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Drown BS, Gupta R, McGee JP, Hollas MAR, Hergenrother PJ, Kafader JO, Kelleher NL. Precise Readout of MEK1 Proteoforms upon MAPK Pathway Modulation by Individual Ion Mass Spectrometry. Anal Chem 2024; 96:4455-4462. [PMID: 38458998 PMCID: PMC11008683 DOI: 10.1021/acs.analchem.3c04758] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/10/2024]
Abstract
The functions of proteins bearing multiple post-translational modifications (PTMs) are modulated by their modification patterns, yet precise characterization of them is difficult. MEK1 (also known as MAP2K1) is one such example that acts as a gatekeeper of the mitogen-activating protein kinase (MAPK) pathway and propagates signals via phosphorylation by upstream kinases. In principle, top-down mass spectrometry can precisely characterize whole MEK1 proteoforms, but fragmentation methods that would enable the site-specific characterization of labile modifications on 43 kDa protein ions result in overly dense tandem mass spectra. By using the charge-detection method called individual ion mass spectrometry, we demonstrate how complex mixtures of phosphoproteoforms and their fragment ions can be reproducibly handled to provide a "bird's eye" view of signaling activity through mapping proteoform landscapes in a pathway. Using this approach, the overall stoichiometry and distribution of 0-4 phosphorylations on MEK1 was determined in a cellular model of drug-resistant metastatic melanoma. This approach can be generalized to other multiply modified proteoforms, for which PTM combinations are key to their function and drug action.
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Affiliation(s)
- Bryon S Drown
- Proteomics Center of Excellence, Departments of Molecular Biosciences, Chemistry, and the Feinberg School of Medicine, Northwestern University, Evanston, Illinois 60202, United States
| | - Raveena Gupta
- Proteomics Center of Excellence, Departments of Molecular Biosciences, Chemistry, and the Feinberg School of Medicine, Northwestern University, Evanston, Illinois 60202, United States
| | - John P McGee
- Proteomics Center of Excellence, Departments of Molecular Biosciences, Chemistry, and the Feinberg School of Medicine, Northwestern University, Evanston, Illinois 60202, United States
| | - Michael A R Hollas
- Proteomics Center of Excellence, Departments of Molecular Biosciences, Chemistry, and the Feinberg School of Medicine, Northwestern University, Evanston, Illinois 60202, United States
| | - Paul J Hergenrother
- Department of Chemistry, Carl R. Woese Institute for Genomic Biology, Cancer Center at Illinois, University of Illinois at Urbana─Champaign, Urbana, Illinois 61801, United States
| | - Jared O Kafader
- Proteomics Center of Excellence, Departments of Molecular Biosciences, Chemistry, and the Feinberg School of Medicine, Northwestern University, Evanston, Illinois 60202, United States
| | - Neil L Kelleher
- Proteomics Center of Excellence, Departments of Molecular Biosciences, Chemistry, and the Feinberg School of Medicine, Northwestern University, Evanston, Illinois 60202, United States
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Brown KA, Morris R, Eckhardt SJ, Ge Y, Gellman SH. Phosphorylation Sites of the Gastric Inhibitory Polypeptide Receptor (GIPR) Revealed by Trapped-Ion-Mobility Spectrometry Coupled to Time-of-Flight Mass Spectrometry (TIMS-TOF MS). J Am Chem Soc 2023; 145:28030-28037. [PMID: 38091482 PMCID: PMC10842860 DOI: 10.1021/jacs.3c09078] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2023]
Abstract
The gastric inhibitory polypeptide receptor (GIPR), a G protein-coupled receptor (GPCR) that regulates glucose metabolism and insulin secretion, is a target for the development of therapeutic agents to address type 2 diabetes and obesity. Signal transduction processes mediated by GPCR activation typically result in receptor phosphorylation, but very little is known about GIPR phosphorylation. Mass spectrometry (MS) is a powerful tool for detecting phosphorylation and other post-translational modifications of proteins and for identifying modification sites. However, applying MS methods to GPCRs is challenging because the native expression levels are low and the hydrophobicity of these proteins complicates isolation and enrichment. Here we use a widely available technique, trapped-ion-mobility spectrometry coupled to time-of-flight mass spectrometry (TIMS-TOF MS), to characterize the phosphorylation status of the GIPR. We identified eight serine residues that are phosphorylated, one in an intracellular loop and the remainder in the C-terminal domain. Stimulation with the native agonist GIP enhanced phosphorylation at four of these sites. For comparison, we evaluated tirzepatide (TZP), a dual agonist of the glucagon-like peptide-1 (GLP-1) receptor and the GIPR that has recently been approved for the treatment of type 2 diabetes. Stimulation with TZP enhanced phosphorylation at the same four sites that were enhanced with GIP; however, TZP also enhanced phosphorylation at a fifth site that is unique to this synthetic agonist. This work establishes an important and accessible tool for the characterization of signal transduction via the GIPR and reveals an unanticipated functional difference between GIP and TZP.
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Affiliation(s)
- Kyle A. Brown
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin, 53706, USA
| | - Rylie Morris
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin, 53706, USA
| | - Samantha J. Eckhardt
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin, 53706, USA
| | - Ying Ge
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin, 53706, USA
- Department of Cell and Regenerative Biology, University of Wisconsin-Madison, Madison, Wisconsin, 53705, USA
- Human Proteomics Program, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, Wisconsin, 53705, USA
| | - Samuel H. Gellman
- Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin, 53706, USA
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Srapyan S, Tran DP, Loo JA, Grintsevich EE. Mapping Molecular Interaction Interface Between Diaphanous Formin-2 and Neuron-Specific Drebrin A. J Mol Biol 2023; 435:168334. [PMID: 37898384 DOI: 10.1016/j.jmb.2023.168334] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2023] [Revised: 10/13/2023] [Accepted: 10/23/2023] [Indexed: 10/30/2023]
Abstract
Actin cytoskeleton is critical for neuronal shape and function. Drebrin and formins are key regulators of neuronal actin networks. Neuron-specific drebrin A is highly enriched in dendritic spines (postsynaptic terminals) of mature excitatory neurons. Decreased levels of drebrin in dendritic spines is a hallmark of Alzheimer's disease, epilepsy, and other complex disorders, which calls for better understanding of its regulatory functions. Drebrin A was previously shown to inhibit actin nucleation and bundling by the diaphanous formin-2 (mDia2) - an actin nucleator that is involved in the initiation of dendritic spines. Characterization of the molecular binding interface between mDia2 and drebrin is necessary to better understand the functional consequences of this interaction and its biological relevance. Prior work suggested a multi-pronged interface between mDia2 and drebrin, which involves both N-terminal and C-terminal regions of the drebrin molecule. Here we used mass spectrometry analysis, deletion mutagenesis, and an array of synthetic peptides of neuronal drebrin A to map its formin-binding interface. The mDia2-interacting interface on drebrin was narrowed down to three highly conserved 9-16 residue sequences that were used to identify some of the key residues involved in this interaction. Deletion of the C-terminal region of drebrin greatly reduces its binding to mDia2 and the extent of its inhibition of formin-driven actin assembly. Moreover, our experiments with formins from different subfamilies showed that drebrin is a specific rather than general inhibitor of these proteins. This work contributes to a molecular level understanding of the formin-drebrin interaction and will help to unravel its biological significance.
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Affiliation(s)
- Sargis Srapyan
- Department of Chemistry and Biochemistry, California State University, Long Beach (CSULB), Long Beach, CA 90840, USA
| | - Denise P Tran
- Department of Chemistry and Biochemistry, University of California, Los Angeles (UCLA), Los Angeles, CA 90095, USA; Sydney Mass Spectrometry, The University of Sydney (USyd), Sydney, New South Wales 2006, Australia
| | - Joseph A Loo
- Department of Chemistry and Biochemistry, University of California, Los Angeles (UCLA), Los Angeles, CA 90095, USA
| | - Elena E Grintsevich
- Department of Chemistry and Biochemistry, California State University, Long Beach (CSULB), Long Beach, CA 90840, USA.
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Barki N, Jenkins L, Marsango S, Dedeo D, Bolognini D, Dwomoh L, Abdelmalik AM, Nilsen M, Stoffels M, Nagel F, Schulz S, Tobin AB, Milligan G. Phosphorylation bar-coding of free fatty acid receptor 2 is generated in a tissue-specific manner. eLife 2023; 12:RP91861. [PMID: 38085667 PMCID: PMC10715726 DOI: 10.7554/elife.91861] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2023] Open
Abstract
Free fatty acid receptor 2 (FFAR2) is activated by short-chain fatty acids and expressed widely, including in white adipocytes and various immune and enteroendocrine cells. Using both wild-type human FFAR2 and a designer receptor exclusively activated by designer drug (DREADD) variant we explored the activation and phosphorylation profile of the receptor, both in heterologous cell lines and in tissues from transgenic knock-in mouse lines expressing either human FFAR2 or the FFAR2-DREADD. FFAR2 phospho-site-specific antisera targeting either pSer296/pSer297 or pThr306/pThr310 provided sensitive biomarkers of both constitutive and agonist-mediated phosphorylation as well as an effective means to visualise agonist-activated receptors in situ. In white adipose tissue, phosphorylation of residues Ser296/Ser297 was enhanced upon agonist activation whilst Thr306/Thr310 did not become phosphorylated. By contrast, in immune cells from Peyer's patches Thr306/Thr310 become phosphorylated in a strictly agonist-dependent fashion whilst in enteroendocrine cells of the colon both Ser296/Ser297 and Thr306/Thr310 were poorly phosphorylated. The concept of phosphorylation bar-coding has centred to date on the potential for different agonists to promote distinct receptor phosphorylation patterns. Here, we demonstrate that this occurs for the same agonist-receptor pairing in different patho-physiologically relevant target tissues. This may underpin why a single G protein-coupled receptor can generate different functional outcomes in a tissue-specific manner.
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Affiliation(s)
- Natasja Barki
- Centre for Translational Pharmacology, School of Molecular Biosciences, College of Medical, Veterinary and Life Sciences, University of GlasgowGlasgowUnited Kingdom
| | - Laura Jenkins
- Centre for Translational Pharmacology, School of Molecular Biosciences, College of Medical, Veterinary and Life Sciences, University of GlasgowGlasgowUnited Kingdom
| | - Sara Marsango
- Centre for Translational Pharmacology, School of Molecular Biosciences, College of Medical, Veterinary and Life Sciences, University of GlasgowGlasgowUnited Kingdom
| | - Domonkos Dedeo
- Centre for Translational Pharmacology, School of Molecular Biosciences, College of Medical, Veterinary and Life Sciences, University of GlasgowGlasgowUnited Kingdom
| | - Daniele Bolognini
- Centre for Translational Pharmacology, School of Molecular Biosciences, College of Medical, Veterinary and Life Sciences, University of GlasgowGlasgowUnited Kingdom
| | - Louis Dwomoh
- Centre for Translational Pharmacology, School of Molecular Biosciences, College of Medical, Veterinary and Life Sciences, University of GlasgowGlasgowUnited Kingdom
| | - Aisha M Abdelmalik
- Centre for Translational Pharmacology, School of Molecular Biosciences, College of Medical, Veterinary and Life Sciences, University of GlasgowGlasgowUnited Kingdom
| | - Margaret Nilsen
- Centre for Translational Pharmacology, School of Molecular Biosciences, College of Medical, Veterinary and Life Sciences, University of GlasgowGlasgowUnited Kingdom
| | - Manon Stoffels
- Centre for Translational Pharmacology, School of Molecular Biosciences, College of Medical, Veterinary and Life Sciences, University of GlasgowGlasgowUnited Kingdom
| | | | - Stefan Schulz
- 7TM Antibodies GmbHJenaGermany
- Institute of Pharmacology and Toxicology, University Hospital JenaJenaGermany
| | - Andrew B Tobin
- Centre for Translational Pharmacology, School of Molecular Biosciences, College of Medical, Veterinary and Life Sciences, University of GlasgowGlasgowUnited Kingdom
| | - Graeme Milligan
- Centre for Translational Pharmacology, School of Molecular Biosciences, College of Medical, Veterinary and Life Sciences, University of GlasgowGlasgowUnited Kingdom
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Dowling P, Gargan S, Swandulla D, Ohlendieck K. Fiber-Type Shifting in Sarcopenia of Old Age: Proteomic Profiling of the Contractile Apparatus of Skeletal Muscles. Int J Mol Sci 2023; 24:ijms24032415. [PMID: 36768735 PMCID: PMC9916839 DOI: 10.3390/ijms24032415] [Citation(s) in RCA: 24] [Impact Index Per Article: 24.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2022] [Revised: 01/20/2023] [Accepted: 01/23/2023] [Indexed: 01/28/2023] Open
Abstract
The progressive loss of skeletal muscle mass and concomitant reduction in contractile strength plays a central role in frailty syndrome. Age-related neuronal impairments are closely associated with sarcopenia in the elderly, which is characterized by severe muscular atrophy that can considerably lessen the overall quality of life at old age. Mass-spectrometry-based proteomic surveys of senescent human skeletal muscles, as well as animal models of sarcopenia, have decisively improved our understanding of the molecular and cellular consequences of muscular atrophy and associated fiber-type shifting during aging. This review outlines the mass spectrometric identification of proteome-wide changes in atrophying skeletal muscles, with a focus on contractile proteins as potential markers of changes in fiber-type distribution patterns. The observed trend of fast-to-slow transitions in individual human skeletal muscles during the aging process is most likely linked to a preferential susceptibility of fast-twitching muscle fibers to muscular atrophy. Studies with senescent animal models, including mostly aged rodent skeletal muscles, have confirmed fiber-type shifting. The proteomic analysis of fast versus slow isoforms of key contractile proteins, such as myosin heavy chains, myosin light chains, actins, troponins and tropomyosins, suggests them as suitable bioanalytical tools of fiber-type transitions during aging.
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Affiliation(s)
- Paul Dowling
- Department of Biology, Maynooth University, National University of Ireland, W23 F2H6 Maynooth, Co. Kildare, Ireland
- Kathleen Lonsdale Institute for Human Health Research, Maynooth University, W23 F2H6 Maynooth, Co. Kildare, Ireland
| | - Stephen Gargan
- Department of Biology, Maynooth University, National University of Ireland, W23 F2H6 Maynooth, Co. Kildare, Ireland
- Kathleen Lonsdale Institute for Human Health Research, Maynooth University, W23 F2H6 Maynooth, Co. Kildare, Ireland
| | - Dieter Swandulla
- Institute of Physiology, University of Bonn, D53115 Bonn, Germany
| | - Kay Ohlendieck
- Department of Biology, Maynooth University, National University of Ireland, W23 F2H6 Maynooth, Co. Kildare, Ireland
- Kathleen Lonsdale Institute for Human Health Research, Maynooth University, W23 F2H6 Maynooth, Co. Kildare, Ireland
- Correspondence: ; Tel.: +353-1-7083842
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