title: Microfluidic Mobility Shift Assay for Real-Time Analysis of Peptide N-Palmitoylation.
abstract: The Hedgehog pathway is a key developmental signaling pathway but is also implicated in many types of cancer. The extracellular signaling protein Sonic hedgehog (Shh) requires dual lipidation for functional signaling, whereby N-terminal palmitoylation is performed by the enzyme Hedgehog acyltransferase (Hhat). Hhat is an attractive target for small-molecule inhibition to arrest Hedgehog signaling, and methods for assaying Hhat activity are central to understanding its function. However, all existing assays to quantify lipidation of peptides suffer limitations, such as safety hazards, high costs, extensive manual handling, restriction to stopped-assay measurements, or indirect assessment of lipidation. To address these limitations, we developed a microfluidic mobility shift assay (MSA) to analyze Shh palmitoylation. MSA allowed separation of fluorescently labeled Shh amine-substrate and palmitoylated Shh amide-product peptides based on differences in charge and hydrodynamic radius, coupled with online fluorescence intensity measurements for quantification. The MSA format was employed to study Hhat-catalyzed reactions, investigate Hhat kinetics, and determine small-molecule inhibitor IC50values. Both real-time and stopped assays were performed, with the latter achieved via addition of excess unlabeled Shh peptide. The MSA format therefore allows direct and real-time fluorescence-based measurement of acylation and represents a powerful alternative technique in the study of N-lipidation.
authors.affiliation: 1 Department of Chemistry, Imperial College London, London, UK.
authors.forename: Thomas
authors.initials: T
authors.lastname: Lanyon-Hogg
authors.affiliation: 1 Department of Chemistry, Imperial College London, London, UK.
authors.forename: Neki V
authors.initials: NV
authors.lastname: Patel
authors.affiliation: 1 Department of Chemistry, Imperial College London, London, UK.
authors.forename: Markus
authors.initials: M
authors.lastname: Ritzefeld
authors.affiliation: 2 Cancer Research UK Cancer Therapeutics Unit, The Institute of Cancer Research, London, UK.
authors.forename: Katherine J
authors.initials: KJ
authors.lastname: Boxall
authors.affiliation: 2 Cancer Research UK Cancer Therapeutics Unit, The Institute of Cancer Research, London, UK.
authors.forename: Rosemary
authors.initials: R
authors.lastname: Burke
authors.affiliation: 2 Cancer Research UK Cancer Therapeutics Unit, The Institute of Cancer Research, London, UK.
authors.forename: Julian
authors.initials: J
authors.lastname: Blagg
authors.affiliation: 3 Molecular Medicine Section, National Heart & Lung Institute, Imperial College London, London, UK.
authors.forename: Anthony I
authors.initials: AI
authors.lastname: Magee
authors.affiliation: 1 Department of Chemistry, Imperial College London, London, UK.
authors.forename: Edward W
authors.initials: EW
authors.lastname: Tate
mesh_terms: D000217:Acyltransferases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D000595:Amino Acid Sequence; D024202:Electrophoretic Mobility Shift Assay / Q000295:instrumentation / Q000379:methods*; D057075:Enzyme Assays; D004791:Enzyme Inhibitors / Q000494:pharmacology; D057809:HEK293 Cells; D053823:Hedgehog Proteins / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D007700:Kinetics; D054878:Lipoylation / Q000187:drug effects; D044085:Microfluidics / Q000295:instrumentation / Q000379:methods*; D011499:Protein Processing, Post-Translational; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D004791:Enzyme Inhibitors; D053823:Hedgehog Proteins; D011994:Recombinant Proteins; C509239:SHH protein, human; D000217:Acyltransferases; C105599:HHAT protein, human
keywords: enzyme assays or enzyme kinetics; fluorescence methods; lipids or lipid metabolism; medicinal chemistry