated proteins, ANT1, which catalyzes ADP-ATP exchange across the inner mitochondrial membrane, was acetylated at lysines 10, 23, and 92. The extent of acetylation of lysine 23 decreased following exercise, depending on insulin sensitivity. Molecular dynamics modeling and ensemble docking simulations predicted the ADP binding site of ANT1 to be a pocket of positively charged residues, including lysine 23. Calculated ADP-ANT1 binding affinities were physiologically relevant and predicted substantial reductions in affinity upon acetylation of lysine 23. Insertion of these derived binding affinities as parameters into a complete mathematical description of ANT1 kinetics predicted marked reductions in adenine nucleotide flux resulting from acetylation of lysine 23. Therefore, acetylation of ANT1 could have dramatic physiological effects on ADP-ATP exchange. Dysregulation of acetylation of mitochondrial proteins such as ANT1 therefore could be related to changes in mitochondrial function that are associated with insulin resistance.
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Affiliation(s)
- Clinton Mielke
- Center for Metabolic and Vascular
Biology, Arizona State University, Tempe, Arizona 85004, United States
| | - Natalie Lefort
- Center for Metabolic and Vascular
Biology, Arizona State University, Tempe, Arizona 85004, United States
| | - Carrie
G. McLean
- Center for Metabolic and Vascular
Biology, Arizona State University, Tempe, Arizona 85004, United States
| | - Jeanine M. Cordova
- Center for Metabolic and Vascular
Biology, Arizona State University, Tempe, Arizona 85004, United States
| | - Paul R. Langlais
- Division of Endocrinology, Mayo Clinic
in Arizona, Scottsdale, Arizona 85259, United
States
| | - Andrew J. Bordner
- Division of Endocrinology, Mayo Clinic
in Arizona, Scottsdale, Arizona 85259, United
States
| | - Jerez A. Te
- Division of Endocrinology, Mayo Clinic
in Arizona, Scottsdale, Arizona 85259, United
States
| | - S. Banu Ozkan
- Center for Metabolic and Vascular
Biology, Arizona State University, Tempe, Arizona 85004, United States
| | - Wayne T. Willis
- Center for Metabolic and Vascular
Biology, Arizona State University, Tempe, Arizona 85004, United States
| | - Lawrence J. Mandarino
- Center for Metabolic and Vascular
Biology, Arizona State University, Tempe, Arizona 85004, United States
- Division of Endocrinology, Mayo Clinic
in Arizona, Scottsdale, Arizona 85259, United
States
- Department of Medicine, Mayo
Clinic in Arizona, Scottsdale, Arizona 85259, United States
- Mayo Clinic in Arizona, 13400 E.
Shea Blvd., Scottsdale, AZ 85259. E-mail: . Phone: (480) 965-8365. Fax: (480) 965-6899
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4
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Hançer NJ, Qiu W, Cherella C, Li Y, Copps KD, White MF. Insulin and metabolic stress stimulate multisite serine/threonine phosphorylation of insulin receptor substrate 1 and inhibit tyrosine phosphorylation. J Biol Chem 2014; 289:12467-84. [PMID: 24652289 PMCID: PMC4007441 DOI: 10.1074/jbc.m114.554162] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2014] [Revised: 03/18/2014] [Indexed: 12/27/2022] Open
Abstract
IRS1 and IRS2 are key substrates of the insulin receptor tyrosine kinase. Mass spectrometry reveals more than 50 phosphorylated IRS1 serine and threonine residues (Ser(P)/Thr(P) residues) in IRS1 from insulin-stimulated cells or human tissues. We investigated a subset of IRS1 Ser(P)/Thr(P) residues using a newly developed panel of 25 phospho-specific monoclonal antibodies (αpS/TmAb(Irs1)). CHO cells overexpressing the human insulin receptor and rat IRS1 were stimulated with insulin in the absence or presence of inhibitors of the PI3K → Akt → mechanistic target of rapamycin (mTOR) → S6 kinase or MEK pathways. Nearly all IRS1 Ser(P)/Thr(P) residues were stimulated by insulin and significantly suppressed by PI3K inhibition; fewer were suppressed by Akt or mTOR inhibition, and none were suppressed by MEK inhibition. Insulin-stimulated Irs1 tyrosine phosphorylation (Tyr(P)(Irs1)) was enhanced by inhibition of the PI3K → Akt → mTOR pathway and correlated with decreased Ser(P)-302(Irs1), Ser(P)-307(Irs1), Ser(P)-318(Irs1), Ser(P)-325(Irs1), and Ser(P)-346(Irs1). Metabolic stress modeled by anisomycin, thapsigargin, or tunicamycin increased many of the same Ser(P)/Thr(P) residues as insulin, some of which (Ser(P)-302(Irs1), Ser(P)-307(Irs1), and four others) correlated significantly with impaired insulin-stimulated Tyr(P)(Irs1). Thus, IRS1 Ser(P)/Thr(P) is an integrated response to insulin stimulation and metabolic stress, which associates with reduced Tyr(P)(Irs1) in CHO(IR)/IRS1 cells.
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Affiliation(s)
- Nancy J. Hançer
- From the Division of Endocrinology, Department of Medicine, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts 02115
| | - Wei Qiu
- From the Division of Endocrinology, Department of Medicine, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts 02115
| | - Christine Cherella
- From the Division of Endocrinology, Department of Medicine, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts 02115
| | - Yedan Li
- From the Division of Endocrinology, Department of Medicine, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts 02115
| | - Kyle D. Copps
- From the Division of Endocrinology, Department of Medicine, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts 02115
| | - Morris F. White
- From the Division of Endocrinology, Department of Medicine, Boston Children's Hospital, Harvard Medical School, Boston, Massachusetts 02115
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5
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Chen CJ, Lai CC, Tseng MC, Liu YC, Lin SY, Tsai FJ. Simple fabrication of hydrophobic surface target for increased sensitivity and homogeneity in matrix-assisted laser desorption/ionization time-of-flight mass spectrometry analysis of peptides, phosphopeptides, carbohydrates and proteins. Anal Chim Acta 2013; 783:31-8. [PMID: 23726097 DOI: 10.1016/j.aca.2013.04.029] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2013] [Revised: 04/11/2013] [Accepted: 04/14/2013] [Indexed: 11/19/2022]
Abstract
To enhance sample signals and improve homogeneity in matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF) analysis, a simple, rapid, and efficient sample preparation method was developed in this study. Polydimethylsiloxane (PDMS) was coated on a stainless steel MALDI plate, forming a transparent, hydrophobic surface that enhanced sample signals without producing observable background signals. Compared to the use of an unmodified commercial metal MALDI plate, peptide signals were enhanced by ~7.1-11.0-fold due to the reduced sample spot area of the PDMS-coated plate, and showed improved peptide mass fingerprinting (PMF) and MS/MS peptide sequencing results. In the analysis of phosphopeptides and carbohydrates with a 2,5-dihydroxybenzoic acid (DHB) matrix, the PDMS-coated plate showed improved sample homogeneity and signal enhancements of ~5.2-8.2-fold and ~2.8-3.2-fold, respectively. Improved sensitivity in the observation of more unique fragment ions by MS/MS analysis, to successfully distinguish isomeric carbohydrates, was also illustrated. In protein analysis with a sinapinic acid (SA) matrix, a ~3.4-fold signal enhancement was observed. The PDMS film coating was easily removed and refabricated to avoid sample carryover, and was applicable to diverse commercial MALDI plates. The PDMS-coated approach is a simple, practical, and attractive method for enhancing analyte signals and homogeneity.
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Affiliation(s)
- Chao-Jung Chen
- Graduate Institute of Integrated Medicine, China Medical University, Taichung, Taiwan.
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6
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Chen XW, Wang H, Bajaj K, Zhang P, Meng ZX, Ma D, Bai Y, Liu HH, Adams E, Baines A, Yu G, Sartor MA, Zhang B, Yi Z, Lin J, Young SG, Schekman R, Ginsburg D. SEC24A deficiency lowers plasma cholesterol through reduced PCSK9 secretion. eLife 2013; 2:e00444. [PMID: 23580231 PMCID: PMC3622177 DOI: 10.7554/elife.00444] [Citation(s) in RCA: 90] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2012] [Accepted: 02/19/2013] [Indexed: 12/14/2022] Open
Abstract
The secretory pathway of eukaryotic cells packages cargo proteins into COPII-coated vesicles for transport from the endoplasmic reticulum (ER) to the Golgi. We now report that complete genetic deficiency for the COPII component SEC24A is compatible with normal survival and development in the mouse, despite the fundamental role of SEC24 in COPII vesicle formation and cargo recruitment. However, these animals exhibit markedly reduced plasma cholesterol, with mutations in Apoe and Ldlr epistatic to Sec24a, suggesting a receptor-mediated lipoprotein clearance mechanism. Consistent with these data, hepatic LDLR levels are up-regulated in SEC24A-deficient cells as a consequence of specific dependence of PCSK9, a negative regulator of LDLR, on SEC24A for efficient exit from the ER. Our findings also identify partial overlap in cargo selectivity between SEC24A and SEC24B, suggesting a previously unappreciated heterogeneity in the recruitment of secretory proteins to the COPII vesicles that extends to soluble as well as trans-membrane cargoes. DOI:http://dx.doi.org/10.7554/eLife.00444.001.
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Affiliation(s)
- Xiao-Wei Chen
- Life Sciences Institute, University of Michigan, Ann Arbor, United States
| | - He Wang
- Life Sciences Institute, University of Michigan, Ann Arbor, United States
| | - Kanika Bajaj
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States
| | - Pengcheng Zhang
- Department of Molecular and Cell Biology, University of California, Berkeley, Berkeley, United States
| | - Zhuo-Xian Meng
- Life Sciences Institute, University of Michigan, Ann Arbor, United States
| | - Danjun Ma
- Department of Pharmaceutical Sciences, College of Pharmacy and Health Sciences, Wayne State University, Detroit, United States
| | - Yongsheng Bai
- Department of Bioinformatics, University of Michigan, Ann Arbor, United States
| | - Hui-Hui Liu
- Department of Molecular Medicine, Cleveland Clinic, Cleveland, United States
| | - Elizabeth Adams
- Program in Cell and Molecular Biology, University of Michigan, Ann Arbor, United States
| | - Andrea Baines
- Program in Cell and Molecular Biology, University of Michigan, Ann Arbor, United States
| | - Genggeng Yu
- Life Sciences Institute, University of Michigan, Ann Arbor, United States
| | - Maureen A Sartor
- Department of Bioinformatics, University of Michigan, Ann Arbor, United States
| | - Bin Zhang
- Department of Molecular Medicine, Cleveland Clinic, Cleveland, United States
| | - Zhengping Yi
- Department of Pharmaceutical Sciences, Wayne State University, Detroit, United States
| | - Jiandie Lin
- Life Sciences Institute, University of Michigan, Ann Arbor, United States
| | - Stephen G Young
- Department of Medicine and Human Genetics, University of California, Los Angeles, Los Angeles, United States
| | - Randy Schekman
- Department of Molecular and Cell Biology, Howard Hughes Medical Institute, University of California, Berkeley, Berkeley, United States
| | - David Ginsburg
- Division of Molecular Medicine & Genetics, Howard Hughes Medical Institute, University of Michigan, Ann Arbor, United States
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7
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Pham K, Langlais P, Zhang X, Chao A, Zingsheim M, Yi Z. Insulin-stimulated phosphorylation of protein phosphatase 1 regulatory subunit 12B revealed by HPLC-ESI-MS/MS. Proteome Sci 2012; 10:52. [PMID: 22937917 PMCID: PMC3546068 DOI: 10.1186/1477-5956-10-52] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2012] [Accepted: 07/31/2012] [Indexed: 11/10/2022] Open
Abstract
UNLABELLED BACKGROUND Protein phosphatase 1 (PP1) is one of the major phosphatases responsible for protein dephosphorylation in eukaryotes. Protein phosphatase 1 regulatory subunit 12B (PPP1R12B), one of the regulatory subunits of PP1, can bind to PP1cδ, one of the catalytic subunits of PP1, and modulate the specificity and activity of PP1cδ against its substrates. Phosphorylation of PPP1R12B on threonine 646 by Rho kinase inhibits the activity of the PP1c-PPP1R12B complex. However, it is not currently known whether PPP1R12B phosphorylation at threonine 646 and other sites is regulated by insulin. We set out to identify phosphorylation sites in PPP1R12B and to quantify the effect of insulin on PPP1R12B phosphorylation by using high-performance liquid chromatography-electrospray ionization-tandem mass spectrometry. RESULTS 14 PPP1R12B phosphorylation sites were identified, 7 of which were previously unreported. Potential kinases were predicted for these sites. Furthermore, relative quantification of PPP1R12B phosphorylation sites for basal and insulin-treated samples was obtained by using peak area-based label-free mass spectrometry of fragment ions. The results indicate that insulin stimulates the phosphorylation of PPP1R12B significantly at serine 29 (3.02 ± 0.94 fold), serine 504 (11.67 ± 3.33 fold), and serine 645/threonine 646 (2.34 ± 0.58 fold). CONCLUSION PPP1R12B was identified as a phosphatase subunit that undergoes insulin-stimulated phosphorylation, suggesting that PPP1R12B might play a role in insulin signaling. This study also identified novel targets for future investigation of the regulation of PPP1R12B not only in insulin signaling in cell models, animal models, and in humans, but also in other signaling pathways.
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Affiliation(s)
- Kimberly Pham
- Center for Metabolic and Vascular Biology, Arizona State University, Tempe, AZ, USA
| | - Paul Langlais
- Center for Metabolic and Vascular Biology, Arizona State University, Tempe, AZ, USA
| | - Xiangmin Zhang
- Center for Metabolic and Vascular Biology, Arizona State University, Tempe, AZ, USA.,Department of Pharmaceutical Sciences, Eugene Applebaum College of Pharmacy/Health Sciences, Wayne State University, 259 Mack Ave., Detroit, MI, USA
| | - Alex Chao
- Center for Metabolic and Vascular Biology, Arizona State University, Tempe, AZ, USA
| | - Morgan Zingsheim
- Center for Metabolic and Vascular Biology, Arizona State University, Tempe, AZ, USA
| | - Zhengping Yi
- Center for Metabolic and Vascular Biology, Arizona State University, Tempe, AZ, USA.,Department of Pharmaceutical Sciences, Eugene Applebaum College of Pharmacy/Health Sciences, Wayne State University, 259 Mack Ave., Detroit, MI, USA
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8
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Chao A, Zhang X, Ma D, Langlais P, Luo M, Mandarino LJ, Zingsheim M, Pham K, Dillon J, Yi Z. Site-specific phosphorylation of protein phosphatase 1 regulatory subunit 12A stimulated or suppressed by insulin. J Proteomics 2012; 75:3342-50. [PMID: 22516431 DOI: 10.1016/j.jprot.2012.03.043] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2011] [Revised: 03/08/2012] [Accepted: 03/26/2012] [Indexed: 10/28/2022]
Abstract
Protein phosphatase 1 (PP1) is one of the major phosphatases responsible for protein dephosphorylation in eukaryotes. So far, only few specific phosphorylation sites of PP1 regulatory subunit 12A (PPP1R12A) have been shown to regulate the PP1 activity. The effect of insulin on PPP1R12A phosphorylation is largely unknown. Utilizing a mass spectrometry based phosphorylation identification and quantification approach, we identified 21 PPP1R12A phosphorylation sites (7 novel sites, including Ser20, Thr22, Thr453, Ser478, Thr671, Ser678, and Ser680) and quantified 16 of them under basal and insulin stimulated conditions in hamster ovary cells overexpressing the insulin receptor (CHO/IR), an insulin sensitive cell model. Insulin stimulated the phosphorylation of PPP1R12A significantly at Ser477, Ser478, Ser507, Ser668, and Ser695, while simultaneously suppressing the phosphorylation of PPP1R12A at Ser509 (more than 2-fold increase or decrease compared to basal). Our data demonstrate that PPP1R12A undergoes insulin stimulated/suppressed phosphorylation, suggesting that PPP1R12A phosphorylation may play a role in insulin signal transduction. The novel PPP1R12A phosphorylation sites as well as the new insulin-responsive phosphorylation sites of PPP1R12A in CHO/IR cells provide targets for investigation of the regulation of PPP1R12A and the PPP1R12A-PP1cδ complex in insulin action and other signaling pathways in other cell models, animal models, and humans.
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Affiliation(s)
- Alex Chao
- Department of Pharmaceutical Sciences, Eugene Applebaum College of Pharmacy/Health Sciences, Wayne State University, Detroit, MI, USA
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9
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Luo M, Mengos AE, Stubblefield TM, Mandarino LJ. High Fat Diet-Induced Changes in Hepatic Protein Abundance in Mice. ACTA ACUST UNITED AC 2012; 5:60-66. [PMID: 33907358 PMCID: PMC8074682 DOI: 10.4172/jpb.1000214] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
Abstract
Nonalcoholic fatty liver disease (NAFLD) is associated with obesity, insulin resistance, type 2 diabetes, and dyslipidemia. The purpose of this study was to identify novel proteins and pathways that contribute to the pathogenesis and complications of NAFLD. C57BL/6J male mice were fed a 60% (HFD) or 10% (LFD) high or low fat diet. HFD induced obesity, hepatic steatosis and insulin resistance (euglycemic clamps, glucose infusion rate: LFD 50.5 ± 6.4 vs. HFD 14.2 ± 9.5 μg/ (g·min); n = 12). Liver proteins were analyzed by mass spectrometry-based proteomics analysis. Numerous hepatic proteins were altered in abundance after 60% HFD feeding. Nine down-regulated and nine up-regulated proteins were selected from this list for detailed analysis based on the criteria of 1.5-fold difference, consistency across replicates, and having at least 2 spectra assigned. Proteins that decreased in abundance were acyl-coA desaturase-I (SCD-1), acetyl-CoA carboxylase (ACC), fatty acid synthase (FAS), pyruvate kinase isozymes R/L (PKLR), NADP-dependent malic enzyme (ME-1), ATP-citrate synthase (ACL), ketohexokinase (KHK), long-chain-fatty acid-CoA ligase-5 (ACSL-5) and carbamoyl-phosphate synthase-I (CPS-1). Those that increased were KIAA0564, apolipoprotein A-I (apoA-1), ornithine aminotransferase (OAT), multidrug resistance protein 2 (MRP-2), liver carboxylesterase-I (CES-1), aminopeptidase N (APN), fatty aldehyde dehydrogenase (FALDH), major urinary protein 2 (MUP-2) and KIAA0664. KIAA0564 and KIAA0664 proteins are uncharacterized and are novel proteins associated with NAFLD. The decreased abundance of normally highly abundant proteins like FAS and CPS-1 was confirmed by Coomassie Blue staining after bands were identified by MS/MS, and immunoblot analysis confirmed the increased abundance of KIAA0664 after 60% HFD feeding. In conclusion, this study shows NAFLD is characterized by changes in abundance of proteins related to cell injury, inflammation, and lipid metabolism. Two novel and uncharacterized proteins, KIAA0564 and KIAA0664, may provide insight into the pathogenesis of NAFLD induced by lipid oversupply.
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Affiliation(s)
- Moulun Luo
- Center for Metabolic and Vascular Biology, Mayo Clinic Arizona, Scottsdale, Arizona; Arizona State University, Tempe, Arizona, USA
| | - April E Mengos
- Center for Metabolic and Vascular Biology, Mayo Clinic Arizona, Scottsdale, Arizona; Arizona State University, Tempe, Arizona, USA
| | - Tianna M Stubblefield
- Center for Metabolic and Vascular Biology, Mayo Clinic Arizona, Scottsdale, Arizona; Arizona State University, Tempe, Arizona, USA
| | - Lawrence J Mandarino
- Center for Metabolic and Vascular Biology, Mayo Clinic Arizona, Scottsdale, Arizona; Arizona State University, Tempe, Arizona, USA.,Department of Medicine, Mayo Clinic Arizona, Scottsdale, Arizona, USA
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10
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Abstract
The adaptor protein raptor is the functional identifier for mammalian target of rapamycin (mTOR) complex 1 (mTORC1), acting to target mTOR to specific substrates for phosphorylation and regulation. Using HPLC-electrospray ionization tandem mass spectrometry, we confirmed the phosphorylation of raptor at Ser696, Thr706, Ser721, Ser722, Ser855, Ser859, Ser863, Thr865, Ser877, Ser881, Ser883, and Ser884 and identified Tyr692, Ser699, Thr700, Ser704, Ser854, Ser857, Ser882, Ser886, Ser887, and Thr889 as new, previously unidentified raptor phosphorylation sites. Treatment of cells with insulin increased the phosphorylation of raptor at Ser696, Ser855, Ser863, and Thr865 and suppressed the phosphorylation of Ser722. Ser696 phosphorylation was insensitive to mTOR inhibition with rapamycin, whereas treatment of cells with the MAPK inhibitor PD98059 inhibited the insulin-stimulated phosphorylation of raptor at Ser696. In vitro incubation of raptor with p42 MAPK significantly increased raptor phosphorylation (P < 0.01), whereas phosphorylation of a Ser696Ala mutant was decreased (P < 0.05), suggesting MAPK is capable of directly phosphorylating raptor at Ser696. Mutation of Ser696 to alanine interfered with insulin-stimulated phosphorylation of the mTOR downstream substrate p70S6 kinase. Incubation of cells with the MAPK inhibitor PD98059 and the phosphatidylinositol 3-kinase inhibitor wortmannin decreased the insulin stimulated phosphorylation of raptor, suggesting that the MAPK and phosphatidylinositol 3-kinase pathways may merge at mTORC1.
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Affiliation(s)
- Paul Langlais
- Center for Metabolic and Vascular Biology, Arizona State University, P.O. Box 874501, Tempe, Arizona 85287-4501, USA
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11
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Langlais P, Mandarino LJ, Yi Z. Label-free relative quantification of co-eluting isobaric phosphopeptides of insulin receptor substrate-1 by HPLC-ESI-MS/MS. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2010; 21:1490-9. [PMID: 20594869 PMCID: PMC2995262 DOI: 10.1016/j.jasms.2010.05.009] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/29/2009] [Revised: 04/30/2010] [Accepted: 05/22/2010] [Indexed: 05/18/2023]
Abstract
Intracellular signal transduction is often regulated by transient protein phosphorylation in response to external stimuli. Insulin signaling is dependent on specific protein phosphorylation events, and analysis of insulin receptor substrate-1 (IRS-1) phosphorylation reveals a complex interplay between tyrosine, serine, and threonine phosphorylation. The phospho-specific antibody-based quantification approach for analyzing changes in site-specific phosphorylation of IRS-1 is difficult due to the dearth of phospho-antibodies compared with the large number of known IRS-1 phosphorylation sites. We previously published a method detailing a peak area-based mass spectrometry approach, using precursor ions for peptides, to quantify the relative abundance of site-specific phosphorylation in the absence or presence of insulin. We now present an improvement wherein site-specific phosphorylation is quantified by determining the peak area of fragment ions respective to the phospho-site of interest. This provides the advantage of being able to quantify co-eluting isobaric phosphopeptides (differentially phosphorylated versions of the same peptide), allowing for a more comprehensive analysis of protein phosphorylation. Quantifying human IRS-1 phosphorylation sites at Ser303, Ser323, Ser330, Ser348, Ser527, and Ser531 shows that this method is linear (n = 3; r(2) = 0.85 +/- 0.05, 0.96 +/- 0.01, 0.96 +/- 0.02, 0.86 +/- 0.07, 0.90 +/- 0.03, 0.91 +/- 0.04, respectively) over an approximate 10-fold range of concentrations and reproducible (n = 4; coefficient of variation = 0.12, 0.14, 0.29, 0.30, 0.12, 0.06, respectively). This application of label-free, fragment ion-based quantification to assess relative phosphorylation changes of specific proteins will prove useful for understanding how various cell stimuli regulate protein function by phosphorylation.
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Affiliation(s)
- Paul Langlais
- ASU/Mayo Center for Metabolic and Vascular Biology, Arizona State University, Tempe, Arizona 85287-4501, USA
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Højlund K, Yi Z, Lefort N, Langlais P, Bowen B, Levin K, Beck-Nielsen H, Mandarino LJ. Human ATP synthase beta is phosphorylated at multiple sites and shows abnormal phosphorylation at specific sites in insulin-resistant muscle. Diabetologia 2010; 53:541-51. [PMID: 20012595 DOI: 10.1007/s00125-009-1624-0] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/16/2009] [Accepted: 11/10/2009] [Indexed: 10/20/2022]
Abstract
AIMS/HYPOTHESIS Insulin resistance in skeletal muscle is linked to mitochondrial dysfunction in obesity and type 2 diabetes. Emerging evidence indicates that reversible phosphorylation regulates oxidative phosphorylation (OxPhos) proteins. The aim of this study was to identify and quantify site-specific phosphorylation of the catalytic beta subunit of ATP synthase (ATPsyn-beta) and determine protein abundance of ATPsyn-beta and other OxPhos components in skeletal muscle from healthy and insulin-resistant individuals. METHODS Skeletal muscle biopsies were obtained from lean, healthy, obese, non-diabetic and type 2 diabetic volunteers (each group n = 10) for immunoblotting of proteins, and hypothesis-driven identification and quantification of phosphorylation sites on ATPsyn-beta using targeted nanospray tandem mass spectrometry. Volunteers were metabolically characterised by euglycaemic-hyperinsulinaemic clamps. RESULTS Seven phosphorylation sites were identified on ATPsyn-beta purified from human skeletal muscle. Obese individuals with and without type 2 diabetes were characterised by impaired insulin-stimulated glucose disposal rates, and showed a approximately 30% higher phosphorylation of ATPsyn-beta at Tyr361 and Thr213 (within the nucleotide-binding region of ATP synthase) as well as a coordinated downregulation of ATPsyn-beta protein and other OxPhos components. Insulin increased Tyr361 phosphorylation of ATPsyn-beta by approximately 50% in lean and healthy, but not insulin-resistant, individuals. CONCLUSIONS/INTERPRETATION These data demonstrate that ATPsyn-beta is phosphorylated at multiple sites in human skeletal muscle, and suggest that abnormal site-specific phosphorylation of ATPsyn-beta together with reduced content of OxPhos proteins contributes to mitochondrial dysfunction in insulin resistance. Further characterisation of phosphorylation of ATPsyn-beta may offer novel targets of treatment in human diseases with mitochondrial dysfunction, such as diabetes.
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Affiliation(s)
- K Højlund
- Center for Metabolic Biology, School of Life Sciences, Arizona State University, PO Box 87370, Tempe, AZ 85287, USA.
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13
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Lu XM, Hamrahi VF, Tompkins RG, Fischman AJ. Effect of insulin levels on the phosphorylation of specific amino acid residues in IRS-1: implications for burn-induced insulin resistance. Int J Mol Med 2009; 24:531-8. [PMID: 19724894 DOI: 10.3892/ijmm_00000262] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
Alterations in the phosphorylation and/or degradation of insulin receptor substrate-1 (IRS-1) produced by burn injury may be responsible, at least in part, for burn-induced insulin resistance. In particular, following burn injury, reductions in glucose uptake by skeletal muscle may be secondary to altered abundance and/or phosphorylation of IRS-1. In this study, we performed in vitro experiments with 293 cells transfected with IRS-1. These studies demonstrated that there is a dramatic change in the phosphorylation pattern of Tyr, Ser and Thr residues in IRS-1 as a function of insulin levels. Specifically, Ser and Thr residues in the C-terminal region were phosphorylated only at high insulin levels. SILAC (stable isotope labeling with amino acids in cell culture) followed by sequencing of C-terminal IRS-1 fragments by tandem mass spectrometry demonstrated that there is significant protein cleavage at these sites. These findings suggest that one of the biological roles of the C-terminal region of IRS-1 may be negative modulation of the finely coordinated insulin signaling system. Clearly, this could represent an important factor in insulin resistance, and identification of kinase inhibitors that are responsible for the phosphorylation may foster new lines of research for the development of drugs for treating insulin resistance.
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Affiliation(s)
- Xiao-Ming Lu
- Surgical Service, Massachusetts General Hospital, Shriners Hospitals for Children and Harvard Medical School, Boston, MA 02114, USA
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14
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Alterations of insulin signaling in type 2 diabetes: A review of the current evidence from humans. Biochim Biophys Acta Mol Basis Dis 2009; 1792:83-92. [DOI: 10.1016/j.bbadis.2008.10.019] [Citation(s) in RCA: 153] [Impact Index Per Article: 10.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2008] [Revised: 10/21/2008] [Accepted: 10/21/2008] [Indexed: 01/03/2023]
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15
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Weigert C, Kron M, Kalbacher H, Pohl AK, Runge H, Häring HU, Schleicher E, Lehmann R. Interplay and effects of temporal changes in the phosphorylation state of serine-302, -307, and -318 of insulin receptor substrate-1 on insulin action in skeletal muscle cells. Mol Endocrinol 2008; 22:2729-40. [PMID: 18927238 DOI: 10.1210/me.2008-0102] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023] Open
Abstract
Transduction of the insulin signal is mediated by multisite Tyr and Ser/Thr phosphorylation of the insulin receptor substrates (IRSs). Previous studies on the function of single-site phosphorylation, particularly phosphorylation of Ser-302, -307, and -318 of IRS-1, showed attenuating as well as enhancing effects on insulin action. In this study we investigated a possible cross talk of these opposedly acting serine residues in insulin-stimulated skeletal muscle cells by monitoring phosphorylation kinetics, and applying loss of function, gain of function, and combination mutants of IRS-1. The phosphorylation at Ser-302 was rapid and transient, followed first by Ser-318 phosphorylation and later by phosphorylation of Ser-307, which remained elevated for 120 min. Mutation of Ser-302 to alanine clearly reduced the subsequent protein kinase C-zeta-mediated Ser-318 phosphorylation. The Ser-307 phosphorylation was independent of Ser-302 and/or Ser-318 phosphorylation status. The functional consequences of these phosphorylation patterns were studied by the expression of IRS-1 mutants. The E302A307E318 mutant simulating the early phosphorylation pattern resulted in a significant increase in Akt and glycogen synthase kinase 3 phosphorylation. Furthermore, glucose uptake was enhanced. Because the down-regulation of the insulin signal was not affected, this phosphorylation pattern seems to be involved in the enhancement but not in the termination of the insulin signal. This enhancing effect was completely absent when Ser-302 was unphosphorylated and Ser-307 was phosphorylated as simulated by the A302E307E318 mutant. Phospho-Ser-318, sequentially phosphorylated at least by protein kinase C-zeta and a mammalian target of rapamycin/raptor-dependent kinase, was part of the positive as well as of the subsequent negative phosphorylation pattern. Thus we conclude that insulin stimulation temporally generates different phosphorylation statuses of the same residues that exert different functions in insulin signaling.
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Affiliation(s)
- Cora Weigert
- Division of Clinical Chemistry and Pathobiochemistry, University Hospital of Tübingen, Tübingen, Germany
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16
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Jalili PR, Ball HL. Novel reversible biotinylated probe for the selective enrichment of phosphorylated peptides from complex mixtures. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2008; 19:741-750. [PMID: 18359247 DOI: 10.1016/j.jasms.2008.02.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/09/2007] [Revised: 02/06/2008] [Accepted: 02/18/2008] [Indexed: 05/26/2023]
Abstract
To improve the detection of phosphorylated peptides/proteins, we developed a novel protocol that involves the chemical derivatization of phosphate groups with a chemically engineered biotinylated-tag (biotin-tag), possessing three functional domains; a biotin group for binding to avidin, a base-labile 4-carboxy fluorenyl methoxycarbonyl (4-carboxy Fmoc) group, and a nucleophilic sulfhydryl moiety on the side-chain of cysteine. Using this approach, the derivatized, enzymatically digested peptides were selectively separated from unrelated sequences and impurities on immobilized avidin. Unlike previously published phosphopeptide enrichment procedures, this approach upon treatment with mild base liberates a covalently bound Gly-Cys analog of the peptide(s) of interest, exhibiting improved RP-HPLC retention and MS ionization properties compared with the precursor phosphopeptide sequence. The results obtained for a model peptide Akt-1 and two protein digests, demonstrated that the method is highly specific and allows selective enrichment of phosphorylated peptides at low concentrations of fmol/microL.
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Affiliation(s)
- Pegah R Jalili
- Protein Chemistry Technology Center, University of Texas, Southwestern Medical Center, Dallas, Texas 75390-8816, USA
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17
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Luo M, Langlais P, Yi Z, Lefort N, De Filippis EA, Hwang H, Christ-Roberts CY, Mandarino LJ. Phosphorylation of human insulin receptor substrate-1 at Serine 629 plays a positive role in insulin signaling. Endocrinology 2007; 148:4895-905. [PMID: 17640984 PMCID: PMC3581341 DOI: 10.1210/en.2007-0049] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
The function of insulin receptor substrate-1 (IRS-1) is regulated by both tyrosine and serine/threonine phosphorylation. Phosphorylation of some serine/threonine residues in IRS-1 dampens insulin signaling, whereas phosphorylation of other serine/threonine residues enhances insulin signaling. Phosphorylation of human IRS-1 at Ser(629) was increased by insulin in Chinese hamster ovary cells expressing the insulin receptor (1.26 +/- 0.09-fold; P < 0.05) and L6 cells (1.35 +/- 0.29-fold; P < 0.05) expressing human IRS-1. Sequence analysis surrounding Ser(629) revealed conformity to the consensus phosphorylation sequence recognized by Akt. Phosphorylation of IRS-1 at Ser(629) in cells was decreased upon treatment with either an Akt inhibitor or by coexpression with kinase dead Akt, whereas Ser(629) phosphorylation was increased by coexpression with constitutively active Akt. In addition, Ser(629) of IRS-1 is directly phosphorylated by Akt in vitro. In cells, preventing phosphorylation of Ser(629) by a Ser(629)Ala mutation resulted in increased phosphorylation of Ser(636), a known negative regulator of IRS-1, without affecting phosphorylation of Tyr(632) or Ser(616). Cells expressing the Ser(629)Ala mutation, along with increased Ser(636) phosphorylation, had decreased insulin-stimulated association of the p85 regulatory subunit of phosphatidylinositol 3'-kinase with IRS-1 and decreased phosphorylation of Akt at Ser(473). Finally, in vitro phosphorylation of a Ser(629)-containing IRS-1 fragment with Akt reduces the subsequent ability of ERK to phosphorylate Ser(636/639). These results suggest that a feed-forward mechanism may exist whereby insulin activation of Akt leads to phosphorylation of IRS-1 at Ser(629), resulting in decreased phosphorylation of IRS-1 at Ser(636) and enhanced downstream signaling. Understanding the complex phosphorylation patterns of IRS-1 is crucial to elucidating the factors contributing to insulin resistance and, ultimately, the pathogenesis of type 2 diabetes.
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Affiliation(s)
- Moulun Luo
- Center for Metabolic Biology, College of Liberal Arts and Sciences, Tempe, AZ 85287-3704, USA
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18
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Yi Z, Langlais P, De Filippis EA, Luo M, Flynn CR, Schroeder S, Weintraub ST, Mapes R, Mandarino LJ. Global assessment of regulation of phosphorylation of insulin receptor substrate-1 by insulin in vivo in human muscle. Diabetes 2007; 56:1508-16. [PMID: 17360977 DOI: 10.2337/db06-1355] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/13/2022]
Abstract
OBJECTIVE Research has focused on insulin receptor substrate (IRS)-1 as a locus for insulin resistance. Tyrosine phosphorylation of IRS-1 initiates insulin signaling, whereas serine/threonine phosphorylation alters the ability of IRS-1 to transduce the insulin signal. Of 1,242 amino acids in IRS-1, 242 are serine/threonine. Serine/threonine phosphorylation of IRS-1 is affected by many factors, including insulin. The purpose of this study was to perform global assessment of phosphorylation of serine/threonine residues in IRS-1 in vivo in humans. RESEARCH DESIGN AND METHODS In this study, we describe our use of capillary high-performance liquid chromotography electrospray tandem mass spectrometry to identify/quantify site-specific phosphorylation of IRS-1 in human vastus lateralis muscle obtained by needle biopsy basally and after insulin infusion in four healthy volunteers. RESULTS Twenty-two serine/threonine phosphorylation sites were identified; 15 were quantified. Three sites had not been previously identified (Thr495, Ser527, and S1005). Insulin increased the phosphorylation of Ser312, Ser616, Ser636, Ser892, Ser1101, and Ser1223 (2.6 +/- 0.4, 2.9 +/- 0.8, 2.1 +/- 0.3, 1.6 +/- 0.1, 1.3 +/- 0.1, and 1.3 +/- 0.1-fold, respectively, compared with basal; P < 0.05); phosphorylation of Ser348, Thr446, Thr495, and Ser1005 decreased (0.4 +/- 0.1, 0.2 +/- 0.1, 0.1 +/- 0.1, and 0.3 +/- 0.2-fold, respectively; P < 0.05). CONCLUSIONS These results provide an assessment of IRS-1 phosphorylation in vivo and show that insulin has profound effects on IRS-1 serine/threonine phosphorylation in healthy humans.
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Affiliation(s)
- Zhengping Yi
- Center for Metabolic Biology, Arizona State University, Tempe, AZ 85287-3704, USA
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Jalili PR, Sharma D, Ball HL. Enhancement of ionization efficiency and selective enrichment of phosphorylated peptides from complex protein mixtures using a reversible poly-histidine tag. JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY 2007; 18:1007-17. [PMID: 17383192 DOI: 10.1016/j.jasms.2007.02.010] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/17/2006] [Revised: 01/24/2007] [Accepted: 02/14/2007] [Indexed: 05/14/2023]
Abstract
To improve the detection of phosphorylated peptides/proteins, a combination of optimized MS-based strategies were used involving chemical derivatization with a polyhistidine-tag (His-tag) and affinity enrichment of the resulting His-tag peptides on a nanoscale Ni(2+)-IMAC column. The phosphoserine and phosphothreonine peptides were derivatized using a one-pot beta-elimination/Michael addition reaction with a reversible His-tag possessing a thiol-containing Cys residue. The His-tag peptides were enriched selectively by Ni(2+)-IMAC and released using either imidazole or cleavage with Factor Xa. This novel capture and enzyme-mediated release provided an additional element of selectivity and yielded phosphopeptide-specific modifications with enhanced MS ionization characteristics. The eluted peptides were mapped using MALDI-TOF MS and QTRAP ESI-MS/MS techniques. The results obtained for a model peptide and two tryptic protein digests show that the method is highly specific and allows selective enrichment of phosphorylated peptides at low concentrations of femtomoles per microliter.
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Affiliation(s)
- Pegah R Jalili
- Protein Chemistry Technology Center, University of Texas, Southwestern Medical Center, Dallas, Texas 75390-8816, USA
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Current literature in mass spectrometry. JOURNAL OF MASS SPECTROMETRY : JMS 2007; 42:127-38. [PMID: 17199253 PMCID: PMC7166443 DOI: 10.1002/jms.1070] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
In order to keep subscribers up‐to‐date with the latest developments in their field, John Wiley & Sons are providing a current awareness service in each issue of the journal. The bibliography contains newly published material in the field of mass spectrometry. Each bibliography is divided into 11 sections: 1 Books, Reviews & Symposia; 2 Instrumental Techniques & Methods; 3 Gas Phase Ion Chemistry; 4 Biology/Biochemistry: Amino Acids, Peptides & Proteins; Carbohydrates; Lipids; Nucleic Acids; 5 Pharmacology/Toxicology; 6 Natural Products; 7 Analysis of Organic Compounds; 8 Analysis of Inorganics/Organometallics; 9 Surface Analysis; 10 Environmental Analysis; 11 Elemental Analysis. Within each section, articles are listed in alphabetical order with respect to author (6 Weeks journals ‐ Search completed at 4th. Oct. 2006)
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